TR 77-593
DRAFT
ANALYSIS AND HYDROLYSIS OF
COMMERCIAL ARYL PHOSPHATES
Philip H. Howard
Padmakar G. Deo
Center for Chemical Hazard Assessment
Syracuse Research Corporation
Merrill Lane
Syracuse, New York 13210
Contract No. 68-01-3250
SRC No. LI279-06
October 1977
Project Officer - Patricia Hilgard
Office of Toxic Substances
U.S. Environmental Protection Agency
Washington, D.C. 20460
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NOTICE
This document is a preliminary draft. It has not been formally released
by EPA and should not at this stage be construed to represent Agency policy.
It is being circulated for comment on its technical accuracy and policy impli-
cations.
1 1
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ABS TRACT
Synthetic aryl phosphate esters are used in large quantities (80 million
pounds per year) as fire retardant hydraulic fluids and plasticizers. Little
information is available on their chemical composition and environment stability.
This report chemically examines some commercial aryl phosphates and studies
their rates of hydrolysis in distilled and natural waters. During the synthe-
sis of isomers of aryl phosphates for identification, a derivative method for
analysis of phenols and alcohols was also developed.
1
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Organophosphate esters, both triaryl and alkyl aryl esters, find wide-
spread usage as plasticizers or as industrial hydraulic fluids where fire
resistance is a desirable or mandatory property. During 1964 to 1973, approx-
imately 847 million pounds of aryl phosphate esters were produced, of which
tricresyl phosphate accounted for about 396 million pounds (1). During 1975,
the reported annual production for aryl phosphate esters was 80 million pounds
(2). Although some phosphate esters may be destroyed during use (sizable quan-
tities were used as gasoline additives for ignition control), large production
and major applications suggest that significant quantities may be released to
the environment and result in environmental contamination and human exposure (1).
Aryl phosphates are produced by a catalyzed reaction between POC1» and a
mixture of phenols and alcohols. Because isomeric mixtures of phenols are
frequently used, resulting aryl phosphates are often complex blends of isomeric
phosphate esters. These isomers appear to have significantly different toxico-
logic properties. For example, di-m-cresyl o-cresyl phosphate, di-£-cresyl
o-cresyl phosphate, and o-cresyl m-cresyl _p_-cresyl phosphate are all more neuro-
toxic than the well-known neurotoxin, tri-o-cresyl phosphate (3).
Thus, an understanding of chemical composition of commercial aryl phosphates
is important for an understanding of toxicity of the product and is also required
for analysis of aryl phosphates in environmental samples. However, little infor-
mation is available on the chemical composition of commercial aryl phosphates.
Recently, Murray (4) has reported some manufacturer's data on IMOL S-140, an
aryl phosphate produced by Imperial Oil Ltd., Canada, and he has determined the
phenols produced after alkaline hydrolysis of IMOL, tricresyl phosphate, and
cresyl diphenyl phosphate made by Electric Reduction Company of Canada and
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Fyrquel GT made by Stauffer Chemical Company. The hydrolysis procedure indi-
cates the composition of the phenolic mixture used to produce aryl phosphates
but does not determine ratios of the individual isomers present. Using a com-
bination of gas liquid chromatography/mass spectrometry (GLC/MS) and GLC reten-
tion times of purchased or synthesized isomers, we have determined the chemical
composition of five commercial aryl phosphates which were selected as being
fairly representative of ten commercial samples received by our laboratory.
During the preparation of aryl phosphate isomers for identification pur-
poses, it became apparent that phosphorylation of alcohols and phenols may be
a desirable derivative method for GLC analysis. Gas-liquid chromatographic
(GLC) separation of alcohols and phenols poses problems because of their vola-'
tility and hydrophilic nature. Over the last few years, several workers (4-9)
have attempted separation and detection of phenols, using flame ionization GLC.
However, since the flame ionization detector is less sensitive and responds to
a variety of compounds, a number of researchers have recently derivatized
phenols for GLC determination with more sensitive detectors (10-12). Coburn and
Chau (10) made acetate derivatives of 3-trifluoromethyl-4-nitrophenol and other
phenols for electron capture GLC analysis. Kawahara (11) separated and quanti-
tatively determined phenols, organic acids, and mercaptans in water samples by
converting them to pentafluorobenzyl derivatives for analysis by electron capture
GLC. Since electron capture detection is very sensitive and responds only to
specific molecules which are strong electron absorbers, Kawahara (11) was able
to detect sub-nanogram amounts of these compounds even with a 95% organic inter-
ference. However, no one has so far phosphorylated phenols for their GLC separa-
tion, although the technique for phosphorylation of phenols is well known.
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Kenner and Williams (13) synthesized a number of aryl diethyl phosphates
(Ar-DEP) by adding triethylamine to a carbon tetrachloride solution of phenol
(ArOH) and diethyl phosphite. The overall reaction is:
ArOH + HOP(ORt)2 + CCl^ + Et3N - >• ArOP(O) (OEt)2
The important change in the above reaction was the conversion of an ArOH to an
Ar-DEP. Since the nature of the Ar-DEP formed will always depend on the nature
of the reacting ArOH, we felt that this reaction could be used for separating
ArOH or even alcohols, if the resulting aryl or alkyl diethyl phosphates could
be conveniently separated. Using a slight modification of the Kenner and
Williams procedure, we phosphorylated 19 alcohols/phenols, both separately and
in mixtures, and the resulting Ar-DE?'s were separaced by GLC and detected by
a flame photometric detector supplied with a 526 nm filter.
