Pub Date : 2020-07-19DOI: 10.6001/chemija.v31i3.4288
Tomas Drevinskas, A. Maruška, Gintarė Naujokaitytė, L. Telksnys, M. Kaljurand, V. Stanys, J. Cowles, Jelena Gorbatšova
6 Département Biologique, Institut Universitaire de Technologie, University of Angers, 4 bd Lavoisier, 49016 Angers, France Capillary electrophoresis often causes unrepeatable peak migration times in the electropherogram due to changes of electroosmosis, yet in some cases this separation technique does not have a replacement alternative. Some attempts to overcome this issue have been performed introducing internal standards into the sample and compensating peak shifting in time. However, existing vector calculation-based methods are computationally intensive for portable instrumentation and usually limited to post-processing applications with 1 or 2 markers. In this work, an original approach of compensating peak migration time shift via signal discretization period correction is proposed. Using the proposed method, the number of reference points or markers that are used for compensation is extended. This method is effective in compensating migration time of peaks in real samples, where high sample injection volumes are used. Using 4 reference peaks in compensation, the method was capable of reducing the relative standard deviation of migration time of the peaks in the electropherograms more than 15 times. Corrected signal discretization periods indicated very high correlations with recorded separation currents, what can be perspective developing an adaptive peak migration time compensation method in capillary electrophoresis.
{"title":"Towards adaptive method for peak migration time correction: discretization period in electropherograms","authors":"Tomas Drevinskas, A. Maruška, Gintarė Naujokaitytė, L. Telksnys, M. Kaljurand, V. Stanys, J. Cowles, Jelena Gorbatšova","doi":"10.6001/chemija.v31i3.4288","DOIUrl":"https://doi.org/10.6001/chemija.v31i3.4288","url":null,"abstract":"6 Département Biologique, Institut Universitaire de Technologie, University of Angers, 4 bd Lavoisier, 49016 Angers, France Capillary electrophoresis often causes unrepeatable peak migration times in the electropherogram due to changes of electroosmosis, yet in some cases this separation technique does not have a replacement alternative. Some attempts to overcome this issue have been performed introducing internal standards into the sample and compensating peak shifting in time. However, existing vector calculation-based methods are computationally intensive for portable instrumentation and usually limited to post-processing applications with 1 or 2 markers. In this work, an original approach of compensating peak migration time shift via signal discretization period correction is proposed. Using the proposed method, the number of reference points or markers that are used for compensation is extended. This method is effective in compensating migration time of peaks in real samples, where high sample injection volumes are used. Using 4 reference peaks in compensation, the method was capable of reducing the relative standard deviation of migration time of the peaks in the electropherograms more than 15 times. Corrected signal discretization periods indicated very high correlations with recorded separation currents, what can be perspective developing an adaptive peak migration time compensation method in capillary electrophoresis.","PeriodicalId":9720,"journal":{"name":"Chemija","volume":" ","pages":""},"PeriodicalIF":0.6,"publicationDate":"2020-07-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47061876","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2020-07-19DOI: 10.6001/chemija.v31i3.4292
Ingrida Radveikienė, Ingrida Pilotaitė, Rimgailė Dainytė, R. Vidziūnaitė
2 Vilnius Gediminas Technical University, 11 Saulėtekio Avenue, 10223 Vilnius, Lithuania Novel fungal laccase isoenzymes (namely L95-1 and L95-2) produced by the Ascomycete Lithothelium sp. isolated from the forest soil were purified. However, only one of them was characterized, because the other isoenzyme lost its activity during purification. Extracellular L95-1 laccase was purified 30-fold using ion-exchange and hydrophobic interaction chromatography, with an overall yield of 88%. The molecular mass of purified L95-1 was estimated to be 85 kDa by SDS-PAGE analysis. L95-1 laccase was stable at temperature 4–22°C and pH 6.0–6.5. The substrate specificity of L95-1 laccase was examined with various compounds. Determined affinity constants (KM) varied in a wide range of 3.7–2020.0 μM, whereas catalytic efficiency constants (kcat/KM) covered a range of 0.008–1.9 μM–1 s–1. The optimum pH for most substrates varied in a range from pH 5.0 to 6.0. Sodium azide and fluoride strongly inhibited L95-1 activity, whereas sulphate salts inhibited weakly. The laccase was immobilized on the Fe3O4 nanoparticles and characterized. Residual activity remained at 20% after ten cycles of ABTS oxidation reaction. The immobilized laccase showed higher tolerance to various metal salts. The properties of L95-1 laccase make it potentially useful in the biotechnological applications.
