United States
Environmental Protection
Agency
Environmental Research
Laboratory
Athens, GA 30613-7799
Research and Development
EPA/600/M-90/009 August 1990
vvEPA ENVIRONMENTAL
RESEARCH BRIEF
Reactive Dyes in the Aquatic Environment: A Case Study of Reactive
Blue 19
Eric J. Weber\ Peter E. Sturrock,2 and Sharon R. Camp.2
Abstract
The hydroxy (RB 19-OH) and vinyl sulfone (RB 19-VS)
derivatives of Reactive Blue 19 were identified in a textile
wastewater using a gradient HPLC with a novel type of
electrochemical detection. RB 19-OH could not be
detected in the effluent of the wastewater treatment facility
receiving the textile wastewater; however, RB 19-VS was
present in significant amounts. In laboratory studies, the
hydrolysis kinetics of RB 19-VS were studied in phosphate
buffer over a pH range of 4 to 11 and a temperature range
of 25 to 85'C. The half-life for RB 19- VS at pH = 7.0 at
25" C was calculated to be 46 years. Similarly, no loss of
RB 19-VS could be detected in a natural water over a 3-
week period. The half-life for the degradation of RB 19-VS
in an anaerobic sediment-water system, however, was 2.5
days.
Introduction
Recent estimates indicate that approximately 12% of the
synthetic textile dyes used each year are lost to waste
streams during manufacturing and processing operations
'and that 20% of these losses will enter the environment
through effluents from wastewater treatment plants (1).
The reactive dyes are a commercially important class of
textile dyes for which losses through processing
operations are particularly significant and for which
treatment is problematic (2). Increasing reports of colored
'Environmental Research Laboratory, U.S. Environmental Protection
Agency, Athens GA 30613
^Chemistry Department, Georgia Institute of Technology, Atlanta GA
30332
effluents from wastewater treatment plants receiving dye
waste from textile mills using reactive dyes indicate the
need to learn more about the transport and transformation
of these chemicals.
Reactive dyes are unique textile colorants because they
contain reactive groups that bind to fibers through
formation of a covalent bond. Approximately 40 types of
reactive groups have been listed for commercial dyes (3).
Of these, the highest volume commercial products are
those containing the 2-sulfatoethyl-sulfone moiety (4).
Reactive Blue 19 (RB 19), which is representative of this
type of reactive dye and is currently the highest volume
reactive dye on the market, is illustrated in Figure 1. The
reactive form of the dye, the vinyl sulfone (RB 19-VS), is
generated in the dye bath by treatment with base. The
dye-fiber adduct is formed in a subsequent reaction in
which the nucleophilic groups of the fiber (-OH, -NH2, -SH)
add to the vinyl sulfone by Michael-type 1,4-addition.
Competing with this reaction is hydrolysis to give the 2-
hydroxyethyl sulfone (RB 19-OH) as shown in Figure 1
(5,6). The term hydrolysis, which is commonly used in the
literature to describe this reaction process, is used in the
broad sense of its meaning. The reaction of hydroxide ion
with a vinyl sulfone moiety is properly classified as
nucleophilic addition.
Hydrolysis of the vinyl sulfone moiety before fixation (i.e.,
before formation of a covalent bond between dye and
fiber) is one of the fundamental problems associated with
reactive dye technology, because the hydrolyzed dye
(e.g., RB 19-OH) will not fix and has no additional affinity
for the fiber (7). For the majority of vinyl sulfone reactive
dyes, the degree of fixation ranges from 75 to 80% on
-------
cotton, which means that 20 to 25% of the dye enters the
waste stream of the textile mill (8). |
In addition to the problem of treating the waste water
containing the highly water soluble hydrolyzed form pf the
dye, it is possible that a portion of the reactive form pf the
dye, the vinyl sulfone, may escape the dye bath and also
enter the waste stream. The vinyl sulfones are
electrophilic compounds and give rise to concern over
their ecotoxicity.