The large volume of aryl phosphate being used is likely to result in
release to the environment either from losses during manufacturing or use
(especially use of hydraulic fluids). A significant loss of some aryl phosphate
hydraulic fluid used in a small steel mill to a Pennsylvania river has recently
been noted by the Pennsylvania Department of Environmental Resources (14).
Because of the possible widespread contamination of water systems by aryl phos-
phates, it is important to understand the fate of these compounds in aqueous
media.
Several investigators have studied the hydrolysis rates of aryl phosphates,
but in most cases the conditions used were not similar to conditions in nature.
Barnard et^ al. (15) found that the hydrolysis first-order rate constant of
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—8 —1
triphenyl phosphate in dioxane-water (3:1 V/V) at 100°C was 6.0 x 10 sec"
(half-life 130 days), while the second-order rate constant under alkaline
conditions in dioxane-water mixture (3:1 V/V) at 24.7°C was 0.0106 1 mole"
sec . The latter value was experimentally determined at pH 13 but should
apply to all alkaline conditions. Using this value, the calculated half-lives
in that solvent system at pH 9.5 and 8.2 are 23 and 472 days, respectively,
at 24.7°C. These rate constants only apply to the first hydrolysis step con-
verting triphenyl phosphate to diphenyl phosphate, since the hydrolysis rate
of diphenyl phosphate under acid and alkaline conditions is extremely slow
[at 100°C, pH 7.47, in water K = 6 x 10~9 sec"1 (16)]. The hydrolysis of
triaryl phosphates under slightly acid conditions has not been studied, although
strong acid rate constants have been determined (16). By analogy with pesticide
organophosphates, it is likely that the hydrolysis of triaryl phosphates under
neutral or slightly acid conditions would be extremely slow in nature (17).
In demineralized river water and in natural river water and sediment
Wageman et al. (18) have studied the rate of degradation of a commercial mix-
ture of triaryl phosphates (IMOL S-140) by following the phosphate production.
They reported half-lives of 52 to 140 days, depending upon the conditions
(demineralized water = 73 days). The starting pH was 7-8 and with time it
increased to 5.6-6.0.
Because of the commercial importance of triaryl phosphates and their
likely release to the environment, we have investigated further the hydrolysis
of these compounds under acid, neutral, and basic conditions in distilled water
and in some alkaline natural waters.
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EXPERIMENTAL
Reagents
(a) Alcohols - Pesticide grade methanol, ethanol, isopropanol
(Matheson Coleman & Bell, Norwood, OH), Fisher certified ACS
grade n-butanol, isobutanol, isoatnyl alcohol, and highest
purity grade sec-butanol (Fisher Scientific Co., Rochester, NY).
(b) Phenols - Phenol (99%), cresols (Gold Label), isopropylphenol
(97-98%), xylenols (97-98%), and cumylphenol (99%) (Aldrich
Chemical Co. , Metuchen, NJ|; _p-nonylphenol (practical) (Fisher
Scientific Co., Pittsburgh, PA).
(c) Chlorophosphates - Diphenyl chlorophosphate, phenyl dichloro-
phosphate, diethyl chlorophosphate (Aldrich Chemical Co.,
Metuchen, NJ), phosphorus oxychloride (Fisher Scientific Co.,
Rochester, NY).
(d) Solvents - benzene - spectrophotometric grade (Aldrich Chemical Co.,
Metuchen, NJ), diethylether, anhydrous, ACS grade (Fisher Scientific Co.)
(e) Triethylamine - 99% (Aldrich Chemical Co., Metuchen, NJ).
Instrumental - Gas liquid chromatography (GLC) was carried out on a Tracor MT 220
Gas Chromatograph equippied with flame photometric detector supplied with a
526 nm filter (P-mode) and fitted with a Pyrex 1.27 cm x 1.82 m U-shaped column
packed with 3% OV-101 on 80-100 mesh Chromasorb WHP obtained from Supelco, Inc.,
Bellefonte, Pennsylvania. Gas flow rates (ml/min) were: hydrogen, 75; air, 80;
nitrogen (carrier gas), 125; and the temperatures for injector, detector, and
column were 225, 200, and 215, respectively.
Gas liquid chromatograph/mass spectrometry (GLC/MS) analysis was performed
with a Finnigan 330 gas liquid chromatograph/mass spectrometer supplied with a
System Industries Data Processor. The operating temperature conditions and
column were the same as before, but the flow rate of nitrogen was between
15-20 ml/min and temperature programming was done from 100-250°C with 10° rise
per minute.
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Commercial Aryl Phosphate Oils
(a) Rronitex — R (tricresyl phosphate) (FMC Corp., Philadelphia, PA).
(b) Santicizer — 140 (cresyl diphenyl phosphate) and Pydraul SOB
(Monsanto Company, St. Louis, MO).
(c) Phosfiex 41—P and Fyrquei. CT (Stauffer Chemical Company, Specialty
Chemical Division, Nfl.
Lake/River Water — Lake Onondaga water was collected from the northeast end of
the lake at Liverpool, New York. The pH of the water was 7.8. Lake Ontario
water was collected from Oswego (New York) at a sight about one—half mile west
of the university campus. The pH of this water was 8.2. Seneca River water was
collected from a site one mile west of the town of Baldwinsvil le (New York).
