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An efficient and sensitive multiresidue method has been developed for quantification and confirmation of 25 phenyl acetanilide pesticides in a wide variety of food commodities including maize, spinach, mushroom, apple, soybean, chestnut, tea, beef, cattle liver, chicken, fish, and milk. Analytes were extracted with acetone-n-hexane (1:2, v/v) followed by cleanup using SPE. Several types of adsorbents were evaluated. Neutral aluminum and graphitized carbon black cartridge showed good cleanup efficiency. The extract was determined by GC-MS in the selected ion monitoring mode using one target and two qualitative ions for each analyte. The limits of detection were 0.01 mg/kg for all analytes. The average recoveries ranged from 66.9 to 110.6% (mean 88.8%) and RSDs were in the range 2.0-19% (mean 10.5%) across three fortification levels. The proposed method was successfully applied to real samples in routine analysis and a satisfactory result was obtained.

A method was developed for the screening, confirmation and quantification of 21 hormones including progesterones, etrogens, glucocorticoids and resorcylic acid lactones in health foods by high performance liquid chromatography-ion trap-time of flight tandem mass spectrometry (HPLC-IT-TOF-MS). The analytes in the sample were extracted with acetonitrile containing 1.0% (v/v) acetic acid and the extract was purified with the mixed QuEChERS sorbents. In the chromatographic analysis, the 21 target compounds were separated on a C18 column with the gradient elution using the mobile phases of acetonitrile and water containing 0.1% acetic acid. The mass analyzer was performed in positive and negative full scan modes in one injection at the same time. The results showed that the linear ranges of the 21 hormones were 5.0-250 microg/L with the correlation coefficients above 0.993 and the limits of quantification (LOQ, S/N > or = 10) were 2.0-5.0 microg/kg and 1.0-2.5 microg/L for capsule and oral solution, respectively. The method validation was carried out at three spiked levels, and the recoveries were 60.2%-116.0% with the relative standard deviations (RSDs) of 7.0%-18.3%. The screening of analytes was performed by precision mass matching and library searching. The secondary fragment ion spectra were employed to the confirmation. This method is simple, fast, reliable, and can be applied to the simultaneous screening and determination of hormones in health foods.

A high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/ MS) analytical method was developed for the simultaneous determination of ten aminoglycoside residues (streptomycin, dihydrostrepmycin, neomycin, kanamycin, tobramycin, gentamycin, apramycin, hygromycin B, paromomycin, and amkacin) in milk and dairy products. The sample was extracted with 5% trichloroacetic acid aqueous solution, then the extract was purified by a hydrophilic-lipophilic balance (HLB) cartridge. The ten aminoglycoside residues were separated by ion-pair reversed phase high performance liquid chromatography. Heptafluorobutyric acid was used as ion pair agent due to its volatility. Then the analytes were detected by electrospray ionization tandem mass spectrometry. The pretreatment condition of the sample, the HPLC condition and the MS operation parameters were optimized. The results showed that the linearities of the ten aminoglycoside residues in 20-1000 microg/L had the correlation coefficient between 0.9946-0.9997. The recoveries ranged from 71.2% and 101.7% with the relative standard deviations of 3.4%-13.8%. The proposed method was successfully applied to the determination of the mass concentrations of the analytes in related samples, which provides a simple, and convenient method for the quality control of milk and dairy products. Furthermore, this method is effective for the safety monitoring of aminoglycoside residues in milk and dairy products.