Alkyl P h t h a l a t e s . Alkyl phthalates used generally as plasticizers in plastic tubing fabrication have become ubiquitous contaminants in the environment. An organic concentrate from a refinery effluent water sample was found to contain low concentrations of di-n-butyl phthalate. The sample consisted mainly of naphthenic acids. The mass spectra of n-dibutyl phthalate shows a characterizing base peak a t mle 149 which results from the decomposition routes shown in Figure 11. The metastable spectrum is shown in Figure 12, top, for pure di-n-butyl phthalate. Figure 12, bottom, shows the search for phthalates in the organic concentrate from the refinery water sample. The presence of phthalate is clearly shown. M T Peaks A and B are due to Transitions A and B shown in the scheme in Figure 11. Even in the presence of other components which form an mle 149 ion on electron impact, the progenitors are sufficiently different in mass so that the phthalate metastable peaks are clearly resolved.
derstood. Once the magnet is set to accept only one preselected mass, say Mz+,the only time the multiplier will produce a signal is when the correct parent ion, MI+, and accelerating voltage, V, are found. All this happens in the presence of many other components and transitions which are ignored. So MA has many of the benefits of GC-MS but doesn’t require an actual separation of molecules. LITERATURE CITED (1) J. A. Hipple and E. U. Condon, Phys. Rev.. 68, 54 (1945). (2) R. G. Cooks, J. H. Beynon, R. M. Copriol, and G. R. Lester, “Metastable Ions”, Elsevier Scientific Publishing Company, New York. N.Y.. 1973. (3) K. R. Jennings, Some Aspects of Metastable Transitions, Mass Spectrometry Techniques and Application”, G. W. H. Milne, Ed., Wiley-lnterscience, New York, N.Y., 1971. (4) R. M. Teeter and W. R. Doty, Res. Sci. lnst.. 37, 792 (1966). (5) H. Budzikiewlcz,J. M. Wilson, and C. Djerassi, J. Am. Chem. SOC.,85,3666 ( 1963). (6) L. Tokes, G. Jones, and C. Djerassi, J. Am. Chem. SOC.,90, 5465 (1968). (7) E. J. Gallegos, Anal. Chem., 43, 1151 (1971). 8) J. W. Otvos and D. P. Stevens, J. Am. Chem. SOC.,78,546 (1956). (9) E. J. Gallegos, Anal. Chem., 47, 1524 (1975).
SUMMARY M T analysis may be applied only if the decomposition processes of the molecular types being searched are well un-
RECEIVEDfor review November 17,1975. Accepted April 16, 1976.
Determination of Sub Parts-per-Million Levels of sec-Butyl Chlorodiphenyl Oxides in Biological Tissues by Plasma Chromatography James C. Tou” and Glenn U. Boggs Analytical Laboratories, The Dow Chemical Company, Midland, Mich. 48640
Plasma chromatography was found to be a reliable quantitative analytical technique exhibiting high sensltlvity and isomer specificity in the cases studied. The precision, in terms of relative standard deviation, of the technique In the determination of sub-ppm levels of sec-butyl chlorodiphenyloxides in biological tissues was determinedto be better than 20% at 9 5 % confidence level. Because of the observed narrow dynamic range, the sample matrix effect is often encountered and must be reduced to a tolerable level by solvent dilution before any reliable result can be obtained. It is essential In thls work that a gas chromatograph be used to provlde separation of matrix components. This reduces the competition of the matrix components in the ion-molecular reactions against the components of interest. The characteristic exponential responses of plasma chromatography and its effect in quantltative analysis are also discussed. The analytical results from plasma chromatography are in excellent agreement with those from other techniques.
