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U'. .u..l I . , . Welwyn Garden Ctfy Hertfordshire Telephone Welwyn Garden 234GG {STD Code 07073) STD Coda trem London Area 06 Telex 2S4251 Iciplast Welwyn ff /a ui .ermuoi Industries Limited Plastics Division To: Subcommittee on Analytical Procedures Technical Tank Group on Vinyl Chloride llosearch i'janufnc t crisp; Cbem Lstc Associate on Your ref Our ref Tel ext Date 11 Fob 19V4 Gentlemen : Attached are description:; of various ICT analytical techniques; relati: : to the determination of VUK concentrauionr. in atmosphere, 1-VO rer;in, and foodstuffs, for discussion at the Juhcoo.'M U.oo muetin/; in Ch-.c:a>;o on t'.c 19th February. V/e shall bo r.blc re make spare copies of the attached nvailaol meeting on the 19th but if you feel, it appropriate to copy t.u.:se docui nt:; to the other members of the committee! in advance, please no sc A V/ Barnes VVC 000000936 IMPERIAL CHEMICAL INDUSTRIES LIMITED PLASTICS DIVISION - V/KLVYN GARDEN CITY research department ANALYTICAL DIVISION The Determination of Vinyl Chloride Monomer in Poly (Vinyl Chloride) Latiees, Slurries, V/et Cohn and Powders: Solution Injection - Gnr> Chromatographic Method Analytical Method P73/8 A R Jcffe N W V/ilson INTRODUCTION Two methods arc used for the determination of vinyl chloride monomer in poly (vinyl chloride) and in both, analysis is carried out on a solution of the sample in tetrahydrofuran. In the first method, a direct injection procedure is used, whilst in the second, headspace sampling is employed. The former procedure, described here, is a general method applicable to the determination of vinyl chloride in the concentration range 0.01 - 5% in latices und v/et cakes as v/ell as powders. It is, however, more suited to the examination of samples having a high monomer content. The sample is dissolved in tetrahydrofuran containing isopropyl chloride as an internal standard. This solution is injected directly into the gas chromatograph for analysis, and the procedure calibrated with known solutions of vinyl chloride monomer prepared in the same internal stanriard/solvent solution. APPARATUS u;ns Garcmaroar.T.'pn Pitted vim a flame icrisatr.oa detector and heated injection port with disposable glass liner. A Perkin Elmer Fll is suitable. Mechanical shaker Volumetric flasks Conical flasks 100 cm3, i>0 cm^ and 10 cm3 50 cm^, stoppered Hamilton syringe Micrometer syringe 10 ]kl 0.5 cm3. An Agla syringe is suitable Pipettes REAGENTS AND SOLVENT/INTERNAL STANDARD SOLUTIONS Tetrahydro furan Laboratory reagent grade. Redistilled Tetrahydrofuran Reflux the solvent over potassium hydroxide and carefully distil rejecting the distillation foreruns. Vinyl chloride Isopropyl Chloride (2-chlorcpropanc) Cylinder containing liquid monomer. B. D. H* uiiVVC 000000937 Solvent/internal standard Solution A Solvent/internal standard Solution B 0.1C$ v/v solution of isopropyl chloride in tetrnhydrofuran. 0.01$o v/v solution of isopropyl chloride in tetrahydrofurnn - prepare by dilution of solution A with redistilled THF. GAS CHROMATOGRAPHIC CONDITIONS Set up the gas chromatograph according to the manufacturers instructions and operate under the conditions detailed below. Column 4.00 Metres 1/8" OD S/S packed with 2Ctf> *Carbowax', 1540 and 0.5^ u/w 'Atpet' 80 on silane (HMDS) treated 'Diatomite C (60-72 mesh). Column temperature Injection port temperature 45 C 150 C Sample size Nitrogen carrier inlet pre sure 1 Ml 15 psi Hydrogen inlet pressure 15 psi Air inlet pressure Amplifier sensitivity 18 psi 1 x 20 for low range, 10^ x 2 for high range. Recorder 1 mV FSD CALIBRATION : LOW RANGE : 100 - 2500 pg VC/25 cm? Accurately weigh a 50 cm? volumetric flack containing approximately 40 cm? tetrahydrofuran. Add approximately 1.5 g vinyl chloride liquid and quickly stopper and reweigh the flask. Make the volume up to the mark with