Figure11
Aliquots fromacanisterbeforeandafter cleaningwith2cyclesofhumidifiedairwhileheated to200 °C.
13
800-356-1688
•
IX.Certifying theCanister
We recommendcertifyingcanisters forbothcleanlinessand foranalyte stability.Tocertifyacanisterclean,
pressurize the canister to 14.7 psig with humidified ultra-high purity air or nitrogen after it has gone
through thecleaningcycles.Thehumidairornitrogen streammustbecertifiedcleanbefore it canbeused
for canister certification.Analyze an aliquot of the canister content byGC/MS orGC/FID/ECD.USEPA
Method TO-14A/15 specifies a canister must contain less than 0.2 ppbv of any target VOC compound
(Figure 11); EPAMethodTO-12 specifies less than 0.02ppmC, as detectedbyGC/FID. If a canister does
notmeet specification, itmust be cleaned again and retested for certification.
Tocertifyacanister foranalyte stability, introducea lowworkingconcentrationof acharacterized testmix
into the canister.Analyze an aliquot of the contents of the canister immediately after introducing the test
mixture and at periodic intervals.We recommendmonitoring for changes for aminimumof 2weeks or
fora timeframe similar toyouranticipatedholdingperiod.Responses shouldnotdecreasemore than20%
over this period.
Commercial standards areavailable for stability testing,butwe recommendyoumakeyourown testmix-
ture that is comparable to the target compound list that thecanisterwill hold.Forexample, if youareana-
lyzing sulfur compound content in ambient air, prepare a sulfur-specific testmix and evaluate the canis-
ter’s performance for sulfurs.Maintain a log sheet for each canister, and record the test results and certi-
fication. This will be a permanent record for each canister. Some labs certify canisters for certain com-
pounds anduse a canister only for this specific application.
Dirtycan
Cleancan
Rtx
®
-1 60m x 0.32mm ID x 1.0µm (cat.#10157); 50°C (hold 1min) to 165°C@ 8°C/min. to 220°C@ 15°C/min. (hold 5min.); flow rate= 1.4mL/min.; Nutech 3550 Preconcentrator
conditions: sample= 300cc from canister, cryotrap= -160°C, desorb= 150°C, cryofocuser= -190°C, desorb= 150°C; MSD conditions: Instrument: HP5971GC/MSD, 5minute sol-
vent delay, scan range= 25-260amu
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