EPA-600/2-78-001
January 1978
Environmental Protection Technology Series
        PERSONAL  MONITOR  FOR  NITROGEN  DIOXIDE
                                        Environmental Sciences Research Laboratory
                                             Office of Research and Development
                                             U.S. Environmental Protection Agency
                                      Research Triangle Park, North Carolina  27711

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                RESEARCH REPORTING SERIES

Research reports of the Office of Research and Development, U.S. Environmental
Protect on Agency, have been grouped into nine series. These nine broad cate-
gories were established to facilitate further development and application of en-
vironmontal technology.  Elimination of traditional grouping was consciously
planned to foster technology transfer and a maximum interface in related fields.
Th3 nire series are:

      1.  Environmental  Health Effects Research
      e'.  Environmental  Protection Technology
      o.  Ecological Research
      i.  Environmental  Monitoring
      £>.  Socioeconomic Environmental  Studies
      £>.  Scientific and Technical Assessment Reports (STAR)
      /'.  Interagency Energy-Environment Research and Development
      £•.  "Special" Reports
      £'.  Miscellaneous Reports

This report has been assigned to the ENVIRONMENTAL PROTECTION TECH-
NOLOGY series. This series describes research performed to develop and dem-
onstrate instrumentation, equipment, and methodology to repair or prevent en-
vitonmental degradation from point and non-point sources of pollution. This work
pravidus the new or improved technology required for the control and treatment
of pollution sources to meet environmental  quality standards.
This document is available to the public through the National Technical Informa-
tion Service, Springfield, Virginia 22161.

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                                         EPA-600/2-78-001
                                         January 1978
   PERSONAL MONITOR FOR NITROGEN DIOXIDE
                     By

   Philip W. West and Kenneth D. Reiszner
         Louisiana State University
  and Agricultural and Mechanical College
            Chemistry Department
        Baton Rouge, Louisiana 70803
            Grant No. 803193-01
              Project Officer

              Eva Wittgenstein
 Atmospheric Chemistry and Physics Division
 Environmental Sciences Research (Laboratory
Research Triangle Park, North Carolina  27711
 ENVIRONMENTAL SCIENCES RESEARCH LABORATORY
     OFFICE OF RESEARCH AND MONITORING
    U.S. ENVIRONMENTAL PROTECTION AGENCY
RESEARCH TRIANGLE PARK, NORTH CAROLINA  27711

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                            DISCLAIMER

This report has been reviewed by the Environmental Sciences Research
Laboratory, U.S. Environmental Protection Agency, and approved for
publication.  Approval does not signify that the contents necessarily
reflect the views and policies of the U.S. Environmental Protection
Agency, nor endorsement or recommendation for use.
                                ii

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                          ABSTRACT
An attempt has been made to develop a personal monitor for assaying
nitrogen dioxide in ambient air.  N02 is collected from the ambient
air by permeation through a silicone membrane into a alkaline thymol
blue solution.  The N02 is converted to nitrite  and determined
colorimetrically.  Maintenance of a carefully controlled flow rate
is not required because the rate of absorption is controlled by
permeation.  The monitor which is sealed may be worn in any
orientation that does not restrict free air movement to the
membrane.

Although it is sensitive to ambient air concentrations of nitrogen
dioxide and exhibits essentially linear response to this pollutant
up to the OSHA limit of 10,000 ug/m3, field evaluation indicates
the monitor yields a much higher ambient air value than that
obtained by the accepted EPA-TGS-ANSA method.  The effect of
temperature and sunlight on the monitor is minimal and other common
pollutants including nitric oxide do not affect the response of the
monitor.

This report was submitted in fulfillment of Grant No. 803193-01
(Grantee Account No. or Identifying No. 115-20-5135) by the U.S.
Environmental Protection Agency.  Work was completed as of 6/30/75.

