Document QMmqYm11nydnY2Y897N02pYr8

DOW CHEMICAL U.S.A. enclosure D-2 BARSTOW BUILDING 2020 DOW CENTER MIDLAND. MICHIGAN 48640 MONITORING SYSTEMS FOR VINYLIDENE CHLORIDE MONOMER R&S 105682 There are two approaches to monitoring vinyl chloride and vinylidene chloride monomers. One is continuous area monitoring and the other is personnel monitoring. The latter is essential and is required by OSHA. However, continuous monitoring is extremely helpful in defining problem areas. At Dow, we have used the halogenated hydrocarbon analyzer for continuous monitoring of vinyl chloride and vinylidene chloride for years. Enclosed is the operating principle, physical description and some pictures of the analyzer. It has been very useful and very effective in our monitoring program. This unit can be used for 6 or 12 sampling points. The sampling lines are made from -1/4-inch Saran tubing and can be extended up to a couple hundred feet. They can be strung overhead and allowed to hang in the breathing zone of the operator. In order to determine where the control points should be, an industrial hygiene survey should be conducted initially to define the areas of greatest exposure. The continuous analyzer gives a 24-hour printout on chart paper and the unit can be hooked up to an alarm system for early warning of potentially excessive exposures. Understandably, the unit itself has to be in a standardized area (outside any explosive .atmosphere of vinyl chloride), and the readout chart can be located anywhere. It is our understandin that a firm in Chicago can make the unit. This firm is A.E.D., Incorporated, 1913 West Irving Park Road, Chicago, Illinois 60613, Telephone A/C 312 348-6550. We have used infrared spectrophotometry in the past, but only recently are v:e using this method for continuous monitoring of vinyl chloride monomer. We have also just installed a continuous monitoring system for vinyl chloride monomer using vapor phase chromatography. The only disadvantage of this system is the lengthy time between samples (approximately 20 minutes as opposed to 2 minutes with IR and less than 1 minute for the conductivity meter). AN OPERATING UNIT OF THE DOW CHEMICAL COMPANY -I RAH#, V*. U, s * f\ \ - :v: 'J3 - <~l * '+UU W*' We have just completed a personnel monitoring method for vinyl chloride which is reliable in the 1 part per million range. This method has been sent to both OSHA and NIOSH. We are including a copy of this method for you. We feel this method can be applicable for vinylidene chloride but more work must be done on desorption and column conditions. For personnel monitoring, in the meantime, we suggest you collect samples in the breathing zone of the worker in Saran film bags and analyze the contents by infrared or gas chromatography. Enclosed is a description of the Saran film bags and the names of the suppliers. We use the 12 liter bags. Using an air mover such as a personnel sampler (MSA Monitaire pump), the bag can be filled (or a series of bags can be filled) and the contents analyzed by VPC. A small piece of transparent tape can be placed on the bag so a hypodermic needle can be inserted into the bag without rupturing it, and the hole can be taped over so the bag can be reused. The conditions described for the VPC analysis in the vinyl chloride personnel monitoring method can be used to analyze for vinylidene chloride collected in Saran film bags. 10-3-74 CCK R&S 105683 _ Pittsburgh PCB 12x30 activated carbon is found to be the most suitable of the commercially available carbons tested for personnel sampling of vinyl chloride, vinylidene chloride, and methyl chloride. The carbon is desorbed with CSV at dry ice temperature or with a thermal desorption technique. enclosure D-1 Monitoring personnel exposure to vinyl chloride, vinylidene chloride and methyl chloride in an industrial