A fast and simple procedure for determination of perfluoroalkyl substances in food and feed: a method verification by an interlaboratory study.

In this study, a simple, fast, and cheap sample preparation procedure for the analysis of three well-known representatives of perfluoroalkyl substances (perfluorooctane sulfonate, perfluorooctanoic acid, and perfluorooctane sulfonamide) was validated in accordance with Commission Decision 2002/657/EC. The method was based on extraction with methanol followed by a dispersive solid phase extraction cleanup step by addition of activated charcoal for fish tissue, fish feed, and milk samples. The novel analytical approach combined with liquid chromatography-tandem mass spectrometry makes it possible to achieve limits of quantification below 1 µg/kg (defined by Commission Recommendation 2010/161/EU). This method provides a high laboratory sample throughput: ten samples in 60 min. The validated procedure was successfully verified in an interlaboratory study.

Stability of liquid metal drops affected by a high-frequency magnetic field.

The dynamic behavior of liquid metal drops submitted to a high-frequency magnetic field is investigated experimentally. The motivation for this study comes from the coating industry. In this industry, liquid metals showing a free surface held in a dome-type shape are evaporated by applying electromagnetic pressure. The Galinstan drops are placed on a curved glass plate. A ringlike inductor fed by an alternating electrical current generates the magnetic field. The surface contour of the drop is observed using a high-speed camera system. The data are analyzed by utilizing image processing methods. In the experiment, we vary the inductor current I and the drop volume V while the frequency is fixed at 20 kHz . Upon increasing the inductor current within the range 0I(C), these symmetric states become unstable to capillary waves. The critical current (critical electromagnetic Bond number) as well as the critical mode number, the critical frequency, and the amplitudes of the waves depend strongly on the volume (Bond number).

Fast temperature programming in routine analysis of multiple pesticide residues in food matrices.

Flash gas chromatographic (GC) analysis of 15 organophosphorus pesticides commonly occurring in food crops was performed using the Thermedics Detection EZ Flash upgrade kit installed in the oven of a HP 5890 Series II Plus gas chromatograph. The temperature program and splitless time period were the main parameters to be optimized. In the first set of experiments wheat matrix-matched standards were analyzed both by: (i) the flash GC technique (resistive heating of a 5 m capillary column), and (ii) the conventional GC technique (moderate oven temperature programming of a 30 m capillary column). Using the flash GC technique, the analysis time was reduced by a factor of more than 10 compared to the conventional GC technique. Dramatically improved detectability of analytes was achieved due to much narrower peak widths. The flash GC technique was compared with another approach to faster GC analysis employing a 5 m column and fast temperature programming with a conventional GC oven. In comparison with this alternative, in the case of flash GC significantly better retention time repeatability was observed. The other superiority of resistive heating is very rapid cooling down (i.e., equilibration to the initial conditions) which contributes to the increased sample throughput.

Determination of polychlorinated biphenyls in biotic matrices using gas chromatography--microwave-induced plasma atomic emission spectrometry.

Basic parameters associated with practical application of gas chromatography coupled with microwave-induced plasma atomic emission spectrometric detection GC-MIP-AED in the determination of seven "indicator" polychlorinated biphenyls (PCBs) in biotic matrices were evaluated. The detection limit for chlorine (Cl-479) was found to be 0.54 pg/s. Under the conditions used for sample analysis (1 microliters of purified extract injected into the GC-MIP-AED system represented 2.5 mg of original fat), this value corresponded approximately to 0.15 mg/kg of the respective congeners in fat. The detector response was linear within the tested range of 0.5-10 ng of each injected PCB. The relative standard deviation of repeated injections for the lowest concentration level of 0.5 ng of PCB per injection ranged between 10.5 and 34.4% depending on the chlorine content of the individual analytes. The results demonstrate a high selectivity of chlorine detection. Carbon (C-496) chromatograms recorded simultaneously demonstrated the efficiency of the clean-up step used. Quantitative results (analytes at levels of 0.1-1 mg/kg) obtained with the atomic emission detector did not differ significantly from those recorded with a conventional electron-capture detector.

Analysis of chlorophenoxy acids and other acidic contaminants in food crops.

