Document 5kMD4r5JYDpK982NajmkdYjxD

R&S 039455 Pittsburgh PCM 12x30 activated carbon is found to be zhe most suitable of iris commercially available carbons tested for personnel samoiing of vinyl chloride, vl-.vlidene chloride, and methyl chloride. The carbon is desorbed with CSi> at dry ice temoerature 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 !. K. SKORY Dc-v Cl'.envea! U.S.A , ,\Vd!and. Michigan 48640 Introduction Erne T3".'. became available linking / die liver !;t rare form of cancer) with occupational exposures :o high .'eve:-; of vinyl chloride. Rending to thR. OSHA R'Cad an Emergen.;-. Id.moo:ary Standard for .ad ehlorn.e c'"> >.;.re, iimitinc diem a a max- u. ft'i ppr- Sub- r.yaertly. a rc.hjc'ion 'f TR standai\l was rropo'Od an I became effec ts.,. vhe:vhy the ~e rmssihle eight. hour '.:oe- rented asvrage : ere may not v\c-_ed I ppm. with a eei.ioy ri p ppm, .v.cr.i-ecd o.cr no : . than if m.b.uv ampum: pvt \ mewd n r Urne a: J - v." tenn pcm.-mic! ,.pd anao. R o: v'.nvt . I*:--t.! j. Meim.' h: -d :i:R n'Se1"- :.:P-'n hrenioc o: them . ` -.'itvchloride. : 4 .4, . .wi, c ; ... ii'jr ; * 4^ .-C -J !. . :. rf'-'-ie ads .. 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 fparts per million by volume in air) vinyl chloride through a 30 ml bed of carbon at a flowrate of approximately 2 1pm filters per minute) representing typical conditions that existed a year ago. Comparison of the parts per million breakthrough versus time is shown in Table f.:' Dow Experimental Carbon (XF4175L). Pittsburgh MSC-V 14X40 mesh and Columbia Carbon showed the best break through characteristics; however, the Dow Ex perimental Carhon and the MSC-V arc not commercially available at this time. Replicate samples of Columbia Carbon : ' ; 'o ".ov tested against those of Pittsburgh v .t * Mv V * *n V' ,ne LuT'* t D rr -ns o* S fi* Lyman K. Skory graduated from Michigan State Univer* sity in 1949 with a B.S. dc* greo in Chemistry and from Pennsylvania State Univer* Mty v,\th an M.S. degree in "rganie Chemistry and -red The Dow Chemical Comoany. Midland. Miehiov', in 1951* is currently \*mn t.nnder in th* Dow Mutual Hyglrn* labor*. r/, Vidland. H* works with OSHA and m health standards and with Product 'TAnrdship for Dow CUS* -Ors. 669 R&S 0394sg TABLE ' Comparison In Porti par Million of Commercial Cannons; 30 ML Bad Voluma, 200 ppm Vinyl Chloride, 1.97 (pm Flowrat* --------------- ------ rwnnr------------- "" SCIENTIFIC WESTVACO COCOANUT COLUMBIA fOTSBUBOH _ TIME NUCHARWVH CARBON CARBON BPL DARCO (H0URS1 0x5 l.C 1.5 2.0 2.5 30 8*30 M---E--S--H- <0.05 <0.05 0.08 , 0.53 5.22 2630 6x14 MESH SMALL MESH 4x10 MESH <0.05 <0.05 <0.05 0.21 0.95 5.45 <0.05 <0.05 <0.05 <0.05 <0.05 0.05 <0.05 0.24 0.S6 1.77 3.15 4x32 MESH <0.02 <0.02 0.02 0.12 0.51 11.80 PITTSBURGH WITCO MSC-v GRADE 360 10x20 ME9H <0.1 <o.: / 0. 1 < C1 <0.1 I' c.t <2 2 4 4 12 40 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 PCB 12X30 Activated Carbon. The bed size was reduced to 1 gram of carbon contained in u stainless steel tube (14 cm x 0.25" O.D. x 0.02S' wail) fitted with Swagelok caps. The test concentrations was reduced to 50 ppm vinyl chloride and the pump flowrate was re duced 0.2 1 pm. Table II shows the Pitts burgh PC13 carbon to be the most suitable for eight hour time-weighted average personnel mum! mg. The 1 gram slugs of PCB carbon 'Acre also tested at 25 ppm with flowrates of 0.5 ai.i 1.0 ipm. Table III gives the results of those test's. Based on these data, the following 'utnniing conditions were recommended for the ` slug ot Pittsburgh PCB 12X30 Acti vated Carbon: (1) 0.2 1 pm for 8 