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Pittsburgh PCS 12x30 activated carbon is found to be the most suitab/e of the commercially available carbons tested for personnel sampling of vinyl chloride, vinyf/dene chloride, and methyl chloride. The carbon is desorbed with CS* at dry ice temperature or with a thermal desorption technique. 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 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 SO ppm. Subsequently, a redaction of this standard was proposed and became effec tive whereby the permissible eight boar timeweighted average exposure may not exceed 1 ppm, with & ceiling of 5 ppm averaged over no more than a IS 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 2pm (liters per minute) representing typical conditions that existed a year ago. Comparison of the parts per million breakthrough versus tune is shown in. Table I.2-3 Dow Experimental Carbon (XF4175L), Pittsburgh MSC-V14X40 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 Loren W. Severs. received B.A. in chemistry from ths University of California, Irvins in 1972. Joined Ths Dow Chemical Company, Analytical Laboratories, Midland. Michigan, attar graduation. Worked on anal* ysi* of trace contaminants in Wats'* and air. Racontly sorvsd as consultant to ths Industrial Hygiene Labors, tory to develop methods af collection and analysis of organic vapors In air. Lyman K. Skory graduated from Michigan Stats Univer sity in 1949 with a 8-8. de gree in Chemistry and from Pennsylvania Stats Univer sity with an M.S. degree in Organic Chemistry and fslnsd Ths Dew Chemical Ccmpr>y, Midland, Michi gan, In 1981. He la currently Group Leader in ths Dow industrial Hygiene Labors, teiy. Midland. He works closely with OSHA and NIOSH In health standards programs and with Product Stewardship for Dow cus tomers. American tnduitrUI Hygiene Aucclttian founts! 669 AP00012692 TABLE ! Comparison In Ports pr Million of Commercial Carbons; 30 ML Bod Volumo, 200 ppm Vinyl Chloride, 1.97 lpm Flewrato '"TOME" SCIENTIFIC WESTVACO COCOANUT COLUMBIA PITTSBURGH TIME NUCHAR WVH CARBON CARBON BPL CARGO (HOURS) 8x30 MCSH 6x14 MESH SMALL MESH 4x10 MESH 4x12 MESH O.S <6.65 < 0.05 <6-6S < 0.05 < 0.62 1.0 <0.05 <0.05 <0.05 0.2* <0.02 l.S 0.0S <0.05 <0.09 0.86 0.02 _2.0 0.53 0.21 < 0.05 1.77 0.12 2.5 3-22 0.99 <0-05 0.51 3.0 26.30 5A5 0.05 3.13 1140 DOW PITTSBURGH W1TC0 EXPERIMENTAL usc-v GRADE 350 OARBON 14,40 MESH 10x20 MESH XF-417SL <6.1 <4 <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 PCS 12X30 Activated Carbon. The bed size was reduced to l 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 t gram slugs of PCB carbon were also tested at 25 ppm with flowrates of 0.5 and 1.0 1pm. Table HI 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 l 1pm. Figure t shows breakthrough within the first minute and approximately 12% breakthrough after 10 minutes. The flowrate for this size tnbe was reduced to 0,2 lpm 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 under 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 CC 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 thaz 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 st SO ppm Vinyl Chloride and 0.2 lpm Flowrate TIME (HOURS) 16 5.S 6.0 6,5 7.0 7.5 PITTSBURGH COLUMBIA CARBON PCS TS-570 12x30 1.6 --<n--------2.5 <0.9 12.0 <0.3 24.0 <0.3 46.0 <0.3 -- <04 670 TABLE III Percent Breakthrough for One Oram of Pittsburgh PCB 12x30 at 25 ppm Vinyl Chloride With 0.5 and 1 lpm Flowrates TIME (HOURS) 1.0 1.23 1.7 11 2.5 2-9 S3 3.S 0.5 LPM < O.oS <0.06 <0.06 0.30 2.80 13.00 1.0 LPM 0.4 O.S _ -- Saptimfcir. 