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A rapid, sensitive and selective method for determining phthalanilic acid residue in bean, fruits and vegetables based on a modified quick, easy, cheap, effective, rugged and safe (QuEChERS) extraction procedure was developed by ultra-performance liquid chromatography/tandem mass spectrometry (UPLC-MS/MS). The samples were extracted by acidified acetonitrile (0.4% (v/v) formic acid) and simultaneous liquid–liquid partitioning formed by adding anhydrous magnesium sulfate (MgSO4) and sodium chloride (NaCl). The extract was then cleaned up by dispersive-SPE using florisil and graphitized carbon black (GCB) as selective sorbent. Parameters including the matrix effect, linearity, precision, accuracy and stability were undertaken. The method showed good linearity in the concentration range of 10–1000 μg L−1, with correlation coefficients ≥0.997. Recovery studies were performed at three fortification levels of 10, 100 and 1000 μg kg−1 in soybean, apple, grape, cucumber, tomato and pepper. Further optimization of sample preparation and determination achieved recoveries ranging between 70.1% and 105.3% for the analyte with 0.7–14.9% intra-day relative standard deviations (RSD) and 0.2–8% inter-day RSD at three spiked levels (10, 100 and 1000 μg kg−1). The limits of detection (LOD) were below 1 μg kg−1, and the limits of quantification (LOQ) did not exceed 3 μg kg−1. The effects of two columns on the separation were also investigated. The method is demonstrated to be convenient and reliable for determination of phthalanilic acid in bean, fruits and vegetables. With the developed method, 60 samples of commercial fruit products (grape, apple), soybean and vegetables (pepper, tomato, cucumber) were analyzed. Phthalanilic acid was not detected in all samples.

An ultra-performance liquid chromatography coupled to tandem mass spectrometry (UPLC-MS/MS) method was developed for the simultaneous determination of thiodicarb and its main metabolite (methomyl and methomyl-oxime) residues in cotton leaves and cotton seeds. The mass spectrometer was operated in multiple reaction monitoring mode with positive electrospray ionization. The samples were extracted by acetonitrile, the extract was cleaned up by Pesti-Carb/NH2 solid phase extraction column, then separated by reversed phase liquid chromatography, and determined by UPLC-MS/MS. It showed that the recoveries ranged from 67.5% to 109.2% at spiked levels of 0.01–0.1 mg kg−1, while the relative standard deviation was 2.8% to 9.1%. The limit of the detection was 0.2–1.3 μg kg−1, and the limit of quantification was 0.9–4.0 μg kg−1.