work environment L. W. SEVERS and L. K- SKORY Dow Chemical U.S.A., Midland, Michigan 48640 :s 4 * .0 A r If I i Introduction Late in 1973, information became available linking angiosarcoma of the liver (a rare form of cancer) with occupational exposures to high levels of vinyl chloride. Reacting to this, OSHA issued an Emergency Temporary Standard for vinyl chloride exposures limiting them a a max imum of 50 ppm. Subsequently, a reduction of this standard was proposed and became effec tive whereby the permissible eight hour timeweighted average exposure may not exceed 1 ppm, with a ceiling of 5 ppm averaged over no more than a 15 minute sampling period.1 A study was undertaken to develop a reliable method for long and short term personnel sampling and analysis of vinyl chloride. Methyl chloride and vinylidene chloride were also in cluded in this investigation because of their chemical similarity to vinyl chloride. Breakthrough Studies Field use of commercially available adsorbent carbon tubes gave significantly differing results than sophisticated chlorohydrocarbon analyzers thus indicating that existing adsorbents were not adequate to quantitatively define vinyl chloride exposures to workers. Available carbons were obtained and studied for breakthrough time by passing 200 ppm (parts per million by volume in air) vinyl chloride through a 30 ml bed of carbon at a flowrate of approximately 2 1pm (liters per minute) representing typical conditions that existed a year ago. Comparison of the parts per million breakthrough versus time is shown in Table I.2*3 Dow Experimental Carbon (XF4175L), Pittsburgh MSC-V 14X40 mesh and Columbia Carbon showed the best break through characteristics; however, the Dow Ex perimental Carbon and the MSC-V are not commercially available at this time. Replicate samples of Columbia Carbon TS-570 were tested against those of Pittsburgh < f l f f 1 Wgf i ( X.?V Loren W. Severs, received a 6.A. in chemistry from the University of California. Irvine in 1972. Joined The Dow Chemical Company, Analytical Laboratories. Midland. Michigan, after graduation. Worked on anal* ysis of trace contaminants in water and air. Recently served as consultant to the Industrial Hygiene Labora tory to develop methods of collection and analysts of organic vapors in air. American Industrial Hygiene Association Journal ' i Lyman K. Skory graduated from Michigan State Univer sity In 1949 with a B.S. de gree in Chemistry and from Pennsylvania State Univer sity with an M.S. degree in Organic Chemistry and joined The Dow Chemical Company, Midland, Michi gan, in 1951- He is currently a Group Leader in the Dow Industrial Hygiene Labora tory, Midland. He works closely with OSHA and NlOSH in health standards programs .md with Product Stewardship for Dow cus tomers. 669 3D fio O) 0 01 0) 09 (a. it-iuewa jj>i. ; i j wy ,im n tf 11 ' .fri, wi.yiniss TOP? : 1 -1 < t fl l '3 i *4i .1 j .< -ris '* " *' TABLE I Comparison in Parts par Million of Commercial Carbons; 30 ML Bad Volume, 200 ppm Vinyl Chlorida, 1.97 Ipm Flowrate _VlSHLR- SCIENTIFIC WESTVACO COCOANUT COLUMBIA PITTSBURGH TIME NUCHAR WVH CARBON CARBON PPL DARCO (HOURS) 8x30 MESH 6x14 MESH SMALL MESH 4x10 MESH 4x12 MESH O.S <0.05 <0.05 <0x05 <0-05 <0.02 1.0 <0.05 <0.05 <0.05 0.24 <0.02 1.S 0.08 <0.05 <0.05 0.86 0.02 2.0 0.S3 0.21 <0.05 1.77 0.12 M 5.22 0.95 <0.05 0.51 3.0 2U0 5.45 0.05 3.15 11.80 DOW PITTSBURGH WITCO EXPERIMENTAL M$C*V GRADE 360 CARBON 14x40 MESH 10x20 MESH XF-4175L <0.1 <2 <0.1 <0.1 2 <0.1 <0.1 4 <0.1 <0.1 4 <0.1 <0.1 12 <0.1 <0.1 40 <0.1 PCB 12X30 Activated Carbon. The bed size was reduced to 1 gram of carbon contained in a stainless steel tube (14 cm x 0.25" O.D. x 0.028" wall) fitted with Swagelok caps. The test concentrations was reduced to 50 ppm vinyl chloride and the pump flowrate was re duced to 0.2 1pm. Table II shows the