Performance of Programmed Temperature Introduction Techniques in the GC-MS Analysis of Flavor Compounds of Chinese Baijiu

The aroma profile of Chinese Baijiu is determined by the combined effects of hundreds of chemical compounds with concentrations ranging from a few percent to parts per billion. Stir Bar Sorptive Extraction (SBSE) is an efficient sample preparation technique widely used for enriching analytes from aqueous samples. It has been successfully applied to the analysis of flavor compounds in wine. After extraction, the compounds are recovered from both stir bars using Thermal Desorption (TD) and subsequently transferred to the analytical system for GC-MS analysis. The SBSE-TD-GC-MS technique provides high recovery rates and exceptionally low limits of detection (LOD), reaching sub-ng/L levels for relatively non-polar solutes (log Kow > 3.0) in aqueous samples.

In 1984, Gerstel introduced the Cooled Injection System (CIS), a Programmed Temperature Vaporization (PTV) type GC inlet. This introduction technique allows compounds to be held in a cold liner and then gradually increasing the temperature to transfer the analytes. This approach not only enhances the method sensitivity in splitless mode, it also reduces the concentration of high-abundance analytes in split mode to improve resolution. The gas chromatography system used in this study is equipped with a GERSTEL LabWorks Platform, which includes a Thermal Desorption Unit (TDU) and a CIS, enabling independent and precise control of the split gas flow during thermal desorption and analyte introduction to the analysis system. The resulting overall split ratio corresponds to the dilution factors. In this study, we combine the techniques of solvent venting in splitless mode and two-step temperature ramping to achieve high sensitivity and ensure excellent performance for the determination of semi-volatile compounds in Chinese Baijiu.