United States EPA-600/R-01-039D
Environmental ProtectionD , ___,.
Agency June 2001 D
vvEPA Research and
Development
Application of Pollution Prevention
Techniques to Reduce Indoor Air Emissions
From Aerosol Consumer Products
Prepared fort
Office of Prevention, Pesticides, and Toxic Substancesn
Andn
Office of Radiation and Indoor Airn
Prepared by
National Risk Managementn
Research Laboratoryn
Research Triangle Park, NC 27711 n
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Foreword
The U.S. Environmental Protection Agency is charged by Congress with
protecting the Nation's land, air, and water resources. Under a mandate of national
environmental laws, the Agency strives to formulate and implement actions leading to
a compatible balance between human activities and the ability of natural systems to
support and nurture life. To meet this mandate, EPA's research program is providing
data and technical support for solving environmental problems today and building a
science knowledge base necessary to manage our ecological resources wisely,
understand how pollutants affect our health, and prevent or reduce environmental risks
in the future.
The National Risk Management Research Laboratory (NRMRL) is the Agency's
center for investigation of technological and management approaches for preventing
and reducing risks from pollution that threaten human health and the environment. The
focus of the Laboratory's research program is on methods and their cost-effectiveness
for prevention and control of pollution to air, land, water, and subsurface resources,
protection of water quality in public water systems; remediation of contaminated sites,
sediments and ground water; prevention and control of indoor air pollution; and
restoration of ecosystems. NRMRL collaborates with both public and private sector
partners to foster technologies that reduce the cost of compliance and to anticipate
emerging problems. NRMRL's research provides solutions to environmental problems
by: developing and promoting technologies that protect and improve the environment;
advancing scientific and engineering information to support regulatory and policy
decisions; and providing the technical support and information transfer to ensure
implementation of environmental regulations and strategies at the national, state, and
community levels.
This publication has been produced as part of the Laboratory's strategic
long-term research plan. It is published and made available by EPA's Office of
Research and Development to assist the user community and to link researchers with
their clients.
E. Timothy Oppelt, Director^
National Risk Management Research Laboratory D
EPA REVIEW NOTICE
This report has been peer and administratively reviewed by the U.S. Environmental
Protection Agency, and approved for publication. Mention of trade names or
commercial products does not constitute endorsement or recommendation for use.
This document is available to the public through the National Technical Information
Service, Springfield, Virginia 22161.
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EPA-600/R-01-039
June 2001
APPLICATION OF POLLUTION PREVENTION
TECHNIQUES TO REDUCE INDOOR AIR
EMISSIONS FROM AEROSOL CONSUMER
PRODUCTS
By
Charlene W. BayerD
Electro-Optics, Environment & Materials Laboratory D
Georgia Tech Research Instituted
Atlanta, Georgia 30332-0820D
Richard A. Browner and Stacy HOD
School of Chemistry & Biochemistry D
Georgia Institute of TechnologyD
Atlanta, Georgia 30332-0400D
Leslie L. Christiansen, Ling Ying Zhao, Per Heiselberg, Mike E. Tumbleson, and Michael M. CuiD
Biochemical Engineering Research Laboratory D
University of Illinois at Urbana-ChampaignD
1304 W. Pennsylvania AvenueD
Urbana, Illinois 61801 n
EPA Cooperative Agreement Number: CR 822007D
EPA Project Officer: Kelly W. LeovicD
National Risk Management Research Laboratory D
Research Triangle Park, North Carolina 27711 n
Prepared forD
U.S. Environmental Protection AgencyD
Office of Research and Development^
Washington, DC 20460D
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Abstract n
Aerosol consumer products potentially are amenable to pollution prevention
strategies that reformulate or redesign products, substitute raw materials, or improve
consumer use procedures. A basic understanding of the behavior of aerosol consumer
products is essential in the development of pollution prevention strategies, which may
reduce occupant exposures and guide manufacturers in the development of more
efficacious, less toxic products. This research project was undertaken to develop tools
and methodologies to measure aerosol chemical and particle dispersion through space.
EPA's National Risk Management Research Laboratory sponsored a cooperative
agreement with the Georgia Tech Research Institute (GTRI), and the University of Illinois
(Ul) to develop tools and methodologies to measure aerosol chemical composition and
particle dispersion through space. These tools can be used to devise pollution
prevention strategies that could reduce occupant chemical exposures and guide
manufacturers in formulating more efficacious products. The GTRI researchers built an
Aerosol Mass Spectral Interface (AMSI), which is interfaced with a mass spectrometer
(MS), that chemically characterizes aerosol consumer products through space. The Ul
researchers developed techniques for measuring aerosol movement indoors by tracking
particle size changes via particle velocity measurements using particle image
velocimetry (PIV). A group of Industry Partners participated in this research project to
ensure that the technologies developed would be useful to industry.
The AMSI was designed, constructed, and optimized to transfer a focused beam
of aerosol particles into a mass spectrometer for chemical analysis. It was shown
experimentally during this project that the AMSI can quantitatively detect compositional
changes as the aerosol travels through space. These data provide important information
for the formulating of aerosol consumer products for pollution prevention strategies. The
PIV system demonstrated a correlation between the material properties of the aerosol
components and the spray pattern. These data were used to develop a model for
prediction of the major characteristics of aerosol spray patterns. The model can be a
useful guide for developing pollution prevention strategies.
This report was submitted in fulfillment of grant number CR822007 under the
sponsorship of US EPA. This report covers a period from July 1994 to September 1997,
and was completed as of December 31, 1997.
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Table of Contents
Abstract iin
List of Tables vn
List of Figures via
Acknowledgments ixn
1.0 Introduction in
1.1 Background in
1.2 Traditional Aerosol Analysis 2D
2.0 Conclusions 4n
2.1 Chemical Composition 4D
2.2 Particulate Behavior 5D
3.0 Recommendations 6n
3.1 Technology Costs 6D
3.2 Technology Limitations 6D
4.0 Technical Approach 8n
5.0 Methods, Results, and Discussion 9
5.1 Surrogate Aerosols 9n
5.2 Chemical Composition 11H
5.2.1 Aerosol Mass Spectral Interface 11 n
5.2.2 Generation of Standard Aerosols 13H
5.2.3 Total Aerosol Consumer Product Analysis 13H
5.2.4 Optimization of AMSI
5.2.4.1 Vacuum Applied to AMSI
5.2.4.2 Reproducibility
5.2.4.3 Skimmer Design
5.2.5^\MSI/MS Analysis 23D
5.2.5.1 Particle Beam Mass Spectrometer (PBMS) 23D
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Contents (Cont.)
5.2.5.2 Atmospheric Triple Quadrupole Mass Spectrometer (API) 25D
5.2.6 Surrogate Aerosols Analysis 26n
5.2.7 Chemical Composition Change Through Space 35D
5.2.8 Particle Size Distribution Selection for Analysis via Steering Gas 37D
5.3 Particulate Spatial Dispersion 38 D
5.3.1 Particle Size Distribution 40D
5.3.2 Aerosol Spray Cone Characterization 47D
5.3.3 Aerosol Transport in Rooms 59n
6.0 Technology Costs to Industry or Other Researchers 66n
6.1 AMSI 66D
6.2 Aerosol Spray Pattern Characterization 66D
7.0. Quality Assurance 70D
7.1 Project Description 70n
7.2 AMSI Development 70D
7.2.1 OCN Calibration 71D
7.2.2 MS Calibration 71 n
7.3 PIV Analyses 71D
7.3 Surrogate Aerosols 72 n
8.0 References 74n
9.0. Appendix 1- Industry Partners 77n
IV
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List of Tablesn
1 . Description of surrogate aerosols [[[ 10
2. Peak assignments for SWP and SWA analyzed by PBMS without the AMSI ..... 16D
3. Results of AMSI skimmer optimization [[[ 22 n
4. Peak assignments for API spectra of SLS ................................................. 27D
5. Peak assignments for APCI spectra of Butyl Cellosolve® ............................. 28D
6. Peak assignments for SWP and SWA analyzed by PBEI without the AMSI./... .30
7. Peak assignments for SWA analyzed by positive API with the AMSI .............. 30D
8. Peak assignments for silicone-ethanol adducts .......................................... 31 n
9.D Range of particle sizes of surrogate aerosols measured with Malvern particle
sizer [[[ 41
10.D PIV determined concentration distribution of surrogate aerosol particles at aD
distance from the spray nozzle [[[ 52 n
1 1 . n Aerosol particle concentration and size distribution in spray jets — PIV system n
costs [[[ 66 D
12. Aerosol particle velocity distribution in spray jets- PIV system costs ............ 67
13.H Aerosol particle concentration distribution in environmental chambers — PIV
system costs [[[ 68
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List of Figures
1. Detailed schematic of AMSI 12n
2. PBMSofAAl 15D
3. PBMSofSWA 16
4. PBMSofSWP 17
5.D Comparison of PBCI response of SWP with and without vacuum pump
connected to AMSI 18
6.D Reproducibility of mass spectral response with skimmer addedn
(AMSI Model B) 19D
7. Different types of skimmers 20D
8. Comparison of SWP response with nozzle angles of 60° and 160° 21 n
9. Optimum skimmer design schematic 23 D
10. Schematic of AMSI coupled to PBMS 24
11. Schematic of AMSI coupled to API 25
12. Interface coupling AMSI to heated nebulizer assembly 26
13. PBMS in Cl mode spectrum of SWA 29
14. API in positive mode spectrum of BC 29 D
15. API in positive mode spectrum of SLS 31
16. AMSI/PBMS in El modeofSNWI 32D
17. AMSI/PBMS in El spectrum of SNW2 32D
18. AMSI/PBMS in El mode spectrum of SNWP 33
19. Product A spectrum by AMSI/API in positive mode 34
20. Product B spectrum by AMSI/API in positive mode 34
21. SLS spectrum by AMSI/API in positive mode 35 D
22. n Detection of m/z 119 ion for SWA by AMSI/MS with increasing distance from
AMSI entrance nozzle 36
23. Depiction of signal intensity of m/z 119 with increasing SWA percentage 36
VI
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Figures (Cont.)
24. Depiction of particle size selection via increasing steering gas flow 37
25. n Distance in still air penetrated by particles with an initial velocity of 2 m/s and 10
m/s 38
26. Settling velocities for particles suspended in air 39
27. n Steady state velocities of particles affected by gravity and different air velocities
opposite to the direction of gravitational field (upward velocity is positive) 39
28. Schematic of Malvern Particle Sizer for droplet size measurement 41
29. n Particle size distribution measured with Malvern analyzer for surrogate air
aerosols 42
30. n Particle size distributions measured with Malvern analyzer for surrogate surface
non-wipe aerosols 42
31. Drop size distributions for SWA and SWP measured with Malvern system 43
32. Depiction of spray cone particle-size distribution measurement scheme 43
33. Particle size distribution forAAl at increasing distance from laser beam 45
34. Particle size distribution for SWA at increasing distance from the laser beam...46
35. Velocity decay of surrogate aerosol particles along the jet centerline 47
36. Sauter Mean Diameters correlated with distance from the spray 48
37. Particle size distribution related to can-fullness 49
38. PIV measurement system 50
39. Schematic of beam sweeping over aerosol particles 50
40. Particle size distribution small view field schematic 51
41. Particle size distribution large view field schematic 51
42. Contour plots of aerosol particle concentrations 53
43. n Surrogate aerosol particle concentration profiles along the radius of the spray
cone 54
44. Velocity measurement interrogation system hardware schematic 55
45. n Surrogate aerosol particle velocity distributions along the axis of the spray
nozzle 56
VII
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Figures (Cont.)
46. Test room for ventilation simulator 60D
47. PIV/environmental chamber system schematic 61
48. PI V/environmental chamber measurement system schematic 63 n
49. n Vector map of instantaneous room air velocities at an air change rate of
5ACH 63
50. n Contour plot of instantaneous particle concentration at an air change rate of 5D
ACH 64 D
51. n Normalized particle concentration in environmental chamber with a circular^
diffuser distributing the air 65n
viiin
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Acknowledgments
This work was supported by the U.S. Environmental Protection Agency's National Risk
Management Research Laboratory under Cooperative Agreement CR 822007. The authors are
grateful for the expertise, guidance, and efforts of the Industry Partners, chaired by Dr. Armin
Globes of SC Johnson Wax. We are especially grateful to the Industry Partners for designing,
preparing, and supplying the Surrogate Aerosols, test aerosols representative of the "World of
Consumer Aerosol Products," used for methodology and instrument development during this
research project. The Industry Partners are listed in Appendix 1.
IX
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1.0 Introduction
1.1 Background
The U.S. EPA has identified indoor air quality (IAQ) as one of the most important
environmental risks to the Nation's health (1 & 2). IAQ mitigation approaches generally have
focused on techniques such as ventilation and source elimination or removal. In the Pollution
Prevention Act of 1990 (3 & 4), Congress declared that pollution should be prevented or reduced
at the source whenever feasible. Modification of equipment, processes, and procedures;
reformulations or redesign of products; substitution of raw materials; and/or improvements in use
procedures may accomplish source reduction.
The U.S. chemical specialties industry is a $50 billion industry employing more than a
million people (5). The products provided by the chemical specialties industry include aerosol
consumer products for such uses as personal care, household cleaning, laundry, pest control,
and automotive maintenance. Aerosol consumer products are an important segment of this
industry. Since the development of the aerosol packaging system during World War II, aerosol
consumer product usage has advanced in the U.S. to nearly three billion aerosol products used
each year and more than 1500 individual aerosol products (5).
Aerosol consumer products potentially are amenable to pollution prevention strategies
that reformulate or redesign products, substitution of raw materials, and improvement in use
procedures. For example, the tools developed under this project may provide the manufacturers
with data showing that products can be reformulated, thereby reducing the required amount of
active ingredient. For example, if 50% more of the active ingredient is reaching the use site than
is needed for efficacy, the manufacturer may be able to reduce the amount of active ingredient in
the product accordingly.
A basic understanding of the behavior of aerosol consumer products can be used to
develop pollution prevention strategies, which may reduce occupant exposures and guide
manufacturers in the development of more efficacious products. This research project was
undertaken to develop tools and methodologies to measure aerosol chemical and particle
dispersion through space. EPA's National Risk Management Research Laboratory sponsored a
cooperative agreement with the Georgia Tech Research Institute (GTRI), and the University of
Illinois (Ul) to develop tools and methodologies to measure aerosol chemical composition and
particle dispersion through space. These tools can be used to devise pollution prevention
strategies that could reduce occupant chemical exposures and guide manufacturers in
formulating more efficacious products. The GTRI researchers built an Aerosol Mass Spectral
Interface (AMSI), which is interfaced with a mass spectrometer, that chemically characterizes
aerosol consumer products through space. The AMSI/MS is unique in that it measures the
spatial chemical composition of the aerosol stream, rather than the more conventional technique
of measuring the chemical composition of single aerosol particles. The Ul researchers developed
techniques for measuring aerosol indoors by tracking particle size changes via particle velocity
measurements using particle image velocimetry (PIV). This technique was used to develop a
model to predict the major characteristics of aerosol spray patterns. A group of Industry Partners
participated in this research project to ensure that the technologies developed would be useful to
industry.
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1.2 Traditional Aerosol Analysis
An aerosol (aerodispersed system) consists of a gas (dispersion medium) in which liquids
or solid substances may be dispersed (6). An aerosol is an unstable system, changing its
concentration and particle-size distribution with volume and time. Aerosols can also change their
state from solid to liquid and vice versa (6). The transient nature of an aerosol makes aerosol
characterization an analytical challenge.
In the aerosol package, a gas is put under enough pressure to liquefy the gas. When the
package nozzle system is activated, the pressure is relieved, and vaporization occurs. An
aerosol can is kept closed by a stem gasket, which seals the opening under the nozzle button.
This gasket is held in place by a spring inside a housing. When the nozzle button is pressed, it
pushes the valve stem down against the spring, relieving the pressure and keeping the gasket
sealed. When the seal opens, the higher pressure inside the can pushes the product through the
dip tube and out of the valve. A controlled amount of propellant in the product vaporizes as it
leaves the can, creating the aerosol spray. A small amount of the liquefied propellant still in the
container also vaporizes, maintaining the pressure constant. The combination of product and
propellant is finely tuned to produce the correct concentration, spray pattern, and particle size for
an effective product. The spray nozzle system is developed for each product. Similar products,
such as aerosol deodorizers with different scents, must each have the spray nozzle system
developed for each scent for effective delivery of the product to the use-site.
Aerosol analysis has traditionally focused on both particle size and distribution
measurement or the chemical analysis by collecting a time-weighted average sample of the
aerosol (7). The aerosol industry usually determines aerosol particle size via measurement of the
spray particle-size distribution via forward light scattering (8). A Malvern Particle Sizer is usually
the instrument used for this particle-sizing time-averaging analytical technique (8 & 9). The
Malvern system uses particle light scattering as its detection technique and has an accurate
particle-size range of 1.2 - 1000 urn. The light scattering angle is inversely proportional to the
particle size. This method provides no data about the chemical composition of the measured
aerosol.
