Document v6jnkd98X4x1w7Gn2BqJj08k8

A' Determination of Vinyl Chloride Monomer at the Sub-ppm Level Using a Personal Monitor S. A. MYERS, H. J. QUINN, and W. C. ZOOK Rohm and Haa.' Company, Laboratory 65, Bristol, Pennsylvania 19007 KtUUtett. MAY 28-1975 American 1 R.N. #HFFlE!CJfc | ft I A Mttod ii firta for pcnonal-bicathiiic-zoae Mmplinf of vinyl chlorMt to mMmI air. Tit procmhnc Whizes adsorption of the fat oa activated ckarcoal followed by lltefBl elatioa onto a pm chromatocrapb. The farnact used to dteoife tha vtayl chloride la daacribed in detail. Tha method waa foond to have a teaodard davtation of Mi at tha J-ppa krai aad a IMt of detection of 20 ppb or lower. The caa alao ho seed to Monitor other Introduction SAMPLING OF ORGANIC VAPORS by collection on solid adsorbents fol lowed by thermal desorption onto a gas chromatograph has been reported in the literature.'-9 Our laboratories have been us ing this technique for several years to meas ure trace quantities of organic materials in workroom environments.10-12 Recent govern ment permanent standards for vinyl chloride monomer (VCM) have necessitated a sam pling and analytical method capable of de tecting VCM at below 1 ppm.13 The tech nique described here provides a method for taking breathing-zone samples of industrial workers with a sensitivity in the sub-ppm range for VCM. The method consists of drawing a known volume of air through a glass tube packed with activated charcoal using a portable bat tery-operated pump. Breathing-Zone samples are collected by attaching the adsorption tube to the individual's lapel and hence represent a sample of the air being breathed. The sam ple is returned to the laboratory and the col lected organic material is backflushed with the aid of heat into a flame ionization gas chromatograph. With the exception of minor modifications, all the equipment necessary for this test is available commercially or can readily be prepared in the laboratory. Apparatus Adsorption Tubes: (See Figure 1.) Pre pared by cutting 80-mm lengths of 5-mm o.d. glass tubing. Both ends were fire-pol ished with the inlet end of the tube partially constricted. Glass wool was packed into the inlet end of the tube to a length of approxi mately 0.5 mm. The tube was filled with 60-80 mesh activated charcoal (Coast Engi neering Laboratory, Redondo Beach, Califomia-Gas Chromatographic Grade) within about 1cm of the open end, and a second wad of glass wool was used to retain the ad sorbent in the tube. The tubes were condi- Figure 1. Charcoal adiorption tube. 332 honed by 3^ of lOml/ma conditioning, capped to pr from the am be purchase Notch Road, log number 5 Gr Cftrd Model I2O0i flame ionized - Conditions * steel packed 101. Oven Te Attenuation-- The area of t! EAI 640 cor gram. Burrtll Py The pytolyzci ging the norm ing the carriei oven. The ms out to at leas 5-mm adsorp: Vi-inch stain! soldered to be furnace (see F was attached shown in Figui Personal M of a MSA pot MSA multiple In actual use, t and the holder under teat. Fou ously to. allow uce 021046 ) Pre5-mm re-pol- aztially nto the pproxid with t Engii, Cali- within second the adcondi- American Industrial Hygiene Association Journal l/B" 5TAINLC99 9TEEL TUHNG INJECTION PORT CAP RUBBER SEPTUM CHECK VALVE 1 !/* 5TAINLE99 STEEL TUBE SILVER SOLDERED TO normal outlet * ABSORPTION TUBE nwovcn wpium Figuri 2. Diagram showing modifications to Burrell Fyrolyzer furnace. tioned by heating at 300C under a flow of 10 ml/min nitrogen for 10 minutes. After conditioning, the tubes were immediately capped to prevent pick-up of organic matter from the ambient air. Satisfactory caps can be purchased from Thomas-Packard, 48 Notch Road, Little Falls, N.J. 07424. (cata log number 521). Gas Chromatograph: Varian Aerograph Model 1200 or equivalent instrument with a flame ionization detector. Conditions: Column--6' x V4" stainless steel packed with 60-80 mesh Chromosorb 101. Oven Temperature--100C isothermal. Attenuation--1 X. Range--10-10 amps/mv. The area of the peaks was determined by an EAI 640 computer with a PACE III pro gram. Burrell Pyrolyzer: Model #340*017-35. The pyrolyzer oven was modified by plug ging the normal inlet to furnace and relocat ing the canier input to the screw cip of the oven. The inside of the screw cap is drilled out to at