Development of a processing factor prediction model for pesticides in processed tomato foods using elastic net regularization.

A novel regularized elastic net regression model was developed to predict processing factor (PF) for pesticide residues, which represents a change in the residue levels during food processing. The PF values for tomato juice, wet pomace and dry pomace in the evaluations and reports published by the Joint FAO/WHO Meeting on Pesticide Residues significantly correlated with the physicochemical properties of pesticides, and subsequently the correlation was observed in the present tomato processing study. The elastic net regression model predicted the PF values using the physicochemical properties as predictor variables for both training and test data within a 2-fold range for 80-100% of the pesticides tested in the tomato processing study while overcoming multicollinearity. These results suggest that the PF values are predictable at a certain degree of accuracy from the unique sets of physicochemical properties of pesticides using the developed model based on a processing study with representative pesticides.

Development of an analytical method for determination of total ethofumesate residues in foods by gas chromatography-tandem mass spectrometry.

Analytical method was developed for determining the total residue of ethofumesate (ET) herbicide using GC-MS/MS. The ET residues were analyzed as a sum of ET, 2-keto-ethofumesate (KET), and open-ring-2-keto-ethofumesate (OKET) and its conjugate. The extracted samples were partitioned with hexane and NaOH solution. For ET analysis, the hexane layer was cleaned up by a silica gel cartridge prior to GC-MS/MS analysis. For the analyses of the metabolites, the aqueous layer was heated with HCl to hydrolyze the conjugates, thereafter, heated in acetic anhydride to convert OKET to KET, and cleaned up by a silica gel cartridge prior to GC-MS/MS analysis. The method was validated for ET, KET, and OKET in garlic, onion, and sugar beet at 0.3 and 0.01 mg/kg. The recoveries were 94-113%, with relative standard deviations of <6%. The limits of detection were 0.0005 mg/kg for all analytes. The proposed method is suitable for regulatory analysis.

Determination of the total tulathromycin residues in bovine muscle, fat, and liver by liquid chromatography-tandem mass spectrometry.

A reliable and accurate liquid chromatography-tandem mass spectrometry (LC-MS/MS)-based method was developed to quantify total tulathromycin residues in bovine tissues. Specifically, the above method relied on the quantification of CP-60,300, a marker produced by tulathromycin hydrolysis, for which maximum residue limits (MRLs) were established by the European Union and several other countries. Sample preparation and LC-MS/MS conditions were thoroughly optimized to allow for accurate quantification. The optimized procedure involved sample homogenization with 2 mol/L hydrochloric acid and ethyl acetate, heating of the resulting aqueous layer to convert tulathromycin and its metabolites into the marker residue, cleanup by a polymer-based cation-exchange cartridge, and subsequent analysis by LC-MS/MS. The developed method was validated for tulathromycin A and the marker residue in bovine muscle, fat, and liver at two levels, namely at the MRL set in Japan and at 0.01 mg/kg. Excellent analytical performance was observed, with the average recoveries of tulathromycin A and the marker residue ranging from 98 to 107%, and relative standard deviations ranging from 1 to 3%. Matrix effects were negligible, and analyte loss during sample preparation was minimal for all matrices tested, which allowed for accurate determination by external standard calibration using a solvent standard. No interfering peaks were observed close to the retention time of the marker residue for all matrices, which was indicative of high specificity. Overall, the developed method was proven suitable for regulatory purpose analysis of total tulathromycin residues.