POPs and PAHs in fish oil-based food supplements at the Czech market.

The objectives of this study were to assess concentrations of three groups of persistent organic pollutants (POPs) and polycyclic aromatic hydrocarbons (PAHs) in 44 fish oil-based food supplements, to estimate their daily intake by consumers and, to evaluate the compliance of the oil samples with the oil origin declarations (cod liver oil or fish oil). The concentrations of ∑PCBs (7 congeners), OCPs (19 compounds, represented mainly by ∑DDTs), ∑PBDEs (10 congeners), and ∑PAHs (16 compounds) found in samples ranged between 0.15-55.7 µg kg-1, 0.93-72.8 µg kg-1, 0.28-27.5 µg kg-1, and 0.32-51.9 µg kg-1, respectively. Besides, the authenticity of the oils was assessed based on the fingerprints obtained by DART-HRMS, an ambient mass spectrometry technique. Four samples declared as fish oil were probably prepared from cod liver oil, which is much cheaper. Furthermore, these samples contained elevated concentrations of halogenated POPs when compared to supplements produced from fish oil.

Assessment of pesticide residues in strawberries grown under various treatment regimes.

The dynamics of pesticide residues in strawberries that involved quantification of pesticide residues in ripe fruits after model treatment was evaluated in repeated field trials conducted over 3 years. Sixteen commercial pesticide formulations in various combinations were employed in applications from 7 to 44 days before harvest. Altogether 21 active ingredients and some of their metabolites were determined in treated strawberries using LC-MS and GC-MS methods. Except for propargite, the concentrations of all active ingredients declined below the respective MRLs (Regulation (EC) No. 396/2005); nevertheless, most of the tested fungicides often persisted above the 0.01 mg kg⁻¹ limit required by baby food producers to avoid the risk of exceeding the 'baby food limit' established in Commission Directive 2006/141/EC. On the other hand, residues of the majority of tested insecticides, namely spinosad, pymetrozine, deltamethrin, lambda-cyhalothrin and azadirachtin, declined below this limit.

Rapid determination of polycyclic aromatic hydrocarbons (PAHs) in tea using two-dimensional gas chromatography coupled with time of flight mass spectrometry.

A simple, fast, and cost effective sample preparation procedure has been developed and validated for the determination of 15+1 European Union Polycyclic Aromatic Hydrocarbons (15+1 EU PAHs) in dried tea leave samples. Based on a critical assessment of several sample extraction/clean-up approaches, the method based on the ethyl acetate extraction followed by the use of PAHs dedicated cartridges with molecularly imprinted polymers (MIPs) has been found as an optimal alternative in terms of time demands and obtained good extract purity. For the final identification/quantification of target PAHs, two dimensional gas chromatography coupled to a time-of-flight mass spectrometry (GC×GC-TOFMS) was used. The performance characteristics of the overall analytical method for individual PAHs determined at three spiking levels (0.5, 2.5 and 5 µg kg(-1)) were in following ranges: limits of quantitation (LOQs) 0.05-0.2 µg kg(-1), repeatabilities 2-9%, and recoveries 73-103%. The recoveries achieved by the newly developed sample preparation procedure when employed for naturally contaminated sample ("incurred" PAHs) were comparable to those obtained by other routinely used approaches employing sonication and/or pressurised liquid extraction for sample analytes isolation. The validated method was subsequently used for the determination of selected genotoxic PAHs in 36 samples of black and green tea obtained from the Czech retail market. The levels of ΣPAH4 (sum of benzo[a]anthracene (BaA), chrysene (CHR), benzo[b]fluoranthene (BbFA) and benzo[a]pyrene (BaP)) in black and green tea leaves ranged from 7.4 to 700 µg kg(-1) and from 4.5 to 102 µg kg(-1), respectively. Contamination of tested tea samples by BaP was in the range of 0.2-152 µg kg(-1).

Streamlining sample preparation and gas chromatography-tandem mass spectrometry analysis of multiple pesticide residues in tea.

In this work, a new rapid method for the determination of 135 pesticide residues in green and black dry tea leaves and stalks employing gas chromatography coupled to tandem mass spectrometry (GC-MS/MS) with a triple quadrupole was developed and validated. A substantial simplification of sample processing prior to the quantification step was achieved: after addition of water to a homogenised sample, transfer of analytes into an acetonitrile layer was aided by the addition of inorganic salts. Bulk co-extracts, contained in the crude organic extract obtained by partition, were subsequently removed by liquid-liquid extraction using hexane with the assistance of added 20% (w/w) aqueous NaCl solution. The importance of matrix hydration prior to the extraction for achieving good recoveries was demonstrated on tea samples with incurred pesticide residues. For most of the analytes, recoveries in the acceptable range of 70-120% and repeatabilities (relative standard deviations, RSDs) ≤20% were achieved for both matrices at spiking levels of 0.01, 0.1 and 1 mg kg(-1). Under optimised GC-MS/MS conditions, most of the analytes gave lowest calibration level ≤0.01 mg kg(-1), permitting the control at the maximum residue levels (MRLs) laid down in Regulation (EC) No 396/2005. The developed method was successfully applied to the determination of pesticide residues in real tea samples.