Plasma chromatography is a relatively new analytical technique and it has been the subject of several reviews (1-3). T h e instrument is capable of forming and detecting both positive and negative gaseous ions, which are generated from ion-molecular reactions a t atmospheric pressure. When dry air is used as the carrier gas introduced into the instrument, the trace amount of water in the air undergoes a series of ion-molecular reactions with the air molecules ionized with the use of a 63Nielectron source in the generation of the major
reactant ions, (H20),H+ and (H20),02-, where n is dependent on both temperature and water concentration. These cluster ions, in turn, react with the trace amount of sample molecules introduced to form the product ions. The resulting mixture of gaseous ions is then pulsed out from the ion-molecular reaction chamber into an ion drift tube where separation occurs. The drift tube has a defined length and is maintained a t a constant electric field. The times for the ions to arrive a t the detector, or the drift times, are characteristic of the ions formed under the experimental conditions. An initial effort of research in plasma chromatography was the correlation of the drift time with the molecular weight in an attempt to utilize the plasma chromatograph as one of the means for the molecular weight determination of a component present a t trace levels; however, after a few years of the correlation study, it is recognized t h a t the error for such determination is about 2% for a homologous series and reaches 20% for a nonhomologous series ( 4 ) .Therefore, the plasma chromatograph is not reliable for such an application. Fundamental correlation studies of the mobility spectra with the molecular structures have been conducted for many classes of compounds, such as alkyl ethers ( 5 ) ,alcohols (6), halides (7), halogenated benzenes (8) and halogenated nietc. However, there is still serious lack of troaromatics (9), knowledge in the interpretation of the mobility spectra. Based on the knowledge now available, it is extremely difficult, if not impossible, to elucidate the structure of an unknown compound from its mobility spectrum. Because of these problems, plasma chromatography will have, in our opinion, a very limited use as a qualitative detector in gas chromatography ANALYTICAL CHEMISTRY, VOL. 48,
NO. 9,
AUGUST 1976
1351
Tektanir
"C and 210 "C depending on the column packing characteristics for a particular application. During GC-PC monitoring of a component of interest, the operating conditions are as follows: PC controller: repetition period, 24 ms; gate width, 0.2 ms. Boxcar integrator (CW-1): gate width, 0.2 ms; time constant, 10 ms. The clean-up procedures of Baughman and Meselson (14), and Shadoff and Hummel (151, were modified for this work. One to two grams of tissue were digested in 5 cm3/g of 20% KOH-5% CH30H solution overnight at room temperature. Fat tissue was first homogenized and digested in the above solution for only 20-30 min. The resulting digested solution was extracted with three 10-cm3portions of hexane. The combined hexane extracts were washed with 10 cm3 of distilled water in a separatory funnel and subsequentlywashed six times with 10 cm3 of concentrated sulfuric acid and finally with a 10-cm3distilled water wash. After washing, the hexane solution was transferred into a 100-cm3beaker, concentrated to approximately 0.5 cm3 and dissolved in 1-2 cm3of 20%benzene in hexane. This hexane solution was added to a 4 X 50 mm column packed with silica gel prewashed with methylene chloride, dried and preconditioned with several cm3 of 20% benzene in hexane solution. The eluent from the silica gel column was collected in a 2-dram vial. Both the beaker and the column were washed with small portions of 20%benzene in hexane until the vial was approximately full. The solution in the vial was gently evaporated to about 0.5 cm3and then transferred to an alumina (activatedat least 24 h at 140 "C) column of the same size as the silica gel column by means of a disposable pipet. The vial was washed with 1 cm3 of hexane, then six times with l-cm3 portions of 2% CCl4 in hexane and finally with 1cm3of hexane. Each of the l-cm3washings, was transferred to the top of the alumina column and the eluent was discarded. The sec-butyl chlorodiphenyl oxides were eluted from the alumina column into a 5-cm3cone-shaped vial with four 1-cm320% CH2C12 in hexane. The collected solution in the cone vial was then evaporated to approximately 100 to 200 fil with a gentle stream of air. The vial was then loosely capped and the remaining solution was evaporated to dryness. The residue was then dissolved in 50 pl of o xylene prior to analysis. For plasma chromatographic analysis,further dilution of this solution was necessary as discussed in the text. An LKB-9000-gas chromatograph-mass spectrometer equipped with an accelerating voltage alternator was used in GC-MS-MIDwork. The electrometer amplifier was modified by replacing the 20-MQ feedback resistor with a 500-MR resistor, resulting in a 25-fold increase in gain. The ion source and the separator were maintained at 290 "C and 250 "C, respectively. The electron energy was 70 eV and the trap current was regulated at 60 MA.
