Gas Liquid Chromatographic An a lysis of ChIo rinated Hydrocarbons with Capillary Columns and Ionization Detectors 0.L. HOLLIS and W. V. HAYES The Dow Chemical Co., Organic Basic Research laboratory, Freeport, rex.
b A variety of chlorinated hydrocarbons were successfully separated on capillary gas liquid chromatographic columns and were detected using four different ionization detectors, Response factors for the triode argon and flame ionization detectors to chlorinated hydrocarbons were determined on weight per cent basis. Under the conditions employed in this study the triode detector showed greater sensitivity ar,d smaller weight per cent correction factors. It is necessary to calibrate the apparatus with standard samples to obtain quantitative data with these systems. The method described should b e useful in the analysis of mixed solvents and crude streams of chlorinated hydrocarbons and for trace constituents in the parts per million range present in finished materials.
D
with capillary gas liquid chromatographic (GLC) columns and ionization detectors, a number of halogenated compounds were successfully separated. Data are presented for their possible value to others interested in analyzing chlorinated solvents. Previous work with chlorinated hydrocarbons using standard packed columns and thermal conductivity detection GLC apparatus had shown that separation of most of the C1 and C3 chlorinated hydrocarbons could be accomplished by the proper choice of partitioning liquid for the GIL! stationary phase, and that trace constituents could be detected by using large sample loads. In the present work, the difficult separations were attempted using relatively nonselective liquid phases on very efficient capillary columns, determining the small quantities involved with highly sensitive detectors such as the triode argon ionization detector of Lovelock (4) and a flame ionization detector similar to that described by MacWilliam and Dewar ('7). Previous work with styrene (3) had indicated this might be possible. The data, particularly that on detector response, are presented only as guides, and for precise Ivork exact URING STUDIES
calibration of each compound in the apparatus being used would be necessary. Instrument variables such as sample splitter and detector voltages could affect response. The splitter used had been shown by the manufacturer to be linear over a wide range of sample sizes and split ratios to hydrocarbons of similar volatilities t o those of chlorinated hydrocarbons tested. The retention data were reproducible as long as the column conditions were maintained after a column was conditioned. The data indicate the usability of these techniques for analysis of chlorinated hydrocarbons. EXPERIMENTAL
Apparatus. Most of these experiments were run on a Barber-Colman Model 10 I D S chromatograph which was modified for capillary columns and the triode argon detector as previously described (3). Three capillary columns were used for these experiments-a 100-foot squalane on 0.01-inch i.d. X 0.0625-inch 0.d. tubing of 304 stainless steel; a 25% G.E. 96-silicone-i5% oxybis(2-ethyl benzoate) on 100 feet of 0.01-inch i.d. x 0.0625-inch 0.d. tubing of 304 stainless steel; and a hexadecane on 200 feet of 0.01-inch i.d. X 0.0625-inch 0.d. tubing of 321 stainless steel. The columns were prepared by the technique previously described (3). The experiments with the standard flame detector and with the argon ionization diode detector were done on a BarberCoIman Mode1 20 chromatograph. The high tempersture flame detector was an experimental model in a Barber-Colman Model 61-C chromatograph. That the sample splitting devices used to obtain the data gave a representative sample for the components used may not always be true because sampling to the column depends on splitter design and materials of construction. Care must be taken t o eliminate surfaces in the system that can react with components in the sample. I n one instance an instrument with copper tubing in the splitter gave response factors for l,ljl-trichloroethane and 1,l-dichloroethane of 0.041 and 0.28 compared with 0.22 and 0.37 on the same instrument with a splitter made entirely of stainless steel; trans-
1-chloro-Zbutene was completely missing after passage through the coppercontaining splitter. The data obtained with the splitter containing copper were obviously unusable. Operating Conditions. Column temperature was in every case allowed to come to the lowest possible for the apparatus without external cooling. I n t h e Barber-Colman Model 10, about 30" C. was used, and in the Barber-Colman Models 20 and 61-C, about 25' C. was used. Depending on ambient temperature, these would normally vary only =t0.50° C . over a 24-hour period. Argon was used in all experiments as carrier gas. FIoiv rates on the columns were adjusted to give elution times of 30 to 40 min. for propylene dichloride or trichloroethylene, whichever was eluted last. This gave column floms of 1 to 2 cc. per minute. The triode argon detector was operated in a 100" C. oven at 1000 volts with 60 cc. per minute flous of argon scavenger. The split flow \+ith the triode was 150 to 300 cc. per minute depending on the sample being analyzed. The flame ionization detectors were all operated at 300 volts with 16 cc. per minute hydrogen flow and 400 cc. per minute air flow. The split flow with the flame detectors was 50 to 150 cc. per minute. The high temperature flame was housed in a 195' C. chamber. Procedure. Samples were delivered to the splitter with a 10-pl. Hamilton syringe. Sample size varied from 2.0 J. for analysis of trace components in pure materials to
