Improved analytical performance of negative 63Ni ion mobility spectrometry for on-line measurement of propofol using dichloromethane as dopant.

On-line monitoring of propofol in exhaled air is a potential way to evaluate the anaesthesia depth for patients during surgery. In this study, a negative (63)Ni ionization high resolution ion mobility spectrometer with Bradbury-Nielsen-Gate-Grid structure was built to measure propofol with reactant ions Cl(-)(H2O) n using dichloromethane as dopant. Instead of forming three propofol ions (M - H)(-), M · O2(-), and (M2 - H)(-) with reactant ions O2(-)(H2O)n, only product ion M · Cl(-) was produced when introducing dichloromethane gas. The peak-to-peak resolution (R p-p) between reactant ions Cl(-)(H2O)n and product ion M · Cl(-) was 17.4, which was 1.6 times larger than that between O2(-)(H2O)n and product ion. Furthermore, the linear response range using reactant ions Cl(-)(H2O)n was 3.5 times wider than that obtained with reactant ions O2(-)(H2O)n.