tetra hydrofuran, mix, and store in a refrigerator. By means of a pipette transfer 1.0 cm? of this solution to a 10 cm? volumetric flask containing a little solvent/internal standard solution B. Dilute to the mark with the solution B and mix well. By means of an Agla micrometer syringe transfer 0.10 cm? of the second solution to a 10 cm? volumetric flask containing a little solvent/internal solution B. Dilute to the mark with the solution B and mix well to give the lower calibration standard, which when prepared from .a starting 5% solution contains the equivalent of 750 }ig vinyl chloride/25 cai? solution. In a similar manner prepare two other standard solutions containing approximately 1500 jig and 2500 ^g vinyl chloride per 25 cm? respectively. Calculate the exact strength of each solution. 000000** 33 YVC Set the chromatograph to the appropriate attenuation rotting and inject 1 pi of one of the standards. Allow the chromatogram to develop and measure the peak height duo to the vinyl chloride rind isopropyl chloride. Repeat thin procedure for the other standards and in each ease calculate the ratio vinyl chloride r>eak hoirht isopropyl chloride peak height Plot a graph relating these peak height ratioG to jig vinyl chloride per 25 cia? solution. CALIBRATION : HIGH RANGE : 2.5 - 25 mg VINYL CHLORIDE/25 cm3 Accurately weigh a 100 cm3 volumetric flask containing 80 cra^ solvcnt/internal standard solution A. Add approximately 2 g vinyl chloride liquid and quickly stopper and reweigh the flask. Make the volume up to the mark with solvent/internal standard solution A. Mix and store in a refrigerator. By means of a micrometer syringe transfer 0.500 cm3 this solution to a 10 cm3 volumetric flask containing a little solvent/internal standard solution A, and dilute to the mark with solution A to give the highest calibration standard. This, when prepared from a smarting 2/,solution contains the equivalent of 25 mg vinyl chloridc/25 cm3 solution. In a similar manner prepare two other standard solutions containing approximately 5 and 10 mg vinyl chloride per 25 cm3 respectively. Calculate the exact strength of each solution. Set the chromatograph to the appropriate attenuation setting and carry out the chromatography exactly as described for the low range calibration. C'alcu"tc the peau height ratios and plot a graph relating these to mg vinyl chloride per 25 cm3. EXAMINATION OF SAMPLES Dry Powders : Low Range Accurately weigh an amount of sample not exceeding 1 g and containing less than 25CO jig vinyl chloride monomer into a 50 cm3 conical flask. Add from a pipette or dispenser 25 cm3 of solvent/internal standard solution f-, immediately stopper the flask and secure the stopper with adhesive tape. Place the fins); on a mechanical shaker until the polymer has dissolved, then carry out. the chromatography on a 1 pi aliquot of the solution exactly as described for the low-range calibration. Latices, Slurries and Wet Cake : High Range Accurately weigh an amount of sample not 'exceeding 1 g and containing less than 25 mg vinyl chloride monomer into a `JO cm conical flask - Add from a pipette or dispenser 25 cm3 of solvent/internal standard solution A, immediately stopper the flask and secure the stopper with adhesive tape. Place the flask on a mechanical shaker until the polymer has dissolved, then carry out the chromatography on a 1 pi aliquot of the solution exactly as described for the high-range calibration. RESULTS WC 000000939 On each sample chromatogram measure the peak height due to vinyl chloride and isopropyl chloride. Calculate the ratio vinvi chloride -peak heii-t.f. isopropyl chloride peak height and by reference to the appropriate calibration graph read eff the equivalent jig or rag vinyl chloride per cm-* solution. Hence calculate the concentrat ion of vinyl chloride in the original cample and quote the result as parts per million or as a percentage w/w as appropriate. NOTE Typical chromatograms arc shown in the figure. 