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ANALYTICAL CHEMISTRY, VOL. 50, NO, 11, SEPTEMBER 1978
to be capable of quantitation of mixtures with a large number of unresolved components. We felt that the differences in the approach of these two methods in handling multiplets were important to the reader and regret that our concept of the status of their method was not accurate. The problem of peak deconvolution is of key importance, obviously, because it is central to the choice of combined gas chromatography-mass spectrometry systems rather than gas chromatography alone for quantitative metabolic profiling.
(2) R. G.Dromev, M. J. Stefik, T. C. Rindfleisch, and A. M. Duffield, Anal. Chem., 48, i 3 6 8 (1976). (3) D. H. Smlth, M. Achenbach, W. J. Yeager, P. J. Anderson, W. L. Fitch, and R. C.Rindfleisch, Anal. Chem., 49, 1623 (1977).
C h a r l e s C. Sweeley* S t e p h e n C. G a t e s John F. Holland Department of Biochemistry Michigan State University East Lansing, Michigan 48824
LITERATURE CITED (1) S.C. Gates, M. J. Smisko, C. L. Ashendel, N. D. Young, J. F. Holland, and C. C.Sweeley, Anal. Chem , 50, 433 (1978).
RECEIVED for review May 8, 1978. Accepted May 26, 1978.
Chlorinated Benzyl Phenyl Ethers: A Possible Interference in the Determination of Chlorinated Dibenzo-p -Dioxins in 2,4,5-Tric hlorophenol and Its Derivatives Sir: The routine determination of the 2,3,7,8-tetrachlorodibenzo-p-dioxin (2,3,7,8-TCDD) content of 2,4,5-trichlorophenol, 2,4,5-trichlorophenoxyaceticacid esters and 2,4,5-trichlorophenoxypropionicacid esters is by a procedure involving silica gel column chromatography sample preparation followed by GC-MS detection ( 2 , 2 ) . The method is quite specific requiring proper elution through the silica gel column, proper retention time in the gas chromatograph, proper molecular weight as monitored at m / e 320, 322, and 324, and proper isotope ratios as measured from the peak heights of each ion monitored. However, a t the high sensitivities required (less than 0.1 ppm) for this determination, other peaks are observed in t h e mass spectrometer output, some of which are in the TCDD retention time region with the correct isotope ratios for tetrachloro compounds. By preparing a larger than normal 2,4,5-trichlorophenol sample, we have been able to identify several "caustic insoluble" components some of which have a potential to be mistaken for chlorinated dibenzo-p-dioxins by GC-MS. EXPERIMENTAL Apparatus. Mass spectra were obtained on an LKB-9000 with a System Industries S-150 computer system. The gas chromatography column was 9 f t X 2 mm i.d. glass packed with 370OV-1 silicone on 80/100 mesh Chromosorb W-HP. The column temperature was programmed from 100 to 240 "C at lO"/min. Accurate mass measurements were performed on an AEI MS-30 GC-MS. The gas chromatography column used was 6 f t X 2 mm i.d. OV-210 silicone on 80/100 mesh Chromosorb W-HP temperature programmed from 125 to 220 "C a t 6'/min. Mass measurements were performed by the DS-50 data system and the results reported are the average of a t least five determinations. The mass chromatograms in Figures 2 and 3 were obtained using a Finnigan 3000 GC-MS with the PROMIM attachment. The gas chromatograpy column used was 6 ft X 2 mm i.d. glass packed with 3% OV-3 silicone on 80/100 mesh Gas Chrom Z. Column temperatures are listed in the Figures. The chromatogram in Figure 1 was obtained by gas chro0003-2700/78/0350-1586$01.00/0
Table I. Mass Spectrum of Chlorobenzyl Trichlorophenyl Ether possible identity mle rel. abund." 320 1.0 0.1 321 1.8 molecular ion, M' 322 0.1 (measd 319.9231, theor. 319.9329) 323 0.8 3 24 0.1 325 196 197 198 199 200
0.8 0.1
167 169 171
2.1 2.1
125 126 127 128
100.0
99 101
11.5 2.5
C,H,Cl'
89 90
31.8 9.9
C7H6'
G3 62 61
14.4
C,H,OCl,',
trichlorophenol ion
0.8
0.1 0.3 C,H,Cl,+
0.8
7.9 39.3 2.5
C,H6Cl+,chlorobenzyl (tropyllium) ion
C,H,+
6.8 3.1
a The relative abundances, especially for the weaker ions, may be in error by + 50% because of the presence of background which was subtracted by the data system.
matography with flame ionization detection using a 10 ft X 2 mm i.d. glass column packed with 1070 OV-101 silicone on 100/120 mesh Gas Chrom Q. The column temperature was programmed from 120 to 250 "C at 8"/min. Reagents. 2,6-Dichlorobenzyl-2,4,5-trichlorophenyl ether was synthesized by refluxing a solution of 2,6-dichlorobenzyl bromide 'C 1978 American Chemical Society
ANALYTICAL CHEMISTRY, VOL. 50, NO. 11, SEPTEMBER 1978
Table 11. Mass Spectrum of Dichlorobenzyl Trichlorophenyl Ether mle
rel. abund.a
possible identity
354 355 356 357 358 359 360
1.2 0.9 1.9 0.2 1.3 0.1 0.3
molecular ion, M' (measd 353.8806, theor. 353.8939)
318 321 323
0.07 0.08 0.03
(M
318 320 322
0.1 0.15 0.05
( M - HC1)'
28 3 285 28 7
0.4 0.4
( M - H, 2C1)'
249 251 253
0.3 0.2 0.05
196 198 200 159 160 161 162 163 164 133 135 137
-
Cl)'
0.1
1.2 1.2 0.3 100. 10.6 66.9 5.3 10.4
( h l - 3Cl)i
C,,H,OCl,+, trichlorophenol ion
C,H,Cl,+, dichlorobenzyl (tropyllium) ion
0.7
3.4 2.3 0.5
C,H,Cl,'
124 5.9 1.4 C7HjC1' 126 13.1 C,H,+ 89 63 9.0 C,H,' 62 6.7 C,H,+ a The relative abundances, especially for the weaker ions, may be in error by i 50% because of the presence of background which was subtracted by the data system.
