• Qinghua Zhou, Enyou Li, Zhenxin Wang, Yulei Gong, Changsong Wang, Lei Guo, and Haiyang Li.
• Key Laboratory of Separation Science for Analytical Chemistry, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian, Liaoning, 116023, People's Republic of China. University of Chinese Academy of Sciences, Beijing, 100049, People's Republic of China.
• J Breath Res. 2015 Mar 1; 9 (1): 016002.

AbstractBased on the adsorption of analytes in the sampling loop, a time-resolved dynamic dilution introduction method was developed for negative ion mobility spectrometry to continuously monitor end-tidal propofol without other sample pre-separation. The dynamic dilution characteristics of propofol and moisture in the Teflon sample loop (4 mm o.d. and 2.4 mm i.d., 150 cm length) were both theoretically and experimentally investigated. The prominent absorption differences between propofol and moisture on the inwall of the sample loop allowed their concentrations to be time-resolved during the injection process, realizing sensitive measurement of end-tidal propofol with a response time of 2 s. At the optimized carrier gas flow rate of 700 mL min(-1), the linear response range for propofol was achieved to be 0.2 to 20 ppbv with a limit of detection (LOD) of 65 pptv. Finally, this method was performed on a patient undergoing mastectomy surgery to continuously monitor the end-tidal propofol with an interval of five respirations and the result nicely demonstrated its fast response to the propofol changes.

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