5 September 1973 AHJ/DCiiS/LLV/R-1/1 VVC 000000940 v ^ . l . ( t l . k..._____ _ . c__a '-IINTTO rx O7 I i.'Umi, , ______ __________________________________ __ t_ rri'Fro IX GT r.;.................................. VVC 0 0 0 0 0 0 9 4 1 IMI'KIU All CilKMTCAL I!: UU: iT U TL". LlMITi:i> hjlitju; ijivjlioii v-m.v.yii lai{Li-.:i civr Rh-ut-lARCtf LiTAkTMCNT ANALYTICAL IHVlbJON Analytical Method: P73/9 M R Ringham The Determination of Vinyl Ohio ride Monomer in Air Prototype Arnlysof. Flame Ionisation Detector DESCRIPTION OP THE ANALYSER The analyser has been developed and used for the determination of vinv] chloride raon'in.or concentrations in plant atmosphere:'-.. The apparatus consists of a name ionisation detector, oven temperature controll er, a.r.rlifier, a gon flow unit and a recorder Conp.-enonts The block diagram, Fig. 1, .indicates the component;- referred to h'-lov.-. A) Heated dual name ionisation cletes tor head, I've Fori.e'" V` -art Mo. modified by removal or one of the 'name deter! (tee note 1 ). 3) Ionisation amplifier Mark .II, Fye Lories 10-l , Part Mo. 791 Py*. C) Detector oven controller, Pye Verier. 10t , Part. Mu. 791711. b.~..;n.* a silicon rerutifir uni;. j.m.a i j iux -i ed. ..of., ar..; i(1 M) Peristaltic Pump - high flow pump, rrranu fae lured ty tLvi' o j j r: r. Du.us; Limited, Uxbridge Pond, Ealing Broadwayt Loudon. p, u:i.).,*; rijiuou rubber b mm bore, 10 mm external diameter. D) A (jan control unit which control.:; four operation:;. 1 Fuel gas flowing to the detector. ,1 Blank carrier rpir. flowing through the d"tee!.or. i Introduction of standard pas for cali hr?\ ti-,.... 4 Introduction of the sample gas. The How ratr-;3 j n operations P, 3 and * must be the same on rnr.ry in'.a the f i. v ion i cai.:i on detector. A block diagram of t. hr control unit r. .own ir Fir. 1-. , 9(ie ration 1 ogcu is piped from n cylirtde* , vising 1/8" copper tubing, l.-'- *"\r b '..nMOi the ga.; control unit. The How rate ir. r-. .ul a t m |,v <vni.t:- .u f e x'C," i iat.or , Kconnected with n Simplex pr.;uj e jpnjip- i t * r i t . v-poij. 9- :air r . upport !-nr. ir pi fieri to thv ibteotn.' rev i ; '.h. . * iuj.il, i'i.r- '.low rate regulated uj rrpu fa to' . our era ' are gauge (L'-"0 p; i As aid' ir reqtij rob t: ' 1. r. e umji ; ' i .;. > VVC 000000942 .is blank gas when the instrument ir, in the standby condition the air line is divided: our.* branch Cor tho fuel gas, the other branch for blank ran. Operation 2 : Blank Carrier Gas Air is piped to the T3-way1 switch valve X, at position 1. Position \ at valve X is connected to '5-way' switch valve Y at position 1. When both val.ves arc in the 'up position' blank air flows through to the detector. The required flow rate of 35 ml/tfin is obtained by placing a standard restriction between the detector and the Watts regulator T of glass capillary, 0,2 mm bore and 23 cm long. The flow rate is indicated by a Simplex pressure gauge (0-30 psi) connected to regulator T. Operation 3 Standard Vinyl Clilori.de Gas Mixture The standard gas mixture is piped from a cylinder to valve X at position 2, and then by the same valves and restriction to the detoelap as in Opeiat.ion 1. When valve X is placer) in the 'down' position tho standard gas mixture flows to valve Y which is loft in tho `up1 position and pusses to tlv' detector. (Introduction of blank aii1 and standard gar is from cyl ind* r:> and therefore on a pressure basin). i Operation 4 : Introduction of Sample The bellows containing the sample gas is connected at. inlet M which i connected through a filter, consisting of a 2n > 1/4" OD glass tube filled with cotton wool, to tho peristaltic pump N. The pump is connected to valve \ a.. po~j. 2 usx rig s t i ij. j*1 c'Ss j.'lcri L '.upxjlary tutu'-/.. ' -h Y in the 'down' position