#-+/* -
Cmtrolkr
htcffacc
Varlan
0
1%
i
I
U
Air
Figure 1. Block diagram of the gas-chromatography/plasma chromatographic unit
as intended by several researchers (10-12). These limitations will also be discussed i n this paper. Therefore, our effort was in t h e use of the plasma chromatography as a quantitative monitoring device for trace amounts of a known compound. One successful quantitative determination reported very recently was the direct monitoring of ppt levels of nickel carbonyl i n air (13).In a two-month field test, excellent agreement between plasma chromatography and Fourier transform infrared spectroscopy were achieved. We are currently interested i n t h e determination of the sec-butyl chlorodiphenyl oxides in biological tissues. Electron capture gas chromatography was found t o exhibit very low sensitivity t o these compounds, while flame ionization gas chromatography can only detect levels of about 0.4 ppm. Below this level, flame ionization gas chromatography has faced interference from the sample matrix for most of t h e samples analyzed. Gas chromatography-mass spectrometric-multiple ion detection (GC-MS-MID) technique was found to be t h e only reliable technique for concentrations below such a level. In this report, we describe the use of plasma chromatography for the analysis of sec-butyl chlorodiphenyl oxides in biological tissues. The isomer specificity, t h e sensitivity, the response dynamic range, the sample matrix effect, the precision, and t h e accuracy of t h e technique will be discussed.
RESULTS A N D DISCUSSIONS Mobility Spectra. T h e see-butyl chlorodiphenyl oxides of interest have the following structures,
EXPERIMENTAL A Model Beta/VII-S plasma chromatograph, manufactured by The Franklin GNO Company of Palm Beach, Fla., was employed in this study. In the initial test of the instrument, it was found that most of gas flowing into the instrument leaked out through the various joints of the instrument housing instead of the gas outlet as desired. For safety reasons, these joints were sealed carefully with silicone rubber RTV 106 sealant of the General Electric Co. and the housing was baked at 200-240 "C for about a month before the instrument became usable. After this treatment, better than 98%of the gas was found to escape through the outlet port to the vent. The plasma chromatographic oven is kept at 206 "C for all the work reported here. As shown in Figure 1, three data acquisition systems are employed 1) a Tektronix scope for a continuous display of the mobility spectrum, 2) a PAR Boxcar integrator, an analog signal averager, for a gas chromatography-plasma chromatographic (GC-PC) monitoring of a component of interest for better SIN, and 3) a Varian CAT, a digital signal averager, for storage of the mobility spectrum of a component eluted from the GC column. The data are recorded with a Moseley model 2D-2A x-y recorder of F. L. Moseley Co., Pasadena, Calif. Dry air was used as the gas into the plasma chromatograph. The following flow rates of dry air are normally maintained, the drift gas: 500 cm3/min, the valve gas: 40 cm3/min. and the carrier gas: 150 cm3/min. Prepurified nitrogen was used as the gas chromatographic carrier gas with flow rate between 10-25 cm3/min. A Pye gas chromatograph was employed and interfaced with the plasma chromatography with a lhe-inch copper covered stainless steel tubing supplied by the GNO company and maintained at 250 "C at all times. The gas chromatographic columns used in this work were all made of ?&inch 0.d. 2-mm i.d. glass tubing. The column temperatures were usually between 150 1352
*
ANALYTICAL CHEMISTRY, VOL. 48, NO. 9, AUGUST 1976
where R represents the sec-butyl group. One aromatic ring is monochloro-substituted while t h e other is either unsubstituted, or is mono- or di-sec- butyl substituted. The compounds described above were found t o give only positive plasma chromtographic responses. Their positive mobility spectra are depicted in Figure 2. Also shown in Figure 2 are the mobility spectra of diphenyl oxide and o-xylene which was used as solvent for t h e biological extracts. It was found that when the plasma chromatograph was operated in t h e positive mode, the positive reactant ions from air are very sensitive t o column bleeding. For most of t h e gas chromatographic columns investigated, the reactant ions disappear and react with the column bleed, contributing t o the baselines and a few weak plasma chromatographic peaks. The best column found for this purpose consists of glass beads coated with 0.1% UCW-98 liquid phase. As shown i n Figure 2, t h e original reactant ions from air are still apparent at a peak with drift time of 8.6 ms. Other peaks due t o column bleed are also clearly apparent. It is commonly suggested that hydrocarbon solvents like hexane, benzene, etc. are used when t h e plasma chromatograph is operated in the negative mode and chlorinated sol-