Pitts burgh PCB carbon to be the most suitable for eight hour time-weighted average personnel sampling. The 1 gram slugs of PCB carbon were also tested at 25 ppm with flowrates of 0.5 and 1.0 1pm. Table III gives the results of those tests. Based on these data, the following sampling conditions were recommended for the 1 gram slug of Pittsburgh PCB 12X30 Acti vated Carbon: (1) 0.2 1pm for 8 hours, (2) 0.5 lpm for 10 to 60 minutes, and (3) 1.0 1pm for 10 minutes. Further breakthrough testing was con ducted with different sized tubes for short time periods. The NIOSH method for vinyl chloride in air4 uses a 150 mg divided charcoal tube. This charcoal tube was tested with 1 ppm and 5 ppm vinyl chloride at a flowrate of 1 lpm. Figure 1 shows breakthrough within the first minute and approximately 12% breakthrough after 10 minutes. The flowrate for this size tube was reduced to 0.2 1 pm and the experi ment repeated at the 5 ppm level. Figure 2 shows that the breakthrough under these conditions is nearly 3% after 15 minutes. The NIOSH method also states that 5 liters of 200 ppm vinyl chloride can be col lected at 0.05 lpm without significant amounts of vinyl chloride being found on the back sec tion. Duplicate test runs undef these conditions showed that substantial breakthrough occurs well before 5 liters of sample has been collected (Figure 2). A direct comparison of the carbon in the NIOSH recommended tubes and PCB 12X30 was made by repacking the NIOSH tube with 150 mg of PCB carbon and repeating the ex periment. Figure 1 shows that the two carbons have similar breakthrough characteristics under these conditions. However, this may be due to carbon bed size than type of carbon. The tubes could be used in a 5 ppm atmosphere at 0.05 lpm for 15 minute sampling; however, only 0.75 liter is collected. Even with a GC sensi tivity of 1 /ig/sample, a less than value of 0.52 ppm is obtained, which is above the action level (0.5 ppm) and much higher than the de sired 0.1 ppm sensitivity. We, therefore, con cluded that the 150 mg NIOSH recommended tube was inadequate for vinyl chloride sampling. Two larger tubes of carbon were tested under similar conditions. A 600 mg charcoal TABLE II Percent Breakthrough for Columbia and Pittsburgh PCB Activated Carbons at 50 ppm Vinyl Chlorida and 0.2 Ipm Flowrate TIME (HOURS) 5.0 5.5 C.0 6.5 7.0 . 7.5 COLUMBIA CARBON TS-570 1.0 2.5 12.0 24.0 46.0 PITTSBURGH PCB 12x30 <0.3 <0.3 <0.3 <03 <03 <03 070' TABLE III Percent Breakthrough for One Gram of Pittsburgh PCB 12x30 at 25 ppm Vinyl Chloride With 0.5 and 1 Ipm Flowrate* TIME (HOURS) 1.0 1.25 1.7 1.6 2.5 2.9 33 - 3.3 0.5 LPM <0.06 <0.06 <0.06 0.30 2.60 13.00 1.0 LPM -- 0.4 0.6 ,-- '--- laptimt 00 On CO con o> cWn ipwwiwui.. jin '-u , '*5.*sW kthrough St after 15 5 stales that 5 an be colcant amounts he back secr\c conditions nigh occurs been collected rarbon in the PCB 12X30 ,H tube with ting the ex two carbons Icristics under isy be due to on^te tubes hiBo.OS vcvff; only i GC sensivalue of 0.52 he action - than the dcerefore, conrecommended oride sampling, were tested mg charcoal 4 Cram of PPm Vinyl Ftowrau* 10 IPM 0.4 o.a Stpttmbar, 1I7S Figure 1 -Vinyl chloride breakthrough, 150 mg tube at 1 Ipm. 22 20 18 16 14 jarB to 12 10 8 * 6 4 600 mg commercial tube 4 25 ppm 700 mg PCB, 12x30, 50 ppm a 700 mg PCB. 12x30. 25 ppm * A 2 0 >4j__ a. 0 20 30 40 50 60 Minutes Figure 3-Vinyl chloride breakthrough, 600 and 700 mg tubes at 1 Ipm. Figure 2-Vinyl chloride breakthrough, 150 mg tube Figure 4-Methyl chloride breakthrough, 100 ppm at reduced flowrates. at 0.2 Ipm for 150 and 600 mg tubes. tube is manufactured by the makers of the 150 mg NIOSH tube. A tube was also made from a disposable glass transfer pipette containing approximately 700 mg of the Pittsburgh PCB AmrlcM Induttrtal Hyfitn* JUtoclitton Journal 12X30 Activated Carbon. Figure 3 shows the results for testing these tubes at 25 and 50 ppm vinyl chloride at 1 1pm. Either tube could be used for .the 15 minute sampling and at 671 l.LWirwjr u--uTM m jy --I'H.