Nyomelem speciáció oldószer mentes mikroextrakciós módszerekkel = Application of solvent free microextraction methods for trace element speciation

Az összes krómtartalom meghatározására tengervízből izotóp hígításos nagyfelbontású induktiv csatolású plazma-ionizációs tömegspektrometriás módszert dolgoztunk ki, melynél a mintabevitelt GC elválasztás után közvetlenül oldottuk meg TFAs derivatizációval. A módszert továbbfejlesztve összevetettük a hatásfokokat ECD EI-MS és ICP-Ms detektálásnál.Megállapítottuk, hogy A metilhigany és etilhigany vegyületek eltérően viselkednek mikrohullámú besugárzás hatására, mely nagy mértékben befolyásolhatja a speciációs meghatározásukat. Lúgos feltárás és fenilezési rekció kidolgozásával SPME-GC-AFS módszert dolgoztunk ki halminták higanyspecieszeinek meghatározására. | For the determination of total chromium concentration in seawater an isotope dilution sector field inductively coupled plasma mass spectrometry method was developed, wher for the sample introduction a GC method after TFA derivatization was used. The efficiency of the method was compared using ECD, EI-MS and ICP-MS detection. The degradation behaviour of methylmercury and ethylmercury under microwave irradiation was invesigated, where the effect of irradiation will change the detectability of species. An SPME-GC-AFS determination of methyladet mercury compunds was developed after alkaline sample degradation and phenylation derivatization

Production of Hypoallergenic Antibacterial Peptides from Defatted Soybean Meal in Membrane Bioreactor: A Bioprocess Engineering Study with Comprehensive Product Characterization

Hipoalergeni antibakterijski peptidi male molekularne mase proizvedeni su iz nemasne sojine sačme u membranskom bioreaktoru. U prvom su koraku proteini sojine sačme razgrađeni pomoću tripsina u šaržnom bioreaktoru. Optimalni uvjeti za razgradnju tripsinom bili su: koncentracija sojine sačme od 75 g/L, temperatura od 40 °C i pH=9. Nakon toga su peptidi male molekularne mase pročišćeni pomoću „cross-flow“ membrane (veličina pora 100 μm), a zatim pomoću keramičke cjevaste membrane (veličine pora koja ne propušta molekule veće od 5 kDa). Ispitan je utjecaj transmembranskog pritiska i primjene statičkih promotera turbulencije na smanjenje koncentracijske polarizacije blizu površine ultrafiltracijske membrane, te je potvrđen njihov pozitivan učinak. Transmembranski pritisak od 3•105 Pa i diskontinuirana dijafiltracija provedena u tri koraka bili su optimalni za filtraciju pomoću ultrafiltracijske membrane. Distribucija molekularne mase peptida pročišćenih pomoću ultrafiltracijske membrane utvrđena je pomoću metode LC-ESI-Q-TOF-MS. Više od 96 % peptida (izraženih kao relativna frekvencija) iz permeata ultrafiltracijske membrane imalo je molekularnu masu manju od 1,7 kDa, a najveća je molekularna masa bila 3,1 kDa. Smanjenje alergenih svojstava proteina za više od 99,9 % nakon obrade tripsinom i membranske filtracije utvrđeno je imunoenzimskim testom. Također je zaključeno da peptidi pročišćeni pomoću ultrafiltracijske membrane pozitivno djeluju na rast bakterije Pediococcus acidilactici HA6111-2, te sprečavaju rast bakterije Bacillus cereus.Hypoallergenic antibacterial low-molecular-mass peptides were produced from defatted soybean meal in a membrane bioreactor. In the first step, soybean meal proteins were digested with trypsin in the bioreactor, operated in batch mode. For the tryptic digestion of soybean meal protein, optimum initial soybean meal concentration of 75 g/L, temperature of 40 °C and pH=9.0 were determined. After enzymatic digestion, low-molecular-mass peptides were purified with cross-flow flat sheet membrane (pore size 100 μm) and then with tubular ceramic ultrafiltration membrane (molecular mass cut-off 5 kDa). Effects of transmembrane pressure and the use of a static turbulence promoter to reduce the concentration polarization near the ultrafiltration membrane surface were examined and their positive effects were proven. For the filtration with ultrafiltration membrane, transmembrane pressure of 3·10^5 Pa with 3-stage discontinuous diafiltration was found optimal. The molecular mass distribution of purified peptides using ultrafiltration membrane was determined by a liquid chromatography–electrospray ionization quadrupole time-of-flight mass spectrometry setup. More than 96 % of the peptides (calculated as relative frequency) from the ultrafiltration membrane permeate had the molecular mass M≤1.7 kDa and the highest molecular mass was found to be 3.1 kDa. The decrease of allergenic property due to the tryptic digestion and membrane filtration was determined by an enzyme-linked immunosorbent assay and it was found to exceed 99.9 %. It was also found that the peptides purifi d in the ultrafi tration membrane promoted the growth of Pediococcus acidilactici HA6111-2 and they possessed antibacterial activity against Bacillus cereus