.. f
6-
E E I
-
-
5
I
~ 6 ' O I % U C W - 9 8 0 n G L C1 0 r 0,10d
Figure 2. Mobility spectra of sec-butyl chlorodiphenyl oxides (RCIDPO) and the related compounds
I
2
5
4
3
6
--In
(A) air (B)axylene, (C) DPO, (0) 0- and pClDPO ( E ) 2,2'-RCIDPO, (FJ4,2'RCIDPO, (G) 2,4'-RCIDPO, (HJ4,4'-RCIDPO, (I) 2,4,2'-R&IDPO. (J) 2,4,4'RpClDPO
VI
7
B
1011
9
1213
(pgl-
Figure 4. The plot of the logarithmic response curve of 4-sec-butyl4'-chlorodiphenyl oxide (0)2 - 4 injection, (0)specified fil injection
t
I
IO
1
1 I I I / I I
0 I
I
Ib3
:A2
-W
( w e i g h t , pq
I I 1 Ill
Ib4
I
I
1
2
3
4
5
6
IIIII
I05
1-
Figure 3. Plasma chromatographic response curves of sec-butyl chlorodiphenyl oxides (A) 6-ft 0.1% UCW-98 on GLC-100 120/140 mesh, 180 OC,(0)2,4' isomer, (0)4.4' isomer: (B) 5 4 3% OV-3 on GCZ, 200 OC. (A)pure 2,4' isomer standard solution, (A)2.4' isomer spiked fish extract
vents like methylene chloride, chloroform, etc. in the positive mode. Here, we are taking different approaches in the use of o -xylene as solvent when the plasma chromatograph is operated in the positive mode. T h e reasons are twofold. o-xylene is relatively nonvolatile. The loss due to evaporation, thus changing the concentration of a prepared solution, can be reduced to a great extent. Furthermore, when o-xylene is eluted from the gas chromatographic column, it reacts with the available reactant ions and the ions from the column bleed in the generation of a new intense ion a t drift time 10.4 ms. It was also observed that the intensity of this ion peak decreased when the sample molecule eluted into the plasma chromatograph from the gas chromatographic column with the formation of a new ion peak due to the sample molecule and recovered when the sample molecule had dissipated in the plasma chromatography. This observation indicates that it is this ion which reacts with the sample molecule producing the product ion, probably through protonation and charge transfer reactions similar to those which were observed in the case of' benzene ( 1 6 ) ;however, the drift times of the product ions shown in Figure 2 were found to be independent of the type of reactant ions whether they are from o-xylene or moisture in the air. I t is noticed in Figure 2 that different
- 1 1 1 1
2
Figure 5. Inherited uncertainty of the plasma chromatographic determinations from the inaccurate measurement of the response curve
isomers, except o- and p-chlorodiphenyl oxides give different drift times. In other words, plasma chromatography is isomer specific in this case. This is the first observation of isomer separation by plasma chromatography. At first glance, this phenomenon is very surprising; however, it can be qualitatively understood from the Langevin equation (17).For a case where the collision cross section, D12, is large, the Langevin equation which describes the ion mobility, k , can be reduced to the following form.
where x is the length of the drift tube, T the drift time, E the electric field strength, P and p are the pressure and the density of the carrier gas in which the ions are traveling, m and M the masses of the carrier gas and the ions, respectively. The reduced mobility, ho, reported in Figure 2 is the mobility at the STP conditions or ho = h(P/760)(273/T).For an experiment with defined experimental parameters, it is obvious that the measured drift time of an ion is proportional to the mass and the collision diameter of the ion, but primarily to the latter when the mass of the ion is significantly larger than that of the carrier gas. The difference in the drift times of different isomers indicate the difference in their collision diameters toward the carrier gas molecules. In this case, it would be of interest and important to evaluate the dependence of the collision ANALYTICAL CHEMISTRY, VOL. 48, NO. 9, AUGUST 1976
1353
n
A
-RETENTION
Figure 6. Sensitivity comparison of p and 0-chlorodiphenyl oxides
TIME&
(A) 0.20 ng of pchlorodlphenyl oxide, (8) 1.88 ng of echlorodiphenyl oxide
