Consideration on the broad quantification range of gaseous reduced sulfur compounds with the combined application of gas chromatography and thermal desorber

摘要

In this work, the dynamic range of gas chromatography (GC) combined with a thermal desorber (TD) was investigated through a series of calibration experiments. To this end, standard gases of reduced sulfur compounds (RSC: H_2S, CH_3SH, DMS, CS_2 and DMDS) covering a relatively wide concentration range (2-100 nmol mol~(-1) (or ppb)) were analyzed by regulating sample loading range from 40 to 1200 mL (3.3-4900 pmol). It shows that the upper limits of GC-TD quantification are far higher than those of GC alone, although the cold trap unit in a TD suffers from breakthrough after a dose of RSC (e.g., 500 (DMDS) to 1600 pmol (H_2S)). Its quantification uncertainties tend to grow systematically with decreases in standard concentrations and sample loading volume, especially with H_2S. According to this study, the use of TD generally reduces the absolute detectability of GC by about one order of magnitude. Such reduction caused by TD application can be compensated efficiently with similar magnitude through the magnification of sample supply. Moreover, the TD system allows to increase sample volume (up to 3 orders of magnitude or above), it can ultimately help extend the practical range of RSC qualification in a fairly reliable manner.