A NEW CALIBRATION METHOD FOR PROCESS GAS CHROMATOGRAPHY

摘要

A new gas chromatograph calibration procedure is described which has increased accuracy and decreased calibration time for certain "hard to calibrate" gas chromatographs. The calibration problems referred to include the following:rn1. Applications where blended gas synthetic samples cannot be used due to inter-component reactions, component adsorption on cylinder walls, or component reaction with cylinder walls.rn2. Parts-per-million applications where synthetic samples are difficult and time consuming to prepare and long term stability is questionable.rnThe method described utilizes the internal volume of a four port liquid sample valve connected to the main sample loop of the process chromatograph in such a way that either volume can be used for sample introduction. Introduction of a pure gas by means of the four port valve will give the same output response normally obtained from a few percent of this gas introduced from the main sample loop. The exact percent represented by the output response is defined by the ratio of the two volumes. Methods for accurate volume ratio determination and examples of in-plant use of this method are discussed.