{"title":"Biosynthesis, purification, characterization and immobilization of laccase from Lithothelium sp.","authors":"Ingrida Radveikienė, Ingrida Pilotaitė, Rimgailė Dainytė, R. Vidziūnaitė","doi":"10.6001/chemija.v31i3.4292","DOIUrl":"https://doi.org/10.6001/chemija.v31i3.4292","url":null,"abstract":"2 Vilnius Gediminas Technical University, 11 Saulėtekio Avenue, 10223 Vilnius, Lithuania Novel fungal laccase isoenzymes (namely L95-1 and L95-2) produced by the Ascomycete Lithothelium sp. isolated from the forest soil were purified. However, only one of them was characterized, because the other isoenzyme lost its activity during purification. Extracellular L95-1 laccase was purified 30-fold using ion-exchange and hydrophobic interaction chromatography, with an overall yield of 88%. The molecular mass of purified L95-1 was estimated to be 85 kDa by SDS-PAGE analysis. L95-1 laccase was stable at temperature 4–22°C and pH 6.0–6.5. The substrate specificity of L95-1 laccase was examined with various compounds. Determined affinity constants (KM) varied in a wide range of 3.7–2020.0 μM, whereas catalytic efficiency constants (kcat/KM) covered a range of 0.008–1.9 μM–1 s–1. The optimum pH for most substrates varied in a range from pH 5.0 to 6.0. Sodium azide and fluoride strongly inhibited L95-1 activity, whereas sulphate salts inhibited weakly. The laccase was immobilized on the Fe3O4 nanoparticles and characterized. Residual activity remained at 20% after ten cycles of ABTS oxidation reaction. The immobilized laccase showed higher tolerance to various metal salts. The properties of L95-1 laccase make it potentially useful in the biotechnological applications.","PeriodicalId":9720,"journal":{"name":"Chemija","volume":" ","pages":""},"PeriodicalIF":0.6,"publicationDate":"2020-07-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43068781","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2020-07-19DOI: 10.6001/chemija.v31i3.4290
Kristina Perminaitė, M. Marksa, L. Ivanauskas, A. Inkėnienė, A. Grigonis, K. Ramanauskienė
3 Department of Analytical and Toxicological Chemistry, Faculty of Pharmacy, Lithuanian University of Health Sciences, 13 Sukilėlių Avenue, 50161 Kaunas, Lithuania Royal jelly is a bee product with a high commercial interest due to its exceptional biological properties and unique composition. In this study, we evaluated the quality of Lithuanian Royal jelly, including the water content, antioxidant activity, amount of polyphenolic compounds and pH. The results indicated that Lithuanian Royal jelly had the values of pH, water content as well as polyphenols that were comparable to the data already published. In the study, we also evaluated the impact of various solvents on the amount of 10-hydroxy-2-decenoic acid (10-HDA), the main fatty acid, naturally occurring only in Royal jelly and which is the quality marker, in solutions obtaining the amount using the HPLC method. According to solubility tests performed, 10-HDA from Royal jelly is best soluble in ethanol of various concentrations, yet in order to be used for exceptional Royal jelly antibacterial and many other biological properties it was important to increase the solubility in aqueous solutions. Addition of β-cyclodextrin has increased the amount of 10-HDA in solution up to the level of ethanol solutions. The antioxidant and antibacterial tests have demonstrated that Lithuanian Royal jelly exhibits positive effects against free radicals, as well as mostly occurring bacterial strains, such as Esherichia coli, Pseudomonas aeruginosa, Enterococcus faecalis and Staphylococcus aureus. As the conclusion of this study, we can assume that the quality assessment methods chosen for this study, are significant for standardizing the procedures for further studies.