the sample gas passes to tho deter to;*. `['ho pr-n and connecting lines can be purged wit!; air by switching valve Y to the 'ip' position and leaving the pump running. iC) Recorder, Smiths Servoscribe, Type Rft 520.20 with a modified scale 0-2C0 Note 1 A heated head is essential to prevent the water formed by combust.ion : t the flame tip condensing within, the defector ami giving rise to consderm io Leo l ricnl. noise. Also any hydrogen eh.l.ori do formed ihu* to tin- >;*!: * ti on of vinyl chloride would form hydrochloric acid in the presence ol moucurr nnd cause serious corrosion within the detector. Note 2 The electrical control unit is normally mounted at trie rear of the analyser oven. An analyser oven is not required for the vinyl chloride detn. cli-u; therefore the silicon control rectifier unit; Cor- the detector oven In.been incorporated in detector oven controller unit. This circuit dir."ram .enould be used in conjunction wi a Fig. iild.d detector oven contrail, -s CJ`;t. No. 122 o-i/2 of the Pyc 104 chromatograph technical manual. VVC 000000943 OPERATING INSTRUCTION 1 Calibration of.Flow Hates through the Detector Flow rates for each gas through the detector are calibrated against the pressures indicated on the gauge by setting these to the required rate using the soap bubble technique and rioting the pressure. The optimum rates are: Hydrogen Air Sample ) Vinyl chloride standard ) blank a'-.r ) 30 ml/min 400 ml/min 3!5 rol/mm ?. Settings on A talyner Detector oven controller sotting Temp. 100-1P0C. Amplifier netting Attenuator Jx 10*-. Hacking ol f range x PolariIy A Backing o/T X Gas flow unit netting Switch valves X and Y in th.' 'up* positions. Lighting Flamo Tojiisat, torj_Dotoctor Switch on recorder. Turn on hydrogen and air supplies. Pressure at hydrogen cylinder regulator - 3 kg per sq cm. Pressure at ;iir cylinder regulator - ?. kg per sq cm. Turn sample regulator T - off. Reduce air pressure to 10 j.hs per sq in. Adjust hydrogen pressure reading to 9 lbs per sq in. Remove cover from flame ionisation detector unit. Presr ignite switch, check Maine is alight by placing a polished swr'sce to the chimney of the. detector to show condensation. When lit inctua.'e air pressure to ].h lbs por sq. in. Adjust regulator T to approximately J tins nor sq in. Perinea cover on flame ionisation detector unit. Wl._ VVc 000000944 t ihrntitii*; Ann'l vsor rt recorder r.peed at 1.20 tnm/hour and millivolt setting at ?. nr?. vag-:i standard vinyl chloride/air cylinder. -iV. itch from -lank )\r<r. to standard gar, at switch valve rthju.-.t sarnpif jtrc1 .".ure -at regulate.), T to give a recorder s-ad-oi; for trie :or.f;".il rat i :>: i.n ppm v/1, of the st'inrl>'-;l .gar mixture b- i.: .isr.;: . \V . Allow > truii'*s;; fe -Mobilise over n p**r. sd < i.u u1,-;'. When reading i.u stable? turn flan stream from standard gnr. l:o hl.nnk gar at switch valve X. The instrument in now calibrated .and ready for camplfc .runs. Turn off standard gac mixture at cylinder. ' Lock control, regulators R, and T. Sampling The air sample is taken using Fletcher bellows (air sampling aspirator Gallenkamp Cat. No. OF 4J0). If an extension lead is required for sampling polyvinyl chloride tubing is used since this does not absorb vinyl chloride monomer. The bellows are filled and emptied three timer before taking the sample. Connect the bellows at M. Switch on and run the.pump for one minute. Switch valve Y to down position and run instrument" for three minuter, or until a stable reading is recorded. Head off in ppm v/v vinyl chloride present from the recorder scale. After the reading ban been taken switch valve Y to `up1 position. When the recorder pen lias returned to jr.ero the nppsrutu: is ready for the next sample. .Sensitivity The analyser is capable of measuring vinyl, chloride concentrations dov.n to 10 ppm v/v at the standard attenuation setting of 10 x .10''- and a pressure setting of 1 psi. The limits of detection or. the ICX- attenuation rarre? arrfroir. 