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                                   CONTENTS

Aostract                                                              iii
Figures                                                               vi
Tables                                                                vi
Sections
1  Introduction                                                       1
2  Conclusions                                                        4
3  Recommendations                                                    c
4  Experimental                                                       6
5  Selection of an Absorber                                          11
6  Selection of a Membrane                                           15
7  Evaluation of Method                                              18
8  Discussion                                                        24
References                                                           25
Inventions                                                           26

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                             FIGURES
Np^                                                        Page
1     Clean Air Preparation Apparatus                       7
2     Personal Monitor                                      9
3     Effect of temperature on Permeability                 16
k     Response Time                                         17
                              TABLES
No.;.                                                         Page
1     Absorber Efficiency                                    12
2     Stability of Absorbed N02 in Thymol-NaOH               Ik
3     Interference Studies                                   19
U     Linearity                                              20
5     Field Valuation                                       22
6     Spiked Air Samples                                     23
                                vi

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                           SECTION |;
                           INTRODUCTION
GENERAL
There has been an obvious need for reliable methods which can be used
for measuring the air pollution levels to which individuals are exposed.
Such personal monitoring seriously restricts* the type of method that
can be used since measuring and/or sampling devices must be consider-
ably, smaller and lighter than those used conventionally.
The need for improvement over present methods encouraged us to develop
methods for determining the average concentrations of S02(l) and CO(2)
in the air using a sampling technique based on gas permeation.  The
sampling step involves placing an absorber on one side of a permeable
membrane while the other side is exposed to air.  The pollutant to be
measured permeates through the membrane at a rate proportional to
concentration and reacts or is absorbed by a suitable absorber.  The
absorbed pollutant or reaction products of the pollutant are then deter-
mined by conventional methods and the concentration is calculated using
a predetermined calibration constant.
The purpose of this project was to develop a personal monitor for N02
based on this unique sampling approach.  Sampling by permeation is
particularly useful for personal monitoring because hardware for such
a monitor can be extremely small and lightweight.  Maintenance of a
carefully controlled flow rate is not required because the rate of
collection is controlled by permeation; consequently, the need for
auxilliary air pumps, flow-meters, critical orifices, flow controllers,
bubblers and impingers is obviated.  Generally these monitors provide
a reliable, sensitive and specific response to individual gases by
careful selection of absorbers and permeable membranes.
OBJECTIVE
The primary objective of this study was to develop a personal monitor
for the determination of the average concentration of N02 in the air.
The proposed system was to involve sampling by permeation through a

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 polymer membrane as with the methods previously described  for S02 and
 CO.  The  permeated pollutant was  then to be absorbed in an appropriate
 medium and  determined by a suitable analytical procedure.   The final
 prototype of the personal monitor was to be- as simple and  compact as
 possible.  •  L   ;.-,/.•   •      .   v   .   •   • .   ; ^   •       ...  • .   .'..-:
 PROGRAM APPROACH      '                              !    ;
 'Several requirements must be met  for the successful development of a
 method based on the permeation sampling * approach* -Firs t$" an absorber
c must be foun<}r£hat irreversibly: absorbs the gasepus^pollutant ,to yield
ja, stable  product;.  Additionally,,  t his. product^must M?jB;>^as4.1y measurable
 and'should  b%form|!ds%>asi,am0un?;,BroportAonauti,tp th^, amount^ o|,b ?i
vt>d^9tapt\ab€or^.ad.;  -Nejrt:, a, mjeplwra^e musfebe obtaAne^ $ha£ ^h^ghly
5>f eTOeab|£!;.to ^h& particular gas^fo.-. b^i measured.^ yet ihaar ft  permj ab-iJ4ty
 whiiah
 system, musfe be sfreea.ofe
                              n- inv^We^a^^dy Wf
 herent  difficulty in methods whl^h
 EPAl (Jacob.s*Hophheise.r ^^«t^od)i^appi?p^h:;(5',^)fi,,|iaj^,jje|: .pjjoyedT satis r
:rfactory,. triethanplamine $as $£py.ed rt& bp p
 Other absorberaiisuchi.asrcithafe used ,.4.n- »th«., Saltjzpan,
 effdcient but Ucj^djfcsiresd,. stability. ,  .^he -first, strep in,,.this; .investi-
 gation vas .to examine the -ef fij?;Leticy of the conversion of N02 to M>2
 -by, 'various .fcbsorbers.'  ,Twa absorbers werre ,,atudie^l_ which: gavje, Mgh ,,
 absorption cifficienc^.  [Continued 'studies, of the ^stabijlity of. .absorbed
 nitrogen Dioxide. .resulted  in one absqrb^ei: being,vd.ijscar.ded. -The, .effect
 of  temperature, time and. .exposure -.to siyi].ight ,on the absorbed . species
 was  determined because of  the  effect these parameters would have on
 the  versatility and reliability of the final measuring device.   The
   '                                        '    '                  '
                               .      .               .      ,    ...
 determination of nitrite was  carried out by conventional diazotization
 '••  •  •-•;' i '  ? 'V ": • i-.''' /• •"<=:.."  .  ..::  •  .•  • .-•' : :.i^  a.;" •' ^i>^:-*.±^ •••  ••<-*. •., •
 and  coupling procedures.
          '               '             '                "                ''

