Andrea Hercegová

Study on pesticide residues in apples, apple-based baby food, and their behaviour during processing using fast GC–MS multiresidue analysis

Food-processing experiments using apples were conducted to obtain more knowledge on the behaviour of pesticides during apple-based baby-food production. The residues were determined in raw material (apples), in intermediate products at different steps of the processing procedure (baby food production) and in final products (apple purée) using a rapid GC–MS method in combination with two different sample-preparation approaches. During 2 years of a monitoring programme, 84 analyses of apple samples and 102 of baby food sample apple purée intermediate and final product samples from baby food production were performed. A pesticide-residue search revealed that residues in fresh apples do not exceed the maximum residue limit for the adult population, but there were some positive findings concerning apples as baby food. The maximal pesticide concentration (fluquinconazole) found in apples was 0.099 mg kg−1. In the processed apple-based baby food the concentration of pesticide residues were mostly below 0.010 mg kg−1.

Isotachophoretic determination of naproxen in the presence of its metabolite in human serum

An isotachophoretic method with conductivity detection was developed to determine naproxen in the presence of its metabolite 6-O-desmethylnaproxen in human serum. The leading electrolyte contained 10 mM hydrochloric acid, beta-alanine, pH 4.0 and 0.1% methylhydroxypropylcellulose. The terminating electrolyte was 10 mM 2-(N-morpholino)ethanesulfonic acid-tris(hydroxymethyl)aminomethane, pH 6.9, containing 20% (v/v) of ethanol. Naproxen was determined in serum supernatant after simple deproteination of the sample with ethanol. The isotachophoretic results were compared with those obtained by synchronous fluorescence spectrometry.

Evaluation of different calibration approaches in pesticide residues analysis in non-fatty food using fast GC-MS.

In the analysis of pesticide residues by GC including GC-MS, adverse effects caused by matrix co-extractives occurs which results in worse precision and trueness of analytical results. Sample extracts of various commodities (fruit and vegetables), prepared by the QuEChERS method were evaluated by gravimetric analysis to compare co-extracted compounds amount. For comparison of matrix background measurement of acetonitrile (MeCN) extracts in full scan mode and SIM monitoring were performed utilising fast GC-MS with quadrupole analyser and narrow-bore columns. In order to evaluate the trueness of quantitative analysis results utilising different calibration standards experiments with synthetic samples (it is a blank sample extract from selected fruit and vegetables–apples, pear, cucumbers and cauliflowers, with the addition of pesticides at the concentration level of 0.05 ng µL−1 (50 µg kg−1)) were performed in this work. This sample represents a simulated real sample, but with the known concentration to check the various calibration approaches utilising calibration standards that would be used in practice: (1) in organic solvent (MeCN) with addition of analyte protectants (APs), (2) matrix-matched standard, (3) matrix-matched standard with addition of APs. For most of studied pesticides very good match of concentration was obtained utilising matrix matched standards (with/without APs). For the majority of the pesticides under study significant overestimation of concentration was observed in acetonitrile standards with APs in all matrices. Repeatability of measurements expressed as relative standard deviations (RSDs) of determined pesticides concentration in all tested matrices was ≤14%.