Performance Comparison\nof Ambient Ionization Techniques\nUsing a Single Quadrupole Mass Spectrometer for the Analysis of Amino\nAcids, Drugs, and Explosives

The\nutilization of ambient ionization (AI) techniques\nfor mass\nspectrometry (MS) has significantly grown due to their ability to\nfacilitate rapid and direct sample analysis with minimal sample preparation.\nThis study investigates the performance of various AI techniques,\nincluding atmospheric solids analysis probe (ASAP), thermal desorption\ncorona discharge (TDCD), direct analysis in real time (DART), and\npaper spray coupled to a Waters QDa mass spectrometer. The focus is\non evaluating the linearity, repeatability, and limit of detection\n(LOD) of these techniques across a range of analytes, including amino\nacids, drugs, and explosives. The results show that each AI technique\nexhibits distinct advantages and limitations. ASAP and DART cover\nhigh concentration ranges, which may make them suitable for semiquantitative\nanalysis. TDCD demonstrates exceptional linearity and repeatability\nfor most analytes, while paper spray offers surprising LODs despite\nits complex setup (between 80 and 400 pg for most analytes). The comparison\nwith electrospray ionization (ESI) as a standard method shows that\nambient ionization techniques can achieve competitive LODs for various\ncompounds such as PETN (80 pg ESI vs 100 pg ASAP), TNT (9 pg ESI vs\n4 pg ASAP), and RDX (4 pg ESI vs 10 pg ASAP). This study underscores\nthe importance of selecting the appropriate ambient ionization technique\nbased on the specific analytical requirements. This comprehensive\nevaluation contributes valuable insights into the selection and optimization\nof AI techniques for diverse analytical applications.