General Operating Procedures continued
ThisTO-14 type technique injectsagasorairsampleusingeithera largesyringe(60mL)oraTedlarbag
(1L). Avacuumpumpmaybeused topull thesample through thesorbent traps. Theamountofsample that
maybe loadedonto the trap(s) is limitedonlyby thecapacityof the trap’sadsorbentpackings. Themoregas
that is loadedonto the traps, the lower thedetection limitwillbe.
Thevolumeandflowofsampleandcarriergasthatcanbefedthroughthetrapswithoutadverselyaffecting
the resultingchromatogram isknownas thebreakthroughvolume. Different adsorbentshavedifferent
breakthroughvolumes. Abreakthroughvolumevalue isdeterminedby thesampleand targetanalytes, the
adsorbentpacking(poresize,naturalaffinitiesforcertaincompounds,etc.), thediameterof the trap,and the
temperatureatwhichthetrapsareloaded. Therefore,agiventrapwillhavedifferentbreakthroughvolumesin
differentanalyticalconditions.
TheSRIPurge&Trapconcentrator isshippedwithablank trapandaTenax
TM
-GR trap installed,anda
Carbosieve
TM
S-IIIpacked trapforoptionaluser installation. TheTenax-GR traphasa lowaffinityforwater,
making itagoodadsorbentfor thepurgeand trap technique. TheCarbosievehasahighaffinityforwater,and
isgenerallyhighlyretentive;SRIrecommendsusing itonlywhenvinylchloride isamong the targetanalytes.
Theblank trap isprovided for theuser topackwith theadsorbentofchoice.
POPULAR CONFIGURATION GCs
BTEX & Environmental
Usingasyringe:
1. Perform
DetectorSteps
1-4. While thedetectorsareheatingandstabilizing, loadorcreateanevent table.
Thevalve(RelayG)mustbe in theLOAD(GOFF)positionwhileanalytesarebeingadsorbedonto the traps.
Thevalve is rotated to the INJECT (GON)positionduringdesorption. See thevalvediagramson the
EPA
StylePurge&Trap Injection
TheoryofOperation
page. RelaysC (trap2)andF (trap1)activate the traps’
heat. Therelaysmayalsobeactivatedby theoperatorduringananalysis:open theRelay/pumpwindowand
clickon the lettercorrespondingwith therelayyouwant to turnONorOFF.
2. Inject thesample into the5030septumnutor the5030/5035syringeport. Alternatively, the5030purge
headmayberemovedbyunscrewingnut
b
,
allowingthesampletobeinjecteddirectlyintothebulkheadfitting
on thefrontof thevalveovenduct (see thephoto,belowright). Dependingon thesyringeyou’reusing,you
mayhave tomakeanadaptorfor injection into thepurgehead.
3. Loadorcreateatemperatureprogramforthecolumnoven. Oncethedetectorsareactivated
andstabilized,begintheanalysis.
GasSampleConcentration
Usingavacuumpump:
1. Connect thevacuumpump to the trapventon thebacksideof thevalveoven.
2. IfyourGChastheoptionalvacuumpumpinterfaceinstalled,plugthevacuumpumpintothat
powersocketon the leftpanelof theGCchassis. Enterevents in theevent table to turn the
vacuumpumppowerONandOFFasdesiredduring theanalysis. IfyourGCdoesn’thave the
vacuumpump interface,plug thevacuumpump intoawalloutlet instead,andcontrol it’sON/
OFFswitchmanuallyduringtheanalysis.
3. Once thedetectorsareactivatedandstabilized,connect theTedlarbag to thepurgeheadseptumnut (
a
),
orremove thepurgeheadandsecure theTedlarbag to thebulkheadfitting in thefrontvalveovenduct. [To
remove thepurgehead: loosen thenut(
b
) thatsecures thepurgehead to thebulkheadfitting in thevalveoven
ductwall. Loosen thenut(
c
) thatsecures thepurgehead to thepurgegas tubing. Leave thesecondfitting(
c
)
on thepurgegas tubingandslide thepurgeheadoffof the tubing. See thephoto,aboveright.] Loadorcreate
a temperatureprogram. Begin theanalysis.
c b
a
