Determination of Abamectin Residues in Avocados by Microwave-Assisted Extraction and HPLC with Fluorescence Detection

Abstract

In this article a new analytical method for the confirmation and quantification of abamectin residues in avocados is described. The method allows a fast analysis of abamectin homologues using microwave assisted extraction (MAE), solid-phase extraction (SPE) and high-performance liquid chromatography (HPLC) with fluorescence (FL) detection using trifluoroacetic anhydride (TFAA) and N-methylimidazole (NMIM) as derivatizing agents. The mobile phase consisted of water, methanol and acetonitrile (5:47.5:47.5 v/v/v) and was pumped at a rate of 1.1 mL min−1 (isocratic elution). Homogenized avocado samples were extracted once with 20 mL acetonitrile:water 4:1 (v/v) in a microwave oven for 26 min at 700 W with a maximum temperature of 80 °C. MAE operational parameters were optimized by means of an experimental design. Extracts were cleaned using C18 SPE cartridges. Average recoveries of the method at four spiked levels (0.005, 0.01, 0.10 and 1.0 mg kg−1) were found to be in the range 90–100% with good precision (RSD < 12%). The limits of detection (LODs) and quantification (LOQs) of the whole method were 0.001 and 0.003 mg kg−1, respectively, which are lower than the maximum residue limit (MRL) established by the Spanish and the European legislation in avocados (0.01 mg kg−1). Several avocado samples previously treated with the pesticide were also analyzed.