Retention time repeatability as a function of the injection automatism in the analysis of trace organochlorinated compounds with high-resolution gas chromatography

Short-term precision in retention time determination of different injection systems (three manual and three autosamplers) is assessed in the present study. This evaluation has been performed on eight different instrumental set-ups equipped with the same type of capillary column (30 m, 5% phenyl-95% methyl) which have been used for the analysis of standard mixtures of alpha-, gamma-, and delta-hexachlorocyclohexanes. The results show that, as expected, retention time repeatability increases with the degree of automatization of the injection system. They also show that only the autosamplers and the manual injector provided with the syringe-operated start device are suitable for analysis of compounds with retention time differences in the order of 0.1 min. Conversely, none of the systems included in the study, not even the autosamplers, is adequate for the analysis of analytes having retention time differences of about 0.01 min. (C) 1997 Elsevier Science B.V.