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 ------- 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 ------- 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 ------- 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 ------- 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. ------- 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 ------- —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. ------- 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. ------- 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 ------- 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 ------- 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. 9 ------- 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. 10 ------- 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. 11 ------- 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 12 ------- 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 ------- 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 ------- 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) 15 ------- 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. 16 ------- 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 17 ------- 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 18 ------- 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 19 ------- 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 ------- REFERENCES (1) Lapp, T.W. (1976), “Study of Chemical Substances from Information Concern- ing the Manufacture, Distribution, Use, Disposal, Alternatives, and Mag- nitude of Exposure to the Environment and Nan. 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