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After a satisfactory absorbing system had been selected, a thorough
study of the permeability properties of silicone rubber was made.
Additionally, an interference study was carried out on the common
possible interferences.  After completion of the laboratory investi-
gations, field evaluation was carried out.  Although all former studies
indicated that under field conditions the method should work reliably,
the field data from the permeation device were about 200 percent high-
er than that obtained from the TGS-ANSA EPA procedure (7,8),.  Future
studies should be directed to eliminate or find what is causing this
discrepancy.

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                             SECTION |
                            CONCLUSIONS
A personal monitor  for measuring NOg concentrations has been developed.
It is considerably  smaller,  lighter and more convenient to use than
other equipment available.   The unit as described, weighing only 56
grams, could undoubtedly ,be reduced even further in size and weight.
All laboratory evaluations  of the developed method indicate that the
monitor, should work reliably.  The method is free, of interference  from
     1            ' "• '' •'•<••' '-'  •'  • »-:->--'  .'•'  'V _i  ".'.'.i~--. '. •-v Si'-  ...:."">;: is L'yiCt, . "!
the common pollutants in the air and is essentially unaffected by  -.
                                                         . \2-..^'.;.>T'.XCJt>
changing environmental conditions.  Unfortunately the field evaluation
revealed a discrepancy between the method developed here and an EPA
developed procedure.  Until this discrepancy is resolved the method
should not bo used  at ambient levels of N02.  The discrepancy dees
not invalidate the  procedure at the much higher occupational levels.
                                 > .4

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                            SECTION 3
                         RECOMMENDATIONS
Although extensive laboratory evaluations indicated the method develop-
ed should work reliably, there was a definite difference between the
field data obtained with the permeation device and that obtained with
the current EPA procedure.  It is recommended that future investiga-
tions attempt to determine what caused this discrepancy.  This work
should include field evaluation at a more conventional sampling site
than the one used here.  Samples for this work were collected
adjacent to a building containing numerous chemical laboratories.
It is also recommended that field evaluation of the device be carried
out at more conventional occupational levels which are often orders
of magnitude larger than amlient levels.

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                            SECTION  ,4
                           EXPERIMENTAL
PREPARATION1OF N02 TEST ATMOSPHERES
        • ...    .... - r.'x          '         >
The large wlumes of air required  for  these  investigations necessitated
the use oi: an ambient air  cleanup  assembly.   Tank air could not conveni-
ently be supplied in required  quantities.  Air ftma the laboratory was
decontaminated by pumping, it over  a. humidifying solution XjwfReagi^s)
through a series of chrornate oxidizers and.NO^ sensitized, charcoal
absorbers (^ep,tion4|^|rand finallv over.a^tiya,t:ed4>cl^arcoa(^ (Fig.: f),,
NQ detectable.amquat -of pp or^NQgwa^. found.  4-n. thi^ajr^  The aj.r was
further dri-ed w£th sil|.car,gelr so,.,t;hat  permeation tuibe!8Qu8edc:Jn-these
investigat:ions would not deter£px,aJ:e,A -JChe.. h^umidify^jag^ solution yas
changed daily and the sensitized charcoal  absorbers vere changed as
needed to maintain  a NO and N02 free  air  stream.  Experience dictated
that about 500g of sensitized  charcoal was needed per day when air was
used at a flow rate of 10  1/min.
Decontaminated air was mixed with  dry  air  that had been passed over
selected permeation tubes or through an ozone generator for the prep-
aration of test atmospheres.   The  test air had an estimated relative
humidity of TO percent and was practically free of C02 because the
N02 absorbers were alkaline.   The  permeation tubes were prepared in
this laboratory by procedures  similar  to those of other authors (9)•
Phosphorus pentoxide was placed inside each  tube to insure more reliable
permeation rates.
REAGENTS
Reagentn and chemicals were ACS reagent grade.  High quality deionized
water was used in preparing all solutions  as well as for making up
losses due to evaporation.
Alkaline Thymol Absorber—Two  tenths gram  of thymol (5-methyl-2-
isopropylphenol)  and kg of sodium hydroxide were dissolved in 100 ml
of water and dilluted to 1 1.

