Document 37m3jN3JYVvZrrKL2q6y259z0
VINYL CHLORIDE SITPLZICNT TO P&CAM 0127 31 May 1974
This document is designed to aid the analyst in adapting the procedures of P&CAM 0127, "Organic Solvents in Air" to the determination of vinyl chloride in workplace air. Since in-house research on vinyl chloride analysis is still in progress, the following information is as yet incomplete. Sampling
In-house experiments on the capacity of the 150-mg two-section activated charcoal sampling tube suggest the following: (1) if a concen tration of vinyl chloride in air of around 2 ppm (v/v) is anticipated, no more than 3.5 l of the atmosphere should be sampled; (2) if a concentration of around 50 ppm (v/v) is anticipated, sample no more than 1.2 Z. Sampling flow rates of 200 ml/min or less are recommended. Sample Storage
Samples of vinyl chloride on charcoal appear to be stable for at least 3 weeks if stored at -20*C or at least 2 days if stored at 25C. During storage at room temperature, the vinyl chloride slowly equilibrates throughout the tube, giving the appearance of migrating to the backup section. At -20BC this equilibration is very slow. .-.-.clytical Fro-cedure
Vinyl chloride is desorbed from the charcoal with CUistssfeer 1.0 ml of CS2. Vials having a volume of 2 ml are used (thus keeping the headspace
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above the solution srall> and are capped with septa after aid! tion of the CS~> to the charcoal. The columns used in the analysis of vinyl chloride by OC include:
Column
Temperature(C)
Reference
20-ft 10% SF-30 on 80-100 mesh Chror.osorb VI AW DMCS
20-ft 10% FFAP on 80-100 mesh Chromosorb W AW DMCS
5-ft 5% SP-1000 on 80-100 mesh Chromosorb W AW DMCS
6-ft 20% Carbowax 600 on C-22 Firebrick
6-ft Porapak Q, 80-100 mesh
60
65 (initial)
65 (initial)
?
30-50 (initial)
in-house in-house in-house
1 2
6-ft Carbowax 20M alkaline on 60-80 mesh Chromosorb W AW
100-ft Squalane coated capillary
? 30
3 4
100-ft 25% GE-96 silicone/75% oxybls(2-ethyl benzonte) coated capillary
200-ft hexadecane coated capillary
25 25
4 4
10-ft 7% 0V-101 on 60-80 mesh Chromosorb G AW
50 5
Using the 20-ft GC column of 10% SE-30 on Chromosorb V at 60C, our
standard curve extends as low as 0-.2 ng/injection. Impurities in the CS2
interfered with the analyses for low levels' of vinyl chloride using the
FFAP or SP-1000 columns;. *1
*i <
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Standards are prepared In either of two ways. (A) Pure vinyl chloride is slowly bubbled into a tared amount of toluene ("* 5 ml) contained in a 10-ml volumetric flask. About 100-400 mg of vinyl chloride are collected in 3 min. The solution is reweighed and diluted to the mark with CS2. Standards are prepared from this stock solution using CS2 for the dilution. (B) A series of standard solutions are prepared by injecting known volumes of pure vinyl chloride (gas) into CS2 in 5- or 10-ml volumetric flasks and diluting to the marks. The relative accuracies of these and other methods has not been determined.
The desorption efficiency is determined using a synthetic atmosphere of vinyl chloride in clean air contained in a Tedlar (in house) or a Seran (reference 5) bag. Known volumes of this atmosphere are sampled using the charcoal tubes and the vinyl chloride desorbed and determined by GC analysis. Concentrations thus obtained are compared with those from GC analyses of 1-ml aliquots of the synthetic atmosphere to give the desorption efficiency (DE):
DE * weight vinyl chloride on charcoal/volume atmosphere sampled concentration of vinyl chloride in atmosphere
In house values of the desorption efficiency for about 300/ig of vinyl chloride on the charcoal tubes have been around 0.8. Since the desorption efficiency may differ with loading on the charcoal, desorption procedure, and charcoal batch, each laboratory should determine its own values, preferably for the loading expected if an atmosphere containing vinyl chloride at the OSHA standard were sampled.
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RETE3TSCES
1. E.A. Boettner and F.A. Dallas, J Gas Chromatog, 3, 190 (1965).
.2 p,y. Williams and M.E. Umstead, Anal Chen, 40, 2232 (1968).
3. E.D. Baretta, R.D. Stewart, and J.E. Mutchler, Am Ind Byg Assoc J. 30, 537 (1969).
4. O.L. Hollis and W.V. Hayes, Anal Chem, 34, 1223 (1962)
5. jL.k. Allemany, L.W. Severs, and L.K. Skory, Dow Chemical Company Analytical Method ML-AM-74-12, "Monitoring Personnel Exposure to Vinyl Chloride in an Industrial Work Environment," 17 April 1974.
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