Analysis of amphetaminic drug compounds in urine by headspace-dielectric barrier discharge ionization-mass spectrometry

Abstract

Rapid detection of trace level amphetaminic drug compounds in urine is essential to monitor consumption of these abuse drugs by athletes. In this work, the amphetaminic drug compounds were spiked in human urine and analyzed using headspace – dielectric barrier discharge (DBD) ionization-mass spectrometry method. In the headspace method, the urine spiked drug compound was treated with alkali solution, thus the free base amphetaminic molecules were released into the gas phase. The gaseous molecules were then ionized by the DBD ion source placed in front of the mass spectrometer inlet under ambient condition. This method provided comparable sensitivity with the solid-phase microextraction (SPME) in analysis of the amphetaminic compounds where no derivatization or adduct formation was required. The present method also facilitated the sensitivity enhancement with about one order of magnitude in urine compared to standard solution. Carbonate alkali solution showed the highest sensitivity for detection of the drug compounds in urine and the sensitivity was enhanced by using NH3. The limits of detection (LODs) of the various amphetaminic molecules were found to be in the range of 0.10–0.80 ng/mL for standard solutions while those for urine were in the range of 0.04–0.40 ng/mL. The analytical figures of merit of this method were evaluated under ambient condition using suitable internal standard. Results suggested the suitability of this method for analytical routine work in detection of amine-based drugs in doping test and/or in forensic laboratories. A mechanism of enhanced sensitivity by the ammoniated carbonate alkali solution in urine is also discussed. Keywords: Amphetaminic drugs, Headspace method, Ambient mass spectrometry, Urine analysis, Enhanced sensitivity