The pH of this water was 8.2. On arrival at the laboratory, the water was
filtered with an 11 micron filter to remove large particles and then refriger-
ated until use.
Phosphorylation of Alcohols and Phenols
Add slight excess of diethyl chlorophosphate to solution of alcohols/
phenols (20—30 mg) in benzene at room temperature. Then add slight excess of
triethylamine until white precipitate (of triethylamine hydrochloride) appears
and/or smell of triethylamine persists. Agitate mixture at 60—70°C in shaker
water bath. Alcohols react almost instantaneously; phenol, isopropylphenols,
and cresols require ca 1 to 1 1/2 hr; xylenols require 3 to 4 hr for best
results. Let contents cool and then wash benzene layer twice with 1! NC1,
four times with 114 NaO}1, and finally 1 to 2 times with water. Dry washed
organic layer with anhydrous Na 2 SO 4 , dilute with benzene to known volume (to
ng level), and inject into gas chromatograph. Sometimes peaks with low reten-
tion times appear if organic layer is not washed carefully. These peaks can,
7
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however, be recognized by simultaneously running blank without alcohols or
phenols. Microgram quantities can also be phosphorylated by similar procedure.
Synthesis of Aryl Phosphates
Using a slight modification of Kenner and Williams’s procedure (13), we
have synthesized most of the isomeric tricresyl phosphates (TCP) and some
phenyl dicresyl (PDCP) and cresyl diphenyl phosphates (CDPP) to identify some
of the components of the commercial aryl phosphate oils. Cresyl diphenyl
phosphates were synthesized by reacting the corresponding cresol with diphenyl
chlorophosphate. Similarly, dicresyl phenyl phosphates were synthesized by
reacting phenyl dichlorophosphate with mixtures of cresols in the desired pro-
portion. For mixed tricresyl phosphates (TCP), we have reacted the respective
cresols with PO d 3 in the same molar proportion as they were supposed to be
present in the resulting TCP. Although the reaction of PO d 3 with a mixture of
cresols provides a mixture of TCP’s, the major product will be the desired TCP
isomer and will provide the Gd retention time required for identification.
The procedure followed by us for synthesis of aryl phosphates is described below.
Add slight excess of the phosphorylation reagent (diphenylchlorophosphate,
phenyl dichiorophosphate, or phosphorus oxychloride) to solution of phenol/cresols
in benzene at room temperature. Then add slight excess of triethylaniine until
white precipitate (of triethylamine hydrochloride) appears and/or smell of
triethylamine persists. Reflux the contents for two hr at 50—60°C. Let contents
cool and then wash the benzene layer twice with 1N HCl, four times with lN NaO}1,
and finally 1 to 2 times with distilled water. Dry washed organic layer with
anhydrous Na 2 SO 4 , dilute with benzene to known volume (ng/pl level), and inject
into gas chromatograph to get the retention time.
8
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Hydrolysis Studies — These were carried out by measuring the disappearance
rates of the triaryl phosphates. Excess amounts of triphenyl phosphate (TPP),
tricresyl phosphates (TCP’s), or the commercial aryl phosphates were separately
shaken with the buffered distilled water or the lake/river waters for two hours,
after which they were filtered with an 11 micron filter which should remove
most undissolved material but pass through the microorganisms in natural waters.
The filtrate was incubated on a rotary shaker at room temperature (21 ± 2°C)
and samples were removed at regular intervals for the determination of residual
amounts of aryl phosphates. For the aryl phosphate determination, the samples
were acidified to pH 1—2 and extracted with ether after adding 15% NaC1. Tn—
butyl phosphate (TBP) was used as an internal standard and was added to the
sample before acidifying it to pH 1—2. The ether fraction was dried on anhy-
drous Na 2 SO 4 , concentrated, methylated with diazomethane, and injected into
the GLC after diluting it to a known volume. Concentrations of the aryl phos-
phates from their peak area values were determined by using a standard curve
of peak area vs. concentration.
Using the procedure just described, we were also able to extract signif i-
cant quantities of diphenyl phosphate (DPP) present in the aqueous phase. Since
we have methylated the ether fraction before injecting into the GLC, we have
found peaks for DPP (as DPP—CH 3 ) whenever it was present. Our recoveries of
DPP from distilled water were around 70%, but they varied greatly in different
samples. The results presented for DPP are based on the amounts which we could
extract by our procedure. They were not corrected for recovery (since the
recovery is not reproducible) and, therefore, may be subject to considerable error.
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Hydrolysis studies under acid conditions were carried out using dilute
HC1 (pH 4—5). For basic degradation studies at pH 9.5 and 8.2, boric acid—
sodium hydroxide and sodium dihydrogen phosphate-disodium hydrogen phosphate
buffers were used, respectively. Degradation studies at neutral pH were
carried out in distilled water. Hydrolysis studies in natural waters were
carried out without any pH control after they were filtered.