Aerosol chemical composition by the indoor research community traditionally has focused
on collecting a time-weighted average sample of the aerosol on a filter, which is then extracted
and analyzed by a chromatographic, MS, or other analytical technique (7 & 10). The industry
primarily uses two different methods for determining the volatile content in aerosol formulation.
The first is a vacuum distillation method that is applicable to anhydrous aerosols that do not
contain methylene chloride or volatile active ingredients (11). This method evaporates away,
under vacuum, the propellant and other volatile components from an aliquot of the aerosol liquid,
which has been withdrawn from the aerosol package. The remaining nonvolatile residue is
weighed, and the total percent of nonvolatile components is calculated.
The second method, the Densimetric Method, is applicable for the determination of the
volatile content of essentially anhydrous aerosol products with nonflammable propellants, which
do not contain solids at low temperature (12). This method is based on the fact that, under
isothermal conditions, the density of an aerosol formulation is almost a linear function of the
volatile or nonvolatile content. This method is primarily used for production control procedures.
The aerosol consumer product sample is chilled to approximately -3O°C. The dispenser is
punctured, and the contents of the package are poured into a chilled hydrometer. The density is
recorded. The composition is calculated from the density by comparing the sample results with
those from a series of known standards via linear regression analysis.
The analysis of aerosol dispersion and fate in rooms traditionally has been conducted by
crude analytical techniques. Spray cone analysis, depiction of the three-dimensional analysis of
the liquid particles, has been done typically by using indicator paper as a target for a sprayer
actuated at a specified distance (13). When the spray hits the target indicator paper, a two-
2D
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dimensional image is formed, which indicates the relative cone pattern and density. It has been
recognized for some time that real-time, on-line analytical methods are necessary to accurately
understand the environmental and human exposure impacts of aerosol products, but to date
these methods do not exist.
The focus on real-time methodology development for aerosol products for environmental
impact assessment, to date, has been on outdoor aerosols. Several different analytical systems
for single particle aerosol analysis have been under investigation. The integration of MS and
laser desorption techniques, particularly time-of-flight (TOP) MS has received considerable
attention (14-18). This integrated system has been successfully used for the elemental analysis
of single aerosol particles. The system is capable of measuring the aerodynamic size and
chemical composition of the particles in situ. This type of system is used for outdoor aerosol
analysis since these aerosols are generally less complex and much more dilute than the aerosols
produced by consumer products.
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2.0 Conclusions
The tools and methodologies developed under this research project can be used to
better understand aerosol consumer product behavior. Once this understanding is achieved,
then effective pollution prevention strategies can be designed. Potential pollution prevention
strategies include product reformulation, raw materials substitution or more pure raw materials
use, and clearer instructions to end users. The tools developed under this project may provide
the manufacturers with data showing that products can be reformulated reducing the required
amount of active ingredient.
The primary objective of this research project was to develop tools and methodologies
to characterize aerosol consumer products in space, which could then be used to develop
pollution prevention strategies. In order for pollution prevention strategies to be devised, it is
necessary to understand the basic behavior of aerosol consumer products during use. This aim
was accomplished successfully by the design and construction of the AMSI for measuring aerosol
particle chemical compositional changes during dispersion through space and the PIV for
measuring dispersion of aerosol particles through space via velocity measurements.
2.1 Chemical Composition
The AMSI can be used by the industry, to determine the chemical composition of
aerosol particles through space. Knowing the chemical composition and the changes in the
chemical composition during particle dispersion through space may guide the industry to make
more efficacious products and devise pollution prevention strategies through product
reformulation.
The AMSI was designed, constructed, and optimized to transfer a focused aerosol
beam of particles into a mass spectrometer for chemical analysis. It was shown experimentally
that the AMSI could detect compositional changes through space, and that the AMSI was
transferring aerosol particles into the mass spectrometer. The data obtained in this project
indicate that the AMSI/MS has the potential for quantitative analysis, but further study is required
to confirm this.
An additional experiment was conducted to ascertain that the AMSI was transferring
aerosol particles in the MS. One function of the AMSI is to strip the propellant solvent from the
aerosol particles prior to transference of the particle into the MS. It was necessary to show that
aerosol particles remain after this stripping occurs. This was done using a Helium/Neon laser to
cause forward off-angle light scattering with photodiode array detection of scattered light. The
detection of light energy above baseline indicates the presence of particles while gases do not
scatter light. Increased light intensity above baseline from particles exiting the AMSI nozzle while
spraying two of the surrogate aerosols (see section 5.1) into the AMSI indicated that aerosol
particles were exiting the AMSI and being transferred into the MS.
One important finding from the chemical compositional research was the importance of
the purity of the starting materials to make the aerosols. A contaminant was found in the sodium
lauryl sulfate (SLS) used to make the test aerosols. This contaminant was also detected in each
of the test aerosols containing SLS. This shows the importance of pure starting materials. This
type of data, which can be determined with the AMSI/MS, can help the industry to formulate the
most pure and least polluting products.
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2.2 Particulate Behavior
Particle size changes are an important aspect of aerosol consumer product behavior
and performance. Changes in particle size indicate aerosol agglomeration, resulting in increasing
particle size and slower velocities, or component evaporation, resulting in decreasing particle size
and increasing velocities. Aerosol agglomeration can prevent the transport of the particles to the
use site, reducing product efficacy since gravitation fall-out of particles is greater for larger sized
particles. The evaporation of components from the aerosol during travel to the use site can
prevent active components from reaching the use site and can result in increased pollutant
transference from the liquid medium to the airborne medium. An understanding of these ongoing
phenomena can provide pollution prevention strategies for product reformulation.
The PIV system was developed to measure particle size via velocity measurements
during aerosol dispersion through space. This camera system allows for the non-intrusive, whole
field measurement of aerosol particle dispersion through space. Particle velocities and the spatial
structure of the particle movements were measured. Additionally the effects of ventilation on the
transport of the particles were determined. This is an important parameter for source control via
ventilation pollution prevention strategies in the indoor environment.
A PIV system was used to determine the particulate characteristics of the spray cone of
aerosol consumer products. The PIV was used to measure particle concentrations and velocity
distributions. These techniques were used in an environmental chamber to investigate the effect
of localized air flow patterns on particle concentration distributions as the aerosols are
transported through space in the indoor environment.
The results from this research project showed that particle transport in room airflow is
influenced primarily by gravitation, convection, and eddy diffusion resulting from turbulent
velocities. These forces generate differences in particle concentration and particle size
distribution throughout a room. Particle movement depends on characteristics of the local airflow
conditions.
Important findings about the particulate behavior of aerosol consumer products were
that compressed gas propellants appeared to result in a wider distribution of particle sizes than
hydrocarbon propellants, and the velocity of the aerosol particles decreased with increasing
distance from the aerosol spray nozzle. More than 90% of the particles were found to be greater
than 25 |im in size. It was also found that room air ventilation did have an effect on aerosol
particle concentration distribution. The particle distribution was stratified so that the particles
were densest in the lower portion of the room and more dilute in the upper portions of the room.
A simplified engineering model was developed to predict the mass, momentum, and
energy flux over space of aerosol consumer products - critical factors for evaluation of aerosol
consumer product efficacy. The velocity of the aerosol particles in the hydrocarbon propellant
driven sprays appeared to be increasing near the spray nozzle. This may have been caused by
evaporation of the liquid propellants near the spray nozzle. The velocity peaked at a distance of
20 mm from the nozzle, and then decreased as the distance from the nozzle increased, probably
due to air drag. This mechanism appeared to control the atomization process near the spray
nozzle.
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3.0 Recommendations
The tools and methodologies developed under this research project can be used to
better understand aerosol consumer product behavior. Once this understanding is achieved,
effective pollution prevention strategies can be designed. The tools developed under this project
may provide the manufacturers with data showing that products can be reformulated reducing the
required amount of active ingredient. For example, if 50% more of the active ingredient is
reaching the use site than is needed for efficacy, the manufacturer can reduce the amount of
active ingredient in the product by 50%. This information can be obtained using the tools
developed during this research project.
The primary recommendation resulting from this project is that the manufacturers begin
using these tools to study their products. The products can be studied to determine the chemical
composition of the products when they reach the use site and determine the minimum amount of
active ingredients necessary for efficacy. The manufacturers can investigate the effects of
product dispersion, and the effects of room air movement on dispersion, to better guide
consumers on actual use conditions. An understanding of the dispersion chemically can aid in
reformulations that minimize cross-media transference during use.
3.1 Technology Costs
Since the AMSI is not commercially available and must be machined, the costs are
dependent upon the individual machine shop. In general, the cost of the AMSI should be below
$1000. The AMSI, in its current form, must be interfaced with a MS with PB or electrospray (or
ion spray) capabilities and preferably with MS/MS capabilities. These systems range from
$150,000 to $500,000, depending on the sophistication. Once the AMSI/MS is operating the
analytical costs will range from a few tens to a few hundreds of dollars per sample. Analysis
requires a few minutes of time per sample. Data interpretation requires the greatest amount of
time and is dependent upon the skill and knowledge of the operator. As a laboratory builds a
database of aerosol products, data interpretation can be cut down to a few minutes of time per
sample.
The final costs of the PIV system are dependent on the particular instrument
manufacturer and features of the component parts. Generally the cost of a system to measure
aerosol dispersion through space is about $75,000 to $90,000. The time requirements for
measurement of aerosol dispersion are considerable since the data interpretation is a labor-
intensive process. Characterization of the aerosol spray pattern requires approximately one hour
for data collection, approximately six hours to calculate concentrations, and approximately 12
hours to calculate the velocity distributions.
3.2 Technology Limitations
There are limitations to the tools developed under this project. The majority of these
limitations can be overcome with additional research.
The AMSI is only applicable to aerosols that exit the nozzle in a spray form, using
either propellant or pump spray systems. Aerosols that are ejected as foams or gels cannot be
introduced into the MS by the AMSI. Also, high viscosity aerosols that are released primarily as
dry particles, such as spray powders or paints, will quickly contaminate the AMSI and MS during
analysis. This limitation will be extremely difficult to overcome, and probably cannot be
6D
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eliminated with the current AMSI design. These types of products will require a different type of
sample introduction method.
Particle size selection with the AMSI is not currently calibrated. It was shown
experimentally that the numbers of smaller particle being transferred into the MS from the AMSI
are reduced, but it is not possible to give the range of particles that are being transferred into the
MS.
The developed PIV system allows for the determination of two-dimensional structures of
full-scale room air flows and particle concentration. Two cameras or holograms are required to
measure particle dispersion in three-dimensional space. The current system measures particle
velocities within 5% accuracy for particles greater than 100 |im in size. A newer and faster PIV
system would increase speed and simplify fate and transport measurements, thus allowing for
smaller particles to be measured with increased accuracy.
7D
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4.0 Technical Approach
Spatial dispersion of aerosols through space can be divided into two different
components: chemical compositional behavior and particulate dispersional behavior. The GTRI
researchers primarily focused on development of the chemical compositional behavior tools, and
the Ul researchers focused on the particulate dispersional behavior tools. The Industry Partners
provided invaluable guidance and assistance assuring that the approaches used by the university
researchers would result in useful methodologies and tools. Over a four-year period, ten
meetings were held with the Industry Partners to maintain interaction and guidance among the
researchers, U.S. EPA, and the Industry Partners. Additional discussions were held with
individual Industry Partners during the project via telephone, e-mail, and meetings. A final
meeting was held in December 1997, at the annual meeting of the Chemical Specialties
Manufacturers Association, to report on the results of the project to the industry. The Industry
Partners met once without the university researchers or the U.S. EPA project officer to develop a
scheme to allow the researchers to investigate the many types of aerosol products without having
to investigate hundreds of products. Also to maintain the objectivity of the project, the Industry
Partners wanted to avoid using actual products to develop the methodology since this could put a
few manufacturers at risk. The Industry Partners developed a scheme of surrogate aerosols to
represent the many types of aerosol consumer products without testing of actual products
(discussed in Section 5.1). These surrogate aerosols were formulated and provided to the
university researchers as needed by the Industry Partners upon request by the university
researchers. The Industry Partners also provided GTRI with four blinded aerosol consumer
products that were actual products to test their chemical characterization system on real
products.
Aerosol chemistry has the possibility to result in chemical compositional changes as the
aerosol disperses through space. These changes can be the result of chemical reactions,
chemical decomposition, particle agglomeration, and/or solvent evaporation. These changes will
be occurring dynamically as the aerosol travels through space. The GTRI researchers developed
the AMSI to be interfaced with a MS so that these changes could be measured (discussed in
Section 5.2). Two types of MS's were used. One with a particle beam (PB) liquid
chromatographic (LC) interface, and one with an atmospheric interface. It was necessary to
introduce the aerosol spray into the MS system as an aerosol; therefore, the MS design had to be
capable of handling this type of sample form. The AMSI was designed to transfer a focused
aerosol beam into the MS separating the propellant from the remainder of the aerosol droplets.
By using MS/MS techniques, it was possible to separate the complex mixture into its component
parts, in a manner similar to a chromatographic separation. The separation is performed by
MS/MS using multiple quadrupoles in series so that the ions passing through the quadrupole
mass filters the ions are separated.
The Ul researchers used PIV and modeling to develop particulate dispersional behavior
tools (discussed in Section 5.3). The PIV system was used to determine the three-dimensional,
constantly changing spray cone characteristics by measuring the particle concentrations and
velocity distributions. The characteristics of the spray cone as the liquid particles are ejected
from the spray nozzle are a major factor in the behavior of the aerosol as it is dispersed through
space. Localized airflow patterns also can affect the dispersion of the aerosol through space;
therefore, the PIV system, in conjunction with an environmental chamber, was used to investigate
the influence of localized airflow patterns on aerosol spatial dispersion. The PIV data were then
used to develop a model for predicting the major characteristics of aerosol spray patterns.
8D
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5.0 Methods, Results, and Discussion
A description of the Surrogate Aerosols is given in Section 5.1. The chemical
compositional methods and results are discussed in Section 5.2. The particle spatial dispersion
methods and results are covered in Section 5.3.
5.1 Surrogate Aerosols
The "World of Aerosols" is immense. In 1993, 340 new products were introduced (19).
A major task was the development of a classification scheme representative of most of the
industry, yet which would divide the industry into a manageable size for meaningful data. Also to
maintain the scientific integrity of the project and full cooperation of the Industry Partners, it was
important that the research focus on generic products rather than any specific manufacturers'
formulations. Since the purpose of the project was to develop generic tools and methods that
could be used by the industry as a whole to develop pollution prevention strategies, it was
important to focus on the end-use of products rather than specific formulations. Aerosol
consumer products are formulated and packaged so that their dispersion results in the products
properly reaching the use site in the appropriate physical form and chemical concentration. For
example, a hair spray is designed to disperse in very fine droplets with a wide spray cone. A
pesticide is designed with a minimally dispersed spray cone for a maximum amount of product
stream reaching the use site over a distance of several feet.
Based on this information, it was decided that to develop effective tools and methods on
aerosol dispersional behavior, the aerosol classification scheme should focus on product uses
since this would have the greatest influence on spatial dispersion. Furthermore, it was decided
that generic products could be used in this project, since there was no value added by using
specific products. A list of twelve surrogate aerosols was developed by the Industry Partners,
representing common formulations and uses: 1) surface wipe aerosols, 2) surface non-wipe
aerosols, 3) and air aerosols. The latter two further subdivided into the categories of liquefied
hydrocarbon propellant and compressed gas propellant aerosols, since the propellant system
could have an influence on aerosol spatial dispersion; and therefore, could be important in the
design of pollution prevention strategies. Also, the surface wipe and surface non-wipe surrogates
were tested both as pressurized and pump delivery systems. Pump delivery systems were
included since these also could influence aerosol spatial dispersion and could be important in
pollution prevention strategies. It is important to realize that pump delivery systems are not true
aerosol consumer products since the product is not a liquefied product under pressure (5). Table
1 outlines the surrogate formulation matrix. The seven surrogate aerosols were designed,
prepared, and supplied by the Industry Partners.
9D
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Table 1. Description of the surrogate aerosols.
