Abstract: DESI-MS was applied to direct simultaneous detection of multiple components of clinic urine samples without any sample pretreatment. Under the optimized working conditions, such as ESI infusion rate, ESI high voltage, incident angle, collective angle, tube lens voltage, etc., for both DESI and LTQ mass spectro-meter, the main components of urine including urea, pyruvic acid, creatinine, oxalic acid, alloxane, menadione were detected as the protonated molecules in positive detection mode using methanol-water(volume ratio 1:1) as the spray solvent in the low mass range(15—200 amu). Sodium and potassium were also detected but mainly in the form of clusters with urea and creatinine. In each case, the corresponding ions were isolated in the ion trap mass analyzer and underwent a collision-induced dissociation process, which yielded characteristic fragments in tandem mass spectra and resulted in confident validation of the analytical results. The average time for single sample analysis was less than 1 min since it required no sample pretreatment. Furthermore, the semi-quantitative analysis of the components was also demonstrated by adding serine as an internal standard into the samples.

Key words: DESI-MS, Clinic urine sample, Tandem mass spectrometry, Simultaneous detection