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Results and Discussion
Alcohol and Phenol Phosphorylation
Following the procedure described, we have been able to phosphorylate
alcohols, phenol, cresols, and xylenols and separate and detect the phosphor—
ylated compounds by GLC using a flame photometric detector in the P mode. A
column temperature of 140—150°C was used for alcohols and 180—195°C for phenol,
cresols, and xylenols. We have phosphorylated each alcohol and phenol separately,
and the retention times of the resulting alkyl or aryl—DEP have been determined
(Table 1). Having estimated the alcohols and phenols separately, we then pre-
pared mixtures. We had no difficulty in most cases in separating and identi-
fying the components of these mixtures. The GLC traces of the three mixtures
are presented in Figures 1—3. In Fig. 1, separate peaks for ethanol and sec—
butanol could not be seen because their retention times are quite close to those
of the preceding alcohols. At points 2 and 5 in Fig. 1, which correspond to
the retention times for the 2 compounds, the recorder pen stopped and then
moved upwards. Similarly, a separate peak for 2,5—xylenol is not seen in
Fig. 2. The retention times of the alcohols and phenols in the mixture were
the same as those obtained for each one separately. Using 7 different alcohols
and phenols (Table 2), we also determined that the limit of detection (10% of
maximum record response) was 10 to 25 ng. The limit of detection for the
methylated derivatives of the same compounds, using GLC with flame ionization
detection, was at least 10 times higher.
The phosphorylation procedure permits GLC analysis of more volatile alco-
hols at reasonable column temperatures (140—150°C). Other procedures, such as
methylation or silylation, provide derivatives which are extremely volatile.
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Table 1. Gas liquid :hrornatographic analysis of phosphorylated
n1 hols and phenols by f!ane photomecric detection
Alcohol /Phenol
Methanol
Ethanol
Isooropyl alcohol
n—Eu ano1
Isobu anol
sec— u tanol
Isoa-2y1 alcohol
Phenol
2.—Cr 2 S ol
tn—Crc so 1
r c so 1
2—Isopropvlphenol
4—I sopropvlpneno 1
2, 3—Di ctItvlp1ienol
2, 4—Dirnethyiphenol
2, 5—Dimethyiphenol
2, 6—Dimeth lpheno1
3 ,4—Dimethyl.phenol
3, 5—Dimeth’ lphenol
Alkyl/aryl diethyl
phosphate (DEP) formed
me thyl-DEP
ethyl-DEP
is op rop ‘i l—D’ (
n-bu tyl—DEP
isobu tyl—DEP
sec—butyl—DEP
isoamyl—DEP
ph e ny l—DP
o—crcsyl—DEP
rn—cresyl—DEP
—cresy1—DEP
2—isopropy lphenyl—Dr:P
4—isopropyiphenyl—DEP
2,3—dimcthvlph nv1—DEP
2, 4—dirnethylphenvl—DEP
2, 5—dimethvlphenvl—DEP
2, 6—dimethyiphenvi—DEP
3 , 4—di: cthylpheny 1—DC?
3 , 5—dime Lhv1ph rw1_DCP
Retention
162
201
224
347
256
287
445
233
247
347
431
558
353
307
265
227
460
323
Column
temp., °C
150
150
150
150
150
150
150
180
180
180
180
180
180
190
190
190
190
190
190
io2
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LU
C l )
2:
0
( I )
uJ
cc
cc
LU
0
cc
C
0
LU
cc
TIME (MINUTES)
Figure 1. Isothermal chromatogram (150°C) of Mixture of
7 phosphorylated alcohols (mg derivatized):
1, methanol (1.75); 2, ethanol (1.25); 3, isopropyl
alcohol (3.00); 4, isobutanol (3.00); 5, sec—butanol
(2.25); 6,n—butanol (3.50); 7, isoamyl alcohol (3.80).
I I I I I I
0123456
13
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LU
C,,
2
0
C t )
LU
cc
cc
LU
0
cc
0
C-)
LU
cc
— a I I I L I
0123456
TIME (MINUTES)
Figure 2. Isothermal chromatogram (190°C) of mixture of
phosphorylated phenols, cresols, and xylenols
(mg derivatized): 1, phenol (2.0); 2, 2,6—xylenol
(1.3); 3, rn—cresol (2.5); 4, 2,5—xylenol (2.4);
5, 2,3—xylenol (2.0); 6, 4—isopropyiphenol (2.2);
7, 3,4—xylenol (2.6).
3
6
7
14
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Figure 3. Isothermal chromatogram (190°C) of mixture of
5 phosphorylated xylenols (mg derivatized):
1, 2,6—xylenol (1.0); 2, 2,5—xylenol (1.7);
3, 2,4—xylenol (2.0); 4, 2,3—xylenol (3.0);
5, 3,4—xylenol (2.3).
LU
C / ,
2
0
c i.
(I )
LU
LU
0
C
U
LU
0123456
TIME (MINUTES)
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Table 2. 1ini urn decec table levels of
alcohols/phenolsa
Alcohol/phenol Mini’nun detectable
quantity in ng
Ethyl alcohol 10
Phenol 10
rn—Cresol 10
2,3—Di-ieth 1 henol 20
2,6—Dimechyiphanol 15
3,4—DLinethvlph nol 25
2—Isopropyiphenol 20
detectable qudncities are amounts that gave l0 of
the rna :imurn recorder r sponse.
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Although we have not directly compared the pentafluorobenzyl derivative
method of Kawahara (I i) or the acetate derivative method of Coburn and Chan (10)
with our derivative method, we are using a flame photometric detector in the
P mode which is very sensitive to organophosphates or compounds which will
form organophosphates with the phosphorylation reagent. In contrast, electron
capture detectors are not specific to a chemical class. The derivatization
procedures are different and each may be more useful with certain samples.