Several chlorophenoxy acids and chlorinated phenols were determined by means of gas chromatography in contaminated samples of cereals. Extraction of plant matrix with acetone/water mixture followed by alkaline hydrolysis was proved to be suitable for isolation of both free and conjugated residues. The use of pentafluorobenzyl bromide for volatilization of analytes, despite of enhanced ECD response, cannot be recommended for routine analysis. Methylation with either methanol/sulphuric acid or methanol/BF3 reagent can substitute diazomethane-based esterification procedure. Mass fragmentography provided the highest selectivity of detection, moreover good sensitivity--5 ppb--was achieved in this way. Even methyl derivatives of monochlorinated analytes could be, contrary to GC/ECD analysis, quantitated at this level.

Organic pollutants in areas impacted by flooding in 2002: a 4-year survey.

This paper summarizes a 4-year survey focused on polycyclic aromatic hydrocarbons (PAHs) and halogenated persistent organic pollutants (POPs) in river sediments, soil and crops collected in the locality impacted by catastrophic floods that occurred in the western part of Bohemia in August 2002. In spite of relatively high levels of polychlorinated biphenyls (PCBs) in river sediments, the increase of these POPs in flooded arable soil was not significant. On the other hand, remarkably higher levels of PAHs and dichlorodiphenyl trichloroethane (DDTs) were found as compared to those in reference soil samples. Regardless of this increased soil pollution, no measurable elevated concentrations of POPs occurred in the wheat grown in this area.

Optimization of the procedure for the determination of polycyclic aromatic hydrocarbons and their derivatives in fish tissue: Estimation of measurements uncertainty.

Three alternative procedures were employed for the isolation of polycyclic aromatic hydrocarbons (PAHs; 15 of 16 US EPA priority pollutants and benzo[e]pyrene), their methyl-derivatives and sulphur analogues from fish tissue: (1) Soxhlet extraction, (2) batch extraction enhanced by sonication, and (3) saponification of the sample followed by re-extraction of analytes into hexane. Soxhlet extraction using hexane-acetone (1:1, v/v) was the most efficient extraction technique, with analyte recoveries in the range 70-108%. Within optimization of the clean-up step, several types of gel permeation chromatography (GPC) systems were tested: two types of polystyrene divinylbenzene copolymer gels (PSDVB), both 'soft' gel type (Bio-Beads S-X3) and 'rigid' gels type (PL gel and Envirogel) in combination with various mobile phases were compared. Bio-Beads S-X3 and mobile phase chloroform were the most appropriate for purifying of crude extracts before the final determinative step. High-performance liquid chromatography with fluorimetric detection (HPLC/FLD) was used for identification and quantification of PAHs in purified fish extracts. The uncertainties of PAHs measurements were estimated by employing two alternative approaches. Both provided similar results: the expanded uncertainties obtained for individual PAHs by the 'top-down' approach were in the range 9-53%, their values resulting from application of the 'bottom-up' approach were in the range 16-52%.

Baby food production chain: pesticide residues in fresh apples and products.

During 3 years of a monitoring programme, 522 samples of fresh apples, six brands of fruit purées and various types of fruit baby food prepared from these materials were analysed. Each sample was examined for the presence of 86 GC amenable pesticide residues. The reporting limits of the procedure employed for sample analyses were in the range 0.003-0.01 mg kg(-1). Pesticide residues were detected in 59.5% of the samples of fresh apples. However, maximum residue levels (European Union MRLs) were exceeded only in 1.4% of samples. The levels of residues in 'positive' fruit purées were substantially lower, overall with residues detected in 33% of samples. Fruit baby food represented the commodity with the lowest incidence of residues being detected in only 16% of samples. The 0.01 mg kg(-1) MRL was exceeded in 9% of these products. Multiple residues were found in 25% of fresh apples and in 10% of fruit purées. None of fruit baby food samples contained more than a single residue. Organophosphorus insecticides and fungicides representing phtalimides, sulphamides and dicarboximides were the most frequently found residues. To obtain more knowledge on the fate of residues during fruit baby food production, processing experiments employing apples with incurred residues (fenitrothion, phosalone and tolylfluanid) were conducted. Washing of apples did not significantly reduce the content of pesticides. Steam boiling followed by removal of peels/stems was identified as the most efficient steps in terms of residues decrease (phosalone) or complete elimination (fenitrothion and tolylfluanid).

