Direct and rapid characterization of illicit drugs in adulterated samples using thermal desorption electrospray ionization mass spectrometry

Sy-Chyi Cheng ^a, You-Da Tsai ^a, Chi-Wei Lee ^b,c, Bai-Hsiun Chen ^d, Jentaie Shiea ^a,e,f,g,*

^a Department of Chemistry, National Sun Yat-Sen University, Kaohsiung, Taiwan

^b Institute of Medical Science and Technology, National Sun Yat-Sen University, Taiwan

^c Department of Emergency Medicine, Kaohsiung Medical University Hospital, Kaohsiung, Taiwan

^d Department of Laboratory Medicine, Kaohsiung Medical University Hospital, Kaohsiung, Taiwan

^e Department of Medicinal and Applied Chemistry, Kaohsiung Medical University, Kaohsiung, Taiwan

^f Research Center for Environmental Medicine, Kaohsiung Medical University, Kaohsiung, Taiwan

^g Rapid Screening Research Center for Toxicology and Biomedicine, National Sun Yat-Sen University, Kaohsiung,

Taiwan

Foods and drinks have been adulterated with illicit drugs to facilitate criminal activities. Unfortunately, conventional analytical methods are incapable of rapidly characterizing these drugs in samples, as serious interferences from sample matrices must be removed through tedious and time-consuming pretreatment. Ambient ionization mass spectrometry (AMS) generally does not require sample pretreatment and is thus a suitable tool for directly and rapidly detecting illicit drugs in samples in different physical states. In this study, thermal desorption electrospray ionization mass spectrometry (TD-ESI/MS), an AMS technique, was utilized to efficiently characterize illicit drugs spiked in samples including drinks, powders, and jelly candies. To perform sensitive analysis, the mass analyzer was operated in multiple reaction monitoring mode to monitor the molecular and fragment ions of the target analytes. The time required to complete a typical TD-ESI/MS analysis was less than 30 s. The limits of detection (LODs) for illicit drugs were found to be 100 ppb in drinks, 100-1000 ppb in instant powders, and 1.3-6.5 ng/mm² on stamp surfaces. FM2 and nitrazepam laced in the inner layer of a jelly candy were detected by TD-ESI/MS, showcasing the advantage of the technique for direct and rapid analysis as opposed to conventional methods.