-'wuMHg*" R&S 105686 ' * ' reduced flowrates (0.2 or 0.1 1pm) for ex vantages over the carbon usee in iue com tended periods of time (7-8 hours) at these levels. mercial tube. Reducing the iipwrate wiii, c course, allow for longer samp;? times, but not Two items of interest are evident from Figures 1 and 3: (1) the breakthrough time and percentages are not directly proportional to those seen for the 150 mg tube, indicating ad ditional factors in adsorption (possibly tube dimension and/or a change of carbon), and (2) the breakthrough curves for 25 and 50 ppm are almost identical, as are those for 1 and 5 ppm on the 150 mg tube. These data indicate that the percentage breakthrough for a given flowrate and tube size is independent of die concentration for at least the 1-50 ppm range. Similar breakthrough testing was per long enough for eight hour samples. T he 600 mg size tube has very good retention capability for vinylidene chloride. A test of 31 pprr. vmylidenc chloride samples at 1 1pm showed less than 0.08% breakthrough after 75 minutes. Thus, with a reduction in flowrate to 0.1 or 0.2 1pm, eight hour sampling is quite pos sible. (These data suggest that the type of car bon has been changed in this size tube because a similiar test run a year ago showed substan tial breakthrough after 60 minutes. The 150 mg and 600 mg tubes were SKC Lot 104 and Lot 105, respectively. SKC has confirmed a 'i formed for methyl chloride and vinvlidene chloride. Methyl chloride was tested at 100 *r ppm (TLV) for various flowrates and tube sizes. Figure 4 shows 150 mg tubes are not suitable for methyl chloride sampling at the current allowable levels, although the PCB carbon appears to have better retention capa JJ fi (/) bilities. The 600 mg size tube might be used for short term samples. Reducing the flowrate below 0.2 1pm would increase the time of sampling. However, by using the 1 gram slug of PCB 12X30 and reducing the flowrate to o Coo>ofl -4 .1 0.1 1pm, sampling times of up to 80-90 min utes are feasible (Figure 5). Tbis figure also shows the increase in sampling time possible by decreasing the flowrate from 0.5 to 0.2 to 0.1 1pm. A sample test of 200 ppm at 0.2 1 pm flowrate is also known for comparison. If methyl chloride and vinyl Figure 5-Methyl chloride breakthrough, 100 ppm at various flows for 1 gram Pittsburgh PCB 12X30 activated carbon. chloride are to be sampled in the same area, J the methyl chloride will be the limiting factor in choosing a sampling period and flowrate. Only by increasing the amount of carbon and/ or greatly reducing the flowrate can eight hour sampling be attempted. change of carbon between the two lots. This change in carbon was recommended to the supplier after NIOSH had received our recom mendations.) One gram of the PCB 12X30 carbon in a stainless steel slug has been run (Methyl chloride breakthrough was also under these conditions-for eight hours with no ; determined on the 1 gram slug of PCB 12X30 detectable breakthrough. j at the 50 ppm level. The breakthrough curves i are the same as those shown in Figure 5 for Carbon Disulfide Desorption 'ii 100 ppm. This further demonstrates that per A desorption technique for vinyl chloride was centage breakthrough for a given flowrate and devised that would ensure the integrity of the 'S tube size is independent of concentration.) sample. An experiment in one of our labora The breakthrough characteristics for tories indicated a 98% recovery was obtained vinylidene chloride are much less severe than when the carbon was slowly added to the CS2 for methyl chloride and vinyl chloride through cooled in a dry ice/acetone slurry.2 The