Commercial Aryl Phosphate Analysis
The components of commercial aryl phosphate esters identified in the
present work are listed in Table 3. The mass spectra of the different com-
pounds found in these commercial samples have been tabulated in Table 4. We
have been able to synthesize all the isomers of triaryl phosphate esters con-
taining phenol and cresols. We could, therefore, identify the presence of
several of these isomers in the commercial samples by comparing their retention
times with those of the synthesized isomers. In the case of higher molecular
weight aryl phosphate esters containing isomeric xylenols and C 3 —phenols, our
identification is only based on the mass spectral data and supported, in part,
by the retention times. Exact identification in the case of xyleuol and C 3 —
phenol TAP esters was not possible, as some of these phenols were not commer-
cially available and none of these aryl phosphates were synthesized.
Using a planimeter, we have measured the area of each peak, and from the
area values we have calculated the relative proportion of the various components
present in each mixture (Table 3). The results clearly indicate that, with the
exception of the Kronitex tricresyl phosphate sample, most of the aryl phosphates
contain significant amounts of triphenyl phosphate. This is consistent with the
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Table 3. Components of Commercial Aryl Phosphate Oils
Scan Mol. Wt.
from
Relative Compound Identified Identification
Parent Ion
Proportion
Criteria, GLC/MS
(m/e)
(%)
and, where indicated,
GLC of Purchased/
Synthesized Compound
Kronitex TCP (FMC)
141 368 20.7 TCP — TmCP Purchased
144 368 38.8 TCP — DmCpCP Synthesized
147 368 30.4 TCP — DpCtuCP Synthesized
151 382 9.2 DCXP
Santicizer 140 CDP (Monsanto)
131 326 14.7 TPP Purchased
141 340 18.6 CDPP—mCDPP Synthesized
145 340 14.4 CDPP—pCDPP Synthesized
151 354 15.2 PDCP
154 354 14.2 PDCP
159 368 6.8 TCP
163 368 7.4 TCP
166 368 5.2 TCP
Fyrquel CT (Stauffer)
127 326 19.2 TPP Purchased
136 340 2.1 CDPP — InCDPP Synthesized
147 354 3.2 PDCP Synthesized
156 382 3.9 DCXP
168 382 32.3 DCXP
192 438 3.9 (C 3 —phenyl) 2 xyleny l
phosphate
205 438 33.2 (C 3 —phenyl) 2 xylenyl
phosphate
Phosfiex 41—P (Stauffer)
126 326 11.9 TPP Purchased
135 340 2.1 CDPP — tnCDPP Synthesized
141 368 14.7 TCP
148 368 9.4 TCP
154 368 16.7 TCP
160 410 9.4 TXP
166 452 10.7 (C 3 —pheny l) 3 phosphate
172 452 9.3 (C 3 —phenyl) 3 phosphate
179 452 5.6 (C 3 —pheny l) 3 phosphate
186 452 3.1 (C 3 —phenyl) 3 phosphate
195 weak spectrum 2.8
206 weak spectrum 1.6
214 weak spectrum 2.5
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Table 3. Components of Commercial Aryl Phosphate Oils (Cont’d)
Scan
Mol. Wt. from
Relative
Compound Identified
Identification
Parent Ion
Proportion
Criteria, GLC/MS
(m/e)
(%)
and, where indicated,
CLC of Purchased/
Synthesized Compound
Pydraul — 50 E (Monsanto)
105
326
18.4
TPP
Purchased
112
0.6
———
———
123
295
0.8
Hydrocarbon
———
132
0.6
———
———
142
0. 8
———
———
151
0. 4
———
———
162
1.2
———
———
189
452
52.8
DPNPP
Synthesized
225
444
24.0
DPCPP
Synthesized
Explanation of Abbreviations Used
Cresyl diphenyl phosphate
Meta cresyl diphenyl phosphate
Para cresyl diphenyl phosphate
—DmCpQrP Di meta—cresyl para—cresyl phosphate
D.pCmCP Di para—cresyl meta—cresyl phosphate
DCXP Dicresyl xylenyl phosphate
DPCPP Diphenyl 4—cumyiphenyl phosphate
DPNPP Diphenyl p—nonylphenyl phosphate
PDCP Phenyl dicresyl phosphate
-TCP’ Tricresyl phosphate
Triphenyl phosphate
TmCP Tn meta—cresyl phosphate
Trixylenyl phosphate
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Table 4. E lass Spectra of Components of Cornniercidi Aryl Phosphate Oils
Sc ii Name of Compound Mel Wt (rem H + I Other Ions
rarent Ion
(ce/e)
0
Krcl’Ito\
T(I’ ( IC)
141
fIL ra—crosyl phosphate
368
(100)
20 9
367
(49.4), 366 (3 4), 243 (6.3), 91 (5 3)
144
r)1_rn_cresyl —cresy1 phosphate
368
(100)
22 6
367
90
(54 8), 279 (6 4), 26L (8 9), 198 (9.3), 165 (6 0), 10? (5.4),
(6 2)
147
Di— —cresy1 n-cresyl phosphate
368
(100)
12 9
367
(66), 279 (9.3), 243 (8.9), 179 (13 1), 108 (18.7), 76 (102)
151
Otcreeyl xytenyl phosphate
382
(100)
24 2
i81
193
105
(21 6), 368 (48 2), .367 (38 7), 293 (6.2), 243 (5 9), 194 (18
(10 4), 180 (9.8), 179 (14 4), 178 (16.0), 121 (8.2), 108 (21
(15 0), 90 (15 0)
6).