197S Figure 1 -Vinyl chloride breakthrough, 150 mg tube et 1 /pm. 22 2D 16 16 3ew U 12 2 CO 10 AT CO 8 at 6 4U 600 mg comnwcial tube 4 25 ppm 700 mg PCS. 12x30, 50 ppm a 700 mg PCB. 12x30, 25 ppm * I 0 20 JL. _1_ -J 40 SO 60 Minutes Figure 3-Wnyf efiforfae breakthrough, 600 and 700 mg tubas at 1 Ipm. Figure 2~Vinyt chloride breakthrough, 150 mg tube Figure 4--Methyl cMoritfe breakthrough, 100 ppm at reduced flowrates. at 0.2 (pm for ISO and 00 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 Amtrtc** industrial Kytltns A**oeiran Joumsl 12X30 Activated Carbon. Figure 3 shows the results for testing these tubes at 25 and 50 ppm vinyL chloride at 1 1pm. Hither tube could be used for the 15 minute sampling and at 671 AP00012694 r reduced flowrates (0.2 or 0.1 1pm) for ex tended periods of time (7-8 hours) at these levels. Two items of interest are evident from Figures I and 3: (I) the breakthrough time arid percentages are not directly proportional to those seen for the 150 rag 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 arc 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 formed for methyl chloride and vinylidene chloride. Methyl chloride was tested at 100 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 bilities. The 600 mg size tube ought be used for short terra samples. Reducing the flowrate below 0.2 1 pm would increase the time of sampling. However, by using the 1 gram slug of PCB 12X30 and reducing the flowrate to 0.1 1pm, sampling times of up to 80-90 min utes are feasible (Figure 5). This 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 1pm flowrate is also known for comparison. If methyl chloride and vinyl chloride are to be sampled in the same area, 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. (Methyl chloride breakthrough was also determined on the 1 gram slug of PCB 12X30 at the 50 ppm level. The breakthrough curves are the same as those shown in Figure 5 for 100 ppm. This further demonstrates that per centage breakthrough for a given flowrate and tube size is independent of concentration.) The breakthrough characteristics for vinylidene chloride are much less severe than for methyl chloride and vinyl chloride through out testing. Figure 6 shows that the 150 mg size tube may be used for short term samples (10-15 minutes) at 1 1pm. However, the PCB 12X30 carbon begins to show definite ad- vantages over the carbon used in the commercial tube. Reducing the flowrate will, of course, allow for longer sample times, but not long enough for eight hour samples. The 600 mg size tube has very good retention capability for vinylidene chloride. A test of 31 ppm vin ylidene chloride samples at 11pm 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 simiitar 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 Flgurm 5--M*thyt chfond* brMfct/iraugft, 100 ppm at various flows for 1 gram Pittsburgh PCB 12X30 activated carbon. change of carbon between die two lots. This change in carbon was recommended to the supplier after NIOSH had received our recoinmendations.) One gram of the PCB 12X30 carbon in a stainless steel slug has been run under these conditions for eight hours with no detectable breakthrough. Carbon DIsulfida Desorption A desorption technique for vinyl chloride was devised that would ensure the integrity of the sample. An experiment in one of our labora tories indicated a 98% recovery was obtained when the carbon was slowly added to the CSs cooled in a dry ice. acetone slurry.2 The follow ing procedure has since proven to be satisfac tory: (1) cool 10 ml of CS* to dry ice tempera ture: (2) slowly add the carbon to the cold CSj; (3) agitate for 30 minutes, keeping cold; (4) 672 September, 1173 ( t ; | ' j { 1 i ] 1 j | ' AP00012695 refrigerate until analysis, analyzing from a wet ice bath. U was found that by thus minimizing the heat generation during desorption, replicate samples have given a recovery range of 93* 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. iiiisttunnOH Figun 6-Vinydene eWorld breakthrough, 20 ppm at 1 fpm tor 150 mg tuba. Recoveries for vinylidene chloride in CSs have a range of 95-100%. Standard Preparation . A technique was adapted from a procedure used at Dow for many years.5 Vinyl chloride is condensed in a tared, narrow neck ampule in dry ice. The ampule is Same sealed and '1 reweighed to constant weight. A small Swage- lok nut is carefully placed over the neck of the ampule and the whole assembly gently lowered into a measured volume of CSs. 