Hollow‐fiber liquid‐phase microextraction for the determination of pesticides and metabolites in soils and water samples using HPLC and fluorescence detection

A new and simple method has been developed for the determination of a group of four benzimidazole pesticides (carbendazim/benomyl, thiabendazole, and fuberidazole), a carbamate (carbaryl), and an organophosphate (triazophos), together with two of their main metabolites (2‐aminobenzimidazole, metabolite of carbendazim/benomyl, and 1‐naphthol, metabolite of carbaryl) in soils. First, an ultrasound‐assisted extraction ( UAE ) was performed, followed by evaporation and reconstitution in water. Then, extraction and preconcentration of the analytes was accomplished by two‐phase hollow‐fiber liquid‐phase microextraction ( HF ‐ LPME ) using 1‐octanol as extraction solvent. Parameters that affect the extraction efficiency in HF ‐ LPME technique (organic solvent, pH of the sample, extraction time, stirring speed, temperature, and ionic strength) were deeply investigated. Optimum HF ‐ LPME conditions involved the use of a 2.0 cm polypropylene fiber filled with 1‐octanol to extract 10 mL of an aqueous soil extract at pH 9.0 containing 20% (v/v) of N a C l for 30 min at 1440 rpm. Separation and quantification was achieved by HPLC with fluorescence detection ( FD ). The proposed optimum UAE ‐ HF ‐ LPME ‐ HPLC ‐ FD methodology provided good calibration, precision, and accuracy results for two soils of different physicochemical properties. LOD s were in the range 0.001–6.94 ng/g (S/N = 3). With the aim of extending the validation, the HF ‐ LPME method was also applied to different types of waters (Milli‐Q, mineral and run‐off), obtaining LOD s in the range 0.0002–0.57 μg/L.