hours. (2) 0.5 (pm for 10 to 60 minutes, and (3) 1.0 Ipm for 10 rnir`',tcs. F;;ru:cr breakthrough testing was conuue'.eb w,rh different sized tubes for short time perix'ds. The NIOSH method for vinyl chloride f: air1 'ises a (50 mg divided charcoal tube. This cl- .rcoai tube was tested with 1 ppm and ' ppm vinyl chior'dc at a flowrate of 1 1pm. I -.hows breakthrough within the first .a and approximately 12% breakthrough ; ' mmutes. The flowrate for this size .. reduced to 0.2 1pm and the experi - at the 5 ppm level. ' d- * - . Figure 2 shows :hat the breakthrough J 1. under these conditions is nearly 3% after 15 ir.'pV : minutes. The NIOSH method also states that 5 liters of 200 ppm vinyl chloride can be col- ;V lcctcd at 0.05 1 pm without significant amounts of vinyl chioridc being found on the back see- _ -$ lion. Duplicate tes' runv under these conditions mS showed that substantiai breakthrough occurs `|a well before 5 liters of <ampie has been collected T5 (Figure 2). . "'4 A direct comparison of ii c carbon in the ' f-j NIOSH recommended tubes and. PCB 12X30 was made by repacking the NIOSH tube with - ^ 150 mg of PCB carbon and re pcating the ex- ' periment. Figure 1 shows that tnc two carbons V;;g| have similarbrcakthrough characteristics under these conditions. However, this may be due to'aHi carbon bed size than type of carbon. The tubes could be used in a 5 ppm atmosphere at 0.05 ^ 1pm for 15 minute sampling; however, only ' i>4j 0.75 liter is collected. Even with a GC sensi- tivity of 1 /jg/sample. a less than value of 0.52 T`, ppm is obtained, which, N above the action level (0.5 ppm) and much higher than the desired 0.1 ppm sensitives-a 'O e. therefore, con-'-'y eluded that tnc 150 m ; 'HOSH recommended tube was inadequate : > inyl chloride sampling. T Two larger tub. . : carbon were tested under similar condi; -\ 600 mg charcoal ' TABLE II : Snmkthrough for Columbia and i res Activated Carbon* at 50 ppm CNorkla and 0.2 Ipm Howrata TS-570 1.0 2.5 12.0 24.0 46.0 "" PITTSBURGH 12x30 <0.3 <0.3 <0.3 <0J < 0.3 . <0-3 - gLE III Percent 8-r. sn lor Onm Gram of Pfttibunti" 1 ' ' 7 ;30 at 25 ppm Vinyl Chloric,.' . ; .r,dl Ipm FtowrataB TIME (HOUR:- ;o 1 zr i/ 1F ? 2" 1* r- lPM - 3.06 _ 0 06 3 06 G,3v` i3.c: 1.0 LPM -- 0.4 o.a _ -- i I j { \ j 1 >,< . vi.^-7:' \ `ir? -. -' , . I'1' Bi a u ,.ouah.* ? Mi le 16 - * 6C0 mg commercial umi 25 oom o 7CXD mg PC3. 12x30, SC ppm * 700 mg PCB, 12x30, 25 ppm ure i-Vinyl chloride breakthrough. 150 mr tube at 1 lorn. 4a oH-1 0 20 30 40 _l 50 60 Minutes Figure 3-Viny! chloride breakthrough. 600 ana 700 mg tubes at 1 /on. 60 j55 50 45 40 35 30 - h p oorr. ? 0.2 >crr: * 200 porn @ 0.05 ion 1 7. -U- , '.A' *: _ v .' : * -, si*-'* *. -7r-.:;X ->7^-:^:- : r ,. .n- '-i.- - n;, . i R&S 039457 % Breakthrough mi- ;;l a si- . O'--4--4- ij___ i___ i_ _l___ I 20 40 60 Minutes 80 Time, Mitaitffi ' r-Vinyl chloride breakthrough. 150 mg tube Figure 4-Methyl chloride breakthrough. 100 ppm at reduced flowrates. tv - 7 at 0.2 Ipm for 150 and 600 mg tubes. tuN; * manufactured by the makers of the i50 m.z > fOSH tube. A tube was also made from a disposable glass transfer pipette containing approximately 700 mg of the Pittsburgh PCB Amurv*' .'Cjitrlal Aioei*t1fl 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 571 vy reduced :'owrates (0.2 or 0.1 1pm) for ex tended periods of time (7-8 hours) at these vantages over die carbon uoti in the com mercial tube. Reducing the flowrate will, ot levels. course, allow for longer sample times, but not long enough for eight hour samples. The 600 Two items of interest are evident from mg size tube has very good