Large‐volume sample introduction into narrow‐bore gas chromatography columns using thermal desorption modulation and signal averaging

A small diameter (50 μm) open‐tubular gas chromatographic column can be made to accept relatively large volume samples. A conventional injection port and a short length of a 530‐μm‐diameter column are used to accept and hold the sample while it is fed slowly into the 50‐μm column. An injection of such large volume and slow speed normally is quite incompatible with this small, fast column. An on‐column thermal desorption modulator at the head of the column matches the sample to the column by chopping the injected sample into many fast concentration pulses. Signal averaging of the resulting fast chromatograms gives a total sample chromatogram. The method is adaptable to either gaseous or liquid samples.