Comparison of the quantification performance of thermal desorption GC-IMS and GC-MS in VOC analysis

Accurate and reproducible quantification of volatile organic compounds (VOCs) is essential in environmental monitoring, clinical diagnostics, and quality control. Thermal desorption gas chromatography (TD-GC) is widely used for VOC analysis, often coupled with mass spectrometry (MS) for reliable identification. Ion mobility spectrometry (IMS) has gained attention for its high sensitivity and rapid detection. While GC-IMS and GC-MS are well established, TD-GC coupled to both IMS and MS has not been systematically investigated. This study presents a comprehensive assessment of a TD-GC-MS-IMS system, combining the strengths of both detectors. A mobile flow- and temperature-controlled sampling unit for TD tubes was developed for standardized applications, designed to introduce both gaseous and liquid samples. The long-term stability of TD-GC-IMS was assessed over 16 months with 156 measurement days using ketones. Relative standard deviations for signal intensities ranged from 3% to 13%, retention time deviations from 0.10% to 0.22%, and drift time deviations from 0.49% to 0.51%. Comparative evaluation showed IMS was approximately ten times more sensitive than MS, achieving limits of detections in the picogram/tube range. In contrast, MS exhibited a broader linear range, maintaining linearity over three orders of magnitude (up to 1000 ng/tube), while IMS retained linearity for one order of magnitude (e.g., 0.1 to 1 ng/tube for pentanal) before transitioning into a logarithmic response. To improve IMS quantification, a linearization strategy extended the calibration range from one to two orders of magnitude. These findings establish a standardized TD-GC-MS-IMS framework, improving reproducibility and comparability for clinical, environmental, and industrial VOC analysis.