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 i in CSa. Methyl chloride standards can be made by following the same procedure. Standards of vinylidene chloride are rou tinely prepared by injecting a measured volume of vinylidene chloride into a known volume of CSi with a microliter syringe. There was some question about standards made by injecting a known volume of gas into a known volume of CSj in a sealed serum vial 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 atone 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 Polyseal 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 CSi desorption. Thermal desorp tion, if perfected, offers several advtanges over carbon desorption, such as reduced health hazards. AffitriCM Induitriil Hytltn* Ulocution Joumtl 673 i AP00012696 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 sampte tubes. Prepurifted nitrogen at a flow rate of 500-800 mi/minute is used as the purge gas. The oven temperature was initially set at 225 3C. 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, t.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 die recovery factor to its original value. Replacement of me inlet/outlet tubing and the nitrogen supply has bad 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 Condition* 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 samples 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'xH* stainless steel 20% DC 200 on Chromosorb W, 80/100 Mesh 80C 30 ml/min Ns 30 ml/min 240 mf/min 250C 0.5 cc with GSV, or 1.0 ml Pressure-Lok Syringe Sample analysis was originally performed oa 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' x V$ * stainless steel Carbowax 4000 on Supclcoport 80/100 Mesh 80C Untreated, on-column injection 2 microUters 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 CS-j; Saran is a trademark of The Dow Chemical Company abroad. 674 SUtiabtf, 1975 I 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 collec 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, vlnylidene 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 CS* desorption. Minutes ffgur* 7-Chromatogram of components on DC 200 column; (i) vinyl ehforitfe, (2) vinylfdene chloride, (3) CS, Acknowledgement The authors wish to express their thanks to A. A. ABemang; R. A. Dommer, R. K. Lee, G. 1. Roush and G,E. Socha for their assistance in this study. small changes la either of these parameters results in loss of resolution. These conditions have proved satisfactory except for samples containing methyl chloride, dicblorodifluoromethane 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: 5' x Vi" stainless steel Porapak QS, 80/100 Mesh 40 ml/mui N* 70C (methyl chloride, dichlorodifluoromethane, vinyl chloride) 115C (methyl chloride, di methyl ether, vinyl chloride) Mlnutai figure 8-Chromatograms of components in air on Carbowax 4000 column; (1) Isobutane. (2) vinyl chloride, (3) vfnylidene chloride, (4) trans-2, 2-c/icfiforoethyJana, (5) mathacrylonltrila, (6) acrylonitrile. American Udmtrfat Hyilin* Anoclitien /nmi) 675 AP000I2698 r Figure 10-Chrometogrem of methyl eWorld# end vinyl eh/or/de In the pretence of Freon* 12 on Porepefc QS column; (1) methyl chloride, (2) Freon-12, (3) vinyl chloride. Mlmitn Figuro 9-Chromatogram of components fn CS on Corbowox 4000 column,* (1) vinyl chlo ride, (3) CS* RiimncM 1. Federal Register 39:194, October 4, 1974. 2. Private Communication, A. A. Amwwa 3. Private communication, R. K. Lee. 4. Vinyl Chloride in Air, NIOSH Analytical Method. J. Stenge*, V. A.. S. A. Shuamoi and A. W. Beshcitooe: Analytical method* for methy bromide, fed. A Chem. (Anal. Ed) 17.-121 (Much 13. 1939). Time, Min. Figure ll-Chrometogrem of methyl chloride end vinyl chloride in presence of dimethyl ether on Porepek QS columns; (1) methyl chloride, (2) dimethyl ether, (3) vinyl chloride. 1 575 *trtM*ar. mi APOOO12699 62-S f - St(o - <// - if> 7/ - 37 7/ ' * 37 7J' - AP00012700