Anal. Chem. 1980, 52, 2066-2069
2066
tilayer accumulation of halogen molecules. Table I summarizes information regarding limit of detection, sensitivity, and reproducibility of the method presented in this paper.
ACKNOWLEDGMENT T h e authors are grateful to J. Paul Devlin for assistance with the photoacoustic infrared studies.
LITERATURE CITED (1) RuiiEka, J.; Hansen, E. H. Anal. Chim. Acta 1975, 78, 145-157. (2) Monola, H. A.; Hanna, A . Anal. Chim. Acta 1978. 700,167-180. (3) Bryan, R . J. In "Air Pollution"; Stern, A. C.; Ed.; Academic Press: New York. 1976; Vol. 3, Chapter 9. (4) Hansen, E. H.; RuiiEka, J. J . Chem. Educ. 1979, 56, 677-680. (5) Rockley, M. G.; Waugh, K. M. Chem. Fhys. Lett. 1978, 5 4 , 597-599. (6) Jacobs. M. 8."The Analytiil Toxicokgy of Industrial Inorganic Poisons": Interscience: New York, 1967; Chapter XVI.
(7) Belcher, R. Anal. Chim. Acta 1949, 3 , 578-588. (8) Bishop, E. In "Indicators";Bishop, E., Ed.; Pergamon Press: New York, 1972; Chapter 8B, p 667. (9) Cramer, F.; Elschnig, G. E. Chem. &r. 1958, 89, 1-12. (IO) Bhaskar, K. R.; Bhat, S. N.; Murthy, A. S. N.; Rao, C. N. R . Trans. Faraday SOC. 1968, 62, 788-794. Str~mme,K. 0.Acta Chem. S c a d . 1959, 73, 275-280. (11) Hassel, 0.; (12) Yamada, H.; Kozima, K. J . Am. Chem. SOC. 1980, 82. 1543-1547. (13) Rao, C. N. A. "Ultra-violet and Visible Spectroscopy. Chemlcal Applications", 2nd Ed: Plenum Press: New York, 1967; p 153. (14) Gilbert, G. A.; Marriot, J. V. R. Trans. Faraday Soc. 1948, 4 4 , 84-93. (15) Beneridge, D. Anal. Chem. 1978, 50. 832A-846A.
RECEIVED for review June 9,1980. Accepted August 5,1980. This work was supported by research funds provided by the National Science Foundation (Grants CHE-76-81587 A02 and CHE-7923956). The authors are grateful for this support.
Determination of Chlorobenzenes in Water by Capillary Gas Chromatography Barry G. Oliver" and Karen D. Bothen Water Chemistry Section, Environmental Contaminants Division, Canada Centre for Inland Waters, Burlington, Ontario, Canada L 7s 1A 1
A capillary gas chromatographic method wtth electron capture detection has been developed for separating and quantltatlng ail 12 chlorobenzenes in water samples after preconcentration into pentane. Concentration factors from water of 1000 or 2500, respectively, are achleved by udng a small column of Chromosorb 102 or by liquid-liquid extraction with pentane. Detection limits of the technique are =0.01 ng/L (ppt) for penta- and hexachiorobenzene, x0.05 ng/L for the tetrachlorobenzenes, xO.1 ng/L for the trkhlorobenzenes, -1 ng/L for the dichlorobenzenes, and 4 0 0 ng/L for monochlorobenzene.
T o date little information is available on the concentration of chlorinated benzenes in aquatic environmental samples mainly because no suitably sensitive or simple analytical technique has been developed. These compounds have high octanol-water partition coefficients (1) so biological accumulation can be expected to occur in the aquatic ecosystem, and, in fact, hexachlorobenzene has been detected in Lake Ontario salmonids ( 2 ) . Although some chlorinated benzenes with high commericial usage have been identified in a polluted river (3, in lakewater (4,and in drinking water ( 5 ) ,very little good quantitative information on aqueous environmental concentrations has been reported for the majority of these compounds. This paper reports a simple capillary gas chromatographic procedure that can be used, after sample preconcentration, to identify and quantify all 12 chlorinated benzenes in water samples. Preconcentration from water with a macroreticular resin (6-8) and with liquid-liquid extraction (9, 10) were studied because these techniques have been successfully used for other chlorinated compounds.