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                     N02  Absorbers
   Silica  Gel
Air in
 PU
"7
                                         K     •
     Humidifier
Activated
                ,. Dry
                  Air
                          Oxidizers         Dehumidifier
                      Figure 1. Clean Air Preparation Apparatus
                                                                Free  Air

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N-(l-napl:hyl)»ethylenediamine (0.05 percent)--fifty milligrams of
N-(l-napt:hyl)-ethylenediamine were dissolved and made up to 100 ml with
water.
Sulfanilami.de in Phosphoric Acid—Thirty-five grams of sulfanilamide
were dissolved in 250 ml water and 250 ml of phosphoric acid.
TGS-ANSA—The reagents for the EPA procedure were made up according to
specifications of Ftrerst and Margeson (8) (appendix D page 37) which
are essentially the dame as the original .method described by Mulik
et. al. (7).
Chromate Oddizer—Ten grams of sodium dichrornate   and 10ml of sulfuric
acid were mixed in water and diluted to 500ml.  After saturating 500g
of silica f?el (8-l6 mesW with water by placing it in a 100 percent
relative humidity environment^for.seYerjJ dayi, the silica gel was add-
ed tp the chromate*solution and allowed to; stand overnight.  The excess
liquid was decanted and the. impregnated.gel was dried.
Sensitized Charcoal Absorbers--Thirty grams^of sodium hydroxide and
1.5g of thymol were dissolved In 150ml water. Tfiis solution was added
to 500g of 6-1^ mesh charcoal ant immediately dried mujer vacuum.
Humidifying-Solution-'Tteenty-five grams af sodium hydroxide and Ig
of thymol were dissolved in §00 m-1 water
APPARATUS
A Beckman IB with 1 cm cells was used throughout these investigations.
The permeation device used in most of the laboratory and field tests
and a suitable exposure chamber was described by Reiszner and West (1).
Neoprene rubber stoppers were substituted for the gum rubber stoppers
used in the original permeation device for reasons given elsewhere in
this report,  the N02 personal monitor shown in figure 2 was sealed
with a 1/16 in.- thick silicqne rubber o-ring.
SAMPLING
Ten milliliters of the alkaline thymol absorber were used to charge
the permeation device or personal monitor.  The monitor was shielded
from direct sunlight so as not to exceed more than 1 hour of exposure
                                 6

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          (.330cm)

           0.130"       (3-81 cm)

                        1.5'
         tir-
Aluminum
                          (4.45cm) »-••

                         . 1.760"	*
           K-
                !.25
                     (5.72cm)
   Membrane
                       (3.81cm)
       0.130
       (. 33 cm)
         h	1.750"
                      (4.45 cm)


                      (5.72 cm)
                           II
                      2.25   -
.  •!•
>f«.nn:
       T  .,
       0.25 (.64cm)
       _S   Tapped  for
             4-32 Screw
                                   } — 1 ^  I.D. x !/8  thick

                                                    0 - ring
                .".".';0.346'.1(.88cm)    r^
                 l.V	__---_«.
•*!
                                  ^"Drilled
                                  'o 	

                                i,   I '/4"'( 64cm)


                                h/^(.79cm)
                                 -H
                                            Alumi num
             Figure 2.   Personal Monitor

