37 research outputs found

    Rapid speciation of Se(IV) and Se(VI) by flow injection-capillary electrophoresis system with contactless conductivity detection

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    A flow injection-capillary electrophoresis system with contactless conductivity detection and hydrostatic-pressure-generated flow was used for the fast and sensitive speciation of Se(IV) and Se(VI). The sample throughput was 25samples per hour using a background electrolyte solution containing 8.75mM l-histidine (His) adjusted to pH4.00 with acetic acid. The repeatability of peak areas (n=8) was better than 1.41% and the limits of detection were 190μgL−1 and 7.5μgL−1 for Se(IV) and Se(VI), respectively. The interference from carbonate, typically present in water samples, was eliminated by using a low-pH electrolyte in which carbonate is uncharged and migrates at the EOF front. The method was applied to the analysis of Se(IV) and Se(VI) in soil samples that were spiked with both selenium species and the results for recovery of both selenium species were in good agreement with their introduced concentration

    Miniaturized Low-Pressure Ion-Exchange Module and Its Application to an Acidic Eluent Generator for Open Tubular Ion Chromatography

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    We describe a miniaturized eluent generator (MEG), which can be integrated into open tubular capillary column ion chromatography (OTCC-IC). The MEG consists of one central eluent channel and two feed acid chambers, with each phase isolated by a cation-exchange membrane (CEM) and an anion-exchange membrane (AEM). Pure water flowed through the central eluent channel while acid solution (HA) was fed to both chambers. Applying the electric field to the MEG, H+ and A- simultaneously and respectively through the CEM and AEM to form HA in the central channel. The MEG successfully produced tartaric acid and 2,6-pyridinedicarboxylic acid as the eluent for cation OTCC-IC. The gradient elution improved the peak resolution and analytical window for five common cations (Na+, NH4+, K+, Ca2+, Mg2+)

    Content of endogenous sulfur dioxide in wines

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    Content of free and total endogenous sulfur dioxide were evaluated by classical iodometric titration in must, during winemaking processes and in bio-wine. No exogenous sulfur dioxide was added in any technological operations to simplify the evaluations. In addition, the results were corrected on the content of reductons (total content of reducing substances). The results confirmed formation of endogenous sulfur dioxide from sulfur containing substances (sulfur containing amino acids etc.) in both experiments. Microbial sulfur dioxide is preferably bound to carbonyl substances. Only minor part is present in the free (active) form of the sulfur dioxide. In addition, total content of polyphenols (TPC) and total antioxidant capacity (TAC) were determined by spectrophotometry at the same time. A procedure OIV-MA-AS323-O4B: R 2009 was used. Contents of "free" and "total" sulfur dioxide (with/without correction on contents of reductons) and total content of reductones were determined after complexing the sulfur dioxide with formaldehyde. A standard spectrophotometric method using Folin-Ciocalteu reagent was applied for determination of total content of polyphenolics (TPC) at 765 nm after 60 min incubation. The results were expressed as tannin equivalents (in mg. L-1). A standard DPPH (2,2'-difenyl-1-picrylhydrazyl dissolved in methanol) spectrophotometric method was applied for determination of total antioxidant capacity (TAC) at 515 nm. Depletion of the color intensity was measured after 60 min incubation against blank (methanol) and absorbance decrease Δ(A) = (A0 - A1)/A0 was calculated and used for construction of calibration curve. The TAC values were expressed as ascorbic acid concentrations (in mg. L-1). © 2018 Potravinarstvo Slovak Journal of Food Sciences

    Air conditioning for reconstruction of catering establishment

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    Import 09/07/2007Prezenční361 - Katedra energetik

    Capillary electrophoresis in clinical diagnosis and monitoring

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    There is a significant potential of CE to provide a useful analytical tool to analyze noninvasive samples of body fluids and stimulate the cooperation between analytical chemists and clinicians in this interdisciplinary field

    Návrh rekonstrukce tepelné izolace rodinného domu

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    Import 20/04/2006Prezenční výpůjčkaVŠB - Technická univerzita Ostrava. Fakulta strojní. Katedra (361) energetik

    Comparison of Antioxidant Properties of Different Mentha Piperita Species and Commercial Teas by Capillary Zone Electrophoresis and Spectroscopy

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    A comparison of antioxidant properties of ten Mentha species and eleven commercially available peppermint teas was performed by electrophoretic fingerprinting of flavonoids and phenolic acids in aqueous infusions and by spectrophotometric determination of total polyphenolic content (TPC) and total antioxidant activity (TAA). Capillary zone electrophoresis with UV detection was used for measurement of fingerprints from the extracts. The antioxidant characteristics were determined by a spectrophotometric method using Folin-Ciocalteu, ABTS radical and DPPH methods. Significant differences were found among various Mentha species and also among different tea brands
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