Pub Date : 2020-04-21DOI: 10.6001/chemija.v31i2.4221
V. Vickackaite, Gintarė Pipiraitė, Vilius Poškus, Ingrida Jurkutė, B. Bugelytė
Department of Analytical and Environmental Chemistry, Vilnius University, 24 Naugarduko Street, 03225 Vilnius, Lithuania Static headspace gas chromatographic method for determination of hexanal as a marker of lipid oxidation was developed. Tetradecane was suggested as a matrix for hexanal release from the sample. Sample equilibration temperature and time, tetradecane volume, injection time were optimized. Benzaldehyde was selected as an internal standard. Under the optimized conditions quality parameters were determined. The calibration curve was linear in the concentration range from 25 μg l–1 to 2 g l–1, the detection limit was 15 μg l–1, RSD was determined by five replication analysis with hexanal concentration 0.1 g l–1 and was 1.2%. The technique was applied for hexanal determination in potato chips and fried potatoes.
立陶宛维尔纽斯Naugarduko街24号维尔纽斯大学分析与环境化学系，邮编03225。建立了测定己醛作为脂质氧化标志物的静态顶空气相色谱法。十四烷被认为是从样品中释放己醛的基质。对样品平衡温度和时间、十四烷体积、注射时间进行了优化。选择苯甲醛作为内标。在优化的条件下确定了质量参数。在25μg l–1至2 g l–l–1的浓度范围内，校准曲线呈线性，检测限为15μg l-1，用己醛浓度为0.1 g l–-1的五次重复分析法测定RSD，RSD为1.2%。该技术用于薯片和炸土豆中己醛的测定。
{"title":"Static headspace gas chromatographic determination of hexanal as a marker of lipid oxidation in fat-rich food","authors":"V. Vickackaite, Gintarė Pipiraitė, Vilius Poškus, Ingrida Jurkutė, B. Bugelytė","doi":"10.6001/chemija.v31i2.4221","DOIUrl":"https://doi.org/10.6001/chemija.v31i2.4221","url":null,"abstract":"Department of Analytical and Environmental Chemistry, Vilnius University, 24 Naugarduko Street, 03225 Vilnius, Lithuania Static headspace gas chromatographic method for determination of hexanal as a marker of lipid oxidation was developed. Tetradecane was suggested as a matrix for hexanal release from the sample. Sample equilibration temperature and time, tetradecane volume, injection time were optimized. Benzaldehyde was selected as an internal standard. Under the optimized conditions quality parameters were determined. The calibration curve was linear in the concentration range from 25 μg l–1 to 2 g l–1, the detection limit was 15 μg l–1, RSD was determined by five replication analysis with hexanal concentration 0.1 g l–1 and was 1.2%. The technique was applied for hexanal determination in potato chips and fried potatoes.","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":"44752793","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.v31i2.4218
A. Survila, S. Kanapeckaitė, L. Gudavičiūtė, O. Girčienė
Center for Physical Sciences and Technology, 3 Saulėtekio Avenue, 10257 Vilnius, Lithuania Electrochemical impedance spectroscopy was used to study the kinetics of reduction of Cu (II) in weakly acidic (pH 4 and 5) solutions of Cu (II) containing glycine (0.04 or 0.1 M) as a complexing agent. A rather slow equilibration was observed at pH 4 and glycine concentration cL = 0.04 M. With increasing pH or cL, the total concentration of intermediate Cu(I) decreases. At the same time, impedance increases over the entire range of frequencies applied. An equivalent circuit with two parallel sub-circuits, each containing the charge transfer resistance and Warburg impedance in series, was used to quantify the impedance spectra. The exchange current densities of two consecutive one-electron transfers were estimated. Their average values are ~1 μA cm–2 and ~0.1 mA cm–2.
