Underwater Gas Chromatograph-Quadrupole Mass Spectrometer for In Situ Analysis of VOCs in Deep Sea

An underwater gas chromatograph-quadrupole mass spectrometer (UGC-qMS) for in situ qualitative and quantitative analysis of volatile organic compounds (VOCs) in the deep sea was developed and evaluated. The UGC-qMS utilizes a membrane inlet, enrichment-thermal desorption, capillary column separation, and EI-quadrupole mass spectrometer detection. The overall dimension of the UGC-qMS is Φ220 mm × 960 mm, 100 kg in air, 58 kg in water, and the design maximum working depth is 6000 m. The UGC-qMS is powered by external power supply with average power consumption ≤ 100 W. The gas consumption is approximately 1 mL/min, supporting over 500 h of underwater operation in a single deployment. Limits of detection for ethane, propane, n-butane, benzene, toluene, and p-xylene under one enrichment process are 0.050, 0.041, 0.028, 0.20, 0.28, and 0.37 μg/L in water, respectively. The linearity of response is approximately 2 orders of magnitude. The UGC-qMS was tested at a depth of 4500 m in the South China Sea to validate its underwater feasibility. This work marks the first successful deployment of GC-MS for in situ analysis in deep sea. Covering a broad boiling point range from ethane to naphthalene, the UGC-qMS surpasses existing underwater in situ analytical devices in VOCs analysis, offering a powerful tool for deep-sea chemical exploration.