On-line measurement of propofol using membrane inlet ion mobility spectrometer

The concentration of propofol in patientʹs exhaled air is an indicator of the anesthetic depth. In the present study, a membrane inlet ion mobility spectrometer (MI-IMS) was built for the on-line measurement of propofol. Compared with the direct sample introduction, the membrane inlet could eliminate the interference of moisture and improve the selectivity of propofol. Effects of membrane temperature and carrier gas flow rate on the sensitivity and response time have been investigated experimentally and theoretically. Under the optimized experimental conditions of membrane temperature 100 °C and carrier gas flow rate 200 mL min−1, the calculated limit of detection (LOD) for propofol was 1 ppbv, and the calibration curve was linear in the range of 10–83 ppbv with a correlation coefficient (R2) of 0.993. Finally, the propofol concentration in an anaesthetized mouse exhaled air was monitored continuously to demonstrate the capability of MI-IMS in the on-line measurement of propofol in real samples.