26 (2020) Scientific papers, Series A
Permanentní URI k tomuto záznamuhttps://hdl.handle.net/10195/76706
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Článekpeer-reviewedpublished Otevřený přístup Effect of long-term storage on degradation of 21 phenolic compounds in green tea(University of Pardubice, 2020) Kalendová, Petra; Meloun, Milan; Česlová, LenkaThe storage resistance of 21 selected phenolic compounds present in ten samples of commercially available green tea was monitored using the HPLC/MS/MS over a 16 weeks period using multivariate statistical analysis to compare the different types of packaging. The HPLC/MS/MS method with the computer-aided analysis enabled the fast evaluation of the long-time storage resistance of valuable compounds present in green tea, yielding useful information to customers about their degradation, which affected the sensory properties of the green tea, such as taste and colour. An explanatory data analysis provided an initial visualization of the multivariate data matrix while a factor analysis, hierarchical cluster analysis and discriminant analysis enabled the classification of the green tea samples into clusters according to the storage resistance of the compounds of interest. A significant reduction in the content of all monitored compounds was indicated after 3 weeks of storage, which was also found to be dependent on the type of packaging used. The samples in a plastic box were more stable during long-time storage in comparison to the samples in a paper box.Článekpeer-reviewedpublished Otevřený přístup Determination of oleocanthal in extra virgin olive oils using high-performance liquid chromatography(University of Pardubice, 2020) Klikarová, Jitka; Jakubů, Klára; Česlová, Lenka; Fischer, JanThis work is focused on the determination of oleocanthal in nineteen extra virgin olive oils plus one sample of the olive pomace oil using reversed-phase high-performance liquid chromatography (RP-HPLC) coupled either with a spectrophotometric detector (set at λ = 275 nm) or a mass spectrometer. Sample pre-treatment including a two-step liquidliquid extraction by polar solvents was performed and thoroughly optimised. The extract of oleocanthal was analysed using Poroshell 120 EC-C18 column (150 × 3 mm, i.d. 2.7 μm) in combination with the binary mobile phases consisting of water and acetonitrile. The sum of oleocanthal hemiacetals was quantified by the calibration curve method and the standard addition method. The content of oleocanthal in the samples was found within a range of 2.8–27.2 mg/100 g. It is shown that the method can also be used for evaluation of the olive oil quality.Článekpeer-reviewedpublished Otevřený přístup Determination of selected pesticides in honey and mead by HPLC(University of Pardubice, 2020) Pravcová, Kateřina; Macháčková, Nikola; Česlová, LenkaThe aim of this study was to monitor selected pesticides (Carbendazim, Acetamiprid, Thiacloprid, Epoxiconazole, Metconazole, Prochloraz, Deltamethrin, and T-fluvalinate) in honey and mead samples by reversed-phase liquid chromatography with spectrophotometric detection after QuEChERS extraction. The final separation was performed on YMC triart C18 column with mobile phase consisting of water and acetonitrile. The identification of selected pesticides in samples of honey and mead was performed on the basis of retention times conformity with the standards and quantification using the calibration curve method.Článekpeer-reviewedpublished Otevřený přístup Comparison of HPLC and electrochemical determination of 5-hydroxymethylfurfural in honey and mead samples(University of Pardubice, 2020) Pravcová, Kateřina; Mikysek, Tomáš; Česlová, LenkaThe content of 5-hydroxymethylfurfural (HMF) in honey and mead is strongly influenced by the technological process of these products and could be used as the parameter of choice to assess the quality of honey and mead. Therefore, the aim of this work was the comparison of well established reversed-phase high performance liquid chromatography (RP-HPLC) with voltammetric determination at the glassy carbon electrode. The final HPLC separation was performed on an Ascentis Express C18 column (150 × 3 mm, 2.7 μm) using isocratic elution with 10 % methanol in water. In total, 9 samples (6 honeys and 3 meads) were used for determination of the content of HMF.