United States
Environmental Protection
Agency
Municipal Environmental
Research Laboratory
Cincinnati OH 45268
I /
Research and Development
EPA-600/S2-84-144 Sept. 1984
&ER& Project Summary
Developing Methods for
Analyzing Oil Dispersants
in Seawater
D. L Haynes, D. G. Kelly, J. H. Smith, and E. L. Fernandez
A study was conducted to develop a
rapid, uncomplicated, sensitive method
for measuring the concentration of
surfactants that occurs in seawater
when oil dispersants containing them
are used for cleanup of spills. Data on
the fate of surfactants in oil dispersants
has been difficult to obtain because of
the inadequacy of current analytical
procedures, particularly under field
conditions.
Seven commercial dispersants now
used for oil spill cleanup were charac-
terized colorimetrically and found to
contain anionic and/or nonionic surfac-
tants, but no cationic surfactants.
The literature was reviewed to
identify suitable methods for collecting,
concentrating, and isolating surfac-
tants, and to select quantification
methods thought to be appropriate for
use in seawater. Based on this review, a
sorbent cartridge. Waters' SEP-PAK
C18>* was chosen as the primary tech-
nique for collecting and concentrating
surfactants from oil-contaminated sea-
water. High performance liquid chroma-
tography (HPLC) was selected as the
preferred separation technique. Two
detection or quantification approaches
were examined: (1) direct measurement
of the surfactant by tensammetry (a
polarographic technique) or by ultra-
violet (UV) spectrometry; and (2) Der-
ivation with phenyl isocyanate followed
by HPLC and UV spectrometry. Though
these methods are not applicable to all
oil dispersants, the derivation of poly-
*Mention of trade names or commercial products
does not constitute endorsement or recommenda-
tion for use
oxyethylated nonylphenol followed by
UV measurement was encouraging and
warrants further investigation.
This Project Summary was developed
by EPA's Municipal Environmental Re-
search Laboratory, Cincinnati, OH, to
announce key findings of the research
project that is fully documented in a
separate report of the same title (see
Project Report ordering information at
back).
Introduction
Surface-active agents (dispersants)are
being used more widely around the world
for the control and elimination of oil spills
on the sea. When applied to a coherent
spill or slick, such dispersants cause the
oil to break up into fine droplets that are
more readily dispersed and degraded by
natural chemical or biological processes.
Although researchers have been able
to study the changes in oil character and
concentration during treatment, the lack
of suitable analytical procedures for
detecting the dispersants, particularly
methods that can be used in the field, has
prevented in-depth study of their
behavior. Thus it has not been possible to
measure dispersant concentrations in
the water column or to investigate their
environmental fate.
The purpose of this investigation wasto
define the requirements for analysis of
surfactants and to develop one or more
analytical procedures that would be
suitable for field measurements at the
relatively low concentrations found in the
seawater column.
Colorimetric analytical methods are
widely used at higher concentrations.
They were applied in this program to
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characterize the anionic, nonionic, or
cationic nature of the surfactant
ingredients of several dispersants widely
used to treat oil slicks on seawater.
Combining this information with a
review of pertinent literature allowed the
authors to identify collection methods
and analytical methods suitable for
dispersants. Methods that have been
used for the analysis of surfactants and
dispersants, particularly in the
laboratory, included colorimetric
methods, gas chromatography, thin-layer
chromatography, and HPLC. Of the
methods known in the literature, the
latter was selected by the authors as the
most suitable for further evaluation. In
addition, a sorbent system was also
selected and evaluated as a technique tor
collecting and concentrating the
dispersant from a seawater sample.
Results
Commercial Dispersant
Characterization
Standard colorimetric tests were used
to identify the surfactant type in each of
seven commercial oil dispersants. These
tests indicated that both anionic and
nonionic surfactants are in use, either
alone or in combination, in these seven
dispersants (see Table 1). No cationic
surfactants were found.
Sample Collection and
Concentration
The literature review carried out by the
authors identified several sorbents for
surfactants. Sorption on carbon and silica
was reported to be irreversible, which
would make them unsuitable for
analytical purposes. Several porous
resins such as Rohm & Haas XAD-2 and
XAD-4 exhibit useful sorption properties,
as do ion exchange resins. These
materials may be preferred for larger-
scale experiments. The SEP-PAK Ci8
cartridge (Waters Associates, Inc.) was
selected for evaluation because no prep-
aration or pretreatment was required.
The sorbent consists of a reverse phase
liquid chromatographic packing suitable
Table 1. Oil Dispersant Types
for collecting samples from a polar
solvent such as water.