EXPERIMENTAL SECTION Reagents. High-purity chlorobenzene (CB), 1,3-dichlorobenzene (1,3-DCB), 1,4-dichlorobenzene (1,4-DCB), 1,2-dichlorobenzene (1,2-DCB), 1,3,5-trichlorobenzene (1,3,5-TCB), 1,2,4-trichlorobenzene (1,2,4-TCB), 1,2,3-trichlorobenzene 0003-2700/80/0352-2066$01 .OO/O
(1,2,3-TCB), 1,2,3,5-tetrachlorobenzene(1,2,3,5-TeCB),1,2,4,5tetrachlorobenzene (1,2,4,5-TeCB), 1,2,3,4-tetrachlorobenzene (1,2,3,4-TeCB), pentachlorobenzene (PeCB), and hexachlorobenzene (HCB) (RFR Corp., Hope, RI) were used as received. The resin for the preconcentration step (Chromosorb 102, Johns Manville Co.) was cleaned by sequential Soxhlet extraction with methanol, acetonitrile and ether as described by Junk et al. (6) and stored in methanol. Glass-distilled pentane (Caledon Ltd., Georgetown, Ontario) in most cases could be used as received, but some batches required cleanup by refluxing with sodium for 48 h followed by glass distillation with a three-step Snyder column to remove interfering volatile chlorinated impurities. Anhydrous Na2S04(BDH Anal&) for drying solvents was heated to 650 OC for 24 h prior to use. Florisil (60-100 mesh, Fisher Scientific Co.) for cleanup of sample extracts was heated to 650 "C and deactivated with 6% water prior to use. Gas Chromatographic Procedures. A Varian 3700 gas chromatograph with a 63Nielectron capture detector and capillary capability was used throughout the course of this research. Two wall-coated open tubular (WCOT) glass capillary columns, 30 m in length, 1mm o.d., 0.25 mm i.d. (Canadian Capillary Co.), were used-a thin phase (.=0.08 pm) Carbowax 20M and a thicker phase ( ~ 0 . 2pm) 0 SP-2100.Nitrogen flow rate through the columns was maintained at 1.3 mL/min. A splitless injection of 5 pL of samples in pentane (reproducible to *5%) was employed in all cases. We used the following temperature program for both columns to minimize analysis time and optimize separation: initial temperature, 33 "C; initial hold, 3 min; program rate, 10 OC/min; final temperature, 180 OC. A Spectra Physics 4000 chromatography data system was used to record peak retention times and peak areas and to calculate concentrations. Preconcentration with Small Resin Columns. A borosilicate glass tube 100 mm long, 3 mm o.d., and 1.5 mm i.d. was tightly packed with Chromosorb 102 resin in a methanol slurry by using a vibrator. The resin was kept in place by two 5-mm plugs of silanized glass wool. Connections to the column were made with l/s-in. Swagelok fittings using PTFE ferrules. A 5 0 h - d water sample in a septum sealed bottle was forced through the column at a flow rate of =5 mL/min using nitrogen pressure. After the water sample was passed through the column, 300 p L of pentane in a gastight syringe was placed on the column for about 30 min. During this period the pentane was moved up and down the column several times. The pentane was finally eluted into 0 1980 American Chemical Society
ANALYTICAL CHEMISTRY, VOL. 52, NO. 13, NOVEMBER 1980
2067
m
0
h
J ,
,
~
,
,
0
,
1
1
,
,
2-0
10
TIME, min
Figure 1. Chromatogram of chlorobenzene mixture in pentane on Carbowax 20M capillary column. Chlorobenzene concentration in pg/L CB (30 000); 1,3-DCB (74); 1,4-DCB (132); 1,P-DCB (72); 1,3,5-TCB (13); 1,2,4-TCB (8.1); 1,2,3-TCB (7.4); 1,2,3,5-TeCB (1.3); 1.2.4.5TeCB (8.9); 1,2,3,4-TeCB (2.9); PeCB (1.4); HCB (1.2).
