Adulteration of foods and beverages with drugs and poisons has frequently occurred with or without intention in various incidents, and has therefore been one of the most important subjects in forensic science. The purpose of this study was to develop a simple, rapid and accurate screening method for allegedly adulterated foods and beverages using probe electrospray ionization mass spectrometry (PESI-MS) with a simple pretreatment procedure. Seven dishwashing detergents, four pesticides and four sleeping pills were selected as foreign substances, which were added to four kinds of beverages: barley tea, sports drink, carbonated beverage and milk tea. These simulation samples were subjected to PESI-MS to investigate the optimal analytical conditions for effective detections of foreign substances. A two-fold dilution of the samples with 2-propanol was adopted as pretreatment for PESI-MS to achieve higher sensitivity. As a result, surfactants, which are the main ingredients in dishwashing detergents, were detected with high sensitivity. The main ingredients were undetectable for some of the pesticides and sleeping pills analyzed; however, coexisting additives like surfactants or lactose were detected with high sensitivity indicating that the tested beverage had been adulterated by a foreign substance. Background subtraction of the reference beverage mass spectra from those of the samples also enabled clearer and more reliable determination of the adulterants. The presented PESI-MS method enables accurate screening in two minutes per sample with only a very simple pretreatment, applicable for large-scale screening of adulterants in foods and beverages. This method can serve as an extremely effective screening tool in combination with confirmatory instrumental analysis methods for identifying foreign products.