retention capability Figures I and 3: (1) the breakthrough time and for vinylidene chloride. A test of 31 ppm vin- percentages are not directly proportional to . . ' ylidene* chloride samples at 1 Ipm showed less those seen for the 150 mg tube, indicating ad - fhan 0.08% breakthrough after 75 minute*. ditional factors in adsorption (possibly tube ' " Thus, with a reduction in flowrate to 0.1 dimension and/or a change of carbon), and (2) the breakthrough curves for 25 and 50 ppm - or 0.2 1pm, eight hour sampling is quite pos sible. (These data suggest that the type of car are almost identical, as are those for 1 and 5 ppm on the 159 mg tube. These data indicate that the percentage breakthrough for a given flowrate and tube size is independent of the concentration for at least the 1-50 ppm range. 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 Similar breakthrough testing was per a ;-.3 formed for methyl chloride and vinylidene ehlor.ee. Methyl chloride was tested at 100 ppm n 1A0 for various flowrates and tube si/cs. Figure i shows 150 mg tubes are not 8il(" suitable for methyl chloride sampling at the ru-rent ailrv-aSie levels, altnouch the PCB tcr'vat'. tirr*'" '1 "eve be*ter retention caca- v,i he n'. /: i*ji* mao: be usc.l i: . n1 term r,unifies. Ficuucmg tne flowrate rstuvA- 0.2 1 pm wouid tnerettse tns time cf sampling. However, by using the I gram slug of PCB 12X.,3 and reducing the flowrate to 0.! i pm. jamming times of up to 80-90 min utes arc feasible t Figure 5). This figure also shows the increase in Ul / I --I____1 in i i sampling time pw'^'e by decreasing the flowrate from o /, .<,,.; 2 ; i !pm. A sample test of 200 p.pm at i.:,2 1 nm flowrate is also known for comcaris.":: it methvi chloride and vinyl Figure 5-Methyl ch'eriie breakthrough, 100 ppm at varices f-'cwr. gram Pittsburgh PCB 12X30 xtvvrtfl carbon. chloride nr - : 1 be sample;: n the same area, the meth;. A..-, doe wiii be the limiting factor in choosing a ' ampung period and flowrate. Obv 'fcrca-s;''.:...... .'mount of carbon and/ or '..read;. f.r licwrate can eight hour 5a-tn'.-r ' - a .c-'-'mi'. i .M.ittii' ' ,.s bre ..through was also At.r-'.in'.' r 1 cram slue of PCB 12X30 <n :-- b The breakthrough curves change of carbon between the two lots. This change in carbon was recommended to the supplier after NTOSH bad received our recom mendations.) One gram of the PCB 12X30 carbon in a stainless ste;'. .lug has been run under these condition*' mght hours with no detectable brcakthrouc:-. s.-r it: siti'.wn in Figure 5 for Carbon Disulfide Dei'^rcl on .'.-I :rdemonstrates that per- A desorption technic .'' r vinyl chloride was for i given flowrate and devised that would cm.the integrity of the ' 1 vn: of concentration.) sample. An cxpcriir.'. nf i:< one of our labora .* ."'t-gh characteristics for tories indicated a ?* '! covery was obtained m :: . ...c .'iic much less severs than methyl -.a ."i.ts and vinyl chloride threugh- I'.'it'erring ' .".uc 6 shows that the 150 mg sdr tube m. used for short term samples110-15 minute:.; at i 1pm. However, the PCB when the carbon war.:.. viy added to the CSi cooled to a dry ice. acr. -nc slurry.2 The follow ing procedure has since proven to be satisfac tory: (1) cool 10 ml CSj to dry ice tempera ture; (2) slow'ly add trie carbon to the cold CS; 'V`l* 12X30 cfi-pon begins to show definite ad (3) agitate for 30 minutes, keeping cold; (4) -aril analysis, analyzing from a wet :ee oath. It was found that by thus minimizing tns heat generation during desorption, replicate a.T.plcs have given a recovery ranee 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 