Development and validation of the HPLC-DAD method for the quantification of 16 synthetic dyes in various foods and the use of liquid anion exchange extraction for qualitative expression determination.

Synthetic dyes can cause many health problems, and their use as food additives is rigorously regulated worldwide. Two methods for the determination of synthetic dyes in food are described in this article. The visual qualitative expression method was based on the extraction of synthetic dyes using a liquid anion exchanger (0.01 M solution of trioctylmethylammonium chloride in chloroform). Using this reagent, an optimal transition of 15 anionic synthetic dyes from the aqueous to the organic phase was achieved (R > 99.8%). It was applicable for testing food that must not contain synthetic dyes (wines, juices, etc.) in a very short time (5-10 min). In the case of colouring of the organic phase, identification and quantification was carried out using the HPLC-DAD method described. The rapid and simple method allows for simultaneous determination of 16 synthetic dyes from all food types. The LOD and LOQ ranged from 0.026 to 0.086 µg mL-1 and from 0.077 to 0.262 µg mL-1 respectively, and recovery was 83.7-107.5%. Hypothesis: anionic synthetic dyes have hydrophobic properties, as a result they are retained on the non-polar stationary phase of the chromatographic column and are easily extracted from aqueous solutions by liquid anion exchangers.

A novel method for the determination of some pesticides in vegetable oils based on dissociation extraction followed by gas chromatography-mass spectrometry.

The distribution of 40 pesticides of basic nature in different extraction systems was studied at 20 ± 1°C. The distribution constants (P) and distribution ratios (D) between n-hexane and polar phases are calculated. It was found that the studied pesticides are most fully and selectively extracted from hexane and vegetable oils by solutions of perchloric acid in acetonitrile. In particular, the acidification of acetonitrile decreases the D-value of fenpropimorph by 29,000 times. This phenomenon was used for the development of an improved technique for the quantitative analysis of widely used pesticides of basic nature in rapeseed, linseed, sunflower and olive oils by GC-MS. The proposed approach allows obtaining much purer sample extracts, compared with the use of standard solvent extraction with further purification by the freezing-out technique. This approach expands the range of pesticides (flutriafol, fenpropidine, metazachlor, cyprodinil and others) that can be determined by GC-MS. The recovery values of the studied pesticides from vegetable oils were between 85% and 115% with RSD values below 10%. The obtained limits of detection ranged from 0.001 to 0.1 mg kg(-)(1), and are below or equal to the maximum residue levels (MRLs) set by the European Union for the corresponding pesticides.