The objective of this research effort was to determine
whether appreciable amounts of the vinyl sulfone and
hydrolyzed form of the dyes enter the textile waste stream
and to what extent they are removed in the wastewater
treatment process. Because textile wastewaters are very
complex, it is necessary to use analytical techniques that
will permit detection of single components. The two-
dimensionality of a classical chromatogram is insufficient
to permit the determination of specific components in
complex systems. The swept-potential electrochemical
detector used in our studies not only can detect dyestuffs
in parts-per-billion concentrations, but it also provides a
third dimension, reduction/oxidation potential, which makes
the identification of components in a complex system
possible. i
The development of such a sophisticated analytical
technique and its application to the study of dye
manufacturing waste streams is important to the staff of
EPA's Office of Solid Waste (OSW) and Office of Policy
Analysis (OPA/OPPE), who are currently developing a
regulatory strategy for selective azo dyes and the aromatic
amines used in their synthesis. In part, the validity of this
effort will depend on the development of analytical
Figure 1. Reaction pathway for the formation of RB 19-VS and
its reaction with cellulose fiber or hydroxide ion
(hydrolysis). i
O NH2 i
19 SO2CH2CH2OSO3NA
pH = 9-12
temp=30-70 °C
O NH2
.SO3Na
O HtsH" XN
RB 19 -VS SO2CH = CH2
Cellulose
S02CH2CH20-Cel.
methods for the analysis of the dyes and their precursors
and reaction products in the waste stream. In fact, this
current research effort grew out of a dye regulatory
workshop sponsored by OSW and OPA/OPPE to address
the concerns of health officials of the state of North
Carolina and regulators in EPA Region IV. The textile mill
and waste water treatment plant from which the samples
were collected for analyses in this study were identified by
the North Carolina state health officials. The attendees of
the workshop visited the site to see firsthand an
ecosystem being impacted by textile dye waste
discharges as evidenced by visible color in the receiving
stream.
Our identification of RB 19-VS in the effluents of both the
textile mill and the wastewater treatment plant indicated
the need to determine the transformation pathways for this
chemical in aquatic ecosystems. To assess the
environmental fate of the vinyl sulfone, we determined the
hydrolysis kinetics of RB 19-VS in buffered aqueous
solutions and its disappearance kinetics in a natural water
sample and an anaerobic sediment-water system. Studies
of this type should be useful to the staff of EPA's Office of
Toxic Substances who can extrapolate these data to
regulate similar dyes entering the pre-manufacturing
notification review process.
Experimental Section
Materials. All chemicals and solvents used were of the
highest purity available and were used without further
purification. Reactive Blue 19 (50% pure) was obtained
from Aldrich Chemical Company. Reagents used were
sodium acetate, sodium perchlorate, sodium hydroxide,
acetic acid, sodium monohydrogenphosphate (Fisher
Scientific Company), tetrabutylammonium perchlorate
(TBAP) (Eastman Kodak Company) and potassium
dihydrogenphosphate (Aldrich).
Preparation of RB 19-VS and RB 19-OH. A standard
solution of RB 19-VS was prepared by stirring a 1.0 x 10-3
M solution of RB 19 at pH = 11 at room temperature for 1
hour. The pH was adjusted to pH = 7 by the addition of 0.1
N HCI. This solution of RB 19-VS was used without further
purification.
A standard solution of RB 19-OH was prepared in the
following manner. A 1.0 x 10-3 M solution of RB 19 at
pH = 11 was heated to a gentle reflux for 3 hours. The
solution was allowed to cool to room temperature and the
pH was adjusted to pH = 7.0 by the addition of 0.1 N HCI.
This solution of RB 19-OH was used without further
purification.
The fast atom bombardment mass spectrum of RB 19-VS
and RB 19-OH prepared as described above were
consistent with the structures shown in Figure 1 and will
be the topic of a future manuscript (9).
Liquid Chromatography. The liquid chromatograph used
for the analysis of the effluent samples was a Spectra
Physics SP8000 equipped with a 500 microliter injection
loop. The chromatographic column was a Phenomenex
Ultrex 5 C8, 4.6 mm x 150 mm. The mobile phase
consisted of an aqueous acetate buffer, 0.02 M, with 3 mM
TBAP, and methanol with 0.01 M sodium perchlorate and 3
millimolar TBAP. The column was equilibrated at 35%.