{"title":"Lithuanian Royal jelly: quality assessment, biological activity and quantitative determination of trans-10-hydroxy-2-decenoic acid in various solvents","authors":"Kristina Perminaitė, M. Marksa, L. Ivanauskas, A. Inkėnienė, A. Grigonis, K. Ramanauskienė","doi":"10.6001/chemija.v31i3.4290","DOIUrl":"https://doi.org/10.6001/chemija.v31i3.4290","url":null,"abstract":"3 Department of Analytical and Toxicological Chemistry, Faculty of Pharmacy, Lithuanian University of Health Sciences, 13 Sukilėlių Avenue, 50161 Kaunas, Lithuania Royal jelly is a bee product with a high commercial interest due to its exceptional biological properties and unique composition. In this study, we evaluated the quality of Lithuanian Royal jelly, including the water content, antioxidant activity, amount of polyphenolic compounds and pH. The results indicated that Lithuanian Royal jelly had the values of pH, water content as well as polyphenols that were comparable to the data already published. In the study, we also evaluated the impact of various solvents on the amount of 10-hydroxy-2-decenoic acid (10-HDA), the main fatty acid, naturally occurring only in Royal jelly and which is the quality marker, in solutions obtaining the amount using the HPLC method. According to solubility tests performed, 10-HDA from Royal jelly is best soluble in ethanol of various concentrations, yet in order to be used for exceptional Royal jelly antibacterial and many other biological properties it was important to increase the solubility in aqueous solutions. Addition of β-cyclodextrin has increased the amount of 10-HDA in solution up to the level of ethanol solutions. The antioxidant and antibacterial tests have demonstrated that Lithuanian Royal jelly exhibits positive effects against free radicals, as well as mostly occurring bacterial strains, such as Esherichia coli, Pseudomonas aeruginosa, Enterococcus faecalis and Staphylococcus aureus. As the conclusion of this study, we can assume that the quality assessment methods chosen for this study, are significant for standardizing the procedures for further studies.","PeriodicalId":9720,"journal":{"name":"Chemija","volume":" ","pages":""},"PeriodicalIF":0.6,"publicationDate":"2020-07-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45151285","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2020-07-19DOI: 10.6001/chemija.v31i3.4286
E. AlShamaileh, M. Esaifan, Qusay Abu-Afifeh
2 Department of Chemistry, Faculty of Science and Arts, University of Petra, Amman, Jordan The formation of metal oxide-based hydroxysodalite by alkali-activation of kaolinite is studied using X-ray diffraction (XRD) study and differential scanning calorimetry (DSC) analysis. Different metal oxides (CoO, MgO, FeO and SiO2) were used to form the metal oxide-based hydroxysodalite. The transformation from kaolinite into hydroxysodalite is confirmed by XRD. In the thermodynamic study, the maximum peak temperatures for DSC curves at various heating rates were used to determine the activation energy (Ea) of the hydroxysodalite formation. With magnesium oxide and cobalt oxide, the formation process was found to be exothermic while it was endothermic with iron oxide.