least 6 mm to accommodate the 5-mm adsorption tube. A short length of 14-inch stainless steel tubing was silver soldered to both the inlet and outlet of the furnace (see Figure 2). The pyrolyzer oven was attached to ^e gas chromatograph as shown in Figures 3 and 4. Personal Monitoring Apparatus: Consists of a MSA portable pump Model G with a MSA multiple tube assembly (see Figure 5). In actual use, the pump is clipped to the belt and the holder to the lapel of the individual under test. Four tubes are exposed simultane ously to allow for replicated determinations of the same sample. The critical orifices in the multiple tube holders were not removed. Standardization One ml of vinyl chloride was diluted to 100 ml with air in a 100-ml glass syringe. The contents were allowed to equilibrate for 30 minutes after which time a uniform mix ture of air and VCM was achieved. The end of the syringe was fitted with a rubber serum bottle cap which allowed aliquots to be re- moved with a Hamilton 250-/U IP5 syringe. The aliquots were injected into the calibra tion apparatus (see Figure 6) and pulled on to the adsorption tube by applying a vacuum and flushing the injection port with approxi mately 0.15 liters of dean air. This volume was measured by attaching a rotameter to the inlet of the scrubber. The standard was then analyzed as described below under Procedure. A typical calibration curve and chromatogram are shown in Figures 7 and 8. ?- ] 1 Figure 5. Personal monitoring apparatus. Figure 6. Calibration apparatus. With (Mr gas line hitti 9A), the njt the pyrolyii|i were inserto portion old* port of Atig contents of t carrier pih and the Map about 300C pyrolyzer cat, c s i* i > * Jf V S; TIME (MINUTtai Figure 8. Chromatogram of 0.23d riayl chlo ride. * f: --M-C Figure V.-(A) two (TOr rie poakioe (lower v ytinge alibralled on acuum pproxivolume eter to rd' older ve end 7 and American Industrial Hygiene Association Journal Sampling In an area of uncontaminated air, the caps from four clean adsorption tubes were re moved and mounted in the multiple tube holder, and the holder was connected to the portable pump. The pump was turned on, and the flow through each tube was meas ured against a calibrated rotameter. The flow rate was adjusted so that at least one liter of air was collected through each tube during the sampling period. Each tube was recapped until the actual time of sampling and recapped immediately after sampling. The tubes were analyzed as described under Procedure. With the three-way valve in the carrier gas line in the by-pass position (see Figure 9A). the tube to be analyzed was placed in the pyrolysis furnace. In all cases, the tubes were inserted so the input end was in the portion of the furnace closest to the injection port of the gas chromatograph (i.e., so the contents of the tube are backflushed by the carrier gas). The tube was sealed in place and the temperature was brought rapidly to about 300C. This was done by turning the pyrolyzer on, applying a voltage to the heat er which will bring the temperature to 250C in about 5 to 10 seconds, then reducing the setting to a predetermined value which would maintain the final temperature of 300C. The temperature was held for 30 seconds then the three-way valve was placed in the inject position (see Figure 9B), and the area of the peaks in the resulting chromato gram were integrated. The results were cal culated by comparison with standards. Precision To test the reproducibility of the method, a standard sample was prepared by mixing 50 /d of vinyl chloride monomer with 50 liters of air in a Teflon bag. The volume of air used for dilution was measured from a gas cylinder through a rotameter and into the bag. Thirteen replicate samples consisting of one liter each were taken through individual charcoal tubes from the bag. The data are given in Table I. INJECTION PONT CHECK VALVE PYROLYSIS FURNACE 336 the VCM onto the absorption tube, in this manner, it was found that at least 5 liters of air could be passed through the tube be fore significant quantities of VCM were lost. When desired to check for breakthrough un der Held conditions, a fifth back-up adsorp tion tube can be placed in series between the multiple tube holder and the portable pump. Tubes to which a known quantity of vinyl chloride