-------
methanol. At injection, the mobile phase was immediately
switched to 50% methanol and ramped to 80% methanol
in seven minutes,-then held at 80% until all of the
compounds had eluted.
For the hydrolysis and fate studies, liquid chromatographic
analyses were performed with a Gilson 302
chromatographic pump equipped with a Kratos
Spectroflow 757 variable wavelength detector and a
Rheodyne 7161 injector containing a 250-pl sample loop.
The column was a Hamilton PRP-1 (25 cm long x 4.6 mm
i.d., 10-iim particle size) protected with an Alltech PRP-1
cartridge guard column. The eluent was MeOH:H2O
(80:20) containing 5 x 10-3 M NaH2PO4 at pH = 7.0.
Electrochemical Detection. The electrochemical instru-
mentation used for the detection of the dyes in the effluent
samples has been described in detail elsewhere (10,11),
and has been used consistently with excellent results in
other studies (12,13). It consists of a microcomputer with
a Z80A processor, 64 kilobytes of RAM and a polarograph.
It is interfaced to a Princeton Applied Research (PAR)
model 310 static mercury electrode. The electrode was
equipped with the flow cell from a PAR model 420
electrode. The initial potential applied to the electrode was
-150 millivolts, and the potential was swept using a square-
wave waveform in -20 millivolt steps to a final potential of -
810 millivolts. The current response from the electrode
was integrated via a gated integrator for 14.647
milliseconds.
The concentrations of RB 19-VS and RB 19-OH in the
effluent samples were determined in the following manner.
Plots of concentration versus current response, which
showed a linear response and similar sensitivity for both
derivatives, were prepared from serial dilutions of the
standard solutions of RB 19-VS and RB 19-OH. Because
the two derivatives were not purified and individually
injected, however, only estimates of their concentrations
can be given. Because Reactive Blue 19 was only 50%
pure as received from Aldrich, the concentration of each
component was based on 50% of the original amount of
parent dye used for the preparation of the standards and
on the ratio of the current response of each of the
standards. This same procedure was used to determine
the detection limits.
Textile mill effluent and wastewater samples. The
textile mill effluent and the treated wastewater samples
were obtained from a textile mill and a publicly owned
wastewater treatment plant in North Carolina. The textile
mill is located approximately 1 mile from the treatment
plant. The dye waste stream is transported to the
treatment plant through the city sewer system. Samples
collected at the mill were taken at the site where the waste
stream enters the sewer system. Samples of the effluent
of the wastewater treatment plant were collected at the site
where the effluent entered a natural stream. The samples
were used as received, and were approximately 2 months
old when analyzed. The samples were stored at 4°C
during this time.
Hydrolysis Kinetics. Hydrolysis kinetics were determined
in phosphate buffers (5.0 x 10-3 M) over a pH range of 4 to
11 and a temperature range of 25 to 85° C. The buffer
solutions were freshly prepared by diluting a 0.5-M stock
solution of either NaH2PO4 or Na2HPO4 to 5 x 10-3 M and
then adjusting to the desired pH by the addition of either
0.1 N HCI or NaOH. pH was measured with a Beckman
071 pH meter, equipped with a temperature probe and an
Orion Ross™ combination pH probe.
Kinetic runs were made with a series of 15-ml screw-
capped test tubes containing a 10-ml solution of the buffer
and RB 19-VS at 1.0 x 10-5 M. At selected time intervals,
a tube from the series was removed from the bath and
treated with 0.5 ml of 0.5 M phosphate buffer at pH = 7.0 in
order to neutralize the solution. For kinetic runs conducted
at elevated temperatures, the tube was first cooled to 4°C
before the addition of buffer. Disappearance of RB 19-VS
and the formation of RB 19-OH were monitored by HPLC.
All kinetic runs were performed in duplicate. For kinetic
runs at elevated temperatures, constant temperature baths
were used to maintain the temperature to within ± 0.1 °C.