Type
Surface Wipe Aerosol
(SWA)
Surface Wipe Pump
(SWP)
Surface Non-wipe 1
(SNW1)
Surface Non-wipe 2
(SNW2)
Surface Non-wipe
Pump (SNWP)
Air Aerosol 1 (AA1)
Air Aerosol 2 (AA2)
Water
QSa
QSa
0%
0%
0%
70%
90%
Volatile Solvent
Butyl Cellosolve®" 5%
Butyl Cellosolve®" 5%
Ethanol 67.5%
Ethanol 92.5%
Ethanol 92.5%
Ethanol 10%
Ethanol 10%
Nonvolatile
Solvent
SLS° 2%
SLS° 2%
Silicone 7.5%
Silicone 7.5%
Silicone 7.5%
0%
0%
Propellant
A31d10%
Trigger
A46d 25%
QSa-C02e
Fine mister
A46d 20%
QSa-C02e
QS = Quantity sufficient to bring to volume
Butyl Cellosolve® = BC
SLS = Sodium lauryl sulfate (a surfactant)
A31 and A46 = liquefied hydrocarbon propellant mixtures of propane and
isobutane
Compressed gas propellant
The surrogate aerosols were formulated to be representative of three common aerosol
product classifications. The surface wipe aerosols represent products such as household
cleaners, dusting aids, and disinfectants. The only difference between SWA and SWP is that
SWA is aerosolized via a hydrocarbon propellant, and SWA is aerosolized via a pump trigger
nozzle. There were three different surface non-wipe surrogate aerosols: 1) SNW1 using a
hydrocarbon propellant, 2) SNW2 using a compressed gas propellant, and 3) SNWP using a
pump mister nozzle. These three surrogate aerosols represent such products as personal care
products, pan no-stick sprays, paints, and adhesives. Two surrogate aerosols were
representative of aerosols such as air fresheners and insecticides: AA1 and AA2. The only
difference between AA1 and AA2 was the propellant. AA1 used a hydrocarbon propellant, and
AA2 used a compressed gas propellant.
Also important in the formulation of the aerosol consumer product systems and in the
design of the surrogate aerosols is the delivery of the aerosol to the site to its use site, the
chemical composition, and the chemical composition and form of the product at its use site. The
efficacy of the product is dependent on how and in what form it arrives at its use site. For
example, a hairspray must be delivered to the hair as a gentle, wide spray that cannot bounce
back off of the hair or it will not meet the user's needs. An insecticide must be delivered in a
hard, tight spray that will reach the pest with a maximum quantity of product. The surrogate
10D
-------
aerosols were designed to represent the three common aerosol product classifications so that the
importance of the aerosol delivery system as related to its intended use could be determined
during the transport in room studies. Pollution prevention strategies formulated must account for
the requirements of the end-use of the product.
5.2 Chemical Composition
The analytical strategy for aerosol chemical characterization was to design and construct
an aerosol inlet interface, which would allow introduction of aerosols into a MS for aerosol
chemical composition determination. The aerosol interface/MS system had to be able to
measure the transient and complex chemical nature of the aerosol stream in real-time.
Chromatographic separation of the components was not a feasible technique for separation of the
chemical components of the aerosol products, since real-time analysis could not be achieved by
chromatographic analysis. Therefore, MS/MS techniques were preferable. The MS/MS uses
quadrupole mass analyzers in series. Ion separations can be achieved by ion filtering with the
quadrupole mass analyzers.
The aerosol inlet interface developed had to provide quantitative data about the chemical
compositional changes related to the distance of the aerosol particles from the aerosol spray
nozzle (spatial chemical compositional changes) and chemical composition versus particle size
distribution of the aerosol spray. Additionally, it was found during the course of this project that
the aerosol inlet interface had to be able to cope with large sample quantities.
5.2.1 Aerosol Mass Spectral Interface
A PB approach (20 & 21) was used. The AMSI was designed, constructed, and
optimized to collect and sort the aerosol particles from the aerosol consumer product and transfer
a focused aerosol beam into a MS for compositional analysis (22). The AMSI is a portable inlet
system for aerosol chemical analysis by MS. The aerosol product is analyzed in real-time using
the MS to perform separations and chemical compositional analysis. Using a gas flow to steer
the particles away from a straight-line trajectory (steering gas), the AMSI can be operated so that
the aerosol particle-size distribution entering the MS can be controlled. The amount of smaller
particles transferring into the MS is decreased with increasing steering gas flow. When no
steering gas is applied, the entire distribution of particle sizes passes into the MS. When the
steering gas is applied, fewer of the smaller size particles enter the MS; only the larger sized
particles pass into the MS. By looking at the results obtained with no steering gas, and those with
increasing amounts of steering gas, it is possible to use pattern recognition subtraction
techniques to determine the chemical composition based on particle size (23-26). The
development of these techniques for this application and the calibration of the particle size
distribution as related to the amount of steering gas flow have not been done in this research
project due to funding limitations. These are additional research avenues for pursuit.
The AMSI is essentially the momentum separator portion of a PB interface (20) (Figure
1). The PB interface is designed to couple a LC to a MS so that the eluting analyte and mobile
11D
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Figure 1. Detailed schematic of AMSI.
,_, Spraying
aerosol products
10
1. Nozzle. 2. O-ring. 3, 4, 6, Spacer. 5. Pump-out unit, for connecting vacuum hose. 7. Skimmer.
8. Connector, connects the AMSI to the MS. 9. Connecting rod. 10. Screw. 11. Gas line. 12.
Swagelok® fitting.
phase mixture exiting the chromatograph can be converted to a form that can be analyzed by the
MS. In the PB interface, the eluding mixture is nebulized by mixing with an inert gas, vaporized,
and separated into the aerosol particles minus the mobile phase. Only the aerosol particles enter
the MS. The momentum separator is the chamber in which the aerosol particles are separated
from the mobile phase. The AMSI serves the function of the momentum separator separating the
aerosol particles from the propellants. The AMSI functions like a two-stage jet separator. The
separator is divided into two chambers, the first between the nozzle and the skimmer(s). The
primary role of the skimmers is to sample only those aerosols moving in a straight trajectory,
thereby focusing the aerosol beam. The aerosol consumer product package nebulizes the
aerosol as it is ejected by mixing the ingredients with the propellant as it leaves the aerosol
package; therefore, the nebulizer of the PB is unnecessary to the AMSI. Immediately after the
aerosol beam formation by the AMSI nozzle, a stream of gas perpendicular to the beam axis is
introduced to size-sort the particles based on their resistance to the steering gas flow. The AMSI
is interfaced directly with a MS so that the aerosols are analyzed without sample collection or
chromatographic separation. Two types of MS's were used; both designed for use with LC
systems. One of the MS's was a quadrupole MS with a LC/PB inlet system. The second MS was
a triple quadrupole system (MS/MS) designed with an atmospheric inlet system (API). The
PBMS was used because it is a commonly available MS in many laboratories. This system is
designed to handle a PB inlet system; therefore is readily adaptable to the AMSI. The API was
selected because of its atmospheric inlet system (27 & 28). The atmospheric inlet allows for
direct sampling of the aerosols from the AMSI. Early in the project, the aerosols were sprayed
directly into the API. This method was unsuccessful since the direct introduction of the aerosols
severely overloaded and contaminated the MS. The API is designed for ultratrace analysis and
was unable to handle the large sample load introduced by the aerosol spray. The API triple
quadrupole system allowed for sample separation to be done by the MS rather than the more
conventional chromatographic system (27 & 29).
12D
-------
An experiment was done to ascertain that the AMSI was transferring aerosol particles
into the MS even though it was known that PB technology passes "dry" aerosol particles into the
MS from previous work (20 & 30). This was done using a 2-mm watt helium/neon laser to cause
forward off-angle light scattering by the aerosol particles using photodiode array detection of
scattered light. The detection of light energy above baseline indicates the presence of particles
since gases do not scatter light. The laser was focused on the particles exiting the first sample
stage immediately after the AMSI nozzle. The laser was set five degrees off-axis in order to
detect forward-scattering light using a photodiode detector. Increased light intensity was detected
above baseline from particles exiting the AMSI nozzle while spraying both SWA and AA1 into the
AMSI, indicating that aerosol particles were exiting the AMSI and being transferred into the MS.
A number of issues and parameters had to be addressed during the development of the
AMSI: 1) generation of standard aerosols, 2) analysis of the total aerosol product without
propellant removal, 3) optimization of the AMSI design, 4) MS analysis of the surrogate aerosols
and selection of identification and quantitation ions, 5) confirmation of the ability to quantitatively
analyze aerosol chemical compositions through space, and 6) development of the particle
distribution sizing system for relating aerosol particle chemical composition to particle size
distribution. These six issues are discussed individually below,
5.2.2 Generation of Standard Aerosols
It was necessary to be able to generate aerosols of a standard size and composition.
The standardized aerosol generation system was required for evaluation of the chemical
characterization system under design, and for quantitation of detected chemical components. An
oscillating capillary nebulizer (OCN) (patent pending), which generates aerosols with size
distributions from 10 urn to < 0.1 urn, was used to generate standardized aerosols (30 & 31). The
OCN is a type of vibrating-orifice generator. Vibrating-orifice generators are designed to produce
highly monodisperse aerosols and are considered to be primary particle-size aerosol generators
(32). Standard aerosols, for this project, were generated using authentic standard mixtures
resulting in standards of known compositions and concentrations over a range of liquid flows (1
uL/min to 1 mL/min).
Standard aerosols were generated for analysis of the surrogate aerosols using both
authentic standards obtained from commercial chemical suppliers and bulk samples obtained
from the Industry Partners. The bulk samples obtained from the Industry Partners were the
compounds used to make the surrogate aerosols. Bulk samples were obtained as individual
compounds and as the liquid mixtures used to prepare the surrogate aerosols.
5.2.3 Total Aerosol Consumer Product Analysis
The AMSI is designed to separate the aerosol particles from the propellant so that the
non-propellant portions of the aerosol are enriched for MS detection. In many aerosol consumer
products, the propellant is used as the solvent system or a major component of the solvent
system. The high concentration of propellants in the aerosol products versus the active
ingredients was expected to mask the presence of the components of interest. The Industry
Partners did state that there were times when they wanted to be able to detect the propellants
also. Therefore, the early analyses of the surrogate aerosols were done without the AMSI.
Initially the surrogate aerosols were sprayed directly into the API atmospheric inlet.
However, the MS was too sensitive for this method of sample introduction, since the MS was
designed for ultratrace analysis. The API was severely overloaded and contaminated by this
13D
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method of analysis. The API is designed to be unable to detect hydrocarbons, but it was possible
to detect the hydrocarbon propellants with the API when the surrogate aerosols were sprayed
directly into the atmospheric inlet. This probably was due to the large amount of sample entering
the MS. When SWA was analyzed, only BC was detected. When AA1, AA2, SNW1, and SNW2
were analyzed, only the molecular ion for ethanol was detected. Only one or two sprays of the
surrogate aerosols could be sprayed into the API before the system was excessively
contaminated and had to be shutdown for maintenance. Both the ion spray and the heated
nebulizer modes were tried with the same results. Then it was decided that the API was
inappropriate for direct analysis of the aerosols without the AMSI.
The PBMS was then used for direct analysis of the surrogate aerosols. This method was
successfully used for direct analysis of the aerosols when the nebulizing portion of the PB was
removed so that the aerosols were sprayed directly into the expansion region of the interface
(31). The mass spectrometer used for this series of experiments was an Extrel Benchmark" MS
equipped with a ThermaBeam interface (the Extrel version of the PB). The source temperature
was set at 285°C. The system was operated in El mode scanning from 35 to 550 amu. The
surrogate aerosols were sprayed individually into the PBMS system with a continuous spray of
approximately 8-9 seconds.
Initially the surrogate aerosol cans were held near the instrument inlet and sprayed. The
width of the spray cone resulted in contamination of the outside of the MS. Over time the aerosol
liquid was running down the instrument contaminating the system. A Plexiglas " box was
designed to prevent the overspray from reaching the instrument. The spraying box was
constructed of 0.64 cm thick Plexiglas™ with the dimensions of 396 cm length x 457 cm width x
366 cm height and open on one side. The open side is where the aerosol can is held for
spraying. A hole the size of the MS inlet was drilled in the side opposite the open side. The
spraying box was regularly cleaned to prevent cross-contamination from the analyses. The
aerosol was held so that the spray was centered at the entrance hole from the box.
Large differences in response were found for the different types of surrogate aerosols
when using this type of MS analysis. AA1 and AA2 contained no non-volatile components and
gave the poorest signals. The aerosols containing silicone, SNW1, SNW2, and SNWP, gave the
strongest signals. This probably is due to the high transport efficiency of silicone, which is
probably the reason that silicone is used in the aerosol products. Unfortunately the silicone also
severely contaminated the MS ion source resulting in frequent shutdowns for cleaning and
maintenance. Aerosols that were more dispersive, such as the surface wipe aerosols, were less
concentrated when reaching the MS; while the more direct aerosols, such as the air aerosols,
were more concentrated when reaching the MS.
As can be seen in Figure 2, the MS of the air aerosols primarily showed the presence of
ethanol. The hydrocarbon propellants are the primary compounds shown in the spectra of SWA
(Figure 3) and SWP (Figure 4). It is possible, with careful MS interpretation, to determine the
presence of the non-propellant components from these spectra (Table 2), but analysis of the non-
propellant compounds is simpler when the AMSI interface is used.
14D
-------
Figure 2. PBMS of AA1. M/z 45 is the molecular ion of ethanol.
6849-1
I' 7«1
1
ffl/Z
15D
-------
Figure 3.DPBMS of SWA. M/z 43, 57, and 83 are major hydrocarbon ions. M/z 207, 221, 281 ,D
295, and 355 are several ion/molecule reaction adducts with silicone in the aerosoln
spray (to be discussed later in the report). M/z 168 is the SLS ion.D
J405-
S
K
o-
4
I
3
J7
ill
¥ »;
1
T T T
il^l.!?..^.. * ., 1 I. ... i: t i» .
iAo a4o 3&>
mji
Table 2. Peak assignments for SWP and SWA analyzed by PBMS without the AMSI
Surrogate Aerosol
SWP & SWA
SWP & SWA
SWP & SWA
SWP & SWA
SWP & SWA
SWP & SWA
SWP & SWA
SWP & SWA
SWP & SWA
SWP & SWA
SWP & SWA
SWA
SWA
SWP & SWA
SWA
SWA
SWA
SWA
SWA
m/z
43
45
57
69
41
83
85
87
97
100
111
140
147
168
207
221
281
295
355
Fragment Assignment
C,H;
HOCH,CH;
C,H;
HOCH,CH,O
C,H;
CSH,;
cflH,;
CH,OC,H;
CH,CJHnCH=CH+
BC-H,O
CBH1S*
C1nH,n
[(BC -H,0) • (BC-OC,HQ)]+
C15H,4
[(BC + OH) + C,HJ
[(BC + OH) + CflHJ
[(BC + H,0) + C0H,n]
[(BC + H,0) + C,nH J
[(BC + H,0) + C,,H,J
Originating Compound
Hydrocarbon propellant
BC
Hydrocarbon propellant
BC
BC and/or SLS
Hydrocarbon propellant
SLS
BC
SLS
BC
SLS
SLS
BC
SLS
SLS & BC
SLS & BC
SLS & BC
SLS & BC
SLS impurity & BC
16D
-------
Figure 4. PBMS of SWP. M/z 43, 57, and 83 are primary hydrocarbon ions. M/z 168 is SLS ion.
7«03-
ifall
l! .....
k
L. . fl
ito
5.2.4 Optimization of AMSI
The optimization of the AMSI looked at several different parameters: 1) vacuum
pumping of the AMSI, 2) reproducibility, and 3) bore size and shape of the skimmers.
5.2.4.1
Vacuum Application to AMSI
The need for a vacuum on the AMSI was investigated by examining the sensitivity of
the system with and without the vacuum pump operating using SWP. The pump sprays
presented the greater challenge to the AMSI since these did not have the aerosol propellant to
add force to the particles moving them into and through the AMSI. The analytical sensitivity was
much greater (approximately 64%) when a small vacuum was applied after the nozzle of the
AMSI, as can be seen in Figure 5. The amount of vacuum was only a few torr and was optimized
for maximum signal height. The vacuum had to be small enough to prevent interference with the
MS vacuum.
17D
-------
Figure 5. Comparison of PBCI response of SWP with and without vacuum pump connected to
AMSI.
TIC of V7:RSI.D
70000-
60000-
50000-
3 40000-
tr
30000-
20000-
Pump on
uji thout
pump ing
^J^^1**^^
u/ith
pump ing
678
T 1 me C m 1 n . )
10 11
5.2.4.2
Reproducibility
In order for the AMSI/MS to be useful for quantitative analyses, the response must be
reproducible. Reproducibility was tested by repeatedly spraying a surrogate aerosol into the
AMSI/MS and examining repeatability of signal. Using the Model A AMSI, which uses no
skimmers after the nozzle, the reproducibility was poor, particularly with the pump-triggered
sprays. When a skimmer was added after the nozzle (Figure 1) (AMSI Model B), a reproducibility
of five percent of the standard deviation from the mean was achieved (Figure 6). As can be seen
in Figure 6, repeated spraying of SWP gave reproducible signal intensities. The primary variance
is the operator pressing on the aerosol actuator. The reproducibility is dependent on the ability to
repeatedly spray the aerosol in a reproducible manner. Variations in the duration of time the
actuator is pressed and the amount of pressure applied to the actuator change the amount of
sample ejected form the aerosol container into the AMSI; and therefore, the changes in signal
intensity. Automatic spraying systems are available for laboratory use, but these were not used
in this project, since the variations in actuating the aerosol actuator has a significant influence on
the impact of the aerosol consumer product on the environment. Understanding this impact and
differences that occur during actuator activation can provide important data for product use
instructions for pollution prevention strategies.
