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A field experiment was conducted to evaluate clofentezine residue levels and dissipation trend in tangerine and soil for the safe application of clofentezine. A modified QuEChERS-HPLC-UVD method was developed to analyse clofentezine in tangerine and soil. Tangerine samples were homogenised and extracted by acetonitrile and then cleaned up with dispersive solid phase extraction (dSPE) by primary and secondary amine (PSA) and C18. Clofentezine residue was determined by high-performance liquid chromatography (HPLC) with a UV detector (UVD) at the wavelength of 268 nm. The presented method achieved the good linear relationship within the range from 0.05 to 5.0 mg kg−1 for clofentezine (R2 > 0.998). At the fortification levels of 0.05, 0.50 and 1.00 mg kg−1 in tangerine pulp, tangerine peel and soil, recoveries ranged from 75.9% to 117.7% with relative standard deviations (RSD) less than 8.2%. In the supervised field trials, the half-lives of clofentezine in tangerine and soil were approximately 11.3 and 8.6 d...

A rapid and simple HPLC-fluorescence detection method has been developed for the determination of abamectin residues in edible oil. Residues are extracted with acetonitrile and by vortexing and then directly derivatized with no need for a time-consuming cleanup step. Trifluoroacetic anhydride and N-methylimidazole were used as derivatizing agents of abamectin. Abamectin was detected and quantitated with fluorescence detection (excitation: 365 nm; emission: 475 nm), and methanol was used as the mobile phase. The LOD was 0.001 mg/kg and the LOQ was 0.003 mg/kg. The recoveriesranged from 86 to 100.4% with satisfactory precision (RSD < 10.1%). This method proved to be sensitive, environmentally friendly, time-saving, and efficient.

In this work, a rapid, environment friendly and sensitive method was established for the extraction and analysis of five organophosphorus pesticides (OPPs) (chlorpyrifos, chlorpyrifos-methyl, isocarbophos, malathion and phorate) in milk samples by means of gas chromatography-flame photometric detection. The pesticides were first extracted with acetonitrile from milk samples by using the modified "quick, easy, cheap, effective, rugged, and safe" (QuEChERS) method. No other clean-up was required after extraction. Then the above-mentioned acetonitrile extract was concentrated by using the dispersive liquid-liquid microextraction combined with solidification of floating organic droplets technique. Several factors that could influence the extraction efficiency, such as type of extraction solvent, disperser solvent, volume of extraction and disperser solvent, salt effect, sample pH, and extraction time, were investigated and optimized. As a result, 15 µL of 1-dodecanol were used as the extractant because of its lower toxicity, 300 µL methanol was chosen as dispersant and the extraction time was set to 1 min. Under the optimized conditions, good linearity was exhibited from 0.01 to 1.0 mg/L with the correlation coefficients higher than 0.9968. The limits of detection of the five OPPs were ranged in 0.1-0.3 μg/L, and the limits of quantification were at the range of 0.3-1.0 μg/L. Moreover, the recoveries of the target analytes from milk samples at spiking levels of 0.01, 0.05 and 0.1 mg/L were between 80.5 and 106.5% with the relative standard deviations varied from 3.6 to 6.3%. This method has been successfully applied to detect OPPs in real milk samples.