Disappearance Kinetics in a Natural Water Sample
and an Anaerobic Sediment-Water System. The
natural water and sediment-water samples for the fate
studies were collected in the Athens, Georgia area. The
method for collecting the water and the sediment-water
and for performing kinetic studies in these systems has
been described in detail elsewhere (14,15). The initial
concentration of RB 19-VS in these studies was 1 x 10-5
M.
Determination of the Rate Constants. Pseudo-first-
order rate constants (kobsd) were obtained using the
integrated first- order rate equation:
ln(Ct/C0) = -kobsd't (1)
where C0 and Ct are the concentrations at time 0 and t,
respectively. The rate constant was taken as the slope of
the line obtained by a linear least-squares analysis of the
data.
Results and Discussion
To identify and quantitate RB 19-VS and RB 19-OH in the
effluents of a textile mill and a wastewater treatment plant,
it was necessary to use an analytical technique such as
liquid chromatography with electrochemical detection that
permits the determination of specific components in
complex systems.
Analysis of ,a mixture of RB 19-VS and RB 19-OH by
HPLC with swept-potential electrochemical detection
demonstrates that the two components can be readily
separated (Figure 2). The characteristic reduction
potential and peak shape, in addition to the retention time,
greatly aids in the identification of these two components
in the complicated effluent of the textile mill shown in
Figure 3. A comparison of the retention times and
reduction potentials of the two chromatograms shows a
match of the vinyl sulfone and hydrolyzed peaks. The
limits of detection for RB 19-VS and RB 19-OH were 0.45
ppb and 0.85 ppb, respectively, based on 2 standard
deviations.
When we applied this method to the analysis of the textile
mill effluent we were able to identify both RB 19-VS and
RB 19- OH. The concentration of the vinyl sulfone in the
textile mill effluent was estimated to be 760 ± 10 ppb,
where the uncertainty is the standard error of regression.
The concentration of RB 19-OH was estimated to be 80 ±
30 ppb.
-------
When we analyzed the effluent of the wastewater
treatment plant receiving the textile mill effluent we were
only able to detect RB 19-VS (Figure 4). The vinyl sulfone
was present at 89 ± 10 ppb. Because the textile mill
effluent accounts for 50% of the flow entering the
wastewater treatment plant, we estimated that
approximately 25% of the amount of vinyl sulfone entering
the wastewater treatment plant was passing through
untreated. Apparently RB 19-OH is removed during the
treatment process. I
In addition to the RB 19-VS and RB 19-OH peaks, we also
observed a number of other peaks. Although it was
beyond the scope of this study to identify all of the
components in the textile mill and the wastewater
treatment effluents, several observations can be made
concerning the complexity of these samples and the use
of HPLC with electrochemical detection for their analysis.
Close inspection of the chromatogram of the textile mill
waste in Rgure 3 indicates the presence of approximately
32 different compounds with some of the compounds co-
eluting. The chromatogram of the effluent of the
wastewater treatment plant in Figure 4 is less complex;
however, it contains 13 different compounds, again with
several co-eluting peaks.
Comparison of the chromatograms of the pretreated and
treated effluent samples in Figures 3 and 4 illustrates a
major problem with present wastewater treatment
methods. Although many of the components in the
untreated sample are not present in the treated sample,
there are components present in the treated sample that
are not present in the untreated sample. Based on the
chromatographic behavior of the new components, we
Figure 2. Chromatogram of RB 19-OH (8.1 min) and RB 19-VS
(9.2 min).
RB 19-VS
RB 19-OH
-320 _800
Potential (mV)
concluded that many of them resulted from the
transformation of textile dyes during the treatment process
and that they cannot be identified simply by comparison
with standards. We cannot, however, rule out the
possibility that these new components are present in the
municipal sewage that mixes with the dye waste as it
enters the waste water treatment plant. This is a problem
that deserves further investigation.
