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I NOTES Trace Determination of Vinyl Chloride by a Concentrator/Gas Chromatography System David H. Ahlstrom,‘ Robert J. Kilgour, and Shirley A. Liebman Armstrong Cork Company, Technical Center, Lancaster, PA 17604

In January of 1974, NIOSH was alerted to the fact that the deaths of several chemical workers may have been related to a long term exposure to vinyl chloride. In a relatively short period of time following this report, the Department of Labor issued an emergency temporary standard for exposure to vinyl chloride. The rule was broad in scope and set the maximum exposure limits for employees a t 50 ppm (127.0 rng/m3). Although no specific method for the determination of the monomer was established, it was required that the procedure should be sensitive to 5 ppm of vinyl chloride with an accuracy of f20%. Furthermore, personnel monitoring was to be accomplished by collecting samples by suitable devices worn by the employee. Recently, a permanent standard of 1 ppm averaged over an 8-hour period has been established. The “action level” (the level a t which medical and physical surveillance of the individual worker must be instituted) is, however, 0.5 ppm. Thus, highly sensitive methods are required for the analysis of the monomer. The object of this work was to establish an accurate, reliable method for the determination of vinyl chloride in industrial atmospheres a t concentrations below 0.5 ppm. It was decided early in the program that the analyses for a number of plants at various locations throughout the United States would be conducted at one central location. A further object of this work was thus to develop a technique by which samples could be easily collected and transported and remain stable between the time of collection and analysis.

EXPERIMENTAL Of the materials tested, activated charcoal, Lot 104, obtained from SKC, Inc., Pittsburgh, PA, was the best adsorbent. Carbosieve B was too strong an adsorbent, while Porapak Q, Chromosorb 102, and Tenax did not quantitatively adsorb vinyl chloride from the atmosphere. A commercially available unit, Component Concentrator-Model 216, (SKC, Inc., Pittsburgh, P A ) , consisting of a thin-walled, 5 i n . X 3/16-in.IJ-shaped, stainless-steel collection tube and pulse heater, was attached directly to the injection port of a Hewlett-Packard Model 7620 chromatograph equipped with dualflame ionization detectors. The columns were 6 f t X f/s-in 0.d. stainless steel packed with 80-100 mesh Porapak QS. At a carriergas flow rate of 20 ml/min, vinyl chloride had a retention time of 6.5 minutes a t 90 ‘C. Data reduction was performed by a HewlettPackard 3352A Data System. Calibration standards containing 46 ppm and 9 ppm vinyl chloride were obtained from Matheson Gas Products, E. Rutherford, NJ. Air samples were collected using a battery-powered pump calibrated from 50 to 300 ml/min. For a typical analysis, the collection tubes were packed with 150 mg of charcoal, and air was sampled at the rate of 300 ml/min for 10 minutes. The collection tube was then attached t o the inlet of the gas chromatograph. The heater module of the SKC unit was set a t 400 ‘C, the sample tube was pulsed a t that temperature for 2 minutes, and the desorbed compounds were swept by the GC heliAuthor to whom correspondence should be addressed.

um carrier gas onto the analytical column. Using this technique, low concentrations of vinyl chloride were routinely determined.

RESULTS AND DISCUSSION Pollution analysis generally requires special sample-handling techniques. The difficulties associated with collecting a truly representative sample and transferring that sample to the analytical laboratory for subsequent analysis can be considerable. Hence, instrumental methods for the on-site analysis of specific pollutants have been extensively developed ( I ) . For the determination of vinyl chloride, both infrared ( 2 ) and chromatographic (3-7) techniques have been shown to be applicable. However, in our initial evaluation of the problem, which took into consideration the economic factors, the number of sites to be tested, and that actual employee exposure was to be monitored, we chose to develop a concentrator/gas chromatography technique. This method can be used for both upper-limit exposure values and for time-weighted average determinations. Furthermore, the separation of vinyl chloride from other substances which are likely to appear in an industrial environment can be achieved by changing the gas chromatographic separation parameters. Using the small collection tubes of the SKC unit attached to a battery-operated pump allowed the employee to wear the sampling device and continue with his normal work practice. The amount of time for sampling could easily be changed by adjusting the flow rate of air passing through the collection tube. Samples collected in the metal tubes were sealed and mailed to Lancaster, PA, where the analysis took place. Thus, the tubes were easily transferred from one location to another with minimal sample loss. Concentration techniques followed by chromatographic analysis, have been discussed by other workers in the literature (8).Mueller and Miller (9) present data on a number of solvents. Using charcoal as the adsorbent and carbon disulfide to desorb the solvents, analytical efficiencies of 95100%were obtained for many of the solvents evaluated. Indeed, the carbon disulfide or solvent desorption process appears to be amenable to a variety of substances. However, our first attempts a t the carbon disulfide procedure led us to the conclusion that unless the solvent was highly purified, flame disruption and peaks due to impurities were observed. Our experience in the field of trace organic analysis brought about through the development of Fixed and Reactive Gas Analyzers used in combustion studies ( I O ) led us to believe that the quantitative adsorption and subsequent thermal desorption of vinyl chloride would be possible. Thermal desorption has the advantag~esof simplicity and speed. Sample handling is kept to a minimum and sensitivity is at a maximum, since all of the adsorbed sample is introduced directly onto the analytical column. The use of ANALYTICALCHEMISTRY, VOL. 47, NO. 8, JULY 1975

