Development of a portable gas chromatography linear ion trap mass spectrometer (GC-LIT-MS) for VOCs analysis in water

The detection of volatile organic compounds (VOCs) in water faces challenges due to the presence of complex matrix interferences and low concentration. This paper presented a portable gas chromatography linear ion trap mass spectrometer (GC-LIT-MS) coupled with dynamic headspace sampling (DHS) system for sensitive and rapid on-site analysis of VOCs in water. The instrument weighs 18 kg and has compact dimensions of 43 cm x 35 cm x 20 cm, offering portability and convenience. A low thermal mass (LTM) chromatographic column, utilizing resistive heating, enables rapid heating and cooling within the runtime of GC. The linear ion trap, for the first time, has been integrated as a mass analyser in portable gas chromatography-mass spectrometer (GC-MS). Its ability to store a greater number of ions within the trap expands the dynamic range of the instrument. The influence of dynamic headspace injection conditions on the purging efficiency of VOCs was investigated and the equilibrium temperature was optimized. The GC-LIT-MS method was demonstrated to be capable to identify and separate 55 VOCs in water within 4 min, with most of them exhibiting detection limits of less than 1 mu g L-1. The calibration of 4 VOCs with concentrations ranged from 2 parts per million (ppm) to 200 ppm showed excellent linearity (R-2 > 0.99) and dynamic range more than five orders of magnitude. Resolution superior to unit mass was achieved within the range of 15 AMU to 550 AMU.