The identification of RB 19-VS in both the effluents of the
textile mill and the wastewater treatment plant indicated a
need to study the fate of this chemical in aquatic
ecosystems. Initially, we determined the hydrolysis
kinetics of RB 19-VS in phosphate buffers over a pH range
of 4 to 11 and a temperature range of 25 to 85°C. In each
case, pseudo-first-order disappearance kinetics were
observed. The kinetic data are summarized in Table I. A
typical data set is illustrated in Figure 5. As the data in
Figure 5 indicate, the hydrolysis of RB 19-VS gives RB 19-
OH in quantitative yield.
To determine the effect of pH on the rate of hydrolysis of
RB 19-VS, we measured hydrolysis rate constants for the
vinyl sulfone over a pH range of 4 to 11 at 85 °C. We
found that it was necessary to perform these experiments
at an elevated temperature because the hydrolysis kinetics
in the neutral and acidic pH ranges were extremely slow at
room temperature. The log of the observed hydrolysis
rate constants versus pH for RB 19-VS is shown in Figure
6. Above pH = 4.8, the observed hydrolysis rate constant
is directly proportional to [OH] concentration, indicating
that the hydrolysis of RB 19-VS is base-mediated and that
hydrolysis by water (neutral hydrolysis) is not a significant
process. Thus, the rate law for the disappearance of RB
19-VS over most environmental pH ranges can be written
as
-d[RB 19-VS]/dt = kb[RB 19-VS][OH']
(2)
Equation 3 was used to obtain the alkaline hydrolysis rate
constant, kb:
where [OH'] was calculated from experimentally measured
pH values and the equilibrium constant for the ionization of
water, Kw, was calculated as a function of temperature
using the Marshall-Franck equation (16). The calculated
values for kb are listed in Table 1.
To extrapolate these hydrolysis data to environmentally
significant conditions, it was necessary to determine the
dependence of the basic hydrolysis rate constant on
temperature. Accordingly, we measured the alkaline
hydrolysis rate constant for the vinyl sulfone over a
temperature range of 25 to 85 °C. The Arrhenius plot of In
kb versus 1/T (K) for the hydrolysis of RB 19-VS at
pH = 11.0 is shown in Figure 7. From this plot, we
calculated an Arrhenius pre-exponential factor, A, of 8.55 x
1013 M'1 h'1 and an activation energy, Ea, of 72.4 KJ/mol.
These data should be particularly useful for calculating
rates of hydrolysis of RB 19-VS in the dye bath where a
wide range of temperatures are encountered.
These hydrolysis data, when extrapolated to
environmentally significant conditions, give an estimated
-------
Figure 3. Chromatogram of the textile mill effluent. Adjusted retention
time in min.
RB 19-VS
11.0
9.0
Time (min)
7.0
5.0.
-240 -810
Potential (mV)
Figure 4. Chromatogram of the wastewater treatment plant
effluent. Adjusted retention time in min.
Figure 5. Hydrolysis of RB 19-VS (i)and appearance of RB 19-
OH ( +) in 5.0 x 10~3 phosphate buffer at pH = 9.0 at
85 °C.
-240
-870
20 40 60
Time (h)
80 100
Potential (mV)
half-life for the base-mediated hydrolysis of RB 19-VS at
pH = 7, typical of natural waters, of approximately 46 years
at 25 °C. This degree of stability of the vinyl sulfones and
the concern over their ecotoxicity suggested the need to
determine whether constituents of natural waters or
sediment-water systems may either enhance or retard the
hydrolysis process or whether reactions with other
environmentally significant nucleophiles (e.g., HS-) will
contribute to degradation of the vinyl sulfone moiety.
To determine if the constituents of natural systems either
catalyze or retard the hydrolysis process, we measured
the disappearance kinetics for RB 19-VS in a filtered
natural water sample and an anaerobic sediment-water
system are shown in Figure 8. Although no disappearance
-------
Figure 6. Log of hydrolysis rate constants versus pH for
RB19-VSat85°C.