{"title":"Formation of metal oxide-based hydroxysodalite by alkali-activation of kaolinite","authors":"E. AlShamaileh, M. Esaifan, Qusay Abu-Afifeh","doi":"10.6001/chemija.v31i3.4286","DOIUrl":"https://doi.org/10.6001/chemija.v31i3.4286","url":null,"abstract":"2 Department of Chemistry, Faculty of Science and Arts, University of Petra, Amman, Jordan The formation of metal oxide-based hydroxysodalite by alkali-activation of kaolinite is studied using X-ray diffraction (XRD) study and differential scanning calorimetry (DSC) analysis. Different metal oxides (CoO, MgO, FeO and SiO2) were used to form the metal oxide-based hydroxysodalite. The transformation from kaolinite into hydroxysodalite is confirmed by XRD. In the thermodynamic study, the maximum peak temperatures for DSC curves at various heating rates were used to determine the activation energy (Ea) of the hydroxysodalite formation. With magnesium oxide and cobalt oxide, the formation process was found to be exothermic while it was endothermic with iron oxide.","PeriodicalId":9720,"journal":{"name":"Chemija","volume":" ","pages":""},"PeriodicalIF":0.6,"publicationDate":"2020-07-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46094227","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2020-07-19DOI: 10.6001/chemija.v31i3.4287
A. Šleiniūtė, Liucija Urbelytė, J. Denafas, A. Kosheleva, G. Denafas
3 Research Group ‘Waste Resources Management’, Institute of Environmental Technology and Energy Economics, Hamburg University of Technology, 40 Eissendorfer Street, Hamburg, Germany The feasibilities of silicon recovering from solar cell waste (SCW) by treatment with nitric acid at its concentrations of 1, 2, 3 and 4M were investigated. The research results have shown that complete leaching of aluminum from the silicon matrix is not possible. It can be explained by formation of aluminum compounds with oxygen and silicon on the aluminum particles. Total silver leaching is achieved at maximal 4M concentrations of nitric acid. The influence of nitric acid concentrations on the leaching efficiency of these metals is significantly reduced at higher temperatures (up to 50°C). Higher metal leaching efficiency is characteristic of larger SCA particles under more favourable spatial conditions for penetration of nitric acid ions.
{"title":"Feasibilities for silicon recovery from solar cells waste by treatment with nitric acid","authors":"A. Šleiniūtė, Liucija Urbelytė, J. Denafas, A. Kosheleva, G. Denafas","doi":"10.6001/chemija.v31i3.4287","DOIUrl":"https://doi.org/10.6001/chemija.v31i3.4287","url":null,"abstract":"3 Research Group ‘Waste Resources Management’, Institute of Environmental Technology and Energy Economics, Hamburg University of Technology, 40 Eissendorfer Street, Hamburg, Germany The feasibilities of silicon recovering from solar cell waste (SCW) by treatment with nitric acid at its concentrations of 1, 2, 3 and 4M were investigated. The research results have shown that complete leaching of aluminum from the silicon matrix is not possible. It can be explained by formation of aluminum compounds with oxygen and silicon on the aluminum particles. Total silver leaching is achieved at maximal 4M concentrations of nitric acid. The influence of nitric acid concentrations on the leaching efficiency of these metals is significantly reduced at higher temperatures (up to 50°C). Higher metal leaching efficiency is characteristic of larger SCA particles under more favourable spatial conditions for penetration of nitric acid ions.","PeriodicalId":9720,"journal":{"name":"Chemija","volume":" ","pages":""},"PeriodicalIF":0.6,"publicationDate":"2020-07-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46305060","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2020-04-21DOI: 10.6001/chemija.v31i2.4223
D. Benítez, M. Comini, Ž. Anusevičius, J. Šarlauskas, V. Miliukiené, Eglė Miliuvienė, N. Čėnas
3 Vilnius University Hospital Santaros Klinikos, 2 Santariškių Street, 08406 Villnius, Lithuania Trypanothione reductase (TR) and trypanothione synthase (TS) are critical for the maintenance of thiol-redox homeostasis and antioxidant protection in trypanosomal parasites, which cause African sleeping sickness and Chagas disease. Both enzymes are absent in mammals. Thus, the design of efficient and specific TR and TS inhibitors represents one of the pathways for a development of new antitrypanosomal drugs. 5-Vinylquinoline-substituted nitrofurans (n = 7), studied in this work, acted as unor noncompetitive to trypanothione inhibitors of Trypanosoma congolense TR. Their inhibition constants (Ki) varied from 2.3 μM to 150 μM. We for the first time observed a parallelism between their antitrypanosomal in vitro activity and their efficacy as TR inhibitors. The inhibition of TS appears not to be a significant factor of trypanocidal activity of examined compounds.
