SIMPLE AND EFFICIENT METHANE-MARKER DEVICES FOR CHROMATOGRAPHIC SAMPLES

摘要

Calculation of the most useful gas chromatographic retention parameters, such as net and specific retention volumes, relative retentions, and retention indices, requires that raw retention data be corrected for gas hold-up time or volume (sometimes called dead time or volume) of the chromatographic system. When a flame-ionization detector is used, a common technique (where it is physically appropriate) is to introduce methane into the sample as a marker to approximate unretained species to correct for hold-up. This is often done by bubbling methane (or natural gas) through the sample just before injection. In this paper, we describe two easily constructed devices that provide continuous release of methane into liquid samples, sustainable for several weeks or even months. This long-term feature makes the techniques especially suitable to extensive retention studies done at multiple temperatures on several stationary phases. Moreover, one of the devices described is applicable to commercially available automatic sampler vials. After a detailed description of the construction of the devices is provided, some applications are discussed.