follow out testing. Figure 6 shows that the 150 mg ing procedure has since proven to be satisfac size tube may be used for short term samples- tory: (1) cool 10 ml of CS2 to dry ice tempera (10-15 minutes) at 1 1pm. However, the PCB ture; (2) slowly add the carbon to the cold CS?; 12X30 carbon begins to show definite ad (3) agitate for 30 minutes, keeping cold; (4) 3 #77 MpttmMr, 197} tj' ' j|g 91 /rwir w iyw* v "-"lyrywi. w is com:ewiil,c: ae^ut not sM600 jnWpability 31 ppm vinshowed less minutes, /rate to 0.1 quite posype of carjbe because d substanThe 150 >t 104 and .firmed a i, 100 ppm 'ittsburgh is. This to the ur rccom12X30 en run 's with no >ride was ty of the laboraobtained the CSi "he followsatisfactempera: cold CSi; Id; (4) v, refrigerate until analysis, analyzing from a wet ice batit. I: was found that by thus minimizing the heat generation during desorption, replicate samples have given a recovery range of 53- 101%. This same desorption technique has been applied to samples of methyl chloride. Over a period of time, 25 known samples have shown a recovery range of 70-97% with an average of 83% 8% (one standard deviation). The wide range of recovery values has not yet been accounted for. Desorption of vinylidene chloride samples is accomplished by the same procedure. A wet ice bath can be used, unless one or more of the low boiling gases are to be determined also. MX) X>40tOK>10m>W Figure 6-Vinyiidene chloride breakthrough, 20 ppm at 1 Ipm for 150 mg tube. Recoveries for vinylidene chloride in CSz have a range of 95-100%. Standard Preparation A technique was adapted from a procedure used at Dow for many years.5 Vinyl chloride gas is condensed in a tared, narrow neck ampule in dry ice. The ampule is flame sealed and reweighed to constant weight. A small Swagelok nut is carefully placed over the neck of the ampule and the whole assembly gently lowered into a measured volume of CS->. The ampule is then broken by shaking the bottle. No bubbles of gas are seen during this operation, indicating that the vinyl chloride is completely dissolving inCS?. Methyl chloride standards can be made by following the same procedure. Standards of vinyiio'ep.'j chloride arc rou tinely prepared by injecting a measured volume of vinylidene chloride into a known volume of CS2 with a microliter syringe. There was some question about standards made by injecting a known volume of gas into a known volume of CS2 in a sealed serum viai at room temperature and wet ice temperature so the above technique was utilized. Condens ing the vinyl chloride in dry ice and using a 10 ml glass syringe cooled to dry ice temperature to prepare a standard proved difficult to duplicate. Sample Storage The flood of inquiries from industrial hygienists, both from industry and government regarding personnel samples taken at one location and forwarding to a laboratory at another location for analysis, set the priority for determining sample storage characteristics. The backlog of samples taken in our own company and limita tions of available manpower and instrumenta tion further substantiated the need to know how much absorbed vapor was being lost during storage or shipment of carbon tubes. Sample of 10 liters of vinyl chloride at 1 ppm on the PCB 12X30 activated carbon were stored in polyethylene tubing for one to three weeks; 10 to 20% loss was noted with increased storage time. The effects of four weeks storage at room temperature were checked with both the stainless steel and glass tubes, and no apparent sample degradation was observed. However, it was found that if samples were removed-from their tubes and placed in small vials sealed with Polvseal caps, up to 40% of the initially loaded vinyl chloride was lost after one week of storage in the freezer. Samples, therefore, should be kept sealed in the original sample tubes until desorbed. The storage effects on vinylidene chloride in glass tubes proved to be within the error (5%) of the analytical method. Effects on methyl chloride samples have not yet been determined. Thermal Desorption Thermal desorption was investigated as an alternate to CSj desorption. Thermal desorp tion, if perfected, offers several advtanges ove carbon desorption, such as reduced health . hazards. Amarkan liKhiatriif Hjrfltm AMOdaHon Journal 673 rrv J-1 "A .1 *n jiaaa.3.