{"title":"5-Vinylquinoline-substituted nitrofurans as inhibitors of trypanothione reductase and antitrypanosomal agents","authors":"D. Benítez, M. Comini, Ž. Anusevičius, J. Šarlauskas, V. Miliukiené, Eglė Miliuvienė, N. Čėnas","doi":"10.6001/chemija.v31i2.4223","DOIUrl":"https://doi.org/10.6001/chemija.v31i2.4223","url":null,"abstract":"3 Vilnius University Hospital Santaros Klinikos, 2 Santariškių Street, 08406 Villnius, Lithuania Trypanothione reductase (TR) and trypanothione synthase (TS) are critical for the maintenance of thiol-redox homeostasis and antioxidant protection in trypanosomal parasites, which cause African sleeping sickness and Chagas disease. Both enzymes are absent in mammals. Thus, the design of efficient and specific TR and TS inhibitors represents one of the pathways for a development of new antitrypanosomal drugs. 5-Vinylquinoline-substituted nitrofurans (n = 7), studied in this work, acted as unor noncompetitive to trypanothione inhibitors of Trypanosoma congolense TR. Their inhibition constants (Ki) varied from 2.3 μM to 150 μM. We for the first time observed a parallelism between their antitrypanosomal in vitro activity and their efficacy as TR inhibitors. The inhibition of TS appears not to be a significant factor of trypanocidal activity of examined compounds.","PeriodicalId":9720,"journal":{"name":"Chemija","volume":" ","pages":""},"PeriodicalIF":0.6,"publicationDate":"2020-04-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41778945","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2020-04-21DOI: 10.6001/chemija.v31i2.4217
V. Kepenienė, R. Stagniūnaitė, Daina Upskuvienė, L. Tamašauskaitė-Tamašiūnaitė, V. Pakštas, Audrius Drabavičius, M. Andrulevičius, E. Norkus
2 Institute of Materials Science of Kaunas University of Technology, 59 Baršausko Street, 50131 Kaunas, Lithuania AuCeO2/C and Au/C catalysts were obtained by adsorption of AuNPs on the CeO2/C and pure carbon (C) substrates from an Au colloidal solution. It has been found that AuNPs of ca. 50 nm in size were adsorbed on the surfaces of CeO2/C and C; however, electrocatalytic activity of the investigated AuCeO2/C and Au/C catalysts was different. Ethylene glycol oxidation current density values are ca. 3 times higher on the AuCeO2/C catalyst as compared to those of the bare Au/C catalyst. Moreover, the AuCeO2/C catalyst showed more positive onset potentials, as well as higher current in the mixed-kinetic-diffusion region towards the oxygen reduction reaction in an alkaline medium compared to that of the Au/C catalyst.
{"title":"Electrocatalytic activity of AuCeO2/C towards ethylene glycol oxidation and oxygen reduction reactions","authors":"V. Kepenienė, R. Stagniūnaitė, Daina Upskuvienė, L. Tamašauskaitė-Tamašiūnaitė, V. Pakštas, Audrius Drabavičius, M. Andrulevičius, E. Norkus","doi":"10.6001/chemija.v31i2.4217","DOIUrl":"https://doi.org/10.6001/chemija.v31i2.4217","url":null,"abstract":"2 Institute of Materials Science of Kaunas University of Technology, 59 Baršausko Street, 50131 Kaunas, Lithuania AuCeO2/C and Au/C catalysts were obtained by adsorption of AuNPs on the CeO2/C and pure carbon (C) substrates from an Au colloidal solution. It has been found that AuNPs of ca. 50 nm in size were adsorbed on the surfaces of CeO2/C and C; however, electrocatalytic activity of the investigated AuCeO2/C and Au/C catalysts was different. Ethylene glycol oxidation current density values are ca. 3 times higher on the AuCeO2/C catalyst as compared to those of the bare Au/C catalyst. Moreover, the AuCeO2/C catalyst showed more positive onset potentials, as well as higher current in the mixed-kinetic-diffusion region towards the oxygen reduction reaction in an alkaline medium compared to that of the Au/C catalyst.","PeriodicalId":9720,"journal":{"name":"Chemija","volume":" ","pages":""},"PeriodicalIF":0.6,"publicationDate":"2020-04-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47328742","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2020-04-21DOI: 10.6001/chemija.v31i2.4219
O. Girčienė, L. Gudavičiūtė, A. Selskienė, A. Kirdeikiene, R. Ramanauskas
Center for Physical Sciences and Technology, 3 Saulėtekio Avenue, 10257, Vilnius, Lithuania The anticorrosive behaviour of the electrogalvanized carbon steel with PZn, PZnCa and PZnNi phosphate layers additionally coated with the conversion layers of cerium oxide in chloride-contaminated media has been studied. The composition and structure of investigated samples were characterized by scanning electron microscope SEM, while the corrosion behaviour was investigated applying voltammetric and electrochemical impedance spectroscopy EIS measurements. The data obtained have shown that all investigated samples additionally coated with cerium oxide conversion coatings exhibited better protective abilities. To summarize the results of electrochemical and SEM measurements it was stated that the most porous (F = ~1–2%) PZnNi/Ce coating exhibited the best protective abilities in a chloride-contaminated solution. Therefore, cerium ions are able to penetrate into the substrate, which is zinc coated steel, through the open pores of the PZnNi layer.