18D
-------
Figure 6. Reproducibility of mass spectral response with skimmer added (AMSI Model B).
Abundance
1400000
1200000
1000000
800000
600000
400000
200000
0
Time->
T!C:Z01PB4C.D
i
^™_____
L
v— _
\
0.80 1.00 1.20 1.40 1.60 1.80 2.00 2.20 2.40 2.60 2.80 3.00 3.20 3.40 3.60 3.80 4.00 4.20 4.40 4.60 4^80
5.2.4.3
Skimmer Design
The primary role of the skimmer in the AMSI is to sample the aerosol particles moving
in a straight trajectory, and to exclude the particles deviating from the straight line between the
nozzle and the skimmer. This is critical for particle-size distribution selection by the steering gas,
since the steering gas will force the smaller particles, those less able to withstand the force of the
gas flow, away from the straight-line trajectory. The size of the entrance hole in the skimmer will
affect the ability of the skimmer to operate properly. Too large of a bore size will allow the
skimmer to sample particles not moving in a straight trajectory. Too small of a hole will reduce
the analytical sensitivity due to signal loss. The shape of the skimmer can also affect its ability to
function correctly. Four skimmer shapes were tested with varying bore hole sizes. The four
skimmer shapes tested are shown in Figure 7, and a detailed list of the skimmers tested is given
in Table 3. The different skimmer shapes were chosen to look at extremes.
Types A and B are convergent skimmers with 60° and 160° angles, respectively. Types
C are concave skimmers with a 145° angle. The height of the cylindrical portion of Type C is 2.54
cm. Type D skimmers were comprised of a, b, and c three pieces with threads. When a, b, and c
are screwed together, the Type D skimmers are concave skimmers similar to the Type C
skimmers with an angle of 145°. When b is removed, convergent skimmers result, which are
similar to Types A and B.
19D
-------
Figure 7.DDifferent types of skimmers. A: 60° angle. B: 160° angle. C-D: 145° angle. In group
D: a, b, and c are joined together to form concave skimmers as in C. Alternatively, a
and c are joined to form skimmers A and B.
(C) SKD, SKE
(AJSK1-SK5
(BJSKI, SKII, SKIII
(D) SKA, 8KB, SKC, SKF
As can be seen in Table 3, the Type A, SK4 skimmer with a 0.076-cm bore size
produced the optimum results. The trend of responses was Type 1 (convergent) > Type B, C, D
(cone only, the convergent configuration) > Type D (concave configuration). The 60° angle
produced better results than the 145° or the 160°. For the Type D skimmers, the responses of the
convergent configurations for SKA, SKC, and SKF were one order of magnitude higher than the
concave configurations. For the SKB Type D skimmer, the response of the convergent and the
concave configurations were approximately the same and the standard deviations were high.
This probably is the result of the turbulence created by this skimmer reducing the amount of
sample passing through the skimmer. The conic shape of the convergent skimmer minimizes the
turbulence resulting in a higher sample efficiency and greater instrumental response. The effect
of the angle can be seen in Figure 8, which compares a 60° nozzle angle with a 160° nozzle
angle. As can be seen in this figure, a good response is obtained with the 60° nozzle angle.
Bore size results were less conclusive. The differences in bore sizes appeared to be
more of a difference in the machine shop's ability to make the skimmer than the actual bore sizes.
Smoothness of the hole appeared to have the greatest effect on the response. Comparing SK4
with SK5, the bore size of SK4 is 40% that of SK5. SK4 had a signal response that was 2.5 times
larger than SK5 with a standard deviation of only 8.91%, while the standard deviation of SK5 was
68.66%. Similar results were found for SKI and SKII. The bore size of SKI was almost two times
greater than that of SKII, but the signal intensities were similar. SKII and SKIII were identical in
bore size and shape, but SKIII was not as smooth as SKII. SKII gave more reproducible results.
SKD and SKC also were identical in bore size and shape, but SKD gave more reproducible and
sensitive results, since SKD was much smoother than SKC. The smoother surface results in less
20D
-------
Figure 8. Comparison of SWP response with nozzle angles of 60° and 160°.
TIC of V7:RS4.D
60 Nozzle
1.0 2.0
3.0
4.0 5.0
T t me ( m 1 n . )
6.0
7.0
8.0 9.0
turbulence to the aerosol beam as it passes through the skimmer. Reducing turbulence appears
to increase sensitivity and reproducibility.
The SK4 skimmer, with the 60° angle and 0.076 cm bore size, was chosen as the
optimum skimmer. It was the one used in all subsequent analyses. A schematic of this skimmer
is shown in Figure 9.
21 D
-------
Table 3. Results of AMSI skimmer optimization
Nozzle
Type A
Type B
TypeC
Type D
Skimmer ID
SK1
SK2
SK3
SK4
SK5
SKI
SKII
SKIM
SKD, concave
SKE, concave
SKA, cone only
SKB, cone only
SKC, cone only
SKF, cone only
SKA, concave
SKB, concave
SKC, concave
SKF, concave
Outer Angle
(degrees)
60
60
60
60
60
159
160
160
145
145
144
145
145
145
144
145
145
145
Bore Size (cm)
0.060
0.061
0.064
0.076
0.190
0.096
0.051
0.051
0.034
0.032
0.127
0.094
0.033
<0.028
0.127
0.094
0.033
<0.028
Material9
Al
Al
Al
Al
Al
Al
Al
Al
SS
SS
Al
Al
Al
Al
Al
Al
Al
Al
Distance
(mm)b
10
10
-
10
10
22
22
22
15
15
11
11
11
11
15
15
15
15
Normalized
Response0
3.36 x 106
5.86 x 106
-
11.87x 106
4.78 x 106
2.80 x 106
2.35 x 106
2.93 x 106
3.41 x 106
0.51 x 106
8.01 x 106
3.89 x 106
1.25x 106
2.55 x 106
0.84 x 106
3.91 x 106
0.46 x 106
0.09 x 106
% Relative
Standard
Deviation
17.57
23.06
-
8.91
68.66
16.07
15.41
40.91
8.38
12.57
11.06
27.54
17.61
32.24
8.22
35.52
9.98
33.28
n
Al = aluminum; SS = stainless steel; b Measured between the nozzle tips and SK3; ° Average of five replicates and normalized.
-------
Figure 9. Optimum skimmer design schematic.
5.2.5 AMSI/MS Analysis
AMSI/MS analysis was done by PBMS and with API. The API had MS/MS capabilities
that allowed for more extensive MS interpretation. The MS/MS capabilities were not as important
for analysis of the surrogate aerosols as they were for the analysis of actual aerosol consumer
products. The components of the surrogate aerosols were known. It is likely that the
components of real products may not be known.
5.2.5.1
Particle Beam Mass Spectrometer (PBMS)
A HP 5989B LC/MS equipped with a HP 59980A PB interface was used in both the
electron impact (El) and chemical ionization (Cl) modes with the AMSI. The source and
quadrupole temperatures were set at 260°C and 100°C, respectively, and the PB desolvation
chamber temperature was set at 55°C. When the system was operated in the Cl mode, the
source pressure was maintained at 2.2 X 10"4 torr in the positive Cl mode and 1.5 X 10"4 torr in
the negative Cl mode. Isobutane was used as the ionization gas. The system was initially
calibrated according to manufacturer's instructions, and then optimized for the aerosol products
by tuning to SLS and BC via flow injections with the oscillating nebulizer.
23D
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The AMSI was coupled with the PB interface (Figure 10) through 0.5 mm o.d. Teflon®
tubing. The two-second spray of the aerosol was drawn into the PB desolvation chamber by a
vacuum pump drawing from behind the nozzle of the AMSI. The spraying box was used to direct
the aerosol into the AMSI. A 0.5 mm o.d. glass tube was used to connect the spraying box to the
AMSI. Helium was used as the steering gas for particle size selection since helium does not
interfere with MS operation.
Figure 10. Schematic of AMSI coupled to PBMS.
AMSI
Model A
HP59980A
PB Interface
Glass Tube
4" Long Nozzle
Teflon
Tube
Momentum
Separator
Pump
Desolvation
Chamber
V >
PB Interface
Pumps
N2 Met
Tests were run to examine the potential that the transfer tube, between the spraying box
and AMSI, was not affecting the aerosol sample. The particles moving forward had enough
forward momentum to be unaffected by the transfer tube. This was due probably to a
combination of the vacuum of the MS drawing the particles forward and the force with which the
particles are ejected from the aerosol package.
24 D
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5.2.5.2
Atmospheric Triple Quadrupole Mass Spectrometer (API)
A Sciex API lllplus triple quadrupole MS (API) equipped with a heated nebulizer was
used. Each of the quadrupoles was individually calibrated using a mixture of polypropylene
glycols. Then the MS was optimized for the aerosol products by tuning to SLS and BC via flow
injections with the OCN. The interface temperature was set to 55°C, and the heated nebulizer
was set at 500°C. The current gas was nitrogen, and the flow rate was 1.2 L/min. The nebulizer
gas flow rate was 0.5 L/min, and the auxiliary gas flow rate was 1.2 L/min. The API source
pressure was maintained at 400 to 500 torr with the AMSI operating.
The AMSI was coupled with the API (Figure 11) via a glass tube into the heated
nebulizer. The schematic of the API coupling assembly is shown in Figure 12. The sprayed
aerosol droplets were drawn into the AMSI with a vacuum pump into a heated glass tube (170°C).
Upon exiting the glass tube, the sample was a mixture of dry particles and solvent vapors. The
solvent vapors were pumped away, and the dry particles moved forward into the atmospheric
entrance portion of the MS due to the high momentum of the particles. The dry particles were
ionized by corona discharge. The generated ions entered the high vacuum portion of the MS for
mass spectrometric detection. Nitrogen was used as the steering gas for particle size selection.
It was necessary to use a more complicated coupling with the API than with the PBMS, since the
API entrance is at atmospheric pressure, so that there was no MS vacuum drawing sample
through the AMSI into the MS.
Figure 11. Schematic of AMSI coupled to API.
AMSI
Model A
Desolvation
Tube
API Interface
Glass Tube
4" Long Nozzle
Teflon Heating
,_Txibe Tape
t
Mass
Spectrometer
Orifice
Pump
25D
-------
Figure 12. Interface coupling AMSI to heated nebulizer assembly.
0.200
120.000
Adaptor for API Interface
Material: SS
Dimensions: in inches.
Date: September, 96
Daughter scans and parents scans were run to identify originating peaks for fragment
ions. The ions m/z 119 and 169 were characteristic ions for BC and SLS, respectively. Two-
second sprays were used to introduce the aerosol product into the AMSI.
5.2.6 Surrogate Aerosols Analysis
AMSI/MS analysis was performed on the surrogate aerosols and on blinded samples
supplied by the Industry Partners. No information - such as type of product, formulation,
ingredients, etc. - was provided with the blinded samples. These two samples only provided
some actual samples against which to test the viability of the AMSI/MS to analyze real products.
The surrogate aerosols and two blinded aerosol products were analyzed using the
AMSI interfaced with both the PBMS and the API. Both MS's were operated in the positive and
negative ionization modes. Additionally, the PBMS was operated in both the El and Cl modes.
The API is a very soft ionization technique resulting in Cl-type spectra. The API was operated in
the MS/MS mode.
SLS and BC bulk samples, obtained from the Industry Partners, and authentic
standards, both individually and mixed, were analyzed using the OCN to generate the aerosol.
The standards were first analyzed to determine the identification and quantitation ions for the
surrogate aerosol components. The SLS bulk sample (Table 4) contained impurities that were
detectable and which participated in ion/molecule reactions of the aerosol products. These
26 D
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impurities were detected in the surrogate aerosols containing SLS. The characteristic SLS ion
was m/z 169, which is the lauryl fragment that results from the loss of the sulfate fragment. The
peak at m/z 197 is most likely the fragment C14H29+, a fragment of the impurity. The identity of the
impurity may be sodium myristyl sulfate. This impurity is present in only a trace amount in the
standard obtained from the chemical supply house. The 169 ion was used for detection and
quantitation of SLS in the surrogate aerosols. SLS, when analyzed by negative ion API, resulted
in a more complicated mass spectrum than that obtained from positive ion API (Table 4).
Table 4. Peak assignments for API spectra of SLS (SLS, C12H25NaSO4, MW=288). M represents
the SLS molecule.
Ion
Polarity
Positive
Negative
m/z
169
197
80
82
97
99
119
177
199
217
265
293
297
321
385
413
487
553
581
Assignments
C12H25+
^14^29+
so;
(H2S04+H-OH)-
HSO;
(H2S04+H)-
(NaS04)~
(SO3 • HSCg-
(S03 • NaSO,)-
[2(HSO4) • Na]'
C12H25S04=(M-Na)-
c14H29so;
[S03 • 2(HS04) • Na]-
c16H33so;
(M • HSO4)-
[(C14H29NaS04) • HSOJ-
[M • (SO3 • NaSCgr
(2M-Na)+
[(C12H25S04) • (C14H29S04) • Na]-
Daughter
Ions
82
97
119
97
97
97
97,217
97
97,265
97, 293
199,265,
407
265
265, 293
Parents Ions
97,98
177,185,217,228,
239,265,293,319,405
Only the negative molecular ion (m/z 118) and the loss of one water fragment (m/z 136)
were detected for BC by negative ion API. The fragmentation pattern was more complex when
BC was analyzed by positive API (Table 5). The ion m/z 119 was chosen to identify and quantify
BC in the surrogate aerosols.
27D
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Table 5. Peak assignments for APCI spectra of Butyl Cellosolve® (BC, HO-CH2CH2-OC4H9,
MW=118). M represents the Butyl Cellosolve® molecule.
Ion
Polarity
Positive
Negative
m/z
45
57
63
89
101
119
145
163
219
237
238
281
337
118
136
Assignments
(HO-CH2CH2)+
C4H9+
[(HO-CH2CH2-OH)+H]+
HO-CH2CH2-OC4H9
(M-H20+H)+
(M+H)+
(2M-H20-OC4H9)+
M • (HO-CH2CH2-OH) • H+
(2M-H2O+H)+
(2M+H)+
(2M+2H) +
M • (M-H20) • (HO-CH2CH2-OH) • H+
(3M-H2O+H)+
M-
(M+H20)-
Daughter Ions
43,57
45,57
45,57, 105
45,47,89, 101
45, 57, 63
45, 57, 63
45,57,89, 101, 107
45,57,89, 101, 107, 145,
163,219
72
Parents Ions
237
219,253,281,337
176,219,237,281,
337
The choice of m/z 119 and m/z 169 for BC and SLS detection and quantitation can be
seen in the PBMS in Cl mode analysis of SWA. The spectrum is shown in Figures 13-15. In
Figure 13, the 119 and 169 peaks are easily detectable; therefore, ongoing ion molecule
reactions are not a problem for aerosol compositional analysis. Figure 14 shows the spectrum of
BC by API in the positive mode. Figure 15 shows the spectrum of SLS by API in the posit mode.
Both of the spectra show that analysis by the selected ions is valid.
Although it appears that the ion/molecule reactions are not a major problem for aerosol
chemical compositional analysis, it was important to determine if the source of ion/molecule
reactions was the AMSI/MS analysis system or the aerosolization process itself. The two surface
wipe surrogate aerosols were chosen to investigate this phenomena since they contained the
surfactant SLS, and one of the surrogate aerosols was activated with a pump spray rather than a
propellant system. The direct analysis without the AMSI of SWA indicated that the propellant-
activated release of the product resulted in ongoing ion/molecule reactions, which did not occur in
SWP. As can be seen in Table 6, all of the detected SWP peaks are fragments of SLS and BC.
There were no reaction adducts of SLS and BC detected. The mass spectrum of SWA contains
the same SLS and BC fragments (Table 5). The AMSI/PBMS in Cl mode analysis resulted in
similar data. The Cl analysis of SWP resulted in only the detection of m/z 119 (BC + hT), 169
(SLS - NaSO4), and 197 (a fragment of an impurity in the SLS solution). The Cl analysis of the
SWA yielded the presence of ion/molecule reactions of SLS and BC, as well as fragments from
BC and SLS (Table7). The ion/molecule reactions were not a result of aerosolization of a mixture
of BC and SLS. A mixture of BC and SLS were analyzed using the OCN to aerosolize the
mixture. No SLS-BC ion/molecule reaction adducts were detected. PBMS analysis is not known
to result in ion/molecule reactions. Ion/molecule reactions do occur with API due to the ionization
method by corona discharge. Since these ion/molecule reactions are occurring with PBMS
spectra with propellant systems only, and not with pump sprays or the OCN, it is presumed that
28D
-------
these are occurring during the aerosolization process as the product is ejected from the package.
In spite of this, as can be seen in Figure 13, it is possible to conduct the chemical compositional
analysis of SWA by scanning the ions 119 and 169 for identification and quantitation.
Figure 13. PBMS in Cl mode spectrum of SWA.