>y^ni!>iw.JWiyy R&S 105688 R&S 105689 The experimental apparatus consist of gas source, a dry test meter for measuring gas volumes, a muffle furnace and a Saran* film bag to collect the expelled vapors. The inlet and outlet tubes are of stainless steel as are the sample tubes. Prepurified nitrogen at aflowrate of 500-800 ml/minute is used as the purge gas. The oven temperature was initially set at 225C, however, the low and erratic recoveries obtained were eliminated by raising the temperature to 430C. The desorption procedure is as follows. Place a 10 liter Saran film bag at the exit end of the outlet tube; connect the sample tube in the line and start the nitrogen flow. Purge the system with approximately 1 liter of nitrogen before placing the tube in the furnace. After placing the tube in the furnace, collect the expelled vapors until the desired volume is obtained. Divert the nitrogen flow from the collection bag and remove the bag for analysis. For samples of approximately 100 liters of 50 ppm vinyl chloride, 4 liters of nitrogen were sufficient to obtain recoveries of 97% 4%. The same was true for 100 liters of 10 ppm. However, for short term samples, e.g., 10 liters collected at 11pm, it was found that more nitrogen was needed. At 25 ppm, 4 liters of nitrogen gave 90% recovery. At the 10 ppm level, 10 liters of nitrogen had to be used to obtain 93% recovery and at 1 ppm, 12 liters of nitrogen were needed to obtain this recovery. Fifteen replicate samples of 1 ppm vinyl chlo ride were analyzed by this method. The aver age recovery was 92% 3.5% (one standard deviation). Subsequent series of tests have shown a recovery factor of 80% 5%. At tempts were made to find the cause of the decrease. Neither the use of glass tubing nor deactivated and conditioned stainless steel tub ing increased the recovery factor to its original value. Replacement of the inlet/outlet tubing and the nitrogen supply has had the same nega tive effect. Although this new factor is lower than what was originally found, it has been reproducible and could, therefore, be effectively used as the recovery factor for this technique. The recoveries of methyl chloride and vinylidene chloride have also been determined by this technique. A recovery of 75% 5% is obtained (one standard deviation) for 6 liters of both 50 and 100 ppm methyl chloride desorbed with 10 liters of nitrogen. Replicate samples of 10 ppm vinylidene chloride gave a recovery of 88% 5% (one standard devia tion) when desorbed with 10 liters of nitrogen. Analytical Conditions Analysis is performed by gas chromatography/ flame ionization detection. No one column or set of conditions can cover all situations in volving analysis for vinyl chloride. A variety of columns have been used depending upon the situation. Figures 7-11 show some of the columns that can be used under varying cir cumstances. Breakthrough was determined by period ically injecting air sanfples drawn from a glass tee placed behind the carbon tube. The follow ing GC conditions were employed. Column: Column Temperature: Carrier Flow: Hydrogen Flow: Detector Temperature: Sample Size: 6' x Vi " stainless steel 20% DC 200 on Chromosorb W, 80/100 Mesh 80C 30 ml/min N* 30 ml/min 240 ml/min 250C 0.5 cc with GSV, or 1.0 mi Pressure-Lok Syringe Sample analysis was originally performed on this same column at 40C. Both vinyl