Dopant for detection of methamphetamine in the presence of nicotine with ion mobility spectrometry

Methamphetamine (MA) is a highly addictive and illegal psychostimulant drug and is currently one of the most commonly abused illicit drugs in the world. The on-site rapid detection of trace amounts of MA and screening illicit drugs in clandestine laboratories is important for drug enforcement agencies and the forensic community in general. However, detecting methamphetamine in the presence of nicotine and cigarette smoke by ion mobility spectrometry faces difficulty due to the overlapped spectral peaks of methamphetamine and nicotine. In this work, a new method was developed to detect MA using pyridine as a dopant in the presence of nicotine by a homemade ion mobility spectrometry. The reduced mobilities of MA and nicotine were measured under the temperatures of the drift tube from 40 to 120 °C and doping with pyridine. The result shows that the temperature of 100 °C is beneficial to resolve the two substances. The concentration of doped pyridine is optimized to be 18 ppm. In this doped experiment, the reaction rate of nicotine is higher than that of MA by measuring the instrumental responses of MA and nicotine. No matter how high the nicotine content is, the interference of nicotine can be eliminated in the detection of MA doped with pyridine. This method is also successfully applied for the determination of MA and nicotine simultaneously in real saliva samples. The limit of detection of MA was measured to be about 0.5 ng/μL. The promising results in this work provide an effective method for on-site detection of MA.