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per sample period.  It was exposed to N02 only while attached  to the
prospective wearer.  Normal sampling periods varied from k hours to
5 days depending on the sensitivity and type of data required, however,
most of the development work was based on sampling times of  2k hours or
less,  evaporative losses were replaced as required to maintain  contact
between the liquid and the membrane.
ANALYSIS
The volume of the trapped sample, was adjusted to  10 ml by adding an
appropriate amount of deionized- water. •  One >milli liter each  of the
N-(,1-n«pt:l-yl) rethylenediamine and the sulfanilamide in phosphoric acid
solutions w 'as add«d and the solution. was stirred for  10 sec.  The
absorbaxice was measured at 5^5 nm between 5 and kO tain, after  the
addition of the color developing reagent* and the total amount. ojE N62 in
the solution was found from a calibration plot.   The concentration  was
calculated from the equation;
                                                                    (1)
where C = concentration qf N02, ug/"tn3
      t = sampling' isime; ,'.hj7
      w = amount of NO  in the ab^prberi ug
      k = constant, usually in the order of ^000 hr/m3.
                                10

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                            SECTION 5
                     SELECTION OF AN ABSORBER
The first step in the development of the NG2 personal monitor was the
selection of the absorber.  The alkaline thymol absorber, which was
first reported by Nash, (11) was chosen after also considering solutions
of triethanolamine, (5) and 0.1N sodium hydroxide.  All absorbers were
analyzed for N02 by the analysis procedure described in the experimental
section.  The 0.1N sodium hydroxide solution was tested because it was
an inherently simple system, and the problems of collection efficiency
(U) associated with this, absorber should be less pronounced in per-
meation sampling techniques because permeation permits much slower
absorption than conventional procedures in which air is bubbled through
an absorber.  This reagent was discarded after reproducibility problems
were encountered with its use as the absorbing reagent in the permeation
device.
Alternative absorbers were tested after erratic results were obtained
which were attributed to the 0.1N sodium hydroxide absorbing reagent.
Particular attention was given to the absorption efficiency of the
various absorbers shown in Table 1.  The efficiency was determined
using conventional coarse fritted glass bubblers.  The conversion
efficiency of N02 to N02 was 90 percent for the.alkaline thymol
(5-methyl-2 isopropylphenol) and 93 percentffor quaiacol (o-methoxyphenol)
(7) solutions and 87 percent for triethanolamine.  The data for guaiacol
(7) and triethanolamine (5) solutions correlated well with those re-
ported by other observers using similar absorbing systems.  Although all
three, absorbers worked well, the thymol absorber was chosen because
guaiacol displayed a slight positive interference with 03 due to the
formation of a colored oxidation product and triethanolamine blanks
were found to increase with time.  Of particular significance was the
fact that the alkaline thymol solution was essentially non-toxic and,
therefore, would not endanger the wearer of a personal monitor.
The effect of environmental conditions that a permeation device would
be exposed to were also considered in the selection of an absorbing
                                11

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                  Table 1.  ABSORBER EFFICIENCY
                                                 Percentage Conversion
Composition                                         of N0g to NOg*
Sodium hydroxide                                        (15-70)
Triethanolamine                                         87 (85)    (5)
Sodium hydroxide                                          90
  add thymol
Triethanolamine j guaiacol                                (95)      (7)
  and sulfite
Guaiacol and sodium hydroxide                             90
"Literature values in parenthesis
                                12

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reagent.  Both guaiacol and thymol solutions darken upon standing
in direct sunlight; however, only moderate shielding was necessary
to eliminate this effect and no shielding was required indoors.
Exposure of the thymol absorber to direct sunlight in a clear pyrex
flask for one hour yielded a value of about 0.05 ug/10ml NOg higher
than that of the anexposed reagent upon analysis.  This corresponded
roughly to the detection limit at the 95 percent confidence level
of the method and was equivalent to 10 ug/m3 for the standard permeation
device or personal monitor.  Therefore, it was considered unlikely to
have any significant effect from sunlight exposure unless the monitor
was exposed to sunlight for several hours because the person wearing
the monitor and the monitor itself will act to shield the absorbing
reagent from sunlight.  Even when the person wearing the monitor faces
the sun the membrane will substantially reduce the amount of light
transmitted to the reagent.
The study of the effect of environmental conditions on .an absorber
must naturally include the investigation of the possible loss of N02
while the monitor is sampling and during the subsequent storage period
before analysis.  The losses of absorbed N02 (i.e., N02) over a 29
day period as displayed in Table 2  were negligible when the thymol
absorber was maintained at J>0°C.  The absorber was also effective in
trapping N02 a month after preparation of the reagent and was efficient
after absorbing considerable quantities of C02.  Thymol dissolved in
sodium carbonate was found to be as efficient an absorber as the more
alkaline solution containing sodium hydroxide.
                                13