-1 •
-3-
-4 -
-5-
•6
10
pH
of RB 19-VS could be detected in the natural water sample
over a period of 3 weeks, which is consistent with the
distilled water half-life of 46 years, the half-life for the vinyl
sulfone in the sediment-water system at 25°C (pH = 6.5)
was 2.5 days. It is interesting to note that no reaction
products could be detected, including the hydrolysis
product, RB 19-OH. This result may be an indicatiorj that
the vinyl sulfone moiety is binding to nucleophilic sites on
the surface of the sediment through the same mechanism
by which the dye binds to cellulose (Figure 1). Further
work will be necessary to determine the importance of this
reaction pathway for the removal of vinyl sulfones from
aquatic systems. '
Summary '
We found that gradient HPLC with electrochemical
detection is a very useful technique for the analysis of
textile wastewaters. This analytical technique enabled us
to detect RB 19-VS in the effluents of a textile mill and a
wastewater treatment plant. We estimated that on the day
we collected samples, approximately 25% of the vinyl
sulfone was passing through the wastewater treatment
plant untreated and into a natural surface water. The
hydrolysis product of the vinyl sulfone, RB 19-OH, was
detected only in the effluent of the textile mill. These
results are evidence that the vinyl sulfone can survive the
conditions of the dye bath, indicating the need to
determine the ecotoxicity of this type of chemical. i
Based on laboratory studies, we estimated the half-life for
the base-mediated hydrolysis of RB 19-VS at pH = 7,
typical of natural waters, to be approximately 46 years at
25° C. Consistent with this estimate is the observation that
no loss of RB 19-VS from a natural water could be
detected over a 3 week period. The half-life for RB 19-VS
in an anaerobic sediment- water system, however, was 2.5
days. We were unable to detect any transformation
products, however, including the hydrolysis product, RB
19-OH. We speculate that the vinyl sulfone moiety
reacted with nucleophilic sites on the sediment surface
through the same mechanism that the dye binds to
cellulose. Future studies will focus on how this interaction
with sediment surfaces will affect the transport and
transformation of vinyl sulfones and other types of reactive
dyes in aquatic ecosystems.
Finally, it is useful to compare the rates of degradation of
the vinyl sulfone in the anaerobic sediment-water system
versus the aerobic environment of the activated sludge
basin of the wastewater treatment plant. Based on a
liquids retention time of 30 h, we calculated a degradation
rate constant of 4.6 x 10-2 h"1 for RB 19-VS in the
Table 1. Summary of Kinetic Data for the Hydrolysis of RB 19-
VS.
T. (°C)
25
32
45
60
78
85
pH* (±0.03)
10.85
10.75
10.39
10.04
9.61
4.20
4.80
5.28
6.02
6.80
7.26
8.06
8.65
9.48
k obsd (IT1)
(1.32 ± 0.17) x 10~2
(1.37 ± 0.02) x 10~2
(3.36 ± 0.13) x 10'2
(3.29 ± 0.10) x 10'*
(6.86 ± 0.53) x TO"2
(7.50 ± 0.62) x 10'2
(4.84 ± 0.1 9) x 10'1
(5.91 ± 0.52) x 70"'
(1.21 ± 0.10)
(1.25 ±0.11)
(3.73 ± 0.15)x10"5
(7.00 ± 0.37) x 10~5
(8.15 ± 1.68)x 10'5
(8.78 ± 3.09) x 10'5
(1.60 ± 0.11) x 10'4
(1.35 ± 0.09) x 10'4
(2.35 ± 0.23) x 10'4
(1,96 ± 0.20) x 10'4
(3.86 ± 0.41) x 10'3
(4.68 ± 0.61) x 10'3
(8.25 ± 0.32) x 10'3
(8.18 ± 1.56)x 10~3
(2.07 ± 0.10) xW'z
(5.48 ± 0.44) x 10'2
(1.73 ± 0.09) x 10'1
(1.79 ± 0.06) x 70"'
(2.33 ±0.11)
(2.17 ± 0.08)
kb (M-i /?-')
78.63
79.33
35.59
34.85
69.82
76.33
467.40
563.40
7278.93
7320.67
4700.63
4477.67
2665.77
2249.79
772.46
594.22
7942.74
2354.72
7439.28
7427.07
572.35
7575.27
7229.53
7272.77
2449.34
2287.74
1 measured at experimental temperature
-------
Figure 7. Arrhenius plot for the hydrolysis of RB 19-VS in 5.0 x
10"3 M phosphate buffer at pH = 11.
