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A liquid chromatography/mass spectrometry/mass spectrometry (LC/MS/MS) method has been developed and validated to detect and confirm the marker residue of eprinomectin (B1a component) in bovine liver when present at levels ≥2400 ng/g. Sample extracts prepared for assay by the LC/fluorescence determinative method (prior to the derivatization step) and standard solutions were used to validate the confirmatory method. The chromatographic retention time of the eprinomectin B1a component and the relative ion intensities of the parent ion ([M + H]+ at m/z 914) and three product ions (m/z 896, 468, and 330) generated by fragmentation of the parent ion are compared to those determined from standards. Keywords: Eprinomectin; residue; confirmatory; bovine liver; LC/MS/MS

A method has been developed for the determination of abamectin in tomatoes. Sample homogenization and extraction are performed simultaneously with acetonitrile/water/hexane. Abamectin and its isomer are selectively concentrated and derivatized by an instantaneous reaction with trifluoroacetic anhydride (TFAA)/1-methylimidazole. Quantification is achieved by HPLC with fluorescence detection

An analytical method has been developed for the extraction, derivatization, and fluorescence HPLC determination of MK-0244 [4"-deoxy-4"-(epimethylamino)avermectin B1 benzoate salt] and its delta 8,9-isomer from lettuce and celery at trace (parts per billion) levels. MK-0244 and its delta 8,9-isomer are extracted with methanol, and the extract is cleaned up on a reverse-phase C8 cartridge followed by a liquid-liquid extraction with ethyl acetate before passing through a propyl sulfonyl cation-exchange cartridge. MK-0244 and its delta 8,9-isomer are then derivatized with trifluoroacetic anhydride/1-methylimidazole/acetonitrile reagent system to form a fluorescent derivative which is separated on a reverse-phase HPLC system and detected with a fluorescence detector. The average recoveries were 95 +/- 10% for celery and 96 +/- 8% for lettuce. For both lettuce and celery matrix, concentrations as low as 2 ppb (S/N = 10) can be detected in a 10-g sample. This method was used to determine the MK-0244 levels in samples from a lettuce field trial.