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                     Table 2.   STABILITY OF
                    ABSORBED NOg IN THYMOL-NaOH
Percentage Loss of                                Initial Concentration
NO;, in g) days at 3Q°C	ug/ 10ml  solution
          16                                               0.5
           3                                               2.Q
           3                                               lf.0
           3                                               8.0
           3                                              16.0
           3                                              32.0

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                            SECTION .6
                     SELECTION OF A MEMBRANE
The choice of a permeable membrane was of utmost importance to the
successful development of a personal monitor.  The membrane must be
highly permeable to N02, yet the permeability must be independent of
climatic variables.  The necessity of high permeability required that
a silicone membrane be used, however,  several different types were
available.  The first choice was the dimethyl silicone rubber that was
used in the development of the S02 permeation device (1), because it is
in general the most permeable of the silicone rubbers.  Fortunately no
further examination of membranes was-necessary because the rate of
permeation was sufficiently high and essentially free of temperature
effects.  There was only 0.25 percent change in the permeation rate
for a 1°C change in temperature when the device was operated over the
range from 0°C to 50°C (Fig. 3).  This is less than one would expect
with most battery operated pump samplers.  A personal monitor with an
11 cm2 membrane was found to detect as little as 10 ug/m3 for a 2U
hour sampling period or 50 ug/m3 for an 8 hr. sampling period.
It is interesting to note that permeation starts almost immediately
after exposure to N02 as evidenced in Figure h.  In this experiment
the exposed sample was removed and the permeation device was recharged
with unexposed reagent every 10 min.  Obviously the permeation rate
exceeds 90 percent of the equilibrium rate in the first 10 min.
                                15

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O)
O


O
JQ
k.
O
   0.25
   0.20
                  Figure 3.  Effect of Temperature on Permeability
                                                               I       I
                    10        20       30        40        50

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0.070
o»
« 0.050
0
(A
^%
A&
<
CM
g 0.030
o>
0)
0.010

O

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                           SECTION  7
                       EVALUATION OF METHOD
INTEKFER.2NCE STUDY
The tata from the interference studies are presented in Table III.
As cea b j eeen there was essentially no interference from rela-
tively high concentrations oflf^, 03, NH3 or HgS.  Although there
was fia interference at concentrations of NO an order of magnitude
higher than the N02 level, no interference was observed at NO levels
that Toirld normally occur in air.  It is interesting to note that the
effect a:: NO on the permeation device at a concentration 1000 ug/m3
N02 was i:he maximum that would be expected from the fact that the
permeation rate of NO is roughly 5 percent of that for N02 (12).
LINEARITY
Genese Hly» the permeation rate of a gas through a membrane is directly
propo -tlrftal to the concentration of that gas over many orders of
magni :u
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                Table 3,_.  INTERFERENCE STUDIES*
N02 ug/ms
Pollutant
S02
03
N%
H2S
NO
NO
NO
UE/m3
2500
500
1200
1700
7600
1000
100
Taken
100
100
100
100
876
100
109C
Found
107
105
106
87
971
153
116
Error^
+7
+5
+6
-13
+12
+53
+6
 Twenty hour exposure, average of three determinations.

 The standard deviation was 5 ug/m3 at 100 ug/m3 "N02-  The average of
-three determinations was used here.               '             •••'.

