Detection of amphetamine-type stimulants using sample derivatization and SALDI-TOF-MS

We have developed a gold nanoparticle-based surface-assisted laser desorption/ionization mass spectrometric (SALDI-MS) method for the analysis of amphetamine-type stimulants (ATS), including methamphetamine (MA), 3,4-methylenedioxy-N-methamphetamine (MDMA), 3,4-methylenedioxy-N-ethylamphetamine (MDEA), and 4-fluoromethamphetamine (4-FMA), by derivatization to form quaternary ammonium species. After derivatization, the ion signal intensities of the derivatives of MA, MDMA, MDEA, and 4-FMA significantly increase as compared to that without derivatization. Moreover, there is no analyte suppression effect in our samples after derivatization. The limits of detection (LODs) for MA, MDMA, MDEA, and 4-FMA are 0.1, 1.0, 91, and 44 ppb, respectively, with the correlation coefficients of these regressions in the calibration curves higher than 0.99. The optimal experimental conditions, including concentration of gold nanoparticles and sample preparation method, were then applied to urine samples. After a simple sample pretreatment, including extraction and derivatization, results show that the average recoveries of the SALDI-MS method for MA and MDMA are 100.87 +/- 5.8% and 98.28 +/- 2.9%, respectively. In summary, we have demonstrated a method to improve the sensitivity of the SALDI method for determination of ATS by derivatization and the method has been validated in the determination of MA and MDMA in urine samples.

Automated summary

A gold nanoparticle-based SALDI-MS method was developed for the analysis of amphetamine-type stimulants (ATS) through derivatization, which significantly increased ion signal intensities. The method was successfully applied to urine samples for the determination of MA and MDMA, demonstrating improved sensitivity and validation.