1 ppm v/v to ir-00 ppm v/v nf vinyl chloride in air at the same v ensure retving. p.iFPARATIOK AND STANDARDISATION OF VINYL CHLCKIDK/AIR MIXTIK E The recommended mixture for calibration is 1S0-200 ppm v/v in air. Prepa rn Lion , ^ A cylinder is evacuated and a calculated volume of vinyl chLor.idi qn: is drawn into the cylinder using a gas burette. The cylinder ;r l.h'-n brought: to a Luiospheric pressure* by allowing air to be drawn a l. a flow rate of `-00 v' / minute. The cylinder is then pressurised to 1400 psi using a ccr ijir.fssed air cylinder at FOOD psi. The cylinder is then allowed to stand for- at least P'J hour.4' to oquilibriate. The vinyl .chloride is then do tom '.is d against a known standard mixture of vinyl chloride in air l>y gas civ v.-mto|j-rnp:iy. Lur.Jurdj ati cn A . emit.! bottom flask of known volume, (calibrated using the water a `hod; is. "^r.iCiiat'edand tilled with clean air to atmospheric pressure. A : an : of .si tab!. e '".so is inner Led intothe neck. An aliquot, of purr- v L 1 rhioviee fa- : injected into Luc flask through liu: . a.bn s. al .is::i . syri: I no type of ring'"- used is a 1.0 ml. *!vii ]. 1 ct Ic be i:ni tar ' a.i .(>. ah' ...sin. . Tin yringf- is flushed out with vinyl chloride rar 6 timers, before i vqu. red vo'i u is measured and injected into the flask. This i*ns Lhs'. VVC 000000945 Mi* syringe is saturated with vinyl, chloride before the r'lrtipl e in l.'ikee. The atma.cphr re ip mixed by piercing the sea 1 with n aped)** attached t* n 10 ml disposable `syringe anu filling and emptying it into trie fJo.-k n lirm-n. Cm* aliquot is injected into the GC apparatus by taking !0 ml and injecting into tho evneuatod sample loop. Only one aliquot can bo Lus.t n nut of the flask and therefore different atmospheres of the same concor-t- ration have to he prepared for duplic:ato determinations. Gas Chromatographic Conditions Detec tor Flame ionisation detector Column 1-metro of silicon elastomer ^pe on acid washed 'Oolite1. Column temperature 40C Hydrogen flow rate 20 ml/minute Nitrogen flov; rate 30 ml/minnto Air flow rate 300 .'jatnpl c loop 3 ern^ The concentration of vinyl chloride is calculated using the joak height method. y hu` I'liibf ' ] '! r Ji J'.kS/iJ^.'/h -1/"' vve 00000094^ in (. 1 F: v' T.~ZX~: e^6000000 3/M n ?rrn fo C? ,v r<" ro c.| ' SI ! >: ; 5" u :* i v " *15 ii t.'! 'aJs U i '* i iV> S js: m !?> :n & si i; 'vi 5S ?f i? 8g ?y Ifi V> '' y. !X u*l. i! 'si iii pi i^ i , _ i n:__:r ~I __iii Oz oP Du ' C, .U ' , 'v. < - k i.i! fp 11 '-- 1 1 !\ ! ' i* ' R5 g*>5 In *>m; ...-- X '-i ss 5' __) pr ,.n Hi L 5?n I*1" iiO />/H,Ow -kb tn** >? IMPERIAL CHEMICAL INDUSTRIES LIMITED PLASTICS DIVISION - WELWYN GARDEN CITY RESEARCH DEPARTMENT ANALYTICAL DIVISION THE DETERMINATION OF VINYL CHLORIDE MONOMER IN NON-ALCHOLIC AND ALCOHOLIC DRINKS AND OTHER AQUEOUS SOLUTIONS OR EMULSIONS f INTRODUCTION The procedures described in this test method are those developed for the determination of low ppm quantities of vinyl chloride monomer leached from PVC bottles into the contained fluids during storage# The method employs a head space sampling gas chromatographic technique*, calibrated by the addition of micro-litre quantities of a standardised solution of vinyl chloride in water, to samples of the particular fluid under test which have not been in contact with poly (vinyl chloride)# t INSTRUMENTATION The Perkin Elmer FkO Multifract head space campling chromatograph is suitable. C.