Determination of Postharvest Fungicides in Fruit Juices by Solid-Phase Extraction Followed by Liquid Chromatography Electrospray Time-of-Flight Mass Spectrometry

A multiresidue method using liquid chromatography−time-of-flight mass spectrometry (LC−TOFMS) has been developed for the quantitative analysis of five widely used postharvest fungicides (carbendazim, thiabendazole, imazalil, prochloraz, and iprodione) and two of their transformation products (imazalil and prochloraz metabolites) in fruit juices. LC−TOFMS in positive electrospray ionization mode was used to quantify and confirm trace levels of these fungicides in fruit juices. The proposed method consists of a sample treatment step based on solid-phase extraction using hydrophilic–lipophilic-balanced polymer-based reverse-phase SPE cartridges (Oasis HLB) and methanol as an eluting solvent. Fruit-juice extracts spiked at different fortification levels (10 and 20 µg L−1) yielded average recoveries in the range of 71–109% with RSD (%) below 15%. Subsequent identification, confirmation, and quantitation were carried out by LC−TOFMS analysis. The confirmation of the target species was based on accurate mass measurements of protonated molecules ([M + H]+) and fragment ions, obtaining routine accuracy errors lower than 2 ppm in most cases. The obtained limits of detection (LODs) of the proposed method were in the range of 0.08–0.45 µg L−1. Finally, the proposed method was successfully applied to the analysis of 23 fruit juice samples collected from different European countries and the United States, showing the potential applicability of the method in routine analysis. Over 50% of the samples tested contained pesticide residues, but relatively low concentration levels were found.