Department of Analytical Chemistry, Nutrition and Food Sciences, IIAA-Institute for Food Analysis and Research, Universidade de Santiago de Compostela, R/Constantino Candeira SN, 15782, Santiago de Compostela, Spain. Electronic address: [Email]
In this work, fabric phase sorptive extraction (FPSE) is investigated for the extraction and preconcentration of ultra-trace level residues of fungicides (19 compounds) and insecticides (3 species) in wine samples. Subsequently, the preconcentrated analytes are selectively determined using ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). Parameters affecting the efficiency and repeatability of the extraction are evaluated in depth; moreover, the proposed method is characterized in terms of linear response range, trueness, precision and limits of quantification (LOQs). The set-up of the extraction process and the type of coating were the variables exerting the most prominent effects in the repeatability and the yield of the extraction, respectively. Under optimized conditions, samples (10 mL of wine diluted with the same volume of ultrapure water) were extracted with a small amount of cellulose fabric (3 discs with 4 mm of diameter: total surface 0.38 cm2) coated with a sol-gel polyethylene glycol sorbent (sorbent amount 3.3 mg), immersed in the diluted sample, without being in direct contact with the PTFE covered magnetic stir bar. Following the overnight extraction step, analytes were quantitatively recovered using only 0.3 mL of an ACN-MeOH (80:20) mixture. Under equilibrium sampling conditions, the linear response range of the method varied from 0.2 to 200 ng mL-1, with limits of quantification (LOQs) between 0.03 and 0.3 ng mL-1. Relative recoveries ranged from 77 ± 6% to 118 ± 4%, and from 87 ± 4% to 121 ± 6% for red and white wines, respectively. Application of the optimized method to commercial wines demonstrated the existence of up to 9 out of 22 investigated compounds in the same wine sample. The compound identified at the highest concentration was iprovalicarb (IPR), with a value of 130 ± 9 ng mL-1 in a commercial white wine.