Collection was evaluated with the
model nonionic and anionic surfactants,
PEO nonylphenol and sodium lauryl
sulfate. Colorimetric tests were used to
measure the residual surfactant in the
cartridge eluate (methanol). Though
certain components of oil interfere with
the colorimetric analysis of nonionic
surfactants (at 610 nm), these
components were sorbed in the cartridge
and not eluted by methanol. With the
anionic surfactant, both seawater and oil
would normally interfere with the
colorimetric analysis. Fortunately, the
interfering species either pass through
the cartridge during the collection and
concentration step or are not desorbed by
methanol during the elution. Conse-
quently, they do not interfere with the
colorimetric analysis of the surfactants.
Quantitative recoveries of both surfac-
tants were achieved, even when starting
with samples too dilute for direct analysis.
Detection and Separation
Methods
As noted earlier, HPLC was selected as
the most appropriate technique for
separating the surfactant from the
samples after they had been collected
and isolated from a seawater-oil matrix
by the sorbent cartridge technique. The
two specific techniques evaluated for
detection and quantification were
tensammetry (a modified polarographic
procedure) after HPLC and derivation
coupled with a second HPLC separation
and UV detection of the derivatives.
An extensive evaluation of the
tensammetric procedure was carried out
using two different HPLC columns.
Waters' fj Bondapak C18 (reverse phase)
and Whatman's Partisil-10SAX, a strong
anion exchange resin, and various
solvent systems. However, it was
impossible to produce a system that
allowed (1) separation of both ionic and
nonionic surfactants, (2) sufficient
electrolyte to dissolve in the solvent for
the needed moderate-to-low cell resist-
Name of Dispersant Manufacturer
Corexit 9527 Exxon Chemical Co.
Gold Crew Ara Chemical Co.
Sea Master. NS 555 Whale Chemical Co.
BP J 100X BP North America
Conco K Continental Chemical Co.
Nokomis 3 Mi-Dee Formula 50 Nokomis International
AP Atlantic-Pacific
Surfactant Type
Anionic. nonionic
Anionic. nonionic
Nonionic
Nonionic
Nonionic
Anionic. nonionic
Anionic
ance, and (3) sufficient differences in cell
current for quantification at levels lower
than those measurable by other tech-
niques such as UV spectrometry.
Nonionic surfactants such as
ethoxylated alcohols can be derived with
phenyl isocyanate to yield urethanes with
UV absorption levels not attainable with
the original aliphatic surfactants. This
approach was applied to two of the
commercial nonionicdispersants, Corexit
9527 and Conco K, as well as to a
standard, polyethoxylated nonylphenol.
After derivation, the surfactant was sep-
arated by HPLC and measured by UV
spectrometry. Both the POE nonylphenol
and Corexit 9527 produced strong
responses at the test level of 2500 ppm.
The method is described more fully in the
report. Unfortunately, the project
schedule did not allow for the continued
development and evaluation of this
procedure.
Conclusions
Colorimetric analysis of several
commercial dispersants indicated that
anionic and nonionic surfactants are
used either alone or in combination. No
cationic surfactants were found in the
dispersants tested.
Both anionic and nonionic surfactants
can be successfully collected and
concentrated on SEP-PAK C18 (Waters
Associates, Inc.). This procedure also
separates the surfactants from potentially
interfering constituents.
Tensammetric (polarographic) detec-
tion of surfactants could not be developed
into a suitable analytical technique, pos-
sibly because of the complexity of the
technique and its limited sensitivity.
Derivation of certain surfactants in oil
dispersants, specifically nonionized sur-
factants such as polyethoxylated nonyl-
phenol, followed by HPLC and detection
and quantification by UV spectrometry,
appears to be a promising technique.
Recommendations
Additional effort is required in several
areas to refine and validate both the
collection (SEP-PAK) and the HPLC
quantification procedure. Specific
recommendations include the following:
1. The effectiveness of the SEP-PAK
cartridge should be evaluated with
other oils and dispersants.
2. Other sorbents such as Rohm &
Haas XAD resins should be
evaluated as alternative adsorbents
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that could be used for larger-scale
experiments.
3. More extensive testing of the
derivation process and the HPLC
separation method is clearly
required. Application of the method
to other nonionic surfactants must
be established.
4. Analytical methods for anionic
surfactants still must be sought.
The full report was submitted in
fulfillment of Grant No. R-807059-01 by
SRI International under the sponsorship
of the U.S. Environmental Protection
Agency.
D. L. Haynes, D. G. Kelly, J. H. Smith, and E. L Fernandez are with SRI
International, Menlo Park, CA 94025.
John S. Farlow is the EPA Project Officer (see below).
The complete report, entitled "Developing Methods for Analyzing OHDispersants
in Seawater, "(Order No. PB 84-238328; Cost: $8.50, subject to change) will be
available only from:
National Technical Information Service
5285 Port Royal Road
Springfield, VA22161
Telephone: 703-487-4650
The EPA Project Officer can be contacted at:
Oil and Hazardous Materials Spills Branch
Municipal Environmental Research Laboratory—Cincinnati &
U. S. Environmental Protection Agency
Edison, NJ 08837
S GOVERNMENT PRINTING OFFICE. 1984 —759-015/7821
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