{"title":"Electrochemical investigations of the anticorrosive behaviour of the phosphated electrogalvanized steel additionally coated with conversion layer of cerium oxide","authors":"O. Girčienė, L. Gudavičiūtė, A. Selskienė, A. Kirdeikiene, R. Ramanauskas","doi":"10.6001/chemija.v31i2.4219","DOIUrl":"https://doi.org/10.6001/chemija.v31i2.4219","url":null,"abstract":"Center for Physical Sciences and Technology, 3 Saulėtekio Avenue, 10257, Vilnius, Lithuania The anticorrosive behaviour of the electrogalvanized carbon steel with PZn, PZnCa and PZnNi phosphate layers additionally coated with the conversion layers of cerium oxide in chloride-contaminated media has been studied. The composition and structure of investigated samples were characterized by scanning electron microscope SEM, while the corrosion behaviour was investigated applying voltammetric and electrochemical impedance spectroscopy EIS measurements. The data obtained have shown that all investigated samples additionally coated with cerium oxide conversion coatings exhibited better protective abilities. To summarize the results of electrochemical and SEM measurements it was stated that the most porous (F = ~1–2%) PZnNi/Ce coating exhibited the best protective abilities in a chloride-contaminated solution. Therefore, cerium ions are able to penetrate into the substrate, which is zinc coated steel, through the open pores of the PZnNi layer.","PeriodicalId":9720,"journal":{"name":"Chemija","volume":" ","pages":""},"PeriodicalIF":0.6,"publicationDate":"2020-04-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45832559","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2020-04-21DOI: 10.6001/chemija.v31i2.4222
Aurita Butkevičiūtė, R. Urbštaitė, M. Liaudanskas, D. Kviklys, J. Viškelis, V. Janulis
2 Institute of Horticulture, Lithuanian Research Centre for Agriculture and Forestry, 30 Kauno Street, 54333 Babtai, Kaunas District, Lithuania Apple (Malus domestica Borkh.) fruits are rich in phenolic glycosides, triterpenic acids and other biologically active compounds. The apples are widely used as food products due to their biologically active compounds that have specific biological effects. It is important to use high quality apples or their recycling products, so it is necessary to investigate the qualitative and quantitative composition of the bioactive compounds. The amount of triterpenic acids varies during different phenological stages of apple development and maturation. In order to determine in which phenological stage of apple growth the quantity of triterpenic acids was highest, high-performance liquid chromatography was applied. The highest total amounts of triterpenic compounds were detected at the beginning of the phenological stage of fruit development. The study showed that the highest amounts of triterpenic acids were detected at the beginning of the phenological stage of apple development, while as the apple matured, the amount of triterpenic acids decreased from 2.63 ± 0.26 mg/g to 1.6 ± 0.28 mg/g. In this study, we identified and quantified four triterpenic compounds, which by the quantitative composition of triterpenic acids could be arranged in the following ascending order: betulinic acid < corosolic acid < oleanolic acid < ursolic acid. In order to use herbal extracts for medical practice it is important to perform biological effects study in vitro and in vivo. Antioxidants with different mechanisms of action neutralize harmful reactive oxygen and nitrogen forms and enhance antioxidants protection systems. The antioxidant activity of apple extracts in vitro varied during different phenological stages of the fruit. The strongest antiradical and reductive activities were observed at the beginning of apple development. In order to determine the relationship between the antioxidant activity of the acetone extracts of apples assessed by DPPH, ABTS, CUPRAC and FRAP assays and the total amount of triterpenic acids in these extracts, a correlation analysis was carried out. The strongest positive correlation was observed between the amount of oleanolic acid and the antioxidant activity assessed by DPPH, ABTS and CUPRAC methods (respectively, r = 0.778, r = 0.784 and r = 0.720).
