Juan F. García-Reyes

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

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.

Comparative evaluation of seven different sample treatment approaches for large-scale multiclass sport drug testing in urine by liquid chromatography-mass spectrometry.

Sample preparation is a critical step in large-scale multiclass analysis such as sport drug testing. Due to the wide heterogeneity of the analytes and the complexity of the matrix, the selection of a correct sample preparation method is essential, looking for a compromise between good recoveries for most of the analytes and cleanliness of the extract. In the present work, seven sample preparation procedures based on solid-phase extraction (SPE) (with 5 different cartridges), liquid-liquid extraction (LLE) and sorbent-supported liquid extraction (SLE) were evaluated for multiclass sport drug testing in urine. The selected SPE sorbents were polymeric cartridges Agilent PLEXA™ and Oasis HLB™, mixed mode cation and anion exchange cartridges Oasis MAX™ and MCX™, and C18 cartridges. LLE was performed using tert-butyl methyl ether and SLE was carried out using Agilent Chem Elut™ cartridges. To evaluate the proposed extraction procedures, a list of 189 compounds were selected as representative from different groups of doping agents, including 34 steroids, 14 glucocorticosteroids, 24 diuretics and masking agents, 11 stimulants, 9 beta-agonist, 16 beta-blockers, 6 Selective Estrogen Receptors Modulators (SERMs), 24 narcotics and 22 other drugs of abuse/sport drugs. Blank urine samples were spiked at two levels of concentration, 2.5 and 25μgL(-1) and extracted with the different extraction protocols (n=6). The analysis of the extracts was carried out by liquid chromatography electrospray time-of-flight mass spectrometry. The use of solid-phase extraction with polymer cartridges provided high recoveries for most of the analytes tested and was found the more suitable method for this type of application given the additional advantages such as low sample and solvent consumption along with increased automation and throughput.