a small septum capped ice-cooled vial, and the small amount of water in the vial cone was removed with a syringe. These sorption and elution methods, which minimize volatilization losses, are similar to those previously diagramed by Glaze et al. (11). Final cleanup was accomplished by eluting the 300-pL extract with pentane from a column of 5 mm Na2S04+ 15 mm deactivated Florisil in a disposable Pasteur pipette (7 mm o.d., 5 mm i.d.) and collecting the first 500 pL in a calibrated vial. Preconcentration by Liquid-Liquid Extraction with Pentane. Gallon solvent bottles (4075 f 25 mL) filled headspace free were used for sample collection and extraction. An 80-mL sample of water was poured out of the bottle and replaced with 75 mL of pentane and a large magnetic stirring bar. The sample was rapidly stirred for several hours (>4 h) to extract the chlorobenzenes into the organic phase. The pentane phase was separated from the sample by using a large separatory funnel and transferred to an evaporation flask (a round-bottle flask with the bottom of a centrifuge tube attached) (6). The sample was then evaporated to =1 mL by using the evaporation flask, a Kuderna-Danish type condenser, and a waterbath at 42 "C. Final cleanup was done by eluting the 1mL concentrate with pentane from a column of 10 mm Na2S04 40 mm deactivated Florisil in a disposable Pasteur pipette and collecting the first 1.6 mL in a calibrated vial.
+
RESULTS AND DISCUSSION Capillary gas chromatograms for the 12 chlorinated benzenes in pentane are shown in Figures 1 and 2. All 12 compounds are separated on the Carbowax 20M column (Figure 1)and all but the 1,2,3,5-TeCBand 1,2,4,5TeCB are separated on the SP 2100 column (Figure 2). T h e retention times of the compounds are seen to be quite different for the two columns (Table I). It should be noted that the retention times early in the chromatogram up to 1,3,5-TCB are less reproducible (*2%) than those of later eluting components (98% of all the chlorobenzenes from water at a flow rate of 5 mL/min. T h e columns are used only once since only a small amount of resin is required ( ~ 6 mg) 0 and repeated usage leads to diminishing recoveries. About 95% of the chlorobenzenes could be extracted back off the column by using 300 pL of pentane. Finally a t least 95% of the chlorobenzenes were eluted from the florisil cleanup column in the first 500 pL of pentane. For the liquid-liquid extraction with pentane, more than 90% of the chlorobenzenes could be recovered from water at a water to pentane ratio of 50 to 1. A t least 95% of all chlorobenzenes were recovered when 75 mL of their pentane solution was evaporated to 1 mL. Again, more than 95% of the chlorobenzenes were recovered from the florisil cleanup step. The recovery efficiencies of the two techniques for low and high concentration spiked distilled water samples are shown in Table 11. Both techniques are seen to recover more than 80% of all the chlorobenzenes. The mininum detection limits in water for the pentane extraction technique for the sample volumes we have used vary from =l ng/L for the least sen1 for HCB. The sitive dichlorobenzene (1,6DCB) t~ ~ 0 . 0 ng/L mininum detection limit for monochlorobenzene is much higher, =500-1000 ng/L, due to the poor response of the electron capture detector to this compound. Our technique is probably not sensitive enough to detect monochlorobenzene in most environmental water samples but may be sufficiently sensitive for wastewaters or industrial effluents. However, our technique should be sensitive enough the detect the other 11 chlorobenzenes in most aqueous environmental samples. T o demonstrate the effectiveness of both preconcentration methods and the gas chromatographic procedure, we determined the concentrations of chlorobenzenes in two filtered riverwater samples (Table 111). All chlorobenzenes with the exception of CB are seen to be present in both samples. Excellent agreement between the resin column and the pentane extraction techniques is apparent for all components in . samples were both samples (maximum deviation, ~ 2 0 % ) All run in duplicate by both techniques with a reproducibility of
% recovery
concn in water, ng/L 25700 62.5 109 64.8 11.5 6.9 6.3
81
82 80 96 93 89 90 89 85 88
resin
pentane
80 80 80 83
82 81
80 80 81 85
81
90 85 87 87
1.1
6.9 2.4 1.6 1.0
83
91 89 88 83 87
83 83
84
Table 111. T h e Analysis of Two Filtered Riverwater Samples after Preconcentration with the Resin Column and Liquid-Liquid Extraction sample 1 concn, ng/L resin pentane
chlorobenzene
sample 2 concn, ngJL
resin
pentane
CB