Figure 7. Matrix effect on the determination of seobutylchlorodiphenyl oxides in a plasma extract
diameter on the ion size, which was assumed to be intermediate between the static and rotational models in the mobility calculations by Horning and co-workers (17). Logarithmic Response Curves. In quantitative analysis, the commonly used wire sample introduction method (12) was first explored. For a pure compound, reasonable reproducibility in quantitation can be achieved; however, totally unreliable results were obtained if the sample matrix were present. This is believed to be primarily because of a phenomenon which will be described later. A reliable sample introduction technique was found to be through a gas chromatograph with which the majority of the matrix components are separated from the components of interest. The sensitivity of the GC-PC technique was found to be dependent strongly on the column properties. As an example, the response curves of 2,4- and 4,4'-sec -butyl chlorodiphenyl oxides are shown in Figure 3 where two types of gas chromatographic columes were employed for comparison. The plasma chromatographic sensitivity with a glass bead column is much better than with the conventional diatomaceous earth columns. It is obvious that column bleed affects not only the sensitivity, but also its dynamic range. The effect on the sensitivity is believed to be caused by the column absorption, while that on the dynamic range by the column bleeding. For the glass bead column, the sensitivity is approximately 20-40 pg or 0.01-0.02 ppm in o-xylene solvent for an injection of 2 11.1and the dynamic range is about two orders of magnitude in every case studied. Detailed study of the response curves show that the responses are not linear with respect to the concentrations, but they are exponential. In order to transfer this characteristic exponential response to an easily calculable expression, the In response (In I ) was plotted vs. In weight (In w )introduced into the plasma chromatograph through a gas chromatograph. One such plot is depicted in Figure 4. The following linear relationship was found in every case,
( A ) I - ~injection I of plasma ( I .26 g) extract in 50 pi exylene, (8)2-p1injection of solution A after 1:20 dilution, (C) 2 4 injectlon of *xylene solvent
In W = 1.26 In I
+ constant
or
w1= w 2
(2) I
1.26
therefore, the amount of a component, w1,can be determined from II,I z , and w2 where I 2 and Wz are obtained from the calibration run. Also shown in Figure 4 are the responses from different volumes of injections (1-5 pl). As expected, the response does not depend on the quantity of solvents injected into the instrument. When chloroform was used as the solvent and a 3% OV-3 column was employed, the reactant ions were 1354
ANALYTICAL CHEMISTRY, VOL. 48, NO. 9, AUGUST 1976
found to originate primarily from the column bleed. In this case, the response curve slope was found to be 1.34 instead of 1.26, as observed in the case of the reactant ions from o-xylene. This may indicate the dependence of response on the mechanism and/or kinetics of the ion-molecular reactions occurring in the plasma chromatograph. Because of the logarithmic characteristics, the accuracy of a plasma chromatographic determination is dependent on the accuracy of the slope determination of the response curve as well as the precision of the technique. An example is given for a hypothetical case where f8% was assumed to be the error in the slope determination. The effect of this error on the analytical determination of an unknown quantity, W1, can be written in the following form: W2
The determined values of W1 should lie within the limits of b+ WZand b- W 2 I 1.26 (1+0.08) and b- = Il 1.26 (1-0.08) where b+ =
(d)
(E)
Therefore, the following expression can be written:
Wi = b ( l f F)W2
+
where b(1 6) = b+ and b ( l - 6) = b-. The resulting uncertainty 6, in W1, as function of 11/12 is shown in Figure 5. Therefore', the resulting uncertainty in the analytical result is highly dependent upon the difference between the concentrations of a component in the solution to be determined and that in the solutions used for the instrument standardization. Therefore, it is suggested t h a t both solutions should have comparable concentrations to maximize the accuracy of the result. The plasma chromatographic sensitivity was also found to be heavily dependent on the molecular property. Surprisingly enough, o - and p -chlorodiphenyl oxides exhibit quite different plasma chromatographic sensitivity as shown in Figure 6. One possible explanation might be that the para isomer has higher proton affinity and/or lower ionization potential than the ortho isomer. Both the proton affinity and the ionization potential govern the reactions of the protonation and the charge transfer, taking place in the plasma chromatograph, in the generation of the detected product ions. Matrix Effect. Ordinarily, the extract from 1-2 g of tissue