1587
Table 111. Mass Spectrum of Trichlorobenzyl Trichlorophenyl Ether rel. possible identity mle abund.a 388 0.3 0.1 3 89 0.5 390 0.03 molecular ion, M' 391 0.4 (measd 387.8595, theor. 387.8550) 392 _.. 39 3 0.1 394 353 0.05 355 0.06 ( M - Cl)' --357 352 0.04 354 0.05 ( M - HCl)' 0.04 356 1 9 3 100. 194 7.9 195 63.9 C,H,Cl,+, trichlorobenzyl (tropyllium) ion 196 6.2 197 33.9 198 2.4 167 6.0 169 5.8 C,H,Cl,' 1.1 171 157 8.9 159 6.7 C,H,Cl,+ 161 3.8 158 5.4 160 4.2 C7H,Cl,+ 162 1.0 133 4.1 C,H,Cl,' 135 2.0 123 8.5 C,H,Cl+ 125 2.3 C,H,CI+ 99 1.8 C,H,CI+ 101 0.6 87 3.0 C7H,+ 63 4.4 C,H,+ a The relative abundances, especially for the weaker ions, may be in error by i 50% because of the presence of background which was subtracted by the data system.
(Ndrich) with 2,4,5-trichlorophenol in dioxane made alkaline with a stoichiometric excess of NaOH (Williamson Ether Synthesis). The crude product was isolated by dilution of the reaction mixture with water and extraction into hexane. The product was -70% desired product and -30% 2,6-dichlorobenzyl bromide starting material as determined by GC-FID. A concentrated solution of the neutral components from 2,4,5-trichlorophenol was prepared by scaling up the literature procedure (1) to accommodate a 100-g sample.
RESULTS AND DISCUSSION In order to identify components eluting near the retention time of TCDD, a highly concentrated extract of 2,4,5-trichlorophenol neutral components was prepared. As shown in Figure 1, mass spectra consistent with a series of p o l y chlorinated benzyl phenyl ethers were observed (Tables 1-111). To confirm the identity, an extract was analyzed with a mass spectrometer capable of accurate mass measurement. The measured masses are consistent with the assigned empirical formulas. One isomer, 2,6-dichlorobenzyl-2,4,5-trichlorophenyl ether,
Figure 1. GC-FID chromatogram of neutral components isolated from commercial 2.4,5-trichlorophenol (The large peak at 52 min. is bis2-ethylhexyl phthalate contamination fr'om the sample preparation)
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ANALYTICAL CHEMISTRY, VOL. 50, NO. 11, SEPTEMBER 1978
C
A A III/
, 0
5
,
y,, ,r;320 ' Omin
Figure 3. Mass chromatograms from an extract of 2,4,5-trichlorophenoxy acetic acid:butoxy ethanol ester concentrated 10: 1, (-) sample, (---)standardsolution of 2,3,7,8-TCDDcorresponding to 0.03 ppm in the sample. GC column temperature, 125-230 O C at 10°/min Figure 2. (A) Mass chromatograms from an extract of 2.4,5-trichlorophenoxy acetic acid:propylene glycol-isobutyl ester concentrated 1O:l. (6) Mass chromatograms from a 3 p g h L solution of 2,6dichlorobenzyl-2,4,5-trichlorophenyl ether. (C) Mass chromatograms from a 0.10 I.cg/mL solution of 2,3,7,8-TCDD corresponding to 0.01 p p m in the sample. GC column temperature, 225 O C was synthesized and its mass spectrum and chromatographic elution characteristics vis-a-vis TCDD were determined. The mass spectrum is identical to the mass spectrum of the substance obtained from 2,4,5-trichlorophenol in Table 11. The elution time is slightly later than 2,3,7,8-TCDD as shown in Figure 2, B and C. It yields a response a t m / e 320, 322, and 324 due to a low abundance fragmentation and may be mistaken for a TCDD isomer if only the molecular ion of TCDD is monitored. A substance with the same retention time and ion response is observed in extracts of the butoxyethyl- and propylene glycol-isobutyl esters of 2,4,5-T as shown in Figure 2A and Figure 3.
LITERATURE CITED (1) W. B. Crurnmetl and R. H. Stehl, Environ. Health Perspectives, 5 , Sept. 1973. (2) T. Ramstad, N. H. Mahle, and R. Matalon. Anal. Chem., 49, 386 (1977). (3) H. R. Buser, J . Chromatogr., 107, 295 (1975).
L. A. Shadoff* W. W. Blaser C. W. Kocher The Dow Chemical Company Analytical Laboratories Midland, Michigan 48640
H. G. Fravel The Dow Chemical Company Organic Chemicals Research Lab Midland, Michigan 48640 RECEIVED for review February 10, 1978. Accepted April 26,
1978.
