Trace analysis of impurities in bulk gases by gas chromatography-pulsed discharge helium ionization detection with 'heart-cutting' technique

摘要

A method has been developed for the detection of low-nL/L-level impurities in bulk gases such as H-2, O-2, Ar, N-2, He, methane, ethylene and propylene, respectively. The solution presented here is based upon gas chromatography-pulsed discharge helium ionization detection (GC-PDHID) coupled with three two-position valves, one two-way solenoid valve and four packed columns. During the operation, the moisture and heavy compounds are first back- flushed via a pre-column. Then the trace impurities (except CO2 which is diverted to a separate analytical column for separation and detection) together with the matrix enter onto a main column, followed by the heart-cut of the impurities onto a longer analytical column for complete separation. Finally the detection is performed by PDHlD. This method has been applied to different bulk gases and the applicability of detecting impurities in H-2, Ar, and N-2 are herewith demonstrated. As an example, the resulting detection limit of 100 nL/L and a dynamic range of 100-1000 nL/L have been obtained using an Ar sample containing methane. (C) 2007 Elsevier B.V. All rights reserved.