ANALYTICAL METHOD FOR DETERMINATION OF AVERMECTINS IN MILK BY LIQUID CHROMATOGRAPHY WITH FLUORESCENCE DETECTION

Abstract

A fast, sensitive and selective method has been developed for quantitative determination of residues of six avermectins - abamectin, doramectin, moxidectin, ivermectin, eprinomectin and emamectin in milk by liquid chromatography with fluorescence detection (HPLC - FLD). Nemadectin is used as an internal standard (IS). Avermectins are used as antiparasitic agents in veterinary medicine. They have maximum residue limits (MRLs) in accordance with Commission Regulation (EU) No 37/2010 in foodstuffs of animal origin. The  substances are extracted by liquid extraction with acetonitrile, followed by clean up step using solid - phase extraction (SPE) with
Strata C18 - E cartridges and derivatization with trifluoroacetic acid anhydride (TFAA), 1 - methylimidazole and the addition of 100 % acetic acid and triethylamine (TEA), to enable fluorescence detection. Chromatographic separation is achieved using Agilent Eclipse XDB - C18 (150 x 4.6 mm, 5 μm) column, equipped with a guard column of the same packing in 15 min. Gradient elution is applied with mobile phase A (acetonitrile) and mobile phase B (water) and a fluorescence detector works with wavelengths at λex = 365 nm and λem = 460 nm. The analytical method is validated according to the requirements of Commission Implementing Regulation (EU) 2021/808. The method has been implemented, and it is used as routine method for control of residues of Avermectins in Central Laboratory of
Veterinary Control and Ecology (CLVCE).