9) ,
Sent iciest
140 00? (l4onsantp)
326
(100)
14 4
325
(66 4), 234 (6 3), 170 ( . l), 76 (2 1)
131
Traplrenyl phosphate
141
rn—C esy1 diphenyl phosphate
340
(100)
14 3
339
(59 6), 338 (5.4), 247 (5.8), 164 (3 9), 76 (6.4)
145
—Creey1 diphenyl phosphate
340
(100)
16 1
339
(51.9), 184 (6 6), 165 (5.3), 76 (13 1), 64 (6.3)
151
Phenyl dicresyl phosphate
354
(100)
25 1
353
(62 0), 352 (5.8), 247 (3.7), 181 (14 9), 90 (5.4)
154
Pherrvl dicresyl phosphate
368
(100)
19 5
353
(51 4), 184 (3 9), 107 (3.0), 76 (3 6), 64 (2 7)
159
Pricresyl phosphate
368
(100)
27.5
367
(38 1), 353 ( Ii 5), 277 (5 2). 195 (64), 109 (5 8)
163
Tricrcsyl phosphate
368
(100)
22 7
367
(53.1), 181 (5.9), 113 (7.2), 99 (6 3), 70 (9 0), 56 (10 4)
166
Tr cresy1 phosphate
368
(100)
21 0
367
165
(47 7). 361 (6 0). 261 (6 8), 198 (6.0), 197 (5)), 195 (5.)),
(5 1). 102 (6 6), 91 (8 2), 76 (3 7)
-------
Table 4. El Mass Spectra of Components of Commercial Aryl Phosphate Oils (Conctd)
382 (23 7) 6 4 369 (6 1). 368 (34.2), 367 (100)
382 (17 2) 4 5 368 (21 6). 367 (100). 76 (10 6)
438 (23.2) 7 8 424 (30 8). 423 (100), 422 (5.5), 367 (22 3), 204 (5 5). 141 (7 5),
99 (9 4), 97 (7.5), 85 (7 4), 56 (11.0)
438 (26.6) 7 6 424 (39.4), 423 (tOO), 367 (ii.?), 204 (6 9)
368 (100) 21.9 361 (9.8), 353 (13 3), 251 (8.7), 250 (9.5), 249 (5.9), us’ (5 9),
118 (13.8), 117 (35.2), 116 (13 8), 102 (8.2). 76 (23.5)
354 (13.8), 353 (100), 352 (1 .3), 117 (8.9). 76 (16 7)
409 (19 1), 396 (7 5), 395 (33.6), 368 (14.5), 367 (72 6), 293 (11 8),
292 (8.8), 202 (9 i), 160 (15 6), 159 (25 9), 144 (29 4), 117 (8 6),
1L6 (7.4). 90 (7 5), 76 (12 7)
452 (12 6) 3.9 410 (100), 409 (16.0), 396 (9.2), 395 (32 8), 353 (10.0), 293 (27 6),
292 (20.1), 277 (18 5), 117 (21 9), 116 (11.8), 102 (10.4), 90 (13.0),
76 (14 6)
452 (26 9) 7 9 437 (7 9), 411 (12 3), 410 (44.1), 409 (12 0), 396 (23.8), 395 (100),
293 (9.5), 159 (9.2), 144 (14 0), 103 (7.9)
452 (16.5) 5.0 411 (10 5), 410 (38 6), 409 (10 6), 396 (23.2), 395 (100), 394 (8.5),
335 (8 1) , 293 (5 7)
45? (100) 29 8 438 (16.7), 437 (44), 409 (23 8), 367 (LI 1), 353 (L5 5), 335 (15 4),
334 (17 8), 319 (16 7), 293 (19 0). 292 (17 9), 277 (16.7), 159 (19 0),
145 ( 15 S), 70 (I I 1), 56 (14 3), 42 (10 7)
1
—)
Fy i flue
156
168
192
CT (Svauffei
DlLre yl ‘celenyl phosphate
Dicresyl xylenyl phosphate
(C 3 —phenyl) 2 mylenyl phosphate
Scan Name ol Compound Mol Wt from N + I Other Ions
Parent Ion
(m/e)
368 (36 2)
410 (100)
205 (C 3 —phenyl) 2 xy lenyt phosphate
Pliosfiex 41—P (Stouffer )
141 Trictesyl phosphate
154 Tricrosyl phosphate
160 Trs’cylenyl phosphate
166 (C 3 —phenyl) 3 phosphate
172 (C 3 —phenyl) 3 phosphate
179 (C 3 —phenyl) 3 phosphate
186 (C 3 —plien yl ) phosphate
86
26 1
-------
Table 4. El Mass Spectra of Components of Commercial Aryl Phosphate Oils (Cont’d)
Scan
N. rne of Compound
Mol Ut. from
P irent Ion
(mje)
N +
Other ions
Pydraul 50 r ( Ion anLo)
123 Hydiocarbon
295 (12
7)
— —
281
197
155
99
(14.5),
(16 3),
(JO 6),
(23 6),
267 (10 9), 239 (12 7), 225 (10 9), 211 (16.3),
183 (21.8), 182 (14 5), 169 (21 8), 168 (10 9),
154 (12 7), 141 (20 0), 127 (27.2), 113 (34.3),
85 (70 7), 71 (12 7), 56 (100)
189
Diphenyl —nony1pheny1
phosphate
452 (2
0)
0 6
423
(10.8),
38L (27.5), 361 (100). 353 (12.8), 339 (6.5)
225
Dlphenyl 4—cumyiphenyl
phosphate
444 (29
5)
6.1
429
(100), J
67 (3 9), 214 (3.2), 178 (5.4), 152 (4 0), 77 (5.6)
NJ
NJ
-------
results of Murray (4) who detected sizable quantities of phenol in his four
hydrolyzed commercial samples. The tricresyl phosphate commercial sample
(Electric Reduction Company of Canada) that Murray (4) examined contained
phenol, whereas the TCP sample we examined contained mostly cresols and small
quantities of xyleno ls.
