Rapid analysis of lithium in serum samples by thermal ionization ion mobility spectrometry

Abstract

A new application of thermal ionization ion mobility spectrometry (TI–IMS) was presented for the fast determination of lithium ion (Li+) in serum samples. This research aims to provide a selective approach to facilitate lithium monitoring for bipolar patients. The method is based on an initial step of quick–burning the organic content of the diluted serum sample on a hot filament followed by the emission of alkali ions remained in the ash. The drift tube temperature was optimized to maximize the separation of signal from the other existing alkali ions, sodium (Na+) and potassium (K+). The filament temperature and the dilution ratio were also optimized for best observation of the Li+ signal among the excess amount of Na+ and K+. The best peak resolution was obtained at 1:200 dilution ratio and drift tube temperature of 160 °C. TI–IMS demonstrated high sensitivity in both diluted standard and serum sample solution (0.21 μM for LOD and 1.50 μM for LOQ). The Relative standard deviation of the lithium determination was obtained to be 5.4%. Method validation was conducted by comparing the results with those obtained through the inductively coupled plasma optical emission spectrometry (ICP–OES) method. A good agreement between the results was observed indicating that the TI–IMS method can be potentially applied to routine analysis of biological samples. Rapidity, ease of operation and low–cost analysis are superior features of the proposed technique over the traditional approaches.