Cloud Point Extraction Coupled with Ultrasonic-Assisted Back-Extraction for the HPLC-MS Determination of 1H-Triazoles in Foods

A method for the determination of tebuconazole, triadimefon, triadimenol, propiconazole, and diniconazole fungicide in vegetables, fruits, and sprouts of wheat and corn by high-performance liquid chromatography coupled to mass detection with cloud point extraction by phases of nonionic surfactant Triton X-114 was developed. The factors influencing the concentration of nonionic surfactant, medium acidity, equilibrium temperature, holding time of solutions in a water bath, and time and speed of centrifugation on extraction parameters were optimized. The complete extraction of analytes into the 0.2% (w/v) Triton X-114 phase occurs in the 2.0–9.0 pH range, provided that the analytes exist in hydrophobic electroneutral molecular forms that effectively transfer to the surfactant-rich phase of the nonionic surfactant at a temperature of 50 °C. The required time for the complete formation of the surfactant-rich phase is more than 15 min when centrifuging solutions at 4000 rpm for 12 min. The developed fungicide determination method is characterized by the limit of detection (3σ) of 0.4–0.8 ng∙mL⁻¹, the limit of quantitation (10σ) of 1.4–2.5 ng∙mL⁻¹, and a working range of 1.4–200 ng∙mL⁻¹. The developed method was applied to the determination of tebuconazole and triadimenol in beets, grapes, and sprouts of wheat and corn after their treatment with industrial fungicide preparations.