x recovery range of 70-97% with an average 83% -- 8% (one standard deviation). The wide range of recovery values has not yet been accounted for. ' '' Desorption of vinylidenc chloride samples is accomplished by the same procedure. A wet Standards of vinylidenc chloride are rou tinely prepared by injecting a measured volume of vinylidenc 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 CSi 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. ` :cc bath can be used, unless one or more of the low boiling gases are to be determined also. Sample Storage The flood of inquiries from industrial hygienists, both from industry and government regarding T tie ix personnel samples taken at one location and / forwarding to a laboratory at another location for analysis, set the priority for determining sampic storage characteristics. The backlog of samnies rake;; in ou* own company and iimR:-.- iior.s of avaacoic manpower and insirurren'a- tion further subsiantiated the need to know how much absorbed vapor was being lost during storage or snipment of caroon 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 Figure 6-Vinylidene chloride breakthrough, 20 ppm checked with both the stainless steel and glass at 1 Ipm (or 150 mg tube. tubes, and no apparent sample degradation was observed. , : Recoveries for vinyiidenc chloride in CSj have : range of 95-100%. However, it was found that if samples were removed-from their tubes and placed in small vials scaled with Polyseal caps, up to 40% of the initially loaded vinyl chloride was Standard Preparation lost after one week of storage in the freezer. . technique was adapted from a procedure . Samples, therefore, should be kept sealed in . : d at Dow for many years.1 Vinyl chloride the original sample tubes until desorbed. condensed in a fared, narrow neck ampule The storage effects on vinylidene chloride icc. The ampule is flame sealed and _ in glass tubes proved to be within the error :'\ed to constant weight. A small Swage- (5%) of the analytical method. Effects on < - ,c'is carefully placed over the neck of the methyl chloride samples have not yet been ,, and the whole assembly gently lowered' determined. "' 1 '' ' y.-~ ' ensured volume of CS*. The ampule 'token by shaking the bottle. No bubbles Thermal Desorption v-/' ; iccn during this operation, indicating .,.C vtnyl chloride is completely dissolving in <.' `Ittthyl chloride standards can be made bv :v:!i;'-nng the same procedure. .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. .T1. || JUwdrtlM Jwfwl m -w*j R&S 039459 7>.: experimental cyca/nttm const.:: cf :.V. .'.'m?. - dry test m`.:r .or meast-rug gas veitmin:, - muffle furnace and a OaranJ fiim to co.iret the expelled vapors. The inlet and outlet tubes arc of stainless steel as axe the sample tubes. Prepurified nitrogen at a flowrate of 500-800 ml/minute is used as the puree gas. The oven temperature was initially set at 225 C. however, the low and erratic recoveries obtained were eliminated by raising the temperature to 430aC. '. The desorption procedure is as follows. Place a 10 liter Saran film bag at the exit end 'he outlet tube: connect the sample tube in the and start the nitrogen flow. Purge the system with approximately 1 liter of nitrogen before placing the tube in the furnace. After flatting the tube in the furnace, collect the cstjclhcc saptsrs until the desired voiurne is f taiivJ. D>s jrt the nitrogen flow from, tr.e .let ':oe her and remove :'-e ban fo` arsivsh- recovery zi Sf-cr ur i . one standard d=v:e iron i when, desorbed with 10 iimm o: niproper:. Anaiyticai Conatiior,; 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 bchinJ the carbon tube. The follow ing GC conditions were employed. Column: W .:; i*" stainless steel 20% !X." 200 or. Chromosorb W. V0 !:m Nfc.