Abstract:

A reversed-phase high performance liquid chromatographic (RP-HPLC) method was developed for the determination of trimethoprim residue in aquatic products. Samples were extracted with a mixture of chloroform, sulfuric acid and methanol (15:14:6, V/V). The resulting extraction solution was alkalized, reextracted with dichloromethane and cleaned up on MCX column. The eluate was pooled, concentrated nearly to dryness, rediluted with the HPLC mobile phase and filtrated through a 0.45 μm pore size membrane. Trimethoprim was detected with an ultraviolet (UV) detector and quantified by external standard method. Good linearity between chromatographic peak area and trimethoprim concentration ranging from 0.05 to 5.0 μg/mL was found (R2 = 0.999967). Average recoveries of trimethoprim in different blank aquatic products spiked at the levels of 20, 40, 200 μg/kg were all more than 80%, with relative standard deviations of less than 7%. The method exhibited a detection limit of 20 μg/kg. Due to the advantages of simplicity, rapidity, little matrix interference and high accuracy and precision, this method is most suitable for the determination of trimethoprim residue in aquatic products.

Key words: trimethoprim, aquatic product, ultraviolet (UV) detection, high performance liquid chromatography