1、7.Apparatus7.1 Gas Chromatography,equipped with either,a massspectrometricdetector,ameionizationdetector(FID),aphotoionization detector(PID),or a Hall electroconductivity detec-tor(HED),backushing valve,and either automatic capabilityor manual sampling(Note 2)and ability to analyze theheadspace vapo
2、rs contained in a sealed vial.NOTE 2If the analyses are to be performed manually(that is,bysyringe injection),then the following equipment will also be needed:(1)Constant-temperature bath or oven capable of maintaining a tem-perature of 90 6 1C.(2)Gas-tight GC syringes for sampling and injection.(3)
3、Sample bottles with uoropolymer faces septa and caps(sizeoptional).(4)Gloves for handling hot syringes.7.2 Chromatographic Column,3%OV-101 on 80/100mesh Chromosorb WHP,18-in.(3.2-mm)outside diameter by2 ft(0.6 m),stainless steel connected through18-in.“tee”to0.19%picricacidon80/100meshCarbopackC,18-
4、in.outsidediameter by 8 ft(2.4 m),stainless steel.NOTE 3Any column packing that will resolve VCM from interfer-ences and elute VCM in a reasonable length of time(1 to 5 min)issatisfactory.For example,a 3-ft(0.9-m)by18-in.(3.2-mm)outsidediameter column containing 0.19%picric acid on 80/100 mesh Car-b
5、opack C can replace the recommended 3%OV101 column.Settingsrecommended in 11.3.1 may have to be modied to suit the packingmaterial being used.7.3 Detector Output Filter/AmplierTheextremesensitiv-ity of this test method is best realized when the detector(usually operated at the maximum sensitivity)ou
6、tput is(1)lteredtoremovethehigh-frequencynoiseand(2)ampliedtogive a visible or measurable signal.7.4 Sample Headspace Vials,glass,23 mL,withuoropolymer-lined septa and aluminum caps.7.5 Vial Sealer.7.6 Analytical Balance,capable of weighing to 60.001 g.8.Reagents and Materials8.1 Vinyl Chloride Mono
7、mer(neat),pure,preferably insmall cylinder.8.2 Standard Cylinders,vinylchloridemonomerinnitrogenat 1 and 10 mg/L by volume.8.3 Hydrogen Cylinder,prepuried gas.8.4 Nitrogen,oxygen-free.NOTE 4Helium may replace nitrogen as the carrier gas.8.5 Air,breathing or water-pumped.8.6 N,N-Dimethylacetamide(DMA
8、c),sparged with nitrogengas for up to a week at room temperature to remove chromato-graphic interferences.9.Hazards9.1 Safety Precautions:9.1.1 Vinyl chloride monomer is a carcinogen and exposurebyinhalationordermalcontact,orboth,istobeavoided.Referto OSHA Standard29 CFR 1919.1017 for regulated leve
9、ls ofexposure.N,N-dimethylacetamide is a teratogen.The use of aproperly functioning hood and septum-sealed sample contain-ers are recommended.9.1.2 Avoid all contact with heated parts of the gaschromatograph,hot syringes,and sample bottles.Handle allelectrical connections with care.9.1.3 Once heated
10、,sample vials are under pressure.Afteranalysis,relievethepressurewithahypodermicsyringeneedlevented into a charcoal slug or vent tube leading to a hoodbefore removing vials from the water bath.10.Sampling and Storage10.1 Keep all polymer samples in tightly sealed jars ortightly wrapped aluminum foil
11、 prior to analysis.Dissolvedpolymersamplesmustbekeptinseptum-sealedvialsorbottlesuntil analyzed.Polymer solutions stored longer than 24 hshould be maintained under refrigeration.11.Preparation of Gas ChromatographNOTE 5All conditions in this section refer to a Headspace Analyzer.If analyses are perf
12、ormed manually,alter the operating procedures asrequired by the instrumentation.11.1 Install the chromatographic column and conditionovernight at 100C,using normal carrier ow.Do not connectthe exit end of the column to the detector or turn on detectorgases during column conditioning.11.2 Set the ow
13、of detector gases as follows:Detector Gas FlowFID Hydrogen 30 to 40 cm3/minAir 300 to 400 cm3/minPID Not requiredHED Hydrogen 30 cm3/min11.3 Set other parameters as follows:11.3.1 Oven Temperature50 to 60C.NOTE 6Higher oven temperatures may be required when otherchromatographic columns are used,or w
14、hen high-boiling solvents andlate-eluting materials are being driven from the column.11.3.2 Dosing Needle150C.11.3.3 Injection Block Temperature200C.11.3.4 Constant-Temperature Bath90 6 1.0C.11.3.5 Carrier-Gas Flow Rate30 cm3/min.NOTE 7Backushing the carrier gas after VCM elutes can consider-ably sh
15、orten analysis time.After backushing,allow adequate time forchromatographic conditions to stabilize before making another injection.11.3.6 Detector Temperature:11.3.6.1 FID250C.11.3.6.2 PID150C.11.3.6.3 HED880C.11.3.7 Filter/AmplierAdjust as needed to remove highfrequencynoiseandtoprovideadequateamp
16、licationofVCMsignal.Typical settings:lter0.05 Hz and amplier2.12.Calibration by Standard AdditionNOTE 8The gas chromatograph is calibrated using either procedure:(1)VCM in nitrogen gas standards and a previously determined partitioncoefficient for VCM between DMAc and headspace,(2)VCM solutionstandards,or(3)a method of standard addition of VCM to polymersolutions.Procedure(3)is preferred to correct for any contribution thepolymer makes to partitioning of VCM.Therefore,only procedure(3)isdescribe
