Development of ultrasound-assisted extraction of commonly used azole antifungals in soils
Azole antifungals in soil are of increasing concern. In this work, a stable, sensitive and reliable method was developed and validated for extraction of azole antifungal pharmaceuticals (clotrimazole, econazole, ketoconazole, and miconazole) and biocides (propiconazole and tebuconazole) in various soils. Ultrasound-assisted extraction using ammonified methanol was used to extract the azole antifungals from soils, which were then quantified by ultra-high-performance liquid chromatography-mass spectrometry. The total organic carbon content of soil was correlated with extraction efficiency. The extraction mechanism of azole antifungals in soils was also preliminarily illustrated. The presence of amino groups in the methanol extractant was important for efficient extraction. Recoveries ranged from 81.1% to 119.0% with relative standard deviations within 10%. The method quantification limits were in the range of 0.1–0.2 ng g−1 (dry weight) in soils. The method was successfully applied to a batch determination of azole antifungals in soils with good recoveries of the surrogate standard ranging from 80.2% to 110.6%, with an average of 95.1% and relative standard deviations within 8.7%. Miconazole, econazole, tebuconazole and propiconazole were occasionally detected at several ng g−1 (dry weight). This method is a valuable tool for investigating the occurrence, behavior, transport, and fate of azole antifungals in soil environments.