-.4 nn f V. F40 !: oi-'UT fr> t.n h <> under the conditions given, in the tabic below Uco standard 2b ml cnr>ac:'.ty r`*0 sample vials and seals arid operate with an equilibration time of at least 3 hourc at 30C before campling. Column 4 Metres 1/8" OD S.S. v/v Carbovax l^t + 0.5% Atpet 80 on silane treated (HMDS) Diatomrite C (60-72 mesh). Column temperature 43C Water bath temperature 30 C Inj ector needle temperature 120C Injection time 5 sec. Analysis time Aqueous solutions (e.g. orange squash) 10 mins Gin, Vodka - 60 rains Whisky - 90 mins Purge time 24 sec Stabilisation time Nitrogen carrier inlot pressure Air inlet pressure 30 sec 2 1.0 Kp/cm 1.2 Kp/cm^ VVC 00000094-9 Hydrogen inlet pressure p 1*0 Kp/cm ' Amplifier sensitivity 1x1 Recorder (2-pen) 2 mV and 10 or 20 mV* Chart speed 1 cm/rain. An integrator can be uced if desired. PREPARATION OF CALIBRATION SOLUTION Prepare a saturated solution of vinyl chloride in water at 25C* by the following method* Place the bubbler assembly shown in Fig* 1 into a water bath thermostatically controlled at 25C. Place 70 cm** water in the tube and bubble vinyl chloride through the absorber for a minimum period of 2 hours* Remove 10 cra^ of this solution into a 125 cm^ Hypo-vial containing 90.0 cn^ distilled water. Immediately seal and store thiG dilute standard solution in a refrigerator at 5C* Remove two further 20 cm^ aliquots of the solution from the bubbler directly into the iodine flasks for standardisation as described below then transfer the remainder of this strong standard solution to a Hypo-vial and immediately seal and store in a refrigerator at 5C. STANDARDISATION OF STRONG STANDARD SOLUTION V Solutions Required Potassium bromide/bromate solution 0*1N Sodium thiosulphate solution 0.1N (standardised) Hydrochloric acid solution Approximately 2N Potassium iodide solution ' 20$ v/v Method Into two 250 cm^ iodine flasks add 25*0 cra^ 0*1N potassium bromide/bromate solution. Add to each flask 20.0 car of the saturated vinyl chloride solution from the bubbler and follow this by 15 cm^ 2N hydrochloric acid solution. Immediately stopper the flasks, shake to mix the contents and seal the stopper with a little 20$ potassium iodide solution. Allow the flasks to stand in the dark for at least 16 hours. Carefully remove the stopper , allowing the potassium iodide to run into the flask, then add a further 10 car of the potassium iodide solution and titrate the liberated iodine with the 0.1N sodium thiosulphate solution. Carry out a blank on all the reagents used, using 20 ern-^ distilled water instead of the aliquot of sample solution. Calculation % w/v vinyl chloride in solution = (Blank titre - sample titre) x O.PO5125 r. ICO 20 VVC 000000950 In our experience the value go obtained should be about 0,17,6 w/v vinyl chloride. The dilute standard solution is labelled at one tenth of this value. i CALIBRATION OF GAS CHROMATOGRAPHIC PROCEDURE Into a series of 25 cra^ capacity F40 vials add 5 cm^ aliquots of the fluid under test which has not been in contact with poly(vinyl chloride). Seal and cap the vials and by means of a Hamilton micro-litre syringe add 0, 2, 5> 10, 20, 30, 70 and 100X~1 of the dilute standard vinyl chloride solution. Place the vials in the F40 thermostat bath at 300 and start the analysis, arranging the minimum 3 hours equilibration before the first standard is sampled by the chromatograph. Measure the peak height of the vinyl chloride peak shown in Fig. 2 for each standard and plot graphs relating peak height toy*'*g vinyl chloride per 5 cm^ solution. -These graphs cover the range 0 - 3/^'g and 0 - 15/*"S vinyl chloride per 5 cor solution. EXAMINATION OF SAMPLES Shake each sample bottle and by means of a pipette transfer 5 ern^ to a 25 cra^ capacity F40 vial. Immediately seal and cap the vial and place it in the F40 thermostat bath at 30C to be processed with a set of calibration standards as described above. RESULTS Measure the peak height due to vinyl chloride in the sample chromatogram and by reference to the appropriate calibration graph, calculate the vinyl chloride content of the liquid under test* Report the result as ppm v/v vinyl chloride. NOTE Most liquors contain "high boiling" constituents, and it is advisable to process no more than eight samples or standards at any one time. The column temperature should thenbe raised to about 100C and allow to purge clear of high boilers. An overnight purge carried out whilst a further set of Scimples or standards are equilibrating is convenient. If available,- an electronic integrator may be used in conjunction with the chromatograph. 