7-
5 5-
3-
2.8
3.0 3.2
1000/T(k'1)
3.4
Figure 8. Disappearance kinetics for RB 19-VS in a filtered pond
water sample and an anaerobic sediment-water system.
-11.0
-11.4 -
-11.8-
1 -72.2-
| -72.6-
5 -13.0 -
-13.4 -
Water
Sediment-Water
20 40
60 80
Time (h)
100 120 140
wastewater treatment plant. This rate constant is
approximately a factor of 4 greater than the disappearance
rate constant measured for RB 19-VS in the anaerobic
sediment-water system. These data suggest that for this
particular type of dye extended treatment in the activated
sludge process would be more advantageous than
additional treatment with an anaerobic digester.
Acknowledgments
We thank Vicki Stickney and Jennifer Buynitzki for their
technical assistance in the laboratory. We also thank
Susan Richardson, Lee Wolfe, Wayne Garrison, Bob
Ryans and John Rogers for their helpful comments in the
preparation of this manuscript.
Literature Cited
1. Clarke, E.A.; Anliker, R. In Handbook of Environmental
Chemistry: Vol 3, Part A, Anthropogenic Compounds;
Hutzinger, 0., Ed.; Springer-Verlag: Berlin and
Heidelberg, 1980; pp 181-215.
2. Abeta, S.; Yoshida, T.; Imada, K. Am. Dyest. Rep.
1984, 73, pp 20-49.
3. Rys, P.; Zollinger, H. In The Theory of Coloration of
Textiles; Bird, C.L; Boston, W.S., Eds.; Dyers Comp.
Publ. Trust: Bradford, England, 1975; pp 326-358.
4. Locke, D. U.S. Environmental Protection Agency,
Washington, DC, personal communication, 1989.
5. Heyna, J.; Angew. Chem. Int. Ed. Engl., 1963, 2, pp
20-23.
6. Siegel, E. In The Chemistry of Synthetic Dyes, Vol. 6.;
Venkataraman, K., Ed.; Academic Press: New York
and London, 1979; pp 1-209.
7. Zollinger, H.; In Color Chemistry: Syntheses,
Properties and Applications of Organic Dyes and
Pigments; VCH Verlagsgesellschaftt: Weinheim, FDR,
1987; pp. 1136-143.
8. Sommer, E.P.; Am. Dyest. Rep. 1958, 47, 895-899.
9. McGuire, J.M.; Richardson, S.D.; Thruston, A.D. U.S.
Environmental Protection Agency, Athens, GA,
personal communication, 1989.
10. Owens, D.S. Voltammetry in Flowing Streams, Ph.D.
Thesis, 1987, Georgia Institute of Technology,
Atlanta, GA.
11. Reardon, P.A.; O'Brien, G.E.; Sturrock, P.E. Anal.
Chim. Acta, 1984, 162, 175-187.
12. Thomas, M. B.; Sturrock, P.E. J. Chrom. 1986, 357,
318-324.
13. Owens, D. S.; Sturrock, P.E. Anal. Chim. Acta, 1986,
188, 269-274.
14. Weber, E.J.; Wolfe, N.L. Environ. Tox. and Chem.,
1987,6, 911-919.
15. Weber, E.J. Studies of Benzidine-Based Dyes in
Sediment-Water Systems. Submitted to
Environmental Toxicology and Chemistry for pub-
lication. 1989.
16. Marshall, W.K.; Franck, E.U. In Ninth Int. Conf.
Properties Steam, Straub, J., Scheffler, K., Eds.;
Pergamon Press: Oxford, 1979; pp 506-512.
Note: Mention of trade names or commercial products
does not constitute endorsement or recommendation for
use by the U.S. Environmental Protection Agency.
-------
United States
Environmental Protection
Agency
Center for Environmental Research
Information [
Cincinnati OH 45268
Official Business
Penalty for Private Use $300
EPA/600/M-90/009
------- |