{"title":"Seasonal variation of the qualitative and quantitative composition of triterpenic compounds and antioxidant activity in vitro in the apple extracts of cultivars grown in Lithuania","authors":"Aurita Butkevičiūtė, R. Urbštaitė, M. Liaudanskas, D. Kviklys, J. Viškelis, V. Janulis","doi":"10.6001/chemija.v31i2.4222","DOIUrl":"https://doi.org/10.6001/chemija.v31i2.4222","url":null,"abstract":"2 Institute of Horticulture, Lithuanian Research Centre for Agriculture and Forestry, 30 Kauno Street, 54333 Babtai, Kaunas District, Lithuania Apple (Malus domestica Borkh.) fruits are rich in phenolic glycosides, triterpenic acids and other biologically active compounds. The apples are widely used as food products due to their biologically active compounds that have specific biological effects. It is important to use high quality apples or their recycling products, so it is necessary to investigate the qualitative and quantitative composition of the bioactive compounds. The amount of triterpenic acids varies during different phenological stages of apple development and maturation. In order to determine in which phenological stage of apple growth the quantity of triterpenic acids was highest, high-performance liquid chromatography was applied. The highest total amounts of triterpenic compounds were detected at the beginning of the phenological stage of fruit development. The study showed that the highest amounts of triterpenic acids were detected at the beginning of the phenological stage of apple development, while as the apple matured, the amount of triterpenic acids decreased from 2.63 ± 0.26 mg/g to 1.6 ± 0.28 mg/g. In this study, we identified and quantified four triterpenic compounds, which by the quantitative composition of triterpenic acids could be arranged in the following ascending order: betulinic acid < corosolic acid < oleanolic acid < ursolic acid. In order to use herbal extracts for medical practice it is important to perform biological effects study in vitro and in vivo. Antioxidants with different mechanisms of action neutralize harmful reactive oxygen and nitrogen forms and enhance antioxidants protection systems. The antioxidant activity of apple extracts in vitro varied during different phenological stages of the fruit. The strongest antiradical and reductive activities were observed at the beginning of apple development. In order to determine the relationship between the antioxidant activity of the acetone extracts of apples assessed by DPPH, ABTS, CUPRAC and FRAP assays and the total amount of triterpenic acids in these extracts, a correlation analysis was carried out. The strongest positive correlation was observed between the amount of oleanolic acid and the antioxidant activity assessed by DPPH, ABTS and CUPRAC methods (respectively, r = 0.778, r = 0.784 and r = 0.720).","PeriodicalId":9720,"journal":{"name":"Chemija","volume":" ","pages":""},"PeriodicalIF":0.6,"publicationDate":"2020-04-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47072947","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2020-04-21DOI: 10.6001/chemija.v31i2.4220
J. Jablonskienė, D. Šimkūnaitė, J. Vaičiūnienė, G. Stalnionis, A. Drabavičius, L. Tamašauskaitė-Tamašiūnaitė, E. Norkus
Center for Physical Sciences and Technology, 3 Saulėtekio Avenue, 10257 Vilnius, Lithuania The carbon supported manganese(IV)–cobalt (II/III) oxides nanoparticles labelled as MnO2–Co3O4/C nanocomposites have been prepared by a simple one-step microwave-assisted heating method using different precursor materials. Scanning electron microscopy (SEM), transmission electron microscopy (TEM) and inductively coupled plasma optical emission spectroscopy (ICP-OES) have been used for the characterization of morphology, structure and composition of the synthesized nanocomposites, whereas the electrochemical performance of the prepared nanocomposites has been evaluated by using cyclic voltammetry (CV). It was determined that the use of different precursor materials for the synthesis of the carbon supported MnO2 and Co3O4 nanocomposites results in a different morphology of the prepared substances. A high specific capacitance (Cs) of 658.8 F g −1 at a scan rate of 10 mV s−1 in a 1 M Na2SO4 solution has been obtained for the MnO2– Co3O4/C-2 nanocomposite that has a spherical shape of nanoparticles. Moreover, it significantly outperforms the MnO2–Co3O4/C-1 nanocomposite that has a lamellar shape of nanoparticles.