-'" I'--- J I ' . 1 - -j- xrte;': * - . iU ixi*> * t for snort icon Seunpies. ::-,.rvd at I lpm. it was found that - .. as needed. At 25 ppm. 4 liters ' gjvc905s recovery. At the 10 'I ' ' 10 liters of nitrogen had to be used 9211 recovery and at 1 ppm. 12 liters .-.cr-'ccn were needed to obtain this recovery. Ff. ;c:` ".'plicate samples of 1 ppm vinyl chlo.ri :c -sere analyzed by this method. The aver se-' -cover.'was 925* -- 3.5% (one standard de*- iat.'-m}. Subsequent series of tests have a recovery factor of 80% -5%. At tempt.-; we re made to find the cause of the ' f`f-'C Neither the use of glass tnbine tier :c.,. to at'.u and conditioned stainless start tub:c a-cm.-sec :hc recovery factor to its original R.c -`.sccment of the inlet/outlet tubing 'he .atrogen supply has had the same negari'.c effect. Although this new factor is lower hat was originally found, it has been rductbic ar.d could, therefore, be effectively -sed as the recovery factor for this technique. The recoveries of methyl chloride and myliderte chloride have also been determined by this technique. A recovery of 75% re5% is obtained fone standard deviation) for 6 liters of both 50 and 100 ppm methyl chloride desorbed wuh 10 liters of nitrogen. Replicate i.-tipies of 10 ppm vinylidenc chloride gave a Dctec.::: Tcmpcrature: Sample Size: 2. ( .? cc with GSV. or 1.0 ml i'rc'-cire-Lok Syringe Sample anuhsh was originally performed on this same column a: 40'C. Both vinyl chloride and vinyiidene chloride can be deter mined (Figure 7); however, light hydrocarbons may interfere with '.he s iryl chloride determi nation, Such intcrf-.-ences were eliminated by employing the following conditions (Figures 8 and 9 :. Column: Column Temperature; Injection Port: Sample Size: 20' s'-" stainless steel (. srhowax 4000 on Supelcopor: 100 Mesh SO-C Crhe-ooj. on*column injection 2 micro-liters Other parameters were the same as pre viously stated. Temperature and carrier flow are quite critical because the vinyiidene chlo ride is not completely separate from the CSj; Sana II tuacn.ti Tij !>, Chmltil ComjMy bro*d. f { l i .i i 574 IfTS _ , R&S 039460 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 0.02S" 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 CS; desorption. Minuttf Acknowledgement The authors wish to express their thanks to A. A. AJlemang. R. A. Dommcr. R. K. Lee. G. J. Roush and G.E. Socha for their assistance in this study. F'Sure 7-Chromatogram of components on DC 200 column: (1) vinyl chloride, (2) vinylidene chloride. (3) CS. 'ma'! changes in cither of these parameters ` in loss of resolution. ': These conditions have proved satisfactory >''. . n for samples containing methyl chloride, dien' rodifluoromethane and/or dimethyl eth -r in addition to vinyl chloride. For these si: .-ns satisfactory separations have been aef; - J under the following conditions (Fig ure, .-i and 11). . 7 3 I5 '.!-join: 5'xW" stainless steel Porapak OS, 80/100 Mesh Ce-- . Flow: 40 ml/min N; .^ ,_':utr.n V-' ,:T - 'r>v-`V Ter-;-. -70C (methyl chloride, dichlo- rodifluoromethane, vinyl chloride) ` 115C (methyl chloride, di methyl ether, vinyl chloride) 0 2 4 . 6 8 10 12 14 16 IB 20 22 24 Figure 3-Chromatograms of components in air on ' Carbowax 4000 column; (1) isobutane, (2) vinyl chloride, (3) vinylidene chloride. (4) trans-1, 2-dichloroethylene, (5) methacrylonitrile. (6) acrylonitrile. kr-in-j.- .--eitrti' Xuoeutvt" louml 875