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CSLR™ - External standard calibration
Key international standard methods (e.g. US EPA TO-17), recommend the vapour phase introduction of external standards onto clean sorbent tubes.
Markes’ CSLR consists of an unheated injector port with a controlled carrier gas supply and a sorbent tube connection point. The sampling end of a fully packed sorbent tube is connected to the CSLR via a ¼” brass nut and combined (one-piece) PTFE ferrule. The carrier gas flow is set, via a needle valve, to between 80 and 100 mL/min. This sweeps the injection port and passes down through the sorbent tube to vent.
The calibration standard (gas or liquid phase) is introduced through the injector septum using a standard GC syringe. The compounds of interest are swept onto the sampling end of the attached tube in the stream of carrier gas and reach the sorbent bed in the vapour phase.
Note: Wherever possible, to simplify the analysis procedure, sufficient volume of carrier gas is allowed to pass through the adsorbent bed to remove the bulk of solvent (liquid standards), whilst compounds of interest are still quantitatively retained.
It is not always possible or convenient to introduce liquid standards in a stream of carrier gas as described above. In these cases, liquid standards can be injected directly using specially packed sorbent tubes (glass recommended) containing a 1 cm bed of Tenax TA held in place by a 1 cm bed of quartz wool.
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