chloride and vinylidene chloride can be deter mined (Figure 7); however, light hydrocarbons may interfere with the vinyl chloride determi nation. Such interferences were eliminated by employing the following conditions (Figures 8 and 9). Column: Column Temperature: Injection Port: Sample Size: 20' xVfc* stainless steel Carbowax 4000 on Supclcoport 80/100 Mesh 80C Unheated, on-column injection 2 microliters Other parameters were the same as pre viously stated. Temperature and carrier flow are quite critical because the vinylidene chlo ride is not completely separate from the CSj; *Siru it a trademark of The Dow Chemical Cotnpeoy abroad. #74 StptMtor, 1173 ,14 +1 4't' rddeyia- . f nitrogen. ins in. variety 5 upon ic of the ' ngcir- y period-' n a glass be follow- el 20% isorb W, 1.0 ml ?e le deterocarbons etermiited by gures el jpelco- injection s prer flow chloCS; pifly wtor, UTS % Conclusions When the vinyl chloride situation arose it was found that existing techniques for personnel sampling and analysis of vinyl chloride expo sures were found to be inadequate because vinyl chloride vapor was easily lost from the sample at several different stages in. the collecr tion and analysis. This study evaluated numerous adsorbing media and found that one specific cocoanut carbon, Pittsburgh PCB 12X30 Activated Carbon, is the most suitable of the commer cially available carbons tested for personnel sampling of vinyl chloride and related com pounds. One gram of this carbon packed in a stainless steel tube (14 cm x 0.25" O.D. x 0.028" wall) can be used satisfactorily to col lect vinyl chloride, vinylidene chloride and methyl chloride according to the sampling conditions developed herein. The study devel oped improved techniques of desorbing the carbon using CS* at dry ice temperature. Thermal desorption was also investigated as an alternative to CSa desorption. Minutes Acknowledgement The authors wish to express their thanks to A. A. Allemang, R. A. Dommer, R. K. Lee, G. J. Roush and G.E. Socha for their assistance in this study. Figure 7-Chromatogram ot components on DC 200 column; (1) vinyl chloride, (2) vinylidene Chloride, (3) CS2 R&S 105690 small changes in either of these parameters results in loss of resolution. * These conditions have proved satisfactory except for samples containing methyl chloride, dichlorodifluoromethane and/or dimethyl ether in addition to vinyl chloride. For these situations satisfactory separations have been achieved under the following conditions (Fig ures 10 and 11). Column: Carrier Flow: Column Temperature: S' xVb" stainless steel Porapak QS, 80/100 Mesh 40 ml/min N2 70C (methyl chloride, dichlo rodifluoromethane, vinyl chloride) 115C (methyl chloride, di methyl ether, vinyl chloride) AmHein Indmtrlal Hyfitii* Auoci*ttM Joumil Minuta Figure 8-Chromatograms of components in air on Carbowax 4000 column; (1) isobutane, (2) vinyl chloride. (3) vinylidene chloride, (4) trans-1, 2-dichloroethylene, (5) me- thacrylonitrile, (6) acrylonitrile. t 675 * Minute* Figure 10-Chromatogram of methyl chloride and vinyl chloride in the presence of Freon12 on Porapak QS column; (1) methyl 'chloride, (2) Freon-12, (3) vinyl Chloride. 0 2 4 6 8 10 Minutes Figure 9-Chromatogram of components in CS2 on Carbowax 4000 column; (1) vinyl chlo ride, (3) CS2. References 1. Federal Register 39.-194, October 4. 1974, 2. Private communication, A. A. Allemang. 3. Private communication, R. K. Lee. 4. Vinyl Chloride in Air, NIOSH Analytical Method. 5. Stenger, V. A., S. A. Shrader and A. W. Beshge- TOOr: Analytical methods for methy bromide. Ind. A Chem. (Anal. Ed.) 11:121 (March 15, 1939). 1 '5 676 Time, Min. Figure 11 -Chromatogram of methyl chloride and vinyl chloride in presence of dimethyl ether on Porapak QS columns; (1) methyl chloride, (2) dimethyl ether, (3) vinyl chloride. Septembtr, 1975