Rapid determination of multiclass fungicides in wine by low-temperature plasma (LTP) ambient ionization mass spectrometry

Abstract

A low-temperature plasma (LTP) probe is a plasma-based technique that permits the direct and rapid ambient ionization and mass analysis of relatively complex samples in their native environment. It belongs to the ambient desorption/ionization mass spectrometry (MS) technique, and these features map well against the requirements of food quality and safety testing. In this study, the application of LTP-MS for the rapid screening and detection of pesticides in wines has been evaluated. Aliquots of a sample extract (3 μL of each solution) were deposited on a heated (120 °C) microscope glass slide for LTP-MS analysis. The analytical performance of LTP-MS has been studied for a set of 10 multiclass fungicides selected according to their relevance and presence in actual wine samples. The compounds included in the study were azoxystrobin, carbendazim, dimethomorph, fenhexamid, flusilazol, metalaxyl, penconazole, tebuconazole, imazalil and thiabendazole. Two different approaches were examined: (i) the direct analyses of wines with no prior treatment besides a simple sample dilution, and (ii) the analyses of sample extracts obtained after a thorough sample preparation step using solid-phase extraction with polymeric cartridges. The proposed approach enabled the detection of the pesticides in wine at low concentration levels in the range from 15 μg L⁻¹ to 300 μg L⁻¹ (fulfilling maximum residue levels (MRLs) set in EU regulations in all cases) by means of tandem mass spectrometry experiments with an ion trap operated in the positive ionization mode. The qualitative results obtained with actual red wine market samples compared well against the reference method based on liquid chromatography/mass spectrometry. Various examples shown demonstrate that ambient LTP-MS can be applied for the detection of these chemicals in beverages without sample treatment steps besides dilution.