Reactions of oxidized lipids with protein. XIII. Interactions of polar groups of lipids with nonlipidic substances.

Contrary to fresh lipids, oxidized lipids form chloroform-insoluble, but methanol-soluble compounds with cellulose. The amount of chloroform-insoluble lipids is significantly higher in mixtures containing cellulose impregnated with albumin. Polar groups of oxidized lipids formed nonextractable compounds with protein more readily than polar groups of a monoglyceride. Compounds insoluble either in chloroform and in chloroform-methanol or methanol were formed in contact of oxidized lipids with protein, contrary to mixtures of lipids with sole cellulose. The formation of these nonextractable compounds is due both to the interaction of protein with hydroperoxides and with non-peroxidic oxidation products.

The fate of ethylenebis(dithiocarbamate) fungicides during processing of contaminated apples.

A spectrophotometric method based on the liberation of carbon disulfide is suitable for the determination of ethylenebis(dithiocarbamate) (EBDC) residues on apples. Homogenization of samples before analysis initiates rapid breakdown of EBDC, resulting in low recoveries. Thermal conversion of mancozeb to ethylenethiourea (ETU) in the course of apple processing was investigated. The formation of ETU from EBDC could be reduced by lowering the pH value. The presence of an antioxidant (ascorbic acid or cysteine) significantly diminished the yields of ETU after heating, but they inhibited its subsequent decomposition. The rate of ETU formation did not correspond to a relatively rapid disappearance of the parent compound. The levels of ETU residues in the canned baby food originating from contaminated apples were evaluated after a 9-months storage period: the reduction of ETU amounts varied from 26 to 70%.

Determination of PCBs in fatty tissues by means of several detection techniques.

Difficulties with harmonization of analytical procedures and consequently poor comparability of generated data represent in the Czech Republic the main reason for the delay in issuing of updated legislation for polychlorobiphenyls (PCBs) in foodstuffs. This study draws attention to possible errors (overestimations) that can occur during routine determination of these residues in the fat portion of biotic matrices. We demonstrate the gas chromatographic (GC) conditions under which interfering contaminants such as phthalates and/or chlorinated pesticides can be separated from analytes. Discussion is focused on the advantages and drawbacks of GC with an electron capture detector, GC mass spectrometry and GC with an atomic emission detector. Various approaches used for calculation of PCBs contents are compared.

Gas chromatographic determination of chlorinated phenols in the form of various derivatives.

Derivatization of chlorophenols prior to gas chromatographic analysis resulted in a significant improvement of their chromatographic behaviour. Chlorophenols in the form of anisoles, acetates, and pentafluorobenzyl ethers were separated either on a HP-1 wide-bore capillary column or on a capillary column coated with a film of SE-54. Due to an enhancement of the poor electron-capture detection response of mono- and dichlorophenols, pentafluorobenzylation made it possible to determine trace amounts in spiked water. Moreover, simultaneous analysis of phenoxyalkanoic acids was accomplished under the same conditions.

Changes in PAH levels during production of rapeseed oil.

The influence of technological operations during rapeseed oil production on polycyclic aromatic hydrocarbon (PAH) concentrations in by-products, intermediate and final oils was evaluated. The decrease of light PAHs, benz(a)anthracene and benzo(a)pyrene during processing of crude oil to the deodorized product was significant at the 95% confidence interval in most batches analysed. Deodorization and alkali-refining were the steps contributing most to the PAH decrease. The relationship between PAH levels in rapeseed (and consequently in refined oil) and the duration of storage period was studied. The contamination of raw material processed a short time after harvesting was significantly higher than that of the rapeseed stored in silos for several months. Analyses of rapeseed samples, which were re-purified in the laboratory, revealed that solid particles, which contaminate rapeseed during harvesting, initial treatment, transport and storage, contributed to PAH contamination to the extent of 36% (light PAHs) to 64% (heavy PAHs) on average. Further experiments demonstrated that PAHs in re-purified rapeseed were concentrated in the cuticular layer, because they were removed well from the whole seeds by simple rinsing with organic solvent in an ultrasonic bath without losses of rapeseed oil. Alternative expressions of total PAH contamination (e.g. various PAH groups and/or differently defined B(a)P toxic equivalents) are discussed and their effect on drawing conclusions about PAH elimination rate has been demonstrated.