Determination of oxytetracycline in tomatoes by HPLC using fluorescence detection

An analytical method for the determination of oxytetracycline (OTC) in tomatoes was developed and validated. Liquid–liquid extraction (LLE) and a solid-phase extraction (SPE) were used for sample preparation. Reversed-phase high performance liquid chromatography (RP-HPLC) using a C18 column and a mobile phase containing MeOH: calcium chloride, disodium ethylenediaminetetraacetate (EDTA) and sodium acetate, pH 7.3 (30:70, v/v), with fluorescence detection at 390 nm excitation and 512 nm emission, was used for separation and quantitation of OTC. The method was validated through the following performance criteria: linearity and linear range, sensitivity, selectivity, intra-day and inter-day precision, detection and quantitation limits and accuracy. Limit of quantitation show that the method developed is suitable for the determination of OTC at a level below the maximum residue limits established by the Brazilian legislations (250 μg kg−1). Of 40 samples analyzed, none contained OTC above the limit of quantitation.