A sandwich temperature control membrane inlet mass spectrometer for dissolved gases and volatile organic compounds in aqueous solution

Yongqiang Cheng; Maoke Liu; Bin Zhao; Li Yang; Cuilian Guo; Linbo Zhang

doi:10.1016/j.talanta.2020.121464

A sandwich temperature control membrane inlet mass spectrometer for dissolved gases and volatile organic compounds in aqueous solution

Talanta. 2021 Jan 1:221:121464. doi: 10.1016/j.talanta.2020.121464. Epub 2020 Jul 28.

Authors

Yongqiang Cheng¹, Maoke Liu², Bin Zhao², Li Yang², Cuilian Guo³, Linbo Zhang⁴

Affiliations

¹ Institute of Eco-Environmental Forensics, Qingdao Institute of Humanities and Social Sciences, Shandong University, China. Electronic address: chengyongqiang6@163.com.
² Institute of Oceanographic Instrumentation, Qilu University of Technology (Shandong Academy of Sciences), Shandong Key Laboratory of Ocean Environmental Monitoring Technology, Qingdao City, Shandong Province, 266001, China.
³ Institute of Oceanographic Instrumentation, Qilu University of Technology (Shandong Academy of Sciences), Shandong Key Laboratory of Ocean Environmental Monitoring Technology, Qingdao City, Shandong Province, 266001, China. Electronic address: guocuilian@163.com.
⁴ Institute of Eco-Environmental Forensics, Qingdao Institute of Humanities and Social Sciences, Shandong University, China.

PMID: 33076084
DOI: 10.1016/j.talanta.2020.121464

Abstract

A sandwich temperature control membrane inlet system based on a miniature mass spectrometer is presented that demonstrates improved analytical performance for the measurement of dissolved gases and volatile organic compounds (VOCs) in aqueous solution. Aqueous solution is directly brought to the monolayer flat membrane interface at a constant flow rate. A heating resistor and a thermocouple are fixed on the side of the membrane and aqueous solution respectively. This new strategy allows for a temperature compensation method, affording an improvement of sensitivity and a reduction of response time compared with the conventional heating solution temperature control strategy. Furthermore, a static heating mode is applied to effectively remove the memory effect. Automatic sampling and measurement are achieved by using the membrane inlet system with silicone sheeting of 50 μm thickness. The vacuum is below 3 × 10^-5 Torr, which can make the instrument work normally. A good linear response is observed for benzene in the range of 0.1 ppm-10 ppm and the detection limit is 50 ppb. The analytical capacity of this system is demonstrated by the on-line analysis of VOCs in aqueous solution, in which the dominant ions are detected rapidly. The results indicate that the sandwich temperature control membrane inlet mass spectrometer (STC-MIMS) has a potential application for on-line analyzing organic pollution in aquatic environments.

Keywords: Dissolved gases; Membrane inlet; Miniature mass spectrometer; Volatile organic compounds.