The only aryl phosphate sample analyzed by both Murray (4) and us was
Fyrquel9 (Stauffer). Our results would suggest that both cresols and xylenols
should be present in the hydrolysis product. Murray (4) found only two long
retention time peaks besides phenol. The two peaks were not cresols and probably
were not xylenols, since Murray (4) had determined the retention times of six
xylenols. We suspect that some isopropyiphenol isomers were present in the
mixture. Stauffer has manufactured isopropylphenol diphenyl phosphate in the
past (1). Both the Fyrquel CT and Phosflex 41—P, which are both produced by
Stauffer, contain components whose mass spectra suggest some type of C 3 — phenol
structure. Trimethylphenols would be expected to have a sizable M—l peak in
the mass spectrum due to loss of one hydrogen from one of the methyl groups to
form a stabilized tropylium ion (see mass spectrum of tricresyl phosphates).
Since the M—l peak is absent and a 1 1—15 peak (loss of —CH 3 ) is present, the
isopropyl structure seems reasonable. However, the molecular weights and mass
spectrum fragmentation pattern could be explained by blends of ethylphenols,
n—propylphenols, or other alkylpheno ls.
The composition of the Pydraul SOE produced by Monsanto seems to be entirely
different from the rest of the commercial samples analyzed. As with other
samples, triphenyl phosphate is present, but significant amounts of two higher
molecular weight aryl phosphates with high retention times are also present.
23
-------
Lombardo (19) examined Pydraul 50E and characterized the last two peaks as
diphenyl nonylphenyl phosphate and diphenyl cumyiphenyl phosphate, respectively,
in order of increasing GLC retention time. We have synthesized the two com-
pounds and have obtained their mass spectra. The spectra of the synthesized
compounds are exactly identical with those of the corresponding Pydraul 50E
peaks.
The small amount (0.8%) of a hydrocarbon was also detected in the Pydraul
50E peaks. The mass spectrum fragmentation pattern is typical of a straight
chain hydrocarbon and the highest m/e peak corresponds to a formula of C 21 H 44 .
The o—cresyl isomers in commercial aryl phosphates can have a consider-
able effect on the neurotoxic potential of the material. In initial studies,
the retention times of some of the diphenyl cresyl and tricresyl phosphate
isomers corresponded to isomers that contained o—isomers. Because the peak
resolutions were not that good, we hydrolyzed both t-he .Santicizer 140 CDP and
the Fyrquel GT by the method used by Murray (4), methylate iolysis
products, and examined the products for o—cresol. We were unable to detect any
o—cresol and, theref re conclude that any amounts of o—cresol-—ilfesent in feed—
stocks used to produce aryl phosphates are probably—’ csmall.
Besides GLC/MS analysis of five samp]. reported in this paper, we also
examined, by gas liquid chromatography, similar commercial products made by
other companies. Our results indicate that the components of one particular
commercial sample made by different companies were almost similar, but their
relative proportion was different. For example, COP’s from FNC Corporation
and IMC Chemical Group had similar peaks as were found in CDP from Monsanto,
but their relative proportions were differ’ent in all three samples. Similar
24
-------
was the case with TCP’s from Stauffer and IMC Chemical Group with respect to
TCP from FTC.
All of the aryl phosphates analyzed were taken from only one sample of
the commercial product received in this laboratory and, therefore, may not be
representative of the products. Chemical processes change, as do feedstocks,
so the proportions and compounds of the commercial mixtures may change con-
siderably.
Hydrolysis
Figure 4 presents the results obtained for the disappearance of triphenyl
phosphate (TPP) and the formation of diphenyl phosphate (DPP) at room tempera-
ture. The slope of the lines is proportional to the rate constants. The dis-
appearance plots very clearly indicate that the hydrolysis rates of TPP are
much faster in alkaline conditions than those in neutral or acid conditions.
The half—lives at pH 9.5 and 8.2 were 1.3 days and 7.5 days, respectively.
Degradation rates under neutral and acid conditions were too slow to reliably
measure the rate constants. Figure 4 also illustrates the pH dependence of
the alkaline hydrolysis which is consistent with the second—order reaction
mechanism (SN 2 attack at phosphor us) which has been frequently proposed for
alkaline hydrolysis of organophosphate esters (20). The increase in the hydrol-
ysis rate with increase in pH has been observed for a variety of organophos—
phate esters (15,20,21).
The hydrolysis rates are within reason relative to the results of Barnard
etal. (15). They used a dioxane—water (3:1 v/v) media which should result in
slower hydrolysis rates than reactions in water. Thus, the calculated alkaline
half—lives (23 and 472 days for TPP at 24.7°C and pH ’s of 9.5 and 8.2, respec-
tively) were considerably higher than our experimental values.
