Modifier assisted differential mobility tandem mass spectrometry method for detection and quantification of amphetamine type stimulants in urine.
An advantage of differential mobility spectrometry (DMS) is it provides an orthogonal mechanism to mass spectrometry (MS) The DMS MS/MS detects analytes in the gas phase on the basis of differences in ion mobility in low and high electric fields, which makes DMS MS/MS an alternative to chromatographic separation MS. One drawback of DMS is its limited resolution and sensitivity, especially for detecting small molecules when using a nonpolar inert gas as the carrier gas. The present work has evaluated the effects on peak capacity of adding chemical modifiers to inert carrier gases (nitrogen, helium, argon and carbon dioxide) Use of a methanol helium mixture gave improvements in both separation and sensitivity. Nine structurally similar amphetamine type stimulants were determined in urine without pretreatment of the samples before analysis. After optimization of carrier gas, nature and concentration of chemical modifier, and DMS temperature, limits of detection ranging from 1.1 to 2.7 ng mL 1, with a linear range of three orders of magnitude (5 5000 ng mL 1) were achieved. Precision was <15% and the accuracy of the quality control samples was 87.6 113.7% For the quantitation of urine samples from drug abusers, data obtained using DMS MS/MS showed reasonable agreement (within 19.5% with that obtained using LC MS/MS. The analysis time for DMS MS/MS was only 1.1 min and a paired sample t test between the two methods gave a p value of 0.0894, which indicates that DMS MS/MS is a reliable method, with comparable precision and sensitivity to LC MS/MS.
Analytica chimica acta