立陶宛维尔纽斯Saulïtekio大道3号物理科学与技术中心，10257。通过使用不同的前体材料，通过简单的一步微波辅助加热方法制备了标记为MnO2–Co3O4/C纳米复合材料的碳负载锰（IV）–钴（II/III）氧化物纳米颗粒。扫描电子显微镜（SEM）、透射电子显微镜（TEM）和电感耦合等离子体发射光谱（ICP-OES）已用于表征合成的纳米复合材料的形态、结构和组成，而使用循环伏安法（CV）评估了制备的纳米复合材料的电化学性能。已经确定，使用不同的前体材料来合成碳负载的MnO2和Co3O4纳米复合材料导致所制备的物质的不同形态。对于具有球形纳米颗粒的MnO2–Co3O4/C-2纳米复合材料，在1M Na2SO4溶液中以10 mV s−1的扫描速率获得了658.8 F g−1的高比电容（Cs）。此外，它显著优于具有纳米颗粒片状形状的MnO2–Co3O4/C-1纳米复合材料。
{"title":"Carbon supported manganese(IV)–cobalt(II/III) oxides nanoparticles for high-performance electrochemical supercapacitors","authors":"J. Jablonskienė, D. Šimkūnaitė, J. Vaičiūnienė, G. Stalnionis, A. Drabavičius, L. Tamašauskaitė-Tamašiūnaitė, E. Norkus","doi":"10.6001/chemija.v31i2.4220","DOIUrl":"https://doi.org/10.6001/chemija.v31i2.4220","url":null,"abstract":"Center for Physical Sciences and Technology, 3 Saulėtekio Avenue, 10257 Vilnius, Lithuania The carbon supported manganese(IV)–cobalt (II/III) oxides nanoparticles labelled as MnO2–Co3O4/C nanocomposites have been prepared by a simple one-step microwave-assisted heating method using different precursor materials. Scanning electron microscopy (SEM), transmission electron microscopy (TEM) and inductively coupled plasma optical emission spectroscopy (ICP-OES) have been used for the characterization of morphology, structure and composition of the synthesized nanocomposites, whereas the electrochemical performance of the prepared nanocomposites has been evaluated by using cyclic voltammetry (CV). It was determined that the use of different precursor materials for the synthesis of the carbon supported MnO2 and Co3O4 nanocomposites results in a different morphology of the prepared substances. A high specific capacitance (Cs) of 658.8 F g −1 at a scan rate of 10 mV s−1 in a 1 M Na2SO4 solution has been obtained for the MnO2– Co3O4/C-2 nanocomposite that has a spherical shape of nanoparticles. Moreover, it significantly outperforms the MnO2–Co3O4/C-1 nanocomposite that has a lamellar shape of nanoparticles.","PeriodicalId":9720,"journal":{"name":"Chemija","volume":" ","pages":""},"PeriodicalIF":0.6,"publicationDate":"2020-04-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41807647","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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