1 . 0E + 5-
B . 0E + 4-
4 . 0E + 4-
2 . BE-t-4-
7 1 85
101 113
170 1S0 190
t
70 60 90 100 110 120 130 140 150 1S0 170 180 190 200
Mass/Ch arge
Figure 14. API in positive mode spectrum of BC.
3,413,530
100
119
237
350
400
29D
-------
Table 6. Peak assignments for SWP and SWA analyzed by PBEI without the AMSI.
Surrogate Aerosol
SWP & SWA
SWP & SWA
SWP & SWA
SWP & SWA
SWP & SWA
SWP & SWA
SWP & SWA
SWP & SWA
SWP & SWA
SWA
SWA
SWP & SWA
SWA
SWA
SWA
SWA
SWA
M/z
41
45
57
69
85
87
97
100
111
140
147
168
207
221
281
295
355
Fragment Assignment
C,H;
HOCH,CH;
C,H;
HOCH,CH,O
CSH1:,
CH,OC,H;
CH,CJH«CH=CH+
BC=H,0
CBH1S*
CinH,n+
[(BC-H,0) • (BC-OC,Hq)]+
C15H,4
[(BC + OH) + C,HJ
[(BC + OH) + CRH J
[(BC + OH) + C0H J
[(BC + OH) + C,nH J
[(BC + OH) + C,,H J
Originating Compound
BC &/or SLS
BC
BC &/or SLS
BC
SLS
BC
SLS
BC
SLS
SLS
BC
SLS
SLS & BC
SLS & BC
SLS & BC
SLS & BC
SLS impurity & BC
Table 7. Peak assignments for SWA analyzed by positive API with the AMSI
m/z
119
136
150
152
169
180
237
254
269
279
286
297
391
Fragment Assignment
BC + H+
BC + H,0
BC + CH,OH
BC + 2OH
C.H,;
[(BC + H+) • HOCH,CH,OH]
2BC + H+
[(BC-OH) + C^HJ
[(BC-H,0) + C19H,J
[(C,.H J • CH,CH,OH+ 2H,0
(C19H,;) + BC
[(BC-H,0) + (C«H J]
[(BC + H,0) + CMHM + C.HJ
Originating Compound
BC
BC
BC
BC
SLS
BC
BC
SLS & BC
SLS & BC
SLS impurity & BC
SLS & BC
SLS impurity & BC
SLS, SLS impurity & BC
son
-------
Figure 15. API in positive mode spectrum of SLS.
2,908,293
Dl
ISV
IN
OR
RO
M1
RE1
DM1
R1
L7
R2
M3
RES
DM3
RX
R3
L9
FP
MU
cc
CG
Dl|iA
CGT
ISv
UV
3
8000
650
35
30
1000
125.8
0.050
28.2
0
10
1000
120.8
0.060
0
-30
-250
-250
-4200
10
o«
2.9
4.0
8163.2
175.9
100-1
300
350
400
The silicon present in the surrogate surface non-wipe aerosols also resulted in
ion/molecule reactions, this time between ethanol and silicone. The primary difference between
the mass spectra of each of the analysis modes was in the abundance of the ions rather than in
fragmentation patterns (Figures 16-18). There were no differences, other than ion abundance,
between the El and Cl spectra. The soft ionization mode of the Cl analysis did not reduce the
formation of the ion/molecule reactants. This indicates that these reactions are occurring during
the aerosolization process as the product is propelled from the aerosol package system. The
silicone-ethanol adducts are given in Table 8. The only peak detected that was not a silicone-
ethanol adduct was the molecular ion for ethanol.
Table 8. Peak assignments for silicone-ethanol adducts.
m/z
45
73
117
133
147
207
221
267
281
295
Possible Structure
CH,Si+(H,)
(CH,),Si+
CH,Si (H,)O(CH,),OCH=CH,
(CH,),SiH-0+=Si(CHO,
(CH,),Si-0+=Si(CHO,
(CHO,SiH (CHO-OSi (CHO,-0+=Si (CH,),
(CHO, Si (CHO-OSi (CHO,-0+=Si (CH,),
CH,Si(H,)[OSi(CH,)J,-0+=Si(CH,)9
(CH,),SiH[OSi(CH,),],-0+=Si(CH,),
(CH,),Si[OSi(CH,),],-0+=Si(CH,),
m/z
327
341
355
369
401
415
429
443
517
591
Possible Structure
H,Si[OSi(CH,),],-0+=Si(CH,),
CH,SiH9[OSi(CH,)J,-0+=Si(CH,)9
(CH,),SiH[OSi(CH,)J,-0+=Si(CH,),
(CHO,Si[OSi(CH,),K-0+=Si(CH,)9
H,Si[OSi(CHO,L-0+=Si(CHO,
CH,SiH,[OSi(CHOJ4-0+=Si(CHO,
(CHO,SiH[OSi(CH,),L-0+=Si(CH,),
(CH,),Si[OSi(CH,),L-0+=Si(CH,)9
(CH,),Si[OSi(CH,),L-0+=Si(CH,),
(CH,),Si[OSi(CH,)JR-0+=Si(CH,),
31 D
-------
Figure 16. AMSI/PBMS in El mode of SNW1.
156689-
fr
s
0-
2
" 1.
* .17 'f ,
7
1
191
. L.I
,
293
28
T
T
f T
L . 1 , !,r . k . T T
ld» 2to 3/a 4*0
m/z
Figure 17. AMSI/PBMS in El mode spectrum of SNW2.
I74I33-
'i
it
0-
i
r
i
1
.....
ita
7
2
i..,.
aio
2:
i
1
[\ T,
2
369
rT
T
JF L L L T -L' T
aAo do
tn/z
32 D
-------
Figure 18. AMSI/PBMS in El mode spectrum of SNWP.
H68O-
1
4
\
f
T.
i
L
. . .'I' 'f ,
7
1 . . '?.'
7
1
2
I T'
T 1 ^1,1 H1 <|5 T
ito ado ado
-------
Figure 19. Product A spectrum by AMSI/API in positive mode.
3,570,667
400
Figure 20. Product B spectrum by AMSI/API in positive mode.
10Ch
279
75
50-
1
cc
205
132
403
305
J . ,k
375
431
100 200
300 400 500
m/z
1,681,667
600 700 800
34 D
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introduced unknowingly to the environment. The impurity is probably sodium myristyl sulfate (m/z
197).
Figure 21.DSLS spectrum by AMSI/API in positive mode. M/z 197 is an impurity peak, which is
probably sodium myristyl sulfate.
Abundance
1200
1100
1000
900
SOO
700
600
500
400
300-
200
100
0
6
r-n-f
1
7
J|
1(i9
85
hUfi
£
I ,'.; I'J
y
L.lL
1
13
1
27
197
185
177
... -.J
213
-,-»;
2
239
265
......
60 70 80 90 100 110 120 130 140 150 160 170 180 190 200 210 220 230 240 250 260 270 280 290 300;
5.2.7 Chemical Composition Change Through Space
In order to meet the needs of the manufacturers in developing pollution prevention
strategies, it was necessary to show experimentally that the AMSI/MS could be used to track
chemical compositional changes through space. The results of this experiment are shown in
Figure 22. In Figure 22, the m/z 119, the primary identification and quantitation ion for BC, can
be detected in SWA with increasing distance of the spray actuator from the ASI inlet. The aerosol
can was moved from 14.6 cm to 42.6 cm with SWA being sprayed into the AMSI at various points
within this range. The BC in SWA was detectable at all points within this range. As the aerosol
dispenser is moved farther from the AMSI entrance nozzle, the spray pattern expands and less of
the sample reaches the AMSI entrance nozzle; therefore, the signal intensity decreases.
It was necessary also to show experimentally the potential of the AMSI/MS to quantitate
the components of an aerosol consumer product. Figure 23 shows these results. During these
experiments, the OCN was used to generate SWA mixtures in methanol. A constant particle size
aerosol was generated by the OCN so that only the concentration of SWA was changing in this
series of experiments. As detector saturation is reached, above 80% SWA, quantitative accuracy
35 D
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decreases. Additional studies are needed to determine the accuracy of measurement and
optimum operating conditions for quantitation.
Figure 22. Detection of m/z 119 ion for SWA by AMSI/MS with increasing distance from AMSI
entrance nozzle.
Ion m/z 119, Increasing distance
40
30
2 20
c 5
10
10
20
30
distance (cm)
40
50
Figure 23. Depiction of signal intensity of m/z 119 with increasing SWA percentage.
Ion 119, Increasing concentation (%
40
30
10
20
40 60
Percentage
80
100
120
These series of experiments show that the AMSI/MS is able to determine quantitatively
the chemical composition of aerosol consumer products during spatial dispersion. Changes in
chemical composition and quantity are measurable with the AMSI/MS. The measurement of the
changes in chemical composition as the aerosol moves through space can provide important data
for formulation of products for pollution prevention. The composition of the product as it arrives at
the use site determines the products efficacy. Knowing the actual composition of the product at
36 D
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the use site will allow for formulating products with maximum efficacy with the least amount of
chemical usage.
5.2.8 Particle Size Distribution Selection for Analysis via Steering Gas
Analysis of chemical composition as related to the particle size is dependent on
selecting the particle size being sent into the MS. The AMSI uses a perpendicular gas stream to
steer the particles away from the straight trajectory path. The momentum of the particles through
the steering gas determines the pathway of the particles through the AMSI and whether or not the
particles will pass into the MS. A stream of nitrogen or helium is introduced perpendicular to the
aerosol beam axis so that the changes occur in the particle-size distribution entering the MS.
Since larger particles have higher momentum and inertia, they stay on the original straight
trajectory path, while the small particles are blown away. As the flow of steering gas is increased,
the mean drop size of particles reaching the MS is increased. This means that the signal
intensity should be greatest when the gas flow is lowest and the greatest number of particles with
the widest particle-size distribution is travelling into the MS. Conversely, the measured signal
intensity reduced as the gas flow is increased since only the larger-sized particles (decreased
particle-size distribution) pass into the MS. This is depicted in Figure 24. With increasing gas
flow (increasing chamber pressure) the signal intensity decreased. It is imperative to ascertain
that the force of the gas not be so strong that the larger particles are splintered into small sized
droplets. In its current form, the AMSI is not calibrated to relate gas flow to particle size
distribution. It has been shown that the technique is viable, but no correlation with actual particle
size versus chemical composition has been made.
The steering gas, with increasing gas flow, changes the aerosol particle-size distribution
being transferred through the AMSI into the MS. Once the AMSI is calibrated so that the particle-
size distribution versus the steering gas flow is known, pattern recognition techniques can be
applied to determine particle size versus chemical composition data (24-27).
Figure 24. Depiction of particle-size distribution selection via increasing steering gas flow.
Increasing Gas Floi
37 D
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5.3 Particulate Spatial Dispersion
Particulate dispersional behavior, as well as the chemical compositional behavior,
needs to be understood to design pollution prevention strategies for aerosol consumer products.
A different set of tools and methodologies were developed to investigate the particulate
dispersional behavior.
Particle transport in room air flow is influenced mainly by gravitation, convection, and
turbulent (eddy) diffusion. These forces generate differences in particle concentrations and
particle size distributions throughout a room. Movement of particles depends on the
characteristics of the local air flow conditions and of the particle. Individual forces that influence
movement of different sizes of particles are 1) the stopping distance, 2) settling velocity, 3) room
air flow velocities, and 4) eddy diffusion resulting from fluctuating air flow velocities.
The stopping distance is the distance in still air that is penetrated by a particle with a
certain initial velocity before falling to rest. The stopping distance for different particle sizes and
an initial velocity of 2 m/s and 10 m/s is shown in Figure 25.
Figure 25. Distance in still air penetrated by particles with an initial velocity of 2 m/s and 10 m/s.
8
i
20 40 60 80
Aerodynamic dameter (urn)
100
The settling velocity of particles suspended in still air is shown in Figure 26. If the air flow
velocity is less than the settling velocity for a given particle of a given size, the particle will
sediment out of the air flow. Settling velocity for particle sizes less than 10 |im will be less than 5
cm/s, and for particle sizes less than 100 |im will be about 23 cm/s.
Velocities in a room typically vary from zero to 20 cm/s in the occupied zone and up to 5
m/s at the room air diffuser. All particles with sizes greater than 100 |im will sediment out of the
air flow in the occupied zone, certain fractions of particles with sizes between 20 and 100 |im
also will sediment out, and particles smaller than 20 |im in size will remain in the air flow. This is
illustrated in Figure 27, showing the steady state velocity for particles affected both by gravity and
an upward air flow at different velocity levels.
38 D
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Figure 26. Settling velocities for particles suspended in air.
20 40 60 60
Aerodynamic diameter (urn)
100
120
Figure 27.D Steady state velocities of particles affected by gravity and different air velocities
opposite to the direction of gravitational field (upward velocity is positive).
20 40 60
Aerodynamic diameter (urn)
80
100
• 20cnfs
•15cnYs
-10crrfs —x—ScnYs
-Qcrtis
Eddy diffusion is another important force acting on particles in room air flow. Eddy
diffusion is caused by fluctuating velocities in the air flow. Diffusion results in a net migration of
particles from regions of high concentration to regions of low concentration. Eddy diffusion
depends partially on air flow characteristics, such as air turbulent kinetic energy, dissipation rate
of the turbulent kinetic energy and viscosity, and partially on particle characteristics, such as
particle diameter and particle density. Eddy diffusion will be a constant for particles below 20 |im
and will be decreasing for larger sized particles.
The spray cone of an aerosol consumer product is the dynamic three-dimensional
projection of the liquid aerosol particles being ejected from the aerosol consumer product spray
39 D
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nozzle into the air (33). The spray cone has a constantly changing length, particle size (and
potentially changing chemical composition), and velocity distribution as the aerosol is dispersed
through space. In the indoor environment, the spray cone is influenced by the localized air flow
patterns in the space created by natural and mechanical ventilation. A basic understanding of
this spray cone behavior is a critical factor in understanding product efficacy and in devising
pollution prevention strategies.
The PIV system was used to determine the spray cone characteristics by measuring
particle concentrations and velocity distribution. These techniques also were used in an
environmental chamber to investigate the effect of localized air flow patterns on particle
concentration distributions as the aerosols are transported through space in the indoor
environment. A Malvern Particle Sizer was used to investigate the particle-size distributions to
understand potential exposures during the use of aerosol consumer products.
5.3.1 Particle Size Distribution
Since the behavior of aerosol particles is dependent on their size and the nature of the
propellant (carrier gas), particle size distribution data was needed to determine the impact of
aerosol consumer products on the environment and consumers (34). This was done by using the
Malvern light-scattering technique to measure the particle size distribution of the surrogate
aerosols down to 1 |im particle size.
The Malvern 2600C Droplet and Particle Sizer has an accurate operating range of 1.2 -
1000 |im. The system consists of a helium-neon laser, a detector, and a computer system and
operates on the Fraunhofer diffraction theory (35) (Figure 28). The Malvern system uses laser-
induced light scattering to determine particle size distribution as a percentage by volume of each
measured size range via mathematical models and calculations. This analysis provided data on
the particle size (drop-size) distribution and the Sauter mean diameter (the diameter of a droplet
with a surface to volume ratio equal to the mean of all the surface-to-volume ratios of the droplets
in a spray distribution also referred to as the mean volume-surface diameter).
The particle size distributions, 13.6 cm from the nozzle (an arbitrarily chosen distance), of
each of the surrogate aerosols are shown in Figures 29, 30, and 31. The results are summarized
in Table 9 showing that the majority of the particles, for each of the surrogate aerosols, are above
25 |im. The Sauter Mean Diameter of each of the surrogate aerosols was above 50 |im. The
figures graphically display these findings. These findings can have a significant impact on
devising pollution prevention strategies to reduce user exposures. In general, these results
indicate that there are few particles ranging in size below 25 |im as the aerosols left the aerosol
package. The particle size distribution for the surrogate aerosols (representing different product-
use types) were different (Figures 29, 30, and 31). Therefore, the dispersion of the aerosols
through space can be expected to be different.
The design of the surrogate aerosols allowed for the comparison of the differences
between hydrocarbon and compressed gas propellants. Examining Figures 29, 30, and 31, it
appears that the compressed gas propellant yielded a larger particle size distribution than the
hydrocarbon propellants. These data may not be statistically significant since multiple sample
analyses on the surrogate aerosols were not conducted. Figure 29 depicts the results for the
surrogate air aerosols AA1 and AA2. The only difference between these two aerosols is that AA1
uses a hydrocarbon propellant and AA2 uses a compressed gas propellant. Similar results are
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Figure 28. Schematic of Malvern Particle Sizer for droplet size measurement.