Table I. Precision of Plasma Chromatographic Determinations of S u b ppm of I-sec-Butyl-4'Chlorodiphenyl Oxide in a Fat Tissue Response in mm (4 mV/mm)
--
0.1 ppm standard in o xylene, 2-p1 injection 228 215 223 205 240 233 258 240 230 215 229 std d e v S 16 2S/X 14%
Fat extract Fat extract 1:500 (1500 dilution) 2-pl dilution) pgApl injection 290 137 152 300 133 280 155 290 135 305 126 280 340 142 133 300 155 325 168 325 304 144 19 13 13% 18%
ppm in fat 0.394 0.437 0.382 0.445 0.388 0.362 0.408 0.382 0.445 0.482 0.413 0.038 18%
-
Table 11. Recovery of Alkyl Chlorodiphenyl Oxides in a Biological Tissue (Female's Kidney) by GC-PC Analysis Theoretical amt added to the tissue Component p-ClDPO 2,4'-C4ClDPO 4,4'-C4ClDPO 2,4,2'-(C4)2ClDPO 2,4,4'-(C4)2ClDPO
ng 234 329 227 61
ppm in tissue 0.27 0.39 0.27 0.073
122
0.15
Amount Recovery, recovered, ng % 150 64 250 77 160 70 55 90 119
---"c-J -RETENTION
TIME-
Figure 8. Matrix effect on the determination of pchlorodiphenyl oxide in a biological tissue extract ( A ) Original tissue extract in 50 pI o-xylene. (B) 1:20 dilution of solution A. (C) Solution B spiked with pchlorodiphenyl oxide. (D)1:20 dilution of solution C. (0Standard solution of pchlorodiphenyl oxide 2,4,2' 2,4,4'
nR
E- MS- M I D 2.4.4
97
was dissolved in 50 ~1 of o-xylene for gas chromatographic and/or GC-&IS-MID analysis. For a GC-PC determination, the plasma chromatograph was first tuned at the characteristic drift time of a compound of interest. When 1 11.1 of the above solution from a controlled tissue was injected into the GC-PC! system, many peaks were observed due to the presence of the matrix components. For the mono- and di-sec-butyl chlorodiphenyl oxides, further dilution of the original solution with o-xylene by a factor of 20 is enough to reduce the interference to a desirable level. An example is given in Figure 7. In the case of p-chlorodiphenyl oxide, however, dilution by a factor of 100 was found to be necessary. A fish extract after being diluted as above, was spiked with different levels of 2-sec-butyl4'-chlorodiphenyloxide. T h e resulting solutions were analyzed by the GC-PC technique and the results are plotted in Figure 3. T h e agreement between the two curves is excellent. Figure 8 shows another quite characteristic matrix effect observed in plasma chromatography. T h e plasma chromatograph was tuned on the p-chlorodiphenyl oxide peak a t drift time of 13.8 ms with a gate width of 0.2 ms. Two pl of the original tissue extract in 50 pl of o-xylene was injected into the GC-PC. T h e GC-PC was saturated by many matrix components in the extract. T h e solution was then diluted by a factor of 20. T h e saturation is still observable. The resulting diluted solution was then spiked with low concentration of p-chlo-
-RETENTION
d .,
, I
TIME-
2pL 0-XYLENE G - C- - P. C-
Y LI
I
\
Y
- RETENTION TIME---+
Figure 9. Comparison of GC-MS-MID and GC-PC responses of an extract of a rat liver tissue containing 0.10 ppm of 2,4-di-sec-butyl-4'chlorodiphenyl oxide GC-MS-MID: 5-wl injection of liver extract, GC-PC: 2 4 injection of liver extract after 1:20dilution
rodiphenyl oxide. No peak a t the expected retention time of p -chlorodiphenyl oxide was observed; however, when the solution was further diluted 20 times, the expected peak was detected as shown in Figure 8. One possible explanation for this phenomenon is that the matrix component(s) eluted a t the same time as p-chlorodiphenyl oxide has much higher ANALYTICAL CHEMISTRY, VOL. 48, NO. 9, AUGUST 1976
1355
Table 111.Comparison of ppm Levels of see-Butyl Chlorodiphenyl Oxides in Biological Tissues by Different Techniques C4ClDP0, ppm in tissue (C&ClDPO, ppm in tissues Sample Liver Kidney Fat Fat Muscle Brain
GC-FI
GC-MS
GC-PC
GC-FI
GC-MS
GC-PC
*.. ...
0.12 0.71
0.039 0.69 24 290 2.4 0.35
... ...
0.41 0.55
0.37 0.49 37 230 3.3
...
29 220 3.2
2.7 0.43
...
Table IV. Relative Isomeric Distributions of see-Butyl Chlorodiphenyl Oxides in Biological Tissues GC-FI GC-MS GC-PC Sample Fat Liver Kidney Muscle a
p=
PPm (total) 29