25 June 1973 DCMS/LJ.-//R-1/G vve 0000095i v'lH'fL CHiOftibt- Re, 1 6>v> p. -l ft. `OK J(\ O D C l rsi C, A SaTu k m ' p 0 Hcjcf < o CT sV.i'^-ri, ( rU. Oiv I Of WC 000000952 VIM V/miSKT m Comikt O <T *S u<y PVC MhaI CSCiTTlFI ' 0-15 ppm /v * Vlr-i'l't. CHLOR'tf- v,>\ V/.vu<>k y Oi.f'S'j PjotTi r C <* R04 ^ rtf* ipi IMPERIAL CHEMICAL INDUSTRIES LIMITED PLASTICS DIVI LION - WELWYN GAHDHl CITY RESEARCH DEPARTMENT ANALYTICAL DIVISION The Determination of Vinyl Chloride Monomer in Poly (Vinyl Chloride) Powders, Compounds and Mouldings : Headspace Sampling Gas Chromatographic Method Analytical Method P73/7 INTRODUCTION A R Jeffs N W Wilson Two methods are used for the determination of vinyl chloride monomer in poly (vinyl chloride) and in both, the analysis is carried out on a solution of the sample in tetranydrofuran. In the first method, a direct injection procedure is used, whilst in the second, headspace sampling is employed. The latter procedure, described here, is particularly preferred for samples containing less than 200 ppm vinyl chloride monomer and has a louer limit of detection of 0.5 ppm. Although the use of an automatic headspace sampling clxror.atograph is specified in this method, the procedure can be modified to use simpler equipment with manual headspace sampling by means of a gas tight syringe into a standard chromatograph. APPARATUS Headspace sampling gas chromatograph The Forkin Elmer F40 Multifract instrument is suitable. Sample vials and seals 25 cm^ F40 vials are suitable. Magnetic stirrer Volumetric flasks 25 cm3 and 10 c r^. Hamilton syringe 10 jil. Micrometer syringe O.5 cm^. An Agla syringe is suitable. REAGENTS PVC homopolymer powder (Monomer free) Tetrahydro furan Store PVC homopolymer powder in a well ventilated situation until 'all residual monomer lias volatilised. Polymer contain ing less than 0.5 ppm as determined by this test method is required. This solvent may contain both high boiling impurities which will prolong the analysis and low boiling constituents which will interfere with the determination of vinyl chloride particularly at low concentration Remove such impurities by refluxing the solvrnt over rotassium hydroxide and careful distillation with rejection of the foreruns. vve 000000954 Vinyl chloride GAS CHROMATOGRAPHIC CONDITIONS Cylinder containing liquid monomer. Set up the F40 chromatograph according to the manufacturer'g instructions to operate under the conditions given in the table below. Use standard 25 cm3 capacity F40 sample vials and seals and operate with an equilibration time of at least 5 hours at 30C before sampling* Column standard 4.00 metres 1/8", OD S/S packed with 20% w/w 'Carbovax' 1540 + 0.5/ v/w 'Atpet' 80 on nilane (HMDS) treated 'Diatomite' C (60-72 mesh). Column temperature 45C. Water bath temperature 30.0C. Injector needle temperature 120 C Injection time 5 sec. Analysis time 30 min. (This time vdll vary v/ith the purity of the tetrahydrofuran solvent and the level of monomer content being determined i.e. the amplifier Getting and millivolt range of the recorder used). Purge time 24 ecc* Stabilisation time 30 sec. Nitrogen carrier inlet pressure Hydrogen inlet pressure Air inlet pressure 1.0 Kp/cm^. 1.0 Kp/cm^. 