Analyser Beam
Detector Plane
Measurement
Electronics
Measured Zone of Spray
Printer
Computer
Table 9. Range of particle sizes of surrogate aerosols measured with Malvern particle sizer
Surrogate Aerosol
AA1
AA2
SNWP1
SNWP2
SNWP
SWA
SWP
Propellant
A46
CO,
A46
CO,
Mister
A31
Trigger
Sauter Mean
Diameter (MID)
82.27
179.74
55.14
64.93
86.57
117.37
59.60
Particles Size
Range (MID)
50 - 300
50 - 550
50 - 200
25 - 200
50 - 200
50 - 350
25 - 500
found in Figure 30 for the surface non-wipe surrogate aerosols. Figure 31 shows the difference
between a hydrocarbon propellant (SWA) and a pump spray (SWP). The particle size distribution
of SWP maximizes at a smaller particle size than SWA and over a broader range (Table 9).
Similar results were found with the PIV techniques (discussed in Section 5.2.2). The PIV data
revealed that the particle size distribution, determined via velocity measurements, is dependent
upon the materials used in the aerosol; therefore, propellants can be expected to have a
significant impact.
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Figure 29. Particle size distribution measured with Malvern analyzer for surrogate air aerosols.
A) AA1 and B) AA2. (AA1 has small Sauter mean diameter and AA2 has large Sauter
mean diameter.)
10 100
Droplet Diameter (um)
1000
Figure 30. Particle size distributions measured with Malvern analyzer for surrogate surface non-
wipe aerosols. A) SNW1, B) SNW2, and C) SNWP. (SNW1, SNW2, and SNWP have
small Sauter mean diameters.)
10 100
Droplet Diameter (um)
1000
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Figure 31. Drop-size distributions for (A) SWA and (B) SWP measured with Malvern system.
(SWA has large Sauter mean diameter and SWP has small Sauter mean diameter.)
10 100
Droplet Diameter (urn)
1000
A
The particle size distribution in pressure-swirl nozzle spray cones, the type most
commonly used for propellant-driven aerosol consumer products, is not the same throughout.
Therefore, the particle size distribution across the spray cone's axial centerline can be
dramatically different (9). For this reason studies were conducted across the spray cone of the
surrogate aerosols, in order to investigate the importance of the position in the spray cone on
particle size distribution. This was done by measuring the particle size of the released particles at
different distances from the aerosol actuator nozzle and across the spray cone in two-
dimensional space (Figure 32). The distances were chosen arbitrarily.
Figure 32. Depiction of spray cone particle-size distribution measurement scheme.
r
J_
~i
_[«u
-«-
-*
E2S..1J
13.6 cm •»-
23.6 c
1
m »-
3 6 cm
*> fm
1 .5 cm
-1.5 cm
-5 cm
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These studies were carried out on three different aerosols: 1) AA1, 2) SWA, and 3)
ethanol using nitrogen as the propellant. These data provided information on the importance of
the propellant gas on the particle size distribution (since aerosol velocity is dependent on the
propellant gas) and the design of the aerosol package for final use.
There was not a significant difference in particle size distribution in the jet core as the
distance from the spray nozzle was increased, although there appeared to be a tendency toward
larger particles with increasing distance from the spray nozzle (Figures 33 and 34). This may
indicate potential agglomeration of the particles with movement through space, but also may be
the result of the particle size decreasing below the Malvern analyzer detectability due to
evaporation. However, in the outer part of the jet, where the velocities are lower, there was a
different particle size distribution in the aerosol jet. This can be explained by particle transport
phenomena - larger particles, due to their larger initial momentum, travel farther than smaller
particles, and diffusion of larger particles is less. Therefore, the particle size distribution is
expected to change toward larger particles in the flow of the jet. This same situation also
occurred in the jet centerline at a greater distance from the spray nozzle, where the velocities
were less.
Centerline velocities for the surrogate aerosols as function of the distance from the
spray nozzle are depicted in Figure 35. The velocities adjacent to the nozzle were higher than
those in room air flow, however at a distance of less than 40 cm from the nozzle the velocities will
be approximately the same. Therefore, flow conditions in surrogate aerosol jet adjacent to the
nozzle are determined by nozzle design, and aerosol transport at distances greater than 40 cm
from the nozzle are determined by the flow conditions in the room.
In Figure 36, the Sauter Mean Diameters are shown correlated with the position of the
spray. The Sauter Mean Diameter for SWA is smallest at the centerline and 1.5 cm above the
nozzle. When ethanol pressurized with nitrogen is tested, the Sauter Mean Diameter is smallest
at 1.5 cm above the nozzle. The ethanol pressurized with nitrogen was investigated to see if a
generic, no use designed, nozzle would change the results. There were no obvious advantages
to analyzing the ethanol pressurized with nitrogen - the generic aerosol.
Another factor that could influence particle size distribution is the amount of product and
propellant in the can, in other words, the "can-fullness". This can potentially be a problem with
aerosol consumer products using compressed gases as the propellants. An experiment was
conducted also to investigate particle size distribution as related to can-fullness. The amount of
product remaining in the can was determined by weighing the can when full, when about half full,
and when almost empty. The particle size distribution was measured with the Malvern system on
a new, full can of AA1. The nozzle was depressed to release product until the can was
approximately half full, as determined by weight. Then the particle size distribution was
measured again. The nozzle was then depressed until the can was almost empty. The particle
size distribution was determined again. The results are shown in Figure 37 showing that the
particle size distribution does not dramatically change until the can is almost empty.
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Relative Volume %
Relative Volume %
Relative Volume %
Oi
n
b
o
3
O
b
o
3
I
o
f
CD
«-*•
a
ff
"1
(Q
CO
CO
0_
CD
£
N
CD
Q.
o
CD
(Q
Q.
O
CD
=T
O
3
CD
!D
3
-------
Relative Volume %
Relative Volume %
Relative Volume %
n
O
o
3
O
O
O
3
§
O
o
3
(Q
I
CO
Tl
!D
3:
0_
CD
CO
N'
CD
Q.
—i
U)
o
CD
(Q
Q.
O
CD
o
CD
Q}
3
-------
Figure 35. Velocity decay of surrogate aerosol particles along the jet centerline.
10 100
Distance from aerosol jet (crn^
1000
5.3.2 Aerosol Spray Cone Characterization
PIV (35-39) was used to characterize aerosol spray cones to determine the particle size
distribution and particle concentrations via velocity determinations (40). With the PIV illumination
and image acquisition systems, quantitatively dynamic structures of aerosol spray cones were
visualized, producing contour plots of the aerosol particle concentrations and particle
concentration profiles along the spray radial direction. Digital images were taken continuously
during the entire spray period to determine the dynamic structures of aerosol sizes,
concentrations and velocities of the random flow process of the aerosol spray jets. Using this
method, the characteristics of aerosol sprays and the transport mechanism in rooms were
studied. An environmental chamber facility equipped with a PIV was used during this project to
investigate the transport mechanisms in a room, and how the transport is affected by room air
ventilation. Since an aerosol spray is a random process, a large number of data points were
needed to mathematically describe the process. The PIV was able to collect the data by rapidly
and automatically recording the data.
The PIV imaging system was applied to analysis of the surrogate aerosol spray cone
patterns. The temperature of the test environment was controlled at 21 + 0.2°C. To ensure that
the pressure inside the containers did not change more than +5%, the pressure in the aerosol
cans was measured before and after the tests.
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Figure 36. Sauter Mean Diameters correlated with distance from the spray.
Air Aerosol #1
leam (cm)
Alcohol w/Nitrogen Pressurized
Distance to LaerB
eam (cm)
eam (cm)
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Figure 37.CParticle size distribution related to can-fullness. A depicts a full can; B depicts < half
full can; and C depicts an almost empty can.
10 100
Droplet Diameter (um)
1000
The PIV measurement system consists of an argon ion laser, a polygon mirror, sheet-
forming optics, two charge-coupled device (CCD) cameras, two frame grabbers, and a host
computer (Figure 38). The measurement system was used to measure particle size distribution,
velocity and concentration, but different test procedures, image interrogation systems and
calibration systems were required for each.
The argon laser provided a beam with constant intensity to illuminate aerosol sprays.
The beam was swept through the view field with a rotating polygon mirror (Figure 39). A
sweeping frequency of 30 frames per second was maintained via a motion controller. Each time
the beam swept through the view field, a photodetector triggered the cameras. Images acquired
by these cameras were sent to the host computer and saved on a hard disk for interpretation.
Each group of data consisted of 120 to 240 images. The size and concentration distributions
were obtained instantaneously. Particle size, concentration and velocity were calculated. These
data then were compiled for calculations of statistical averaged values.
The measurement system capability covered the size range of the majority of particles
in the surrogate aerosol products. Under current experimental conditions, particle sizes in the 20
|im range were measured in a view field of 200 x 150 mm. Two images covered the majority of
the surrogate aerosol jets. Smaller view fields (11 x 7.5 mm), particles as small as 1 |im, can be
detected; but due to funding and instrumentation limitations, this level was not achievable during
this project. Measurement accuracy depended on the calibration system view field and particle
size. Practical accuracy achieved was within 5% and was generally in good agreement with
computer simulations.
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Figure 38. PIV measurement system.
Photo detector
Aerosol
can
Controller
\ X Polygon mirror
Argon laser
Pulse generator
Host computer
Figure 39. Schematic of beam sweeping over aerosol particles.
Polygon mirror
{] Argon
laser
Aerosol particles
A small view field (Figure 40) was used for particle size distribution measurements. The
whole flow field of the spray jet was divided into several smaller view fields allowing some overlap
between the individual view fields in order to measure the overall size distribution information. A
50 n
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computer-controlled step motor directed the camera position. Size distribution was calculated as
the number of particles as a function of particle size. At the first stage, particle size was in pixels,
the particle size in "image space". Particle size in "object space" was proportional to the size in
"image space" and was calculated via a calibration curve.
Figure 40. Particle size distribution small view field schematic.
Camera 2
View field
Only a relatively low-resolution image acquisition system was required for particle
concentration measurements. The whole flow field was separated into two parts (Figure 41).
Particle images were recorded by two CCD video cameras and saved on computer hard
disk for later interpretation. Particle concentrations were calculated from picture light intensity
values. A particle counter (CI-7350) from Climet Instruments was used to calibrate the
relationship between particle concentrations and the reflected light intensity.
Figure 41. Particle concentration measurements large view field schematic.
30.5 cm
30.5cm
Camera 2
View field
The two basic quantities used to describe the structure of aerosol sprays were aerosol particle concentration
and velocity distribution. Since these two parameters are important in determining aerosol particle
transport over space, they are important in the evaluation of aerosol product efficacy.
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The concentration of particles is defined as the number of particles in a unit volume.
C =
An
AV
where C is the concentration, n is the particle number and V is the volume. In preliminary tests,
volume was chosen to be 3.18 x 2.29 x 0.25 cm. Statistical averaged results are obtained by
using a large number of data sets.
The particle concentration results were obtained in two different formats: 1) contour plots
of the aerosol particle concentration (Figure 42), and 2) profiles of the particle concentration along
the spray radial direction (Figure 43). The contour plots for the surrogate aerosols are shown in
Figure 42. The contour plots are useful for visualizing particle trajectories and behavior of the
aerosol jets.
The particle concentration profiles along the spray radial direction are useful for
visualizing the size spectrum of the aerosol particles with increasing distance from the spray
nozzle. The profiles of the particle concentration along the radius of the spray cone are shown in
Figure 43 for the surrogate aerosols.
The particle concentrations varied markedly among the surrogate aerosols products.
From Figure 43 and Table 10, it can be seen that the surrogate aerosols that used hydrocarbon
propellants had a smaller particle concentration distribution than the compressed gas surrogate
aerosols. The surrogate surface non-wipe aerosols, particularly SNW2, had the widest particle
concentration distribution. These data may be useful for the development of pollution prevention
strategies for product reformulation.
Table 10.DPIV determined concentration distribution of surrogate aerosol particles at a distance
from the spray nozzle.
Surrogate Aerosol
AA1
AA2
SNW1
SNW2
SWA
SWP
Propellant
A46
CO2
A46
CO2
A31
Trigger
Distance from Spray Nozzle of Peak
Concentration Distribution (cm)
0.00-3.18
3.18-6.35
9.52-12.7
3.18-12.7
3.18
6.35
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Figure 42. Contour plots of surrogate aerosol particle concentrations in the aerosol jets (1 in. =
2.54 cm):
AIR AEROSOL 1 (nsptlcatlon 1)
2 4 « 6 10 12
horizontal distance from the nozzle (inch)
SURFACE NONWtPE 1 (replication 8)
2 4 6 8 10 IS
horizontal distance from the nozzle (inch)
AIR AEROSOL 2 (replication 2)
0 2 4 K « m
horizontal distance from the nozzle (inch)
SURFACE NONWIPE 2 (replication 1)
a z jt « a 10 12
horizontal distance from the nozzle (inch)
f A rr/=
fc^fe^SsJ^-^-v^^^pv^A L/\ \ .xvvs
0 2 . < « 8 10 12
horizontal distance from the nozzle (inch)
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Figure 43. Surrogate aerosol particle concentration profiles along the radium of the spray cone.
x« 0.00 mm
x - 63.5 mm
x = 127 mm
x » 190.5 mm
-x * 31.75 mm
-x • 95.25 mm
-x • 158.75 mm
-x E 222 mm
10 20 30 40
Instantaneous concentration of partlclis
10 IS
oncentration of p«rt1cl»«
-X* 0.00 mm
—X * 63.5 mm
—x * 127mm
—x « 1BO 5mm
-x • 31.75mm
-x. 85.25mm
-x - 1S8.75 mm
S 10 15 20 25 30
Intununoui conctntration of partfcl**
35 40
x > 9S.25 mm
x « 158.75 mm
x = 222 mm
I 10 IS
IntUntaniou* parttcl* cononlratlon
54 D
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A relatively high-resolution image acquisition system was required for particle velocity
measurement in order to identify the individual particles in aerosol spray jets due to the high
particle concentrations. Particle images were recorded either by video camera or photographic fil,
sent to a PIV computer-based interrogation system, and digitized. The 1024 x 1024 pixel image
was stored and divided into eight sub-images. Processing was performed in two array processor
boards (mc860vs), each with four i860 microprocessors (Figure 44). After the interrogation
procedure, velocity vector maps and velocity distributions were obtained.
Figure 44. Velocity measurement interrogation system hardware schematic.
Imaging Technology
VSI-tSO
Frame Grabber
Inter-board Bus
160 MB/s
Cross Bar Switch (480 MB/s)
Cross Bar Switch (480 MB/s)
MC860VS Board 1
MC860VS Board 1
Unidex X-Y-Z
Translation Stage
SUN SPARCstation 370
(Host Computer)
Laser Doppler Velocimetry (LDV) also was used to measure particle velocities;
the comparison of results from the two different techniques determined the measurement
accuracy. The LDV unit used in the test was a TSI SUREPOINT laser probe with an IFA550
signal processor operating on a host computer. For each data point, 8000 samples were used to
calculate the averaged velocity value. The LDV data were found to be oin good agreement with
the PIV data, within 5%.
The surrogate velocity data are depicted in Figure 45. These data are presented as a
function of distance from the spray can nozzle. The velocities of the centerlines do not change
significantly for the different surrogate aerosols. The velocity decreases as the distance from the
nozzle increases. The range of the velocity is between 2 and 14 m/s when the distance from the
nozzle changes from zero to 100mm.
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Figure 45. Surrogate aerosol particle velocity distributions along the axis of the spray nozzle.
Air aerosol 1
20 40 60 80 100
Distance torn nozzle (mm)
13-
f'2'
f 1
1 10-
Air aerosol 2
10 20 30 40 50 60|
Distance from nozzle (mm)
16 -,
14 -
^10
| 8
| 6 •
I *
2
0
Surface nonwipe 1
20
40 60 80
Distance from nozzle (mm)
100
120
wipe 2
20 40 60
Distance from nozzle (mm)
100
Model
A model, which can predict the major characteristics of aerosol spray patterns, can be
useful to guide in the development of pollution prevention strategies. A simplified engineering
model for aerosols was developed previously based on turbulent jets (42). This model assumes
that 1) the jet emerges from a circular orifice into a stream of uniform velocity, Us; 2) the flow of
the mixtures of aerosol particles with air is turbulent with axis-symmetric mean values; 3) the jet
velocity is larger than ambient stream velocity; and 4) the turbulent region is relatively narrow in
the radial direction. Based on these assumptions, mass balance and momentum balance
equations in a cylindrical coordinate system, (r,z) can be written:
56 D
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Where U r and U z are r and z components of the mean velocity of the mixture of aerosol and
surrounding air, and ur and uz are r and z components of fluctuating velocity of the mixture of
aerosol and surrounding air.
These equations can be solved numerically. This research project required the
development of a simplified analytical model, which could be used easily in engineering practice;
therefore similarity methods were chosen (33) to simplify the equations, and since the velocity
and concentration profiles can be measured experimentally. These equations are outlined by Cui
(34). Cui introduced a similarity variable, £2, ar)d several similarity functions, f, g, and h. The
original variables, U r, U z, ur, and uz can be defined as functions of the similarity variable and
functions.