Measured by EPA procedure.
                                19

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                      Table 4..  LINEARITY


Taken
38
78
139
258a
k98*

1159
3953
10,700
Concentration, ug/m3
Permeation Device
U9
90
167
291
1^79
b
1159
M03
10,006

EPA Procedure (8)
37
78
1^2
272
14.50

HIT
NvD.
9908
The permeation tube, used din these experiments experienced a. somewhat
variable permeation rate.
Calibration

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blank values with the uncontamlnated air prepared by this procedure
it was found necessary to use fresjkly soaked and washed neoprene
rubber stoppers in the permeation devices.  Gum rubber stoppers can
cause high and varying blanks (8).  Contamination from rubber stoppers
does not occur with the personal dosimeter because it uses no rubber
seals and rubber does not come in contact with the absorbing reagent.
FIEU) EVAIBATION
Field testing a method is one of the most important aspects in the
development of a method.  Unfortunately the method was compared only to
the EPA procedure (TGS) and the data are difficult to interpret.  Lack
of time and equipment made further examination particularly at
occupational levels, infeasible.  Field evaluation consisted of sampling
air that had been drawn from directly outside the laboratory through a
single Teflon tube.  Simultaneous samples were taken by the permeation
procedure and the EPA procedure for periods of about fib hrs.  The data
from these studies which are shown in Table 5 indicate a dramatic
difference in the two analytical procedures.  A reasonable explanation
of the higher results obtained with the permeation device is not avail-
able at the present time, however, two experiments were designed to
characterize this phenomena.
The results of these two experiments are shown in Table T6».  Both
experiments involved spiking air in the laboratory with known quantities
of N02.  The data indicate that the permeation procedure and the EPA
procedure responded to the spike in roughly the same fashion that would
be expected by the laboratory evaluations i.e.  linearity, etc.  This
leads one to believe that both methods are working reliably and does
not yield an explanation of the field results from the two methods
which differ by a factor of about three.
                                21

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                    Table 5.   FIELD EVALUATION
                         Concentration,  ugj m£
Sampling Date            Permeation Device              EPA Procedure
    7-21                         85                          36
    7-22                        112                          31
    7-S^                         80                          29
    7-28                         9-S..                         36
    7-30                         ®k                          32
    7-31                         7fer                         25
                                22

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                  Table  6:.  SPIKED AIR SAMPLES

Concentration

Permeation Device
EPA Procedure
Permeation Device
EPA Procedure
AmbieAt
88
27
82
'-5fe
, ug/ms
Sj*ifc«d Ambient
197
97
215
1*
Difference,
Generated
85
85
92
92
, ug/m3
Found
109
70
133
102
*The permeation devices were charged with the EPA absorbing reagent.
 The calibration constant vas .assumed identical to that obtained with
 the alkaline thymol absorber.
                                23

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                             SECTION H'
             . _________  ......    DISCUSSION
 The permeation method described  here can detect as little as 30 ug/m3
 NO* based on the 95  percent confidence Level of the blank for an 8  hr.
  •         -  -. . '        -_.'?.•'        \ ,j     ...<•'
 sampling period and  as  little as 10 ug/m3 for a £h hr, sampling period.
 The monitor devised  to  use  this  method is extremely light-weight and
 compact and, can be easily worn by personnel- in the performance of the
          " -                   •'•^'          :J       <;-jj /_£ iro.r;r...>ar .-'.•-";:
^tnoflt demanding tasks without  restricting the wearers movements.  The
••••          •-                   >-'C.--           -4'.    .        ;•••.:;; 03 n OT'1 .V. '!
 method yields essentially  linear response to N02 from Uo to 10,000 ug/m3
    -' has practically  no  inteff erehc^e nfforn; other; .cjommpn-i aiTt; pollutants .
 However, there was a marked  discrepancyifb.etw.eexi .ambj,ents;ailfe j-evejsi
 that were obtained with the  new method and the EPA procedure that the
 method was compared with.  Laboratory studies indicated that both
 methods should work reliably.   It is as difficult to believe that the
 permeation procedure could yield results higher than the true concen-
 tration as it is to believe  that the EPA procedure could yield low
 values.  This is particularly  true in light of the fact that for the
 permeation device to respond excessively the permeation rate must
 change or some constituent in  the air must be chemically transformed
 to NO;:, at it passes through  the membrane and is absorbed.  A change
 in perme&tion rate is  inconceivable and the chemical transformation
 is considered to be unlikely.

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                           REFERENCES
1     Reiszner, K. D. and P. W. West.  Environ. Sci. Technol. 7: 526
      (1973).

