STRATEGIES FOR RAPID GC IMPURITY ANALYSIS OF HIGH-PURITY SOLVENTS .1. INSTRUMENTATION AND PROCEDURES

Timing considerations are discussed for an instrumentation system designed for the rapid determination of impurities at part-per-million (ppm) levels in high-purity solvents. isothermal retention times in the range from a few seconds to about 20 s are obtained using 2-4-m lengths of 0.25-mm i.d. fused-silica capillary columns. The use of a cryofocusing inlet with flow direction control for performing solvent flush and backflush operations is described. A model is presented for the operation of the cryofocusing inlet system. The system can be used to collect a vapor sample at either end of the cryofocusing trap and reinject it as a relatively narrow plug. The effects of inlet system injection temperature on retention time are considered for samples injected from both the upstream and downstream ends of the trap.