To solve the balance equations, the following similarity relations are introduced:
U,-\
Where z - -a is the position of the "origin of similarity*; d Is the diameter of the orifice; Up is the
issuing velocity of the mixture of the aerosol, propellant, and air, f, g, and ft are the similarity
functions; and
rld
[(
Substituting the similarity relations into mass and momentum balance equations, the
constants d, r, q, and , %> can be determined to be -1, -1, 1, and -2, respectively. If an eddy
viscosity, em, is introduced:
01} t
57 D
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the velocity distribution can be obtained by setting the ambient stream velocity to zero, Us = 0:
TT I f T f \ I
U, L U,,m&(z + a) _2
_ = J I + ,,...> £gM|2 L
f/z.max I * J
For the concentration distribution, the equation of transport can be written as: •
where
Cp is the value for C for the issuing fluid, and y is the fluctuating part of the concentration.
Cui (34) introduced a simitar relationship involving a diffusion tensor:
p z + a
where k is the similarity function:
z+a
_ —_ £C
Cui then determined the concentration profile:
c ( ~
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Cui applied PraudU's tnbdng4ength hypothesis to further simplify the result:
e.
d U,
V.
t.nax.
Upd
d U,
'i.mn
where /m and 4 are mixing lengths.
The expression of concentration distribution of aerosol particles can be written as:
where the velocity distribution and the constants SB,, so, lm, and k depend on the material
properties of the aerosols.
Once the similarity functions are applied to the model, the mass, the momentum, and
energy fluxes can be determined by using the velocity and concentration distribution for the
aerosol. The amount of effective materials carried by the aerosols to the use site can be
calculated from these quantities. The uniformity of the materials distributed at the use site also
can be evaluated. The characterization of the aerosols in this manner may guide in the
development of pollution prevention strategies and more efficacious products.
Applying the model to the surrogate aerosol data, Cui (33) found that the spray pattern
correlated with the material properties of the liquids. The velocity of the aerosol particles in the
propellant driven sprays appeared to be increasing near the spray nozzle. This may have been
caused by the evaporation of the liquid propellants near the nozzles. The velocities peaked at a
distance of 20 mm from the nozzle and decreased as the distance from the nozzle increased.
This was probably due to air drag. This mechanism appeared to control the atomization process
near the spray nozzle.
5.3.3 Aerosol Transport in Rooms
When the PIV was combined with large-scale environmental chamber technology, the
effects of room air ventilation, both natural and mechanical could be measured. The
PIV/environmental chamber system also allowed for the measurement of particle velocities in a
whole room. This allows for the calculation of changes in particle size distributions in the indoor
environment. Both understanding the effect of ventilation and the particle size distribution
throughout a room can lead to valuable data for development of more efficacious, less toxic, and
59 D
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more user friendly products. These data may guide manufacturers to design effective pollution
prevention strategies.
The PIV/environmental chamber system primarily has three subsystems which
illuminate flow structure, acquire images and interrogate the images. These three subsystems
allow calculation of velocity and particle-concentration distribution in the indoor environment (27).
The whole field is illuminated with light, either laser or white, to visualize particle flow. Films or
electronic media record images of visualized particles. The recorded images are interrogated by a
computer system to obtain positions, displacements and concentrations of particles. If particles
are neutrally buoyant and small, the particle velocity will be the same as air velocity. Otherwise,
the particle velocity will be different from velocity of the carrying media and the distribution of
particles will deviate from the distribution of the air.
The PIV/environmental chamber system consisted of a test room (28); heating,
ventilation and air-conditioning (HVAC) system; illumination system; image shift technique; flow
seeding technique using particles; image interrogation and statistic data analysis technique.
The aerosol test room was constructed in the Room Ventilation Simulator (Figure 46),
which consists of an adjustable inner room and an outer room for controlling ambient
environmental conditions of the inner test room. The outer room is an insulated building used to
simulate climatic conditions. The front and left side of the aerosol test room (Figure 47) are made
of clear, tempered glass permitting optical access to the room interior. The other two walls are
made of black painted wood for an optimal optical environment. The aerosol test room was
designed and constructed to allow for easily changing room configurations, such as types and
locations of diffusers and returns. The supply air to the room enters through a closed loop fan
system.
Figure 46. Test room for ventilation simulator.
1.
1. OUTER ROOM
2. OUTER ROOM AMBIENT
SIMULATOR
3. OUTER ROOM
SUPPLY AIR DUCT
4. OUTER ROOM
SUPPLY AIR DIFFUSER
5. OUTER ROOM RETURN AIR
6. INNER ROOM
7. INNER ROOM EXHAUST TO BE
DUCTED TO INNER ROOM A/C SYSTEM
8. CONDENSING UNIT FOR INNER
ROOM AIR CONDITIONING SYSTEM
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Eight halogen lamps were used to illuminate the aerosol test room so that the particle
flow patterns were visualized and recorded. The light was controlled by eight cylindrical lenses
installed in front of 1500 watt light bulbs. These lenses changed the five point light sources to a
line light source. The lens focal length was 90 mm. the depth of the field was calculated as:
5 = 4(1 +M)2/2}.
where 8 is the depth of field, M is the camera magnification, f is the camera f-number, and A, is the
wave length of the illumination light.
Figure 47. PIV/environmental chamber system schematic.
4o
VJ
«-4-tU
Computer
Camera
Glass
\
-j
'
"^ JO/U ^-
Wood
\
Aerosol
Testroom ^-
\
t
8446
1
\Glass
Laser/light C^
equipment \
Room Ventilation Simulator (all dimensions are in mm).
To maximize the light intensity, the minimum value of the f-number was used in the
experiments. The thickness of the light sheet was uniform and was chosen to be 50 mm as the
depth of field. To reduce light scattering from the space around the lens, lamps were placed in an
air ventilated box. The light resolution images of the flow patterns were captured with a Nikon
N8008 AF35 mm camera. Light intensity, shutter speed, exposure time, and lens aperture were
optimized so that relatively small particles were illuminated in the aerosol test room. The best
exposure time determined experimentally was 1/30 sec.
Since room air flows have large inverse velocities, image shift techniques were used to
determine the direction of velocity. The shift velocity was calibrated, using both stationary images
and measurements of shift velocity. The velocity of shift (Us) was determined by camera
magnification (M) and maximum flow velocity (0.9 m/s) near the diffuser and by analysis of test
images; minimum shift speed was determined. The camera was shifted by a step motor moving a
constant speed of 0.2 m/s.
For velocity measurements, the acquired images were interrogated to obtain a velocity
vector map. The images were processed by a computer system for the PIV. The PIV photograph
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was divided into a high resolution grid of interrogation spots. Each spot contained a sufficient
number of particle images defining a local, instantaneous velocity. The photographic analysis was
done automatically with a DEC Microvax computer with an attached Numerix 432 array processor
using a 2-D Fast Fourier Transform algorithm. A velocity vector map resulted from the image
interrogation. From the velocity vector map, the flow pattern, velocity, turbulence of the flow field
was calculated. The velocity vectors were sufficiently accurate to differentiate instantaneous out-
of-plane vorticity fields. The velocity statistics obtained with the PIV system were in good
agreement with those obtained by computer simulation and LDV measurements.
Three different types of particles were used to investigate aerosol transport in rooms.
The first type was neutral, buoyant helium-filled bubbles, 1 mm in diameter, and generated by a
bubble generation system. Since these bubbles behave as a low pass filter, the flow structure that
was obtained is applicable only to particles greater than or equal to 1 mm. Flow structures smaller
than 1 mm in diameter were extrapolated from the helium bubble results as average effects. The
second type of particles used was plastic microspheres. These particles were heavier than air
and ranged in size between 10 and 50 |im. The third type of particles was from the surrogate
aerosols. The size ranges of these products were found to be between 25 and 500 |im. These
particles also were heavier than air.
The HVAC system was operated for 30 minutes at each air change rate to ensure that
room airflow had reached steady state conditions. Helium bubbles or the plastic microspheres, or
the surrogate aerosols were seeded into the test room. When the density of particles reached the
required value (5 to 7 bubbles/mm2 for the helium bubbles), the light was switched on, the image
shifting step motor started, and simultaneously the image was acquired. The step motor
controlled by the computer triggered the camera automatically. The light was on only during
image acquisition, 0.5 minutes. If a large number of images was needed for statistical analyses,
the process was split into a few short sessions. The acquired images were analyzed by a
completely automatic system incorporating a DEC Microvax computer with an attached Numerix
432 array processor. Velocity vector maps were obtained after the interrogation procedure.
Statistical analysis was used to analyze the large amount of data.
Concentration measurements were done with a CCD camera, obtaining images of
scattered light intensity from particles, an optical particle counter (CI-7350 from Climet
Instruments) for system calibration, and a host computer for storing and analyzing the images
(Figure 48). Because light intensity scattered by particles is proportional to their concentration, it
was not necessary to resolve individual particles. The test was started with uniformly distributed
particles. The image was acquired after the HVAC system was turned on. The time intervals
between the images were kept constant. The particle images were first saved on hard disk and
processed later. The particle concentration measurement was calibrated by using the optical
particle counter to quantify the relationship between the particle concentration and the reflected
light intensity.
Experiments were done for two dimensional, isothermal airflow conditions with air
change rates of 5 and 10 air changes per hour (ACH). Depending on room structures, air flows
and seeding particle density, 2000 to 8000 vectors were obtained for the size of the given two-
dimensional view field. The small-scale structures of airflow are depicted in Figure 49. This
capability is critical for the study of diffusion effects dominated by small structures in the indoor
environment, which in turn is important for aerosol particle transport. From the obtained
instantaneous airflow patterns, it can be demonstrated that room airflow is turbulent with low
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Figure 48. PIV/environmental chamber measurement system schematic.
S Halogen lamps
Particle disperser
\
Step motor
Camera
Poynting products
Frame grabber
Numerix-432
Array processor
Micro Vax II
Host computer
Laser printer
/ Display
Figure 49. Vector map of instantaneous room air velocities at an air change rate of 5 ACH. The
image is taken in the middle of the room.
mm
JOOO i-
500
1000
1500
mm
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mean velocities and high velocity fluctuations. The system measures instantaneous and time-
averaged velocity distribution in a view field of 2000 x 1500 mm with 1 mm seeded particles.
Velocity statistics from PIV ensemble averaged vector maps show resemblance and good
agreement with computer simulations and LDV measurements. The particle velocity was
measured with an accuracy of 5%.
A contour plot of the particle concentration at 5 ACH are shown in Figure 50. Numbers
in the plots are thousand particles per cubic feet. Although the concentration distribution of the
particles was found to be complicated, the particle concentrations were denser in the lower part of
the room and more dilute in the upper part of the room. This phenomenon is difficult to see in
Figure 50, but could be visually observed and is evident in the concentration measurements
(Figure 42). This is an important finding for designing products with the greatest efficacy. If the
use site for the product is high in the room, less of the product will reach the use site; and
therefore, more of the product will be required for satisfactory results. Nozzle designs can be
evaluated and optimized using this technique.
The HVAC system and its design has an impact on the particle distribution and settling
rate in rooms. The shape of the diffusers used to distribute the air in indoor space can affect the
particle concentrations and settling within a room. Figure 51 shows what the impact of a circular
diffuser has on particle concentrations. The concentration of particles in the air closer to the spray
nozzle, decreased from time 0 to 4 minutes, but increased at greater than 1.6 m from the spray
nozzle. This is probably due to the turbulent airflow suspended the particles. The data show that
the particle movement is influenced by local airflow conditions.
Figure 50. Contour plot of instaneous particle concentration at an air change rate of 5 ACH.
The images were taken in the middle of the room. (1 ft. = 3 m).
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Figure 51. Normalized particle concentration in environmental chamber with a circular diffuser
distributing the air.
2
1.8
1.6
0.6
0.4
0.2
A*r change rate « 15 ACH
0.75 0.8 0.85 0.8 O.9S
Normalized particle concentration
1.05
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6.0 Technology Costs to Industry or Other Researchers
6.1 AMSI
Since the AMSI is not commercially available and must be machined, the costs are
dependent upon the particular machine shop. In general the cost of the AMSI should be below
$1000. The AMSI, in its current form, must be interfaced with a MS with particle beam or
electrospray (or ion spray) capabilities, preferably with MS/MS capabilities. These systems range
from $150,000 to $500,000 depending on the sophistication. Once the AMSI/MS system is
operating, the analytical costs will range from a few tens to a few hundreds of dollars per sample.
Analysis requires a few minutes of time per sample. Data interpretation requires the greatest
amount of time and is dependent upon the skill and knowledge of the operator. As a laboratory
builds a database of aerosol products, data interpretation can be cut down to a few minutes of
time.
6.2 Aerosol Spray Pattern Characterization
The expense of the PIV imaging system is decreasing with the rapid developments of
computer hardware and software techniques. There are considerable price and feature variations
among companies manufacturing these systems. Table 11 and Table 12 show typical prices for
the components needed. The argon laser, pulse generator, photo detector and peripheral
instruments can be used in both velocity measurement and concentration measurement. These
components cost $21,000-$23,000.
Table 11. Aerosol particle concentration and size distribution in spray jets—PIV system costs.
Component
Video Camera
Frame Grabber
Argon Laser
Host Computer
Software
Pulse Generator
Photo Detector
Peripheral Equipment
Particle Counter
TOTAL
Quantity Needed
2
2
1
1
1
1
1
1
10
Price/ Component
$2000-$3000
$4500-$5000
$10000-$12000
$5000-$6000
$2500
$5000
$1000
$5000
$10,000
$51 ,500 -$57,500
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Table 12. Aerosol particle velocity distribution in spray jets — PIV system costs.
Component
Video Camera
Frame Grabber
Argon Laser
Host Computer
Software
Pulse Generator
Photo Detector
Peripheral Equipment
TOTAL
Quantity Needed
1
1
1
1
1
1
1
7
Price / Component
$20000-$25000
$15000-$16000
$10000-$12000
$10000-$15000
$10000
$5000
$1000
$5000
$76,000-$89,000
(A more expensive camera will be required for measurement of smaller particle sizes. Additional
equipment and instrumentation will be required for three-dimensional analysis.)
The measurement frequency was 24 frames per second. For each surrogate aerosol
product 240 frames were taken for concentration measurement and 24 frames for velocity
measurements. After image acquisition procedure, the data are interpreted to extract velocity,
size and concentration distribution information. This process requires about 6 hours for
concentration information and 12 hours for velocity distribution information test.
The component costs for the PIV/environmental chamber system are decreasing with
rapid development and costs vary for each component. Tables 13 and 14 approximate the
current component prices.
During the velocity measurement procedure, 3 to 5 minutes are needed for each frame
image. During concentration measurements, 10 frames of images can be taken in 1 second. For
each type of surrogate aerosol product, 250 frames of images were taken for the concentration
measurements, and 24 frames were taken for velocity measurements. For each aerosol test, the
imaging time is about 1 hour for concentration distribution measurements and 3 hours for velocity
measurements.
After the image acquisition procedure, the data are analyzed to obtain velocity, size and
concentration distribution information. Normally, for concentration measurements, 10 frame
images are taken as 1-minute transfers for average data, and as 10-minute transfer for
concentration distribution data. For velocity measurements, one interrogation spot requires 0.3
second and one frame image containing nearly 10,000 vectors. Approximately 1 hour is required
for a relative velocity vector map. Therefore, it takes approximately 6 hours to obtain
concentration information, and 26 hours to obtain velocity distribution information.
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Table 13.D Aerosol particle concentration distribution in environmental chambers — PIV system
costs.
Component
Video Camera
Frame Grabber
Halogen Lamp
Host Computer
Software
Peripheral Equipment
Particle Counter
TOTAL
Quantity Needed
1
1
5
1
1
1
10
Price / Component
$2000-$3000
$4500-$5000
$20-$30
$5000-$6000
$2500
$5000
$10000
$29,1 00-$31, 650
Table 14. Aerosol particle velocity distribution in environmental chambers - PIV system costs.
Component
Sinar p2 4x5 Camera
Lens
Frame Grabber
Halogen Lamp
Host Computer and Software
Optical Instrument and Table
Peripheral Equipment
Position Control Motor
Negative Reading Video
Light Instruments
TOTAL
Quantity Needed
1
1
1
10
1
1
1
1
17
Price/ Component
$5000
$1400
$15000-$16000
$ 20-$30
$20000-$25000
$20000
$5000
$10000
$1000
$5000
$82,600-$88,700
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In order for a PIV system to detect smaller particle sizes and in three-dimensions, a more
sophisticated camera is required. Table 15 estimates the cost of new PIV system.
Table 15. New PIV system costs for aerosol particle distribution measurement in an
environmental chamber.
Component
Digital Camera
Laser
Host Computer
Software
Peripheral Equipment
Pulse Generator
Photo Generator
TOTAL
Quantity Needed
1
1
1
1
1
1
6
Price/Component
$15, 000 -$20, 000
$15, 000 -$20, 000
$10, 000 -$15,000
$10,000
$1,000
$5,000
$1,000
$57,000 - $72,000
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7.0. Quality Assurance
Quality assurance activities were an integral part of this research program. The work
was conducted under the principles outlined in the U.S. Environmental Protection Agency's
AEERL Quality Assurance Procedures Manual for Contractors and Financial Assistance
Recipients (November 1991 Draft) and specifically applied to this research project through the
"Quality Assurance Project Plan for "Application of Pollution Prevention Techniques to Reduce
Indoor Air Emissions from Aerosol Consumer Products". The quality assurance plan was
prepared, revised, and approved prior to onset of the laboratory portions of the research project.