2     Bell, D. R., K. D. Reiszner, and P. W. West.  Anal. Chim-Acta.
      77: 245 (1975).

3     Jacobs, M. B. and S. Hochheiser.  Anal. Chem. 30: 426 (1958).

4     Mauser, T. R. and C. M. Shy.  Environ. Sci. Technol. 6: 890 (1972).

5     Levaggi, D. A., W. Sui, and M. J. Feldstein.  Air Poll. Control
      Assoc. 23: 30 (1973).

6     Saltzman, B. E.  Anal. Chem. 26: 1949 (1954).

7     Mulik, J.;,5 R. Fuerst, M. Guyer, J. Meeker, and E. Sawicki.
      Intern.  J. Environ. Anal. Chem. _3: 333 (1974).

8     Fuerst, R. G. and J. H. Margeson.  pg. 36-47, Publication No.
      EPA-650/4-74-047, (1974).

9     O'Keeffe, A. E. and G. C. Ortman.  Anal. Chem. 38: 760 (1966).

10    Scaringelli, F. P., A. E. O'Keeffe, E. Rosenberg, and J. P. Bell.
      Anal. Chem. 42: 871 (1970).

11    Nash, T. J.  Chem. Soc., A, 3023 (1970).

12    General Electric Bulletin, GEA-8685A, "General Electric Permselec-
      tive Membranes," (1970).
                               25

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                  INVENTIONS AND PUBLICATIONS
A.  Personal Monitor for N02 Using the Permeation Sampling Approach,
    Reiszner, K. D. and P. W. West, in preparation.

B.  The fKL personal monitor could be considered an .invention.
                               26

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                                   TECHNICAL REPORT DATA
                            (Please read Instructions on the reverse before completing)
1. REPORT NO.
    EPA/600/2-78-001
                              2.
                                                           3. RECIPIENT'S ACCESSION-NO.
4. TITLE AND SUBTITLE

   PERSONAL MONITOR FOR  NITROGEN DIOXIDE
               5. REPORT DATE
                 January 1978
                                                           6. PERFORMING ORGANIZATION CODE
7. AUTHORS)
                                                           8. PERFORMING ORGANIZATION REPORT NO.
 P. tfest  and K. Reiszner
9. PERFORMING ORGANIZATION NAME AND ADDRESS
 Louisiana State University  and Agricultural
 and ftechnical  College Chemistry Department
 Baton  Rouge, Louisiana  70803
                                                            10. PROGRAM ELEMENT NO.
                  1TAB712
               11. CONTRACT/GRANT NO.


                803193
12. SPONSORING AGENCY NAME AND ADDRESS
 Environmental  Sciences Research Laboratory - RTPS  NC
 Office  of Research and Development
 U. S. Environmental Protection Agency
 Research  Triangle Park, NC   27711
                                                            13. TYPE OF REPORT AND PERIOD COVERED
                3 TYPE
                Final
               14. SPONSORING AGENCY CODE


                EPA/6QO/09
15. SUPPLEMENTARY NOTES
16. ABSTRACT
      An attempt was made to develop a personal monitor to measure nitrogen dioxide.
 Sampling of nitrogen dioxide  is  accomplished by permeation through a silicone
 membrane into a alkaline thymol  blue solution.  The  nitrogen dioxide is  converted to
 nitrite and is then quantitated  by colorimetric analysis.  Since collection of the
 nitrogen dioxide through the  silicone membrane depends only on permeation, maintenance
 of carefully measured sampling rates are not required.  A small-.scale field evaluation
 of this method with the accepted EPA-TGS-ANSA equivalent method  for N0'2 showed that
 the personal monitor gave much higher results.  This difference must be  resolved
 before this personal monitor  can be considered as  a  viable equivalent method for
 nitrogen dioxide.
17.
                                KEY WORDS AND DOCUMENT ANALYSIS
                  DESCRIPTORS
                                              b.IDENTIFIERS/OPEN ENDED TERMS
                             c. COSATI Field/Group
 *Air pollution
 *Nitrogen dioxide
 *Moni tors
                                 13B
                                 07B
18. DISTRIBUTION STATEMENT

  RELEASE TO PUBLIC
  19. SECURITY CLASS (This Report)
   UNCLASSIFIED
                                                                         21. NO. OF PAGES
33
                                              20. SECURITY CLASS (This page)
                                                UNCLASSIFIED
                                                                         22. PRICE
EPA Form 2220-1 (9-73)
27

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