Selenium tolerance, accumulation, localization and speciation in a Cardamine hyperaccumulator and a non-hyperaccumulator

Cardamine violifolia (family Brassicaceae) is the first discovered selenium hyperaccumulator from the genus Cardamine with unique properties in terms of selenium accumulation, i.e., high abundance of selenolanthionine. In our study, a fully comprehensive experiment was conducted with the comparison of a non-hyperaccumulator Cardamine species, Cardamine pratensis, covering growth characteristics, chlorophyll fluorescence, spatial selenium/sulfur distribution patterns through elemental analyses (synchrotron-based X-Ray Fluorescence and ICP-OES) and speciation data through selenium K-edge micro X-ray absorption near-edge structure analysis (μXANES) and strong cation exchange (SCX)-ICP-MS. The results revealed remarkable differences in contrast to other selenium hyperaccumulators as neither Cardamine species showed evidence of growth stimulation by selenium. Also, selenite uptake was not inhibited by phosphate for either of the Cardamine species. Sulfate inhibited selenate uptake, but the two Cardamine species did not show any difference in this respect. However, μXRF derived speciation maps and selenium/sulfur uptake characteristics provided results that are similar to other formerly reported hyperaccumulator and non-hyperaccumulator Brassicaceae species. μXANES showed organic selenium, "C-Se-C", in seedlings of both species and also in mature C. violifolia plants. In contrast, selenate-supplied mature C. pratensis contained approximately half "C-Se-C" and half selenate. SCX-ICP-MS data showed evidence of the lack of selenocystine in any of the Cardamine plant extracts. Thus, C. violifolia shows clear selenium-related physiological and biochemical differences compared to C. pratensis and other selenium hyperaccumulators

Follow-up of the fate of imazalil from post-harvest lemon surface treatment to a baking experiment

<div><p>Imazalil is one of the most widespread fungicides used for the post-harvest treatment of citrus species. The separate use of peel during food preparation and processing may hitherto concentrate most of the imazalil into food products, where specific maximum residue limits hardly exist for this fungicide. In order to monitor comprehensively the path of imazalil, our study covered the monitoring of the efficiency of several washing treatments, the comparison of operative and related sample preparation methods for the lemon samples, the validation of a sample preparation technique for a fatty cake matrix, the preparation of a model cake sample made separately either with imazalil containing lemon peel or with imazalil spiking, the monitoring of imazalil degradation into α-(2,4-dichlorophenyl)-1H-imidazole-1-ethanol because of the baking process, and finally the mass balance of imazalil throughout the washing experiments and the baking process. Quantification of imazalil was carried out with an LC-ESI-MS/MS set-up, while LC-QTOF was used for the monitoring of imazalil degradation. Concerning the washing, none of the addressed five washing protocols could remove more than 30% of imazalil from the surface of the lemon samples. The study revealed a significant difference between the extraction efficiency of imazalil by the EN 15662:2008 and AOAC 2007.1 methods, with the advantage of the former. The use of the model cake sample helped to validate a modified version of the EN 15662:2008 method that included a freeze-out step to efficiently recover imazalil (>90%) from the fatty cake matrix. The degradation of imazalil during the baking process was significantly higher when this analyte was spiked into the cake matrix than in the case of preparing the cake with imazalil-containing lemon peel (52% vs. 22%). This observation calls the attention to the careful evaluation of pesticide stability data that are based on solution spiking experiments.</p></div

Determination of Aminophosphonate Herbicides in Glutamate Loaded Spice Mix by LC-IDMS and Method Extension to Other Food Matrices

The accumulation of organophosphorus type herbicides has been observed worldwide in the environment (i.e. soil, water), together with their appearance in foods of plant origin. This paper reports a new liquid chromatography–isotope dilutiontandem mass spectrometric method (LC-IDMS) for the analysis of glufosinate (GLUF), glyphosate (GLY) and its main metabolite, aminomethylphosphonic acid (AMPA), in challenging food samples. Sample preparation is based on aqueous extraction with ethylenediaminetetraacetic acid solution, followed by solid-phase extraction (SPE) on mixed-mode cation exchange cartridges to remove matrix constituents before derivatization with -fluorenylmethoxycarbonyl chloride (FMOC-Cl). Derivatized samples were cleaned up on hydrophilic modified polymeric SPE cartridge. This two-step SPE supported sample preparation approach, and the LC-IDMS separation carried out in negative ionization mode resulted in fit-for-purpose recovery (81–118%) and precision (4–18%) in the validation of glutamate loaded spice mix, mushroom, maize and cherry samples. Amino acid content influencing FMOC derivatization efficiency was estimated with a HILIC-MS/MS setup. Mul- tiple reaction monitoring (MRM) was assisted with high-resolution (QTOF) accurate mass data on the FMOC-derivatized GLUF, GLY and AMPA standards. The limit of quantification (LOQ) was 0.005 mg/kg for all the three analytes. The method was successfully applied on quality control samples (oat and arugula) with fit-for-purpose accuracy (99–120%) and on other nineteen real samples, where GLY and AMPA were detected in the range between 0.005 and 0.069 mg/kg