This project is a Category IV project, a research and development project in support of a
proof of concept. In this project tools and methods were developed for real-time characterization
of aerosol consumer products. Since this was a developmental research project, specific quality
objectives were developed during the project for each task based on the experimental objectives
and good laboratory practices.
7.1 Project Description
This research project was a cooperative agreement among academia, government, and a
group of Industry Partners (listed in Appendix 1). The primary objective of the project was to
develop characterization tools and methodologies that can be used by manufacturers to develop
pollution prevention strategies for aerosol consumer products. The Industry Partners stated that
the tools would be used to "develop the most efficacious and least toxic" products. This objective
was met by:
1.D Designing the AMSI for spatial chemical compositional characterization of
aerosol consumer products;
2.D Application of PIV and PIV/environmental chamber technology to particulate
characterization of aerosol consumer products; and
3.D Transferring of the technology among industry, governmental agencies, and
researchers.
The tools from this research project are the starting point for development of standard methods
for aerosol analysis by the aerosol industry. Once these standard methods are developed,
pollution prevention strategies can be formulated.
7.2 AMSI Development
The AMSI had to provide spatial chemical compositional data. The ability of the AMSI to
provide quantitative data also had to be shown. In order to meet these requirements, standard
aerosols were generated from authentic standard compounds of SLS, BC, ethanol, and water so
that comparisons to the MS data from the surrogate aerosols and the authentic standards could
be made. This ascertained that the MS identifications were accurate. Results from authentic
standards obtained from a chemical supply house and from bulk standards obtained from the
Industry Partners were compared. The bulk SLS standard from the Industry Partners contained a
traceable impurity. This impurity was detected in the surrogate aerosols containing SLS. The
spectra obtained from the surrogate aerosols had to match the spectra obtained from the
authentic standards.
The standard aerosols were also used to generate a series of standards of known
composition so that the potential for quantitation could be assessed, and to understand the limits
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of the analytical system (Figure 2). These were generated in aerosol form with the OCN. The
AMSI/MS was found to go out of linearity, severely affecting quantitation accuracy at greater than
80% aerosol composition.
Reproducibility of response was an additional issue for the AMSI. Multiple sprays of the
surrogate aerosols into the AMSI/MS (Figure 16) determined reproducibility. Reproducibility was
found to be within 5% of the standard deviation from the mean peak area. The greatest source of
error was found to be the operator pushing the aerosol actuator button. With practice, an
operator can achieve the 5% reproducibility. Reproducibility was determined by comparing the
area counts from replicate analyses. The relative standard deviation was calculated from a
minimum of five repetitive injections.
7.2.1 OCN Calibration
The particle size generated by the OCN was calibrated using the Malvern analyzer, which
was calibrated using a standard calibrated glass graticule. The graticule was referenced to
optical microscopy measurements, referenced to NIST standards. The chemical composition of
the OCN generated aerosol was determined by comparison to flow injection of the authentic
standards of SLS, BC, ethanol, and water. Flow injection was accomplished by using a syringe
pump to flow the standard solution into the MS. All authentic standards were prepared in HPLC-
grade methanol.
7.2.2 MS Calibration
The PBMS and API systems were tuned to manufacturers' specifications. (All instrument
operators are trained in the tuning specifications of the instrument. The tuning instructions are
available in the instrument manuals, which are stored in the rooms housing the MS's.) The
PBMS systems used PFTBA to calibrate with tuning algorithms supplied with the instruments.
The API was tuned to manufacturers' specifications for a mixture of polyethylene glycols. The
tuning parameters of each MS were adjusted for maximum sensitivity for detection of SLS by flow
injection of an SLS authentic standard. (Authentic standards were analyzed for each of the
analytes in the surrogate aerosols, but tuning with SLS optimized the analytical system for the
aerosol analyses. SLS had the lowest instrumental response of the surrogate analytes. By
maximizing on SLS, maximum sensitivity was achieved.) Instrument calibrations were performed
daily for each day of operation for multiple points. The instruments had to achieve calibration
within 5% of the tuning specifications before analyses were performed. These specifications
included peak height, peak shape, and isotopic abundance of at least four ions in the calibration
compounds. If an instrument did not achieve the specified response, corrective maintenance
procedures were taken prior to sample analyses.
7.3 PIV Analyses
The PIV and PIV/environmental chamber systems had to provide accurate velocity
measurement data for the calculation of particle concentration distribution data. Table 16
summarizes the capability and accuracy of the PIV measurement system. The velocity
measurements obtained from the PIV were compared, whenever possible, to LDV data, a more
conventional method of analysis. Particle concentration measurements were calibrated with an
optical particle counter, which is calibrated by the manufacturer. These data were compared with
aerodynamic particle sampler data. The experimental derived velocity statistics were compared
to computer simulations and LDV measurements. The laser generator, controller, pulse
generator, photodetector, cameras, frame grabbers, and host computer were tested according to
the manufacturers' specifications. Each operator was trained in the proper operation and testing
of the instrumentation. The system was referenced to known standards.
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Precision of the measurements was obtained by collecting the samples in replicate to
reduce experimental error. For the velocity measurements, 24 replicates were done and the data
were averaged. Ten to 12 replicates were performed for the concentration measurements. The
number of replications was based on an analysis of variance based on the F-test among the
replications.
Statistical data analysis techniques were used to process the measurement data. This
reduced the measurement errors to within 5% limits and established confidence in accuracy of
the analytical results. Standard data processing programs were used to obtain the concentration
contour plots, velocity vector maps, and the size distribution curves as a function of time and
spatial location.
7.3 Surrogate Aerosols
The surrogate aerosols were supplied in two batches to the university researchers.
Stability, based on chemical composition, was monitored by MS analysis. Early in the project, it
was found that the surrogate aerosols using carbon dioxide as the propellant were unstable,
since corrosion prohibitors were not included in the surrogate aerosols. These surrogate
aerosols were used within a few days of receipt and then not used again during the project.
Replicate analyses were used to monitor the stability of the other surrogate aerosols. Differences
between the surrogate aerosol batches were less than 10%, and were considered to be
insignificant, since this was a method development project. The surrogate aerosols were merely
a means to develop the tools and methodologies, rather than being exact measurements.
Uniformity between batches sent to the two university laboratories was not an issue since each
laboratory developed tools for different characterization issues.
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Table 16. Summary of PIV system capability and accuracy.
AEROSOL JET MEASUREMENT SYSTEM
Size
Distribution
Concentration
Velocity
View Field
11.0 x 7.5 mm
200x150 mm
200 x 150 mm
200 x 150 mm
Capability
>1 |im
> 18 |im
Accuracy
Varies
inversely with
particle size
Depends on calibration
system. Accuracy of
relative concentration
measurement is high
> 18 |im
5%
Evaluation
Approximates
a point
measurement
technique
Capable of
measuring air
& particle
velocity as a
function of
particle size &
density
Alternate
Measurement
Methods
Particle
Counter,
Malvern
Analyzer
No alternate
whole field
method
No alternate
whole field
method
ROOM AIR MEASUREMENT SYSTEM
Concentration
Velocity
200 x 150 mm
2000x1500
mm
200 x 150 mm
Depends on calibration
system. Accuracy of
relative concentration
measurement is high
> 18 |im
> 1 80 |_im
5%
Cannot
resolve
individual
particles
Capable of
measuring air
& particle
velocity as a
function of
particle size &
density
Capable of
measuring
velocities of
room air &
large particles
in large flow
fields
No alternate
whole field
method
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8.0 Referencesn
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Problems, EPA-230/2-87-025a-e (NTIS PB88-127030). Office of Policy, Planning and
Evaluation, Washington, DC, 1987.
2.D U.S. EPA. Reducing Risk: Setting Priorities and Strategies for Environmental Protection,
SAB-EC-90-021. Science Advisory Board. Washington, DC, 1990.
3.D Pollution Prevention Act of 1990, Public Law No. 0-508, Vol. 42 U.S.C. Sec 13101-
13109. (West Supp. 1991). 1990.
4.D Habicht, Henry F., II. Memorandum: EPA Definition of Pollution Prevention. U.S. EPA,
May 28, 1992.
5.D Chemical Specialties Manufacturers Association. The Consumer Products Handbook.
Inc., Washington, DC, 1992.
6.D Spurny, K.R. Physical and Chemical Characterization of Individual Airborne Particles;
K.R. Spurny, Ed.; Halsted, a division of John Wiley & Sons, New York, NY, 1986; p. 17.
7.D Lehtimaki, M., and Willeke, K. "Measurement Methods." In Aerosol Measurement:
Principles, Techniques, and Applications, ed. K. Willeke and P.A. Baron, Van Nostrand
Reinhold, New York, NY, 1993, p. 112-145.
8.D White, A.W.C., Martin, R., and Lowe, J.A. The importance of particle size analysis in
spray systems. Spray Technology, Product Development/International, 1993.
9.D Graynor, A. Spray Pattern Duality: A Scientific Dilemma. Research & Development,
1993.
10.D Spagnolo, G.S., and Paoletti, D. Automatic system for three fractions sampling of
aerosol particles in outdoor environments. J Air & Waste Management Assoc 44: 702-
706(1994).
11 .D Chemical Specialties Manufacturers Association. Aerosol Guide, 7th edition, Washington,
DC, 1981, p. 119-120.
Chemical Specialties IV
DC, 1981, p. 121-123.
12.D Chemical Specialties Manufacturers Association. Aerosol Guide, 7th edition, Washington,
13.D Chemical Specialties Manufacturers Association. Aerosol Guide, 7th edition, Washington,
DC, 1981, p. 77-78.
14.D Nordmeyer, T., and Prather, K.A. Real-time measurement capabilities using aerosol
time-of-flight mass spectrometry. Anal Chem 66: 3540-3542 (1994).
15. Prather, K.A., Nordmeyer, T., and Salt, K. Anal Chem 66: 1403-1407 (1994).
16. Winkler, P.C., et al. Anal Chem 66: 1403-1407(1994).
17.D Lui, D.Y., Rutherford, D., Kinsey, M., and Prather, K.A. Real-time monitoring of
pyrotechnically derived aerosol particles in the troposphere. Anal Chem 69: 1808-1814
(1997).
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18. Qian, M.G., and Lubman, D.M. Anal Chem 67: 234A-242A (1994).
19.D Dorman, S. Spray Technology & Marketing's 10th annual new product roundup. Spray
Technology & Marketing, August: 24-40 (1993).
20.D Greaser, C.S., and Stygall, J.W. Particle beam liquid chromatography-mass
spectrometry: Instrumentation and applications. Analyst 118: 1467-1480(1993).
21 .D Noble, C.A., et al. Aerosol characterization using mass spectrometry. Trends in
Analytical Chemistry 13: 218-222(1994).
22. D Bayer, C.W., et al. Design of an aerosol mass spectral interface. Engineering Solutions
to Indoor Air Quality Problems, Air & Waste Management Association, 1997, in press.
23. Veltkamp, P.R.,efa/. J Geophy Res 101(014): 19495-19504(1996).
24. Henry, R.C.,etal. Atmos Environ W: 1507-1515(1984).
25.D Breiman, L, et al. Classification and Regression Trees, Wadsworth Int. Group, Belmont,
CA, 1984.
26.D Breiman, L. Automatic Identification of Chemical Spectra, Technical Report, Technology
Service Corporation, Santa Monica, CA, 1978.
27. D Huang, E.G., et al. Atmospheric pressure ionization mass spectrometry. Anal Chem 62:
713A-724A(1990).
28. Wachs, T., et al. Liquid chromatography-mass spectrometry and related techniques via
atmospheric pressure ionization. J of Chromatog Sci 29: 357-369 (1991).
29.D McLuckey, S.A., Glish, G.L., and Grant, B.C. Simultaneous monitoring for parent ions of
targeted daughter ions: A method for rapid screening using mass spectrometry/mass
spectrometry. Anal Chem 62: 56-61 (1990).
30. Wiloughby, R.C., and Browner, R.F. Anal Chem 56: 2626 (1984).
31.D Ho, S.Z. Aerosol sample introduction mass spectrometry. Ph.D. Dissertation, Georgia
Institute of Technology, Atlanta, GA. August 1997.
32. D John, W. "The Characteristics of environmental and laboratory-generated aerosols." In
Aerosol Measurement: Principles, Techniques, and Applications, ed. K. Willeke and P.A.
Baron, Van Nostrand Reinhold, New York, NY. 1993, p. 60.
33.D Cui, M.M., et al. A study of structure of spray cones utilizing digital particle image
velocimetry. Engineering Solutions to Indoor Air Quality Problems VIP-51, Air & Waste
Management Association, 1995: pp. 214-225.
34. Lee, R.E., Jr. Science. 178: 567-575,4061(1972).
35.D Wiener, B.B. "Particle and droplet sizing using Fraunhofer diffraction." In Modern
Methods of Particle Size Analysis. Ed. H.G. Barth, John Wiley & Sons, New York, NY,
1984.
36.D Adrian, R.J. Particle-imaging techniques for experimental fluid mechanics. Annual
Review of Fluid Mechanics 23: 261-304(1991).
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37.D Keane, R.D., and Adrian, R.J. Optimization of particle image velocimeters. Part II:
Multiple pulsed systems. Measurement Science and Technology 2: 1202-1215 (1990).
38.D Meinhart, C.E., Prasad, A.K., and Adrian, R.J. A parallel digital processor system for
particle image velocimetry. Measurement Science and Technology 4: 619-626 (1993).
39.D Cui, M.M., et al. A novel, whole-field, non-intrusive diagnostic technique for improvement
of indoor air quality. Engineering Solutions to Indoor Air Quality Problems VIP-51, Air &
Waste Management Association, 1995; pp. 95-99.
40.D Wu, J., et al. Adjustable room ventilation simulator for room air and air contaminant
distribution modeling. Indoor Air'90. Proceedings of the Fifth International Conference
on Indoor Air Quality and Climate 4b: 237-242 (1990).
41 .D Bayer, C.W., and Browner, R.F. Characterization of aerosol consumer products.
Engineering Solutions to Indoor Air Quality Problems VIP-51, Air & Waste Management
Association, 1995; pp. 205-207.
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9.0. Appendix 1
Industry Partners
1 .D Armin Globes, Ph.D. (Chair)
SC Johnson Wax
1525 Howe Street, MS 145
Racine, Wl 53404
414-631-2351 FAX: 414-631-4428
2.0 G.P. Ananth
SC Johnson Wax
1525 Howe Street, MS 145
Racine, Wl 53404
414-631-2113 FAX: 414-631-4015
3.D Ron M. Davis
CCL Custom Manufacturing
1 West Hegeler Lane
Danville, IL 61832
217-442-1400 FAX: 217-442-0902
4.D John DiFazio
Chemical Specialties Manufacturers Association, Inc.
1913 Eye Street, NW
Washington, DC 20006
202-872-8110 FAX: 202-872-8114
5.D Douglas Dykstra
Guardsman Products, Inc.
2960 Lucerne, SE
Grand Rapids, Ml 49546
616-285-7857 FAX: 616-285-7870
6.D William A. Frauenheim III
Diversified CPC International, Inc.
PO Box 490
Channahon, IL 60410
815-423-5991 FAX: 815-423-5627
7. Larry Jacobs
Procter and Gamble
5299 Spring Grove Avenue
Cincinnati, OH 45217
513-627-6090 FAX: 513-627-6668
8. Carleen Kreider
Seaquist Valve
1160 N. Silver Lake Road
Gary, IL 60013
708-639-2124 FAX: 708-639-1186
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9.D Robert P. Paulein
Chemical Specialties Manufacturers Association, Inc.
1913 Eye Street, NW
Washington, DC 20006
202-872-8110 FAX: 202-872-8114
10. Douglas Raymond
Sprayon Products
26300 Fargo Avenue
Bedford Heights, OH 44141
216-498-6049 FAX: 216-498-6140
11. Bryan R. Ruble
SC Johnson Wax
1525 Howe Street, MS 122
Racine, Wl 53403
414-631-2443 FAX: 414-631-3752
12. Dennis Stein
3M Company
3M Center Building, 225-3N-02
St. Paul, MN 55144-1000
612-736-1596 FAX: 612-736-9278
13. Laura Vaccaro
Reckitt and Colman
1 Philips Parkway
PO Box 425
Montvale, NJ 07645-0425
201-573-636 FAX: 201-573-6046
14. Theodore Wernick
Gillette Company
401 Professional Drive
Gaithersburg, MD 20879
301-590-1543 FAX: 301-590-1535
15. Jesse Williams
Bissell, Inc.
PO Box 1888
Grand Rapids, Ml 49501
616-791-7740 FAX: 616-453-1383
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