1*2 Kp/cm^. Amplifier sensitivity 1x1. Recorder Servoscribe (2-pen). The mV ranges used depend on the level of monomer content determined i.e. 0.66 mV and 5 mV respectively are used for 0.2-8 pg. 2 mV and 20 mV respectively are used for 5-30 pg. 20 mV and 100 mV respectively are used for 30-500 jig. Chart speed 1 ctti/rain. VVC 000000955 CALIBRATION : HIGH RANGO : 0 - 4CO pg .VTi.'TL CIILGI'IDB Accurately weigh a 25 cm3 volumetric flask containing approximately 20 cm^ redistilled tetrahydrofuran. Add about 1 g vinyl chloride liquid and quickly stopper and reweigh the flack. Hoke the volume up to the mark with redictilled tetrahydrofuran, mix and ntore in a refrigerator. Calculate the exact strength of this standard vinyl chloride solution. Weigh 0.500 g +_ 1 mg portions of monomer-free polymer into a series of 25 cm capacity F40 vials. Add 5*0 cm-^ redistilled tetrahydrofuran and immediately seal and cap the vials. Allow the polymer to dissolve. The addition of tetrahydrofuran to the polymer pov/der can cause gelation so that complete solution takes several hours, even with mechanical shaking. Solution within a few minutes can be obtained by use of a magnetic stirrer. The F40 vial containing the polymer and magnetic bar are placed on the stirrer and 5.0 cm^ of tetrahydrofuran added rapidly from a syringe or dispenser. Small stirrer bars are conveniently made from short lengths of steel wire, sealed into glass melting point tubing. When the solutions are ready, by means of a 10 pi Hamilton syringe add, through the caps of separate vials 0, 1, 3, 7 and 10 pi aliquots of the standard vinyl chloride solution to give a range of standards, which when prepared from a starting 4# solution, cover the range 0-400 pg vinyl chloride Place the prepared vials together v/ith any sample vials in the F40 thermostat bath at 30C and after allowing a minimum equilibration period of 5 hours start the automatic analysis sequence. On each chromatogram measure the height of the peak due to vinyl chloride and plot a graph relating peak height to pg vinyl chloride per vial* CALIBRATION : LC',/ RANGE : 0 - 20 pg VINYL OlE.ORinE By means of a micrometer syringe transfer 0.500 cm^ of the standard vinyl chloride solution, prepared for the high-range calibration, to a 10 cm^ volumetric flask containing a little redistilled tetrahydrofuran. Dilute to the mark with redistilled tetrahydrofuran, mix and store in a refrigerator Calculate the c-xact strength of this dilute standard vinyl chloride solution. Using this solution carry out the procedure described for the high range calibration. When prepared from a dilute standard solution containing 0.2# vinyl chloride these standards cover the range 0-20 pg monomer. EXAMINATION OF SAMPLES Powder samples should be stored in tightly scaled containers whilst awaiting analysis. As quickly as possible, weigh 0.500 g + 1 mg of the sample into an F40 vial. Add 5*0 cm^ redistilled tetrahydrofuran and immediately seal and cap the vial. Dissolve the polymer as described for the high range calibration, and when solution is complete transfer the vial together with the standards to the F40 thermostat bath to complete the analysis. Measure the peak height due to vinyl chloride on the chromatogram produced. RESULTS Refer the peak height due to vinyl chloride in the samole chromatogram to the appropriate calibration graph and hence calculate the vinyl chloride content of the sample. Report the result as ppm w/w vinyl chloride. vve 000000956 NOTES If available, an electronic integrator may be used in conjunction with the chromatograph. It is often convenient to purge the chromatographic column free of accumulated high boiling constituents by increasing the column temperature to 100C over night. During this time a further set of samples and/or standards can be equilibrating in the 30C thermostat bath. Typical chromatograms are shown in the figure. 7 September 1973 AHJ/DCMS/LEW/N-1/1 VVC 000000957 >\9% \U I C'I'ttT |A'C'tiil ni-l TiC", SnnPlL CC'-rTftiHtfJC, MO Vir.it. t fill I<iiil ( Ji'-uvf "i ,,,,) \\i (> it \ C mu nn't.i.rt i\ f'l fiK'i I r>' PVC v',s 11 S'V /*' ^ 1 1 '