was added have been kept in the laboratory up to two weeks before analysis without significant losses. Discussion The technique described represents a method of sampling and analysis which meets the current Federal requirements for moni toring vinyl chloride. The sensitivity is such that a level of 100-ppb VCM can easily be detected in a 1-liter sample or 20-ppb in a 5-liter sample. Since the electrometer used in the above work was on the lO10 range, it is conceivable that the lower limit of detec tion could be reduced to 1 ppb by increas ing the operating sensitivity of the instru ment. Although written specificaily for VCM, the procedure is generally applicable to a large number of organic vapors. Our lab oratory has used adsorption tubes packed with Porapak Q, silica gel, activated alumina, and activated charcoal to sample air for acrylic and methacrylic esters as well as various industrial organic compounds and solvents (see Table II). Acknowledgment The authors wiA to acknowledge the ad vice and assistance given by Drs. K. McCallum and L. Frankel of the Rohm and Haas Company, Research Division, in the initial development of the pyrolysis technique de scribed. References 1. West, P. W.. B. Sen, and N. A. Gibson: GasLiquid Chromatographic Analysis Applied to Air Pollution. Anal. Chtm. 50.1390 (1958). . 2. Brenner, N., and L. S. Ettre: Condensing Sys TABLE n Breakthrough Volumes of some Organic Compounds Compound Breakthrough Adsorbint Volume (liters) Butyl acrylate Porapak Q Benezene Porapak Q Chloroform PorapakQ Ethyl acetate PorapakQ Ethyl acrylate Porapak Q Ethyl propionate Porapak Q Ethylene dichloride Porapak Q Methanol Silica Gel Methyl acrylate PorapakQ Methyl cellosolve Porapak Q Methyl methacrylate Porapak Q Methyl ethyl ketone Porapak Q Methylene dichloride Porapak Q Naptha PorapakQ (-Butanol Porapak Q Toluene Porapak Q Vinylidene chloride Activated Alumina Xylene Porapak0 >7 >7 >7 2 >7 >7 >7 1.3 >7 >7 >7 5 0.15 6 3 >7 2.5 >7 1 r i V ? 1 -i *. ? t t tem for Determination of Trace Impurities in Gas by Gaa Chromatography. Anal. Chem. 57:1815 (1959). 3. Altshuller, A. P., T. A, BeUar, and C. A. Clemons: Concentration of Hydrocarbons on Silica Gel Prior to Gas Chromatographic Anal ysis. Amtr. Ind. Hyg. Aisoc. J. 23:164 (1962). 4. Cropper, F. R., and S. Kaminsky: Determina tion of Toxic Organic Compounds in Admix ture in the Atmosphere by Gas Chromatogra phy. Anal. Chem. 35:735 (1963). 5. Bellmr. T. A.. M. F. Brown, and J. E. Sigsby: Determination of Atmospheric Pollutants in the Part-Per-Billion Range by Gas Chroma tography. Anal. Chem. 35:1924 (1963). 6. Williams, F. W, and M. E. Unstead: Deter mination of Trace Contaminants in Air by Concentration on Porous Polymer Beads. Anal. Chem. 40:2233 (1968). 7. Dravnieki, A., B. K. Krotoszynski, J. Whit field, A. O'Donnell, and J. Burgwald: High Speed Collection of Organic Vapors from tile Atmosphere. Env. Sci. and Tech. 5.1220 (1971). 8^Shadof, L. A., G. i. Kafloe, and I. S. Woods: Determination of Bis-(cllloromethyl) Ether in Air by Gas Chromatography--Mass Spectrom etry. Anal. Chem. 45:2341 (1973). 9. Bertsch, W., R. C. Chang, and A. Zlatkic The Determination of Organic Volatiles in Air Pollution Studies: Characterization of Profiles. Chrom: Sci. J. 12:173 (1974). 10. Collier, L.: Determination of Bikchlorometkyl) Ether at the PPB Level in Air Samples by High-Resolution Mast Spectroscopy. Env. Sci. fc." and Tajik 11. Wilkins^ 3.807ah April*Hk 12. Franks^; * JS ^ - V E X? J ' ^& if ucc 021050 rganic akthrough ime (liters) >7 >7 >7 2 >7 >7 >7 1J >7 >7 >7 J 0.15 6 1 >7 2.3 >7 npurities in naU Chem. and C. A. carbons on aphic Anal164 (1962). Determinain Admix* romatogra- E. Sigsby: >Uutants in s Chroma963). cad: Deterin Air by leads. Anal. i, J. Whitwald: High s from the 220(1971). S. Woods: I) Ether in < Spectrom- A. Zlatkis: 'tiles in Air of Profiles. loromethyl) samples by J. Env. Sci. I I i American Industrial Hygiene Association Journal and Tech. 6.930 (1*>72 >. 11. Wilkins. R. L., and L. S. Frankel: U.S. Patent 3.807J17. Analytical Monitoring System, April 30. 1974. 12. Frankel. L. S., K. S. McCallum, and L. Col- 337 tier: Formation of Bis(chloromethyl) Ether from Formaldehyde and Hydrogen Chloride. Env. Sci. and Tech. 8:356 (1974). 13. Federal Register. 39:35896 (October 4. 1974). I *