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Table I. Standard Analyses of Vinyl Chloride Sample

Flou rate

45-ppm standard

50 ml/min

Table 11. Precision of Vinyl Chloride Measurement

T i m e , Vinyl chloride min detccted, ul

1 2 2 3

2.168 4.506 4.508 6.866

Tenax ( 1 1 ) ,porous polymers (12), and graphitized carbon black (13) as adsorbents for solvents and hydrocarbons followed by thermal desorption has been shown to be a useful technique. However, analytical procedures based on the thermal desorption of activated charcoal directly onto a chromatographic column have not been extensively reported in the literature, although a most recent commercially available unit does utilize this process (Bendix Process Instruments Div., Ronceverte, WV). A simple test was devised to evaluate the performance of the adsorbent. A collection tube was attached directly to the 45-ppm VC1 standard lecture bottle and the gas flow was adjusted to 50 ml/min. Samples were collected for 2minute periods and then chromatographed. The efficiency of the adsorption-desorption process was evaluated by comparing the results obtained from the tubes with those of pure vinyl chloride injected with a gas syringe. The values were in good agreement. Data for duplicate analyses of vinyl chloride collected for 2 minutes as well as single values for 1-minute and 3-minute sample times are shown in Table I. The precision of the thermal-desorption method is shown in Table I1 for four standard runs a t the 1-ppm level. A relative standard deviation of 1.2% was calculated for the four runs. Standard samples of vinyl chloride collected on the charcoal adsorbent were also allowed to stand for several weeks before analysis with no apparent loss of monomer. For the analysis, an external standard technique was used. Peak areas were directly related to microliters of sample injected. Thus, the concentration of any given sample was calculated in parts per million by volume from the known volume of air sampled. A test of the overall efficiency of the method was devised using the 518-liter NBS smoke chamber. T o the sealed chamber was added 4500 111 of pure vinyl chloride. Air samples were then withdrawn from the chamber through one of the sampling lines a t the rate of 300 ml/min. The concentration of vinyl chloride in the chamber was calcuiated to

Run N o .

Retention time, min

VCI, ppm

1

6.51 6.51 6.47 6.50

1.248 1.217 1.225 1.218

2 3 4

be 8.7 ppm. Analysis of the three samples taken gave values of 8.8, 8.2, and 8.2 ppm resulting in an overall analytical efficiency of 96% for vinyl chloride. CONCLUSIONS The use of activated charcoal as an adsorbent for vinyl chloride followed by thermal desorption of the monomer directly onto a chromatographic analytical column has been shown to be an accurate, reliable method. The technique can be used for either personnel or environmental monitoring. Samples can he taken a t any location, and easily transferred to the analytical laboratory for subsequent analysis. In separate work, we have also shown that, with a minimum of expense and effort, the entire sampling and analysis process can be automated. The details of such an automated system have been reported a t the 1st National FACSS meeting (14). LITERATURE C I T E D (1) 8. G. Liptak, lnstrum. Technol., 2 1 ( l ) , 43 (1974). (2) 0 . S. Lavery and P. A. Wilks. Jr., Amer. Lab., 6 ( l o ) , 53 (1974). (3) Analytical Instrument Development, Inc., Avondale, PA, Appl. Rep., GCAN-127. (4) C. A. Burgett, Hewlett-Packard Co., Avondale, PA, Appl. Note, ANGC8-74. (5) Carle Instruments, Inc., Fullerton, CA, Bull., 9500-P. (6) Baseline Industries, Inc., Lyons, CO, Bull., FMIOOOB. (7) NIOSH Manual of Analytical Methods, HEWPubl. No. (NIOSH) 75-121. (8) L. D. White, D. G. Taylor, P. A. Mauer, and R. E. Kupel, Amer. lnd. Hyg. Assoc. J., 31, 225 (1970). (9) F. X. Mueller and J. A Miller, Arner. Lab., 6(5), 49 (1974). (10) S. A. Liebman, D. H. Ahlstrom, C. I. Sanders, E. J. Quinn. and C. D. Nauman, J. Fire Flammability, Combust. Toxicol. Suppl., 1, 78 (1974). (11) W. Bertsch, R. C. Chang, and A. Zlatkis, J. Chromatogr. Sci., 12, 175 (1974). (12) J. P. Mieure and M. W. Dietrich, J. Chromatogr. Sci., 11, 559 (1973). (13) A. Raymond and G. Guiochon, Environ. Sci. Technol., 8, 143 (1974). (14) S. A. Liebman. D. H. Ahlstrom, and C. I, Sanders, Abstracts 1st Annual Meeting, Federation of Analytical Chemistry and Spectroscopy Societies, Atlantic City, NJ, Nov. 1974, No. 160.

RECEIVEDfor review January 20,1975. Accepted February 27, 1975.

Determination of Water and Ethylene Glycol in Used Crankcase Oils by Gas Chromatography R. A. Putinier, T. A. Norris, and F. P. Moore Texaco Inc., P. 0. Box 509, Beacon, NY 12508

An important phase of the testing of used crankcase oils from gasoline and diesel engines is the detection and determination of water and ethylene glycol. These substances are common contaminants in used crankcase oils and a knowledge of their concentration can yield important clues 1412

ANALYTICAL CHEMISTRY, VOL. 47, NO. 8, JULY 1975

concerning engine performance and, in preventative maintenance programs, give early warning of impending engine trouble. A gas chromatographic method has been developed for the determination of water and ethylene glycol in used