25
-------
6
TPP pH 9.5
I I I I
0 1 2 3 4 5 6 7 8 9 10 11 12 1314 15 16
Days
Figure 4 . Triplienyl PhosphaLe (TPP) Loss and Diphenyl
Phosphate (DPP) Appe.irance in Distilled Water
C
5
TPPpH 4.5
4
x
+
U
0
C)
C
3
2
7 DPP pH 8.2
1
26
-------
Figure 4 also presents data on the formation of diphenyl phosphate under
the two alkaline conditions. Although the data points are scattered because
of poor reproducibility in the extraction procedure, the results indicate that
diphenyl phosphate is formed faster at higher pH which is expected from the
disappearance kinetics. The analytical procedure used would also have detected
monophenyl phosphate and its lack of detection is consistent with the stability
of diphenyl phosphate under acid and alkaline conditions (16).
Figure 5 presents the disappearance rates for triphenyl phosphate in some
alkaline natural waters. Triphenyl phosphate is considerably less soluble in
these natural waters (0.2—0.3 ppm) than in alkaline distilled water (1.4—1.6 ppm).
The disappearance rates for all three natural waters are interesting in that
very little degradation occurs for the first two days, but then a very rapid
loss occurs at a rate that is faster than in distilled water at comparable pH.
For example, after two days the pseudo—first—order rate constant for Lake Ontario
(initial pH 8.2) is 0.64 days , while for the Seneca River (initial pH 8.2) the
rate constant is 0.34 days 1 . However, the pseudo—first—order rate constant for
buffered distilled water at pH 8.2 is 0.093 days 1 . Some of the difference
between distilled and natural waters may be due to temperature differences,
since the temperature was not exactly the same (21 ± 2°C) for the distilled
and natural water runs. However, all the natural water runs were run under
the same conditions so that temperature cannot explain the difference between
Lake Ontario and Seneca River results. The reason for the initial delay is
unknown. If microbial enzymatic hydrolysis is important as has been observed
previously (22), this period may be required for acclimation. However, since
_ _ -
the rate is so much slower than what would be expected for chemical hydrolysis,
27
-------
Lake Ontario pH 8.2
at 8 days-not detectable)
10 11 12 13 14
Disappearance of Triphenyl Phosphate (TPP)
from Lake and River Waters
N
C ’,
LU
C%J
5
cc
+
0 )
0
0
C
4
3
2
1
Lake Onondaga
pH 7.8
(at 8days-
not detectable
Seneca River pH 8.2
0
0
1
Days
Figure 5.
28
-------
it is suspected that some type of adsorption process, either on microorganisms
or on the suspended solids that passed through the 11 micron filter, may be
regulating the degradation rate initially. The exact mechanism of triphenyl
phosphate loss in natur &al waters in unknown.
The disappearance of pure isomers of tricresyl phosphate in Lake Ontario
water has also been studied (Figure 6). Here again, the initial lag period
was observed, followed by a rapid disappearance of the tricresyl phosphate.
The ortho—isomer degraded slightly faster than the meta—isomer and both isomers
were degraded faster than the ara—isomer, which degraded about as fast as tn—
phenyl phosphate.
In order to determine if the commercial aryl phosphates degraded in the
same manner as the pure aryl phosphates, we studied the degradation (disappear-
ance) of four commercial aryl phosphates by Lake Ontario water (initial pH 8.2)
at concentrations equal to their solubilities. Our results (Figure 7) clearly
indicate that even the more complex aryl phosphates undergo rapid degradation
by lake water. The degradation was slow during the first 48 hours. Neverthe-
less, all four aryl phosphates tested showed very rapid degradation by the lake
water in 5—6 days, with most of the major components disappearing and new coni—
pounds with lower retention time being formed.
The methylated ether extract of the water samples containing the commercial
aryl phosphates was analyzed by GLC—MS. Considerable change between the GLC—MS
of the hydrolyzed and unhydrolyzed commercial samples was noted. The GLC—NS of
the water samples was extremely complex and contained many interfering hydro-
carbons. However, in several of the samples small amounts of the methyl ester
of diphenyl phosphate were detected.
29
-------
+
c i
0
0
Figure 6.
Loss of Tricresyl Phosphate (TCP)
Isomers in Lake Ontario Water
N
I - .
r.J
4
p — TCP
1
m— TCP
0
1
2
34
Days
30
-------
mm. x 10—2
TCP ( l2Ohrs.
Figure 7. Disappearance of Commercial Aryl Phosphate in
Lake Ontario Water (pH 8.2) Using GLC—FPD
Q
350-360
-4
‘ -4
mm. x 10—2
CDP(Ohr
mm. x 102
CDP ( 120 hrs.
min.x 10—2
Fyrquel GT (Ohr.)
mm. x ,o 2
FyrqLIeI GT ( l2Ohrs.)
575
628
315
mmm i. x 10-2
TCP ( Ohr.
flhifl x 10_2
Phosfiex 41•
nmmn. x 102
P. ( l2Ohrs.
31
-------
Our results for commercial samples in natural waters are much faster than
the half—lives of 52 to 140 days for the degradation of IMOL S—140 in Old Krow
River water (18). The difference in their results may be due to: (a) the use
of acid natural waters and (b) the measurement of orthophosphate formed rather
than the loss of the triaryl phosphate.
In summary, it appears that triaryl phosphates will degrade at appreciable
rates in distilled and natural waters under alkaline conditions found in nature
to apparently stable, water—soluble products such as diaryl phosphates. The
mechanism of degradation in alkaline natural waters is not well understood and
the rate of degradation of triaryl phosphates in natural waters under neutral
or acid conditions needs to be studied further.
32
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