Vol. 9, Issue 6 (2020)

Author(s):
Nadezhda Stoilova, Iskra Boneva and Spaska Yaneva

Abstract:
Food safety is a part of the Bulgarian policy, by means of the National monitoring program for control of residues (NMPCR), performed by Central laboratory of veterinary control and ecology (CLVCE) part of Bulgarian Food Safety Agency (BFSA). Herein, two analytical methods are proposed - for simultaneous determination of regulated nitroimidazoles and their by Liquid chromatography with mass spectrometry (LC-MS/MS) and for determination of N-methyl carbamates in liver samples by high-performance liquid chromatography with fluorescence detection (HPLV-FLD). The sample pre-treatment for nitroimidazoles involves one step liquid extraction and purification by solid-phase extraction. The nitroimidazoles were separated on Gemini C18 chromatography column with gradient eluting program. Residues were quantified down to 1.0 µg kg^-1 with limits of detection and quantification ranging below from determinate limits of 3 ppb. The recoveries at the minimum required performance limits (MRPL) level were between 77 and 120% with RSD values lower than 20%. N-methyl carbamates are part of group B2(c) carbamates and pyrethroids. Four compounds were validated in liver as a target organ - methomyl, aldicarb, carbofuran and propoxur. The separation is performed on a 25cm, C18 column from Pickering and determination by HPLC-FLD with post-column derivatization. The reliability of the method is ensured by validation in accordance with SANTE document. Limits of quantification (LOQs) are below the maximum residue levels (MRLs) with recoveries between 85 and 105% and measurement uncertainty (MU) below 50%, as recommended.