Validation and expanded uncertainty determination of pesticides in water; and their survey on paddy rice irrigation water from Argentina

A solid-phase microextraction (SPME) coupled to gas chromatography-mass spectrometry method was validated for the simultaneous determination of penconazole, cyproconazole, epoxiconazole, deltamethrin, azoxystrobin and kresoxim-methyl in paddy rice irrigation water. Different SPME fiber coatings and pH values were tested. Polydimethylsiloxane (PDMS) and pH 7 were chosen to optimize extraction. All pesticides presented a recovery percentage between 90.5 and 104.2%; and detection and quantification limits were 0.03 and 0.05 mu g/kg for azoxystrobin and cyproconazole, 0.02 and 0.05 mu g/kg for deltametrhin and epoxiconazole, 0.02 and 0.03 mu g/kg for kresoxim-methyl, and 0.01 and 0.02 mu g/kg for penconazole. The expanded uncertainty was estimated for all pesticides showing results lower than 20%. A total of 100 paddy rice irrigation water samples, collected in different rice fields from Argentina, were evaluated. The study showed that 86 of them presented residues. The concentrations exceeded the values that were set by European legislation and the frequencies were higher than 86% so the agricultural practices should be revised.