立陶宛维尔纽斯Saulïtekio大道3号物理科学与技术中心使用电化学阻抗谱研究了Cu（II）在含有甘氨酸（0.04或0.1M）作为络合剂的弱酸性（pH 4和5）溶液中还原的动力学。在pH 4和甘氨酸浓度cL=0.04M时观察到相当缓慢的平衡。随着pH或cL的增加，中间体Cu（I）的总浓度降低。同时，阻抗在所施加的整个频率范围内都会增加。使用具有两个并联子电路的等效电路来量化阻抗谱，每个并联子电路都包含串联的电荷转移电阻和Warburg阻抗。估算了两次连续单电子转移的交换电流密度。它们的平均值分别为~1μA cm–2和~0.1 mA cm–2。
{"title":"Impedance of copper electrode in slightly acid Cu(II)-glycine solutions","authors":"A. Survila, S. Kanapeckaitė, L. Gudavičiūtė, O. Girčienė","doi":"10.6001/chemija.v31i2.4218","DOIUrl":"https://doi.org/10.6001/chemija.v31i2.4218","url":null,"abstract":"Center for Physical Sciences and Technology, 3 Saulėtekio Avenue, 10257 Vilnius, Lithuania Electrochemical impedance spectroscopy was used to study the kinetics of reduction of Cu (II) in weakly acidic (pH 4 and 5) solutions of Cu (II) containing glycine (0.04 or 0.1 M) as a complexing agent. A rather slow equilibration was observed at pH 4 and glycine concentration cL = 0.04 M. With increasing pH or cL, the total concentration of intermediate Cu(I) decreases. At the same time, impedance increases over the entire range of frequencies applied. An equivalent circuit with two parallel sub-circuits, each containing the charge transfer resistance and Warburg impedance in series, was used to quantify the impedance spectra. The exchange current densities of two consecutive one-electron transfers were estimated. Their average values are ~1 μA cm–2 and ~0.1 mA cm–2.","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":"48902623","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 : 2020-02-26DOI: 10.6001/chemija.v31i1.4169
K. Ishikawa, A. Kareiva
2 Institute of Chemistry, Vilnius University, 24 Naugarduko Street, 03225 Vilnius, Lithuania Calcium phosphate (CP)-based biomaterials, especially nanostructured ones, show a high biocompatibility and increased biological properties. The coatings composed of stoichiometric hydroxyapatite have been extensively used to improve integration of metallic implants in the host bone. However, these coatings exhibited several drawbacks that limited their successful application. It was concluded in numerous articles that the sol–gel derived coatings can undergo cracking and delamination and are scarcely uniform. In this review article the recent advances on the sol–gel synthesis of different phosphate coatings and thin films are summarized. The attention is paid to coatings and thin films of calcium hydroxyapatite (CHAp), other phosphates, bioglasses and different composite materials. The state of the art, limitations, potentialities, open challenges, and the future scenarios for the application of CP bioceramics are highlighted in this study.
{"title":"Sol–gel synthesis of calcium phosphate-based coatings – A review","authors":"K. Ishikawa, A. Kareiva","doi":"10.6001/chemija.v31i1.4169","DOIUrl":"https://doi.org/10.6001/chemija.v31i1.4169","url":null,"abstract":"2 Institute of Chemistry, Vilnius University, 24 Naugarduko Street, 03225 Vilnius, Lithuania Calcium phosphate (CP)-based biomaterials, especially nanostructured ones, show a high biocompatibility and increased biological properties. The coatings composed of stoichiometric hydroxyapatite have been extensively used to improve integration of metallic implants in the host bone. However, these coatings exhibited several drawbacks that limited their successful application. It was concluded in numerous articles that the sol–gel derived coatings can undergo cracking and delamination and are scarcely uniform. In this review article the recent advances on the sol–gel synthesis of different phosphate coatings and thin films are summarized. The attention is paid to coatings and thin films of calcium hydroxyapatite (CHAp), other phosphates, bioglasses and different composite materials. The state of the art, limitations, potentialities, open challenges, and the future scenarios for the application of CP bioceramics are highlighted in this study.","PeriodicalId":9720,"journal":{"name":"Chemija","volume":" ","pages":""},"PeriodicalIF":0.6,"publicationDate":"2020-02-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49131959","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 : 2020-02-26DOI: 10.6001/chemija.v31i1.4168
J. Jablonskienė, D. Šimkūnaitė, J. Vaičiūnienė, A. Selskis, Audrius Drabavičius, V. Jasulaitienė, L. Tamašauskaitė-Tamašiūnaitė, E. Norkus
Center for Physical Sciences and Technology, 3 Saulėtekio Avenue, 10257 Vilnius, Lithuania MnO2/C nanocomposites have been prepared using a simple onestep microwave heating method by applying different concentrations of cationic surfactant – cetyl trimethylammonium bromide (CTAB). The morphology and composition of the prepared MnO2/C nanocomposites have been investigated using X-ray photoelectron spectroscopy (XPS), field-emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), and inductively coupled plasma optical emission spectroscopy (ICP-OES). The electrochemical performance of the prepared nanocomposites has been analysed using cyclic voltammetry. It was found that a high specific capacitance (Cs) of 742 F g −1 at a scan rate of 10 mV s−1 in a 1 M Na2SO4 solution has been obtained for the MnO2/C nanocomposite that has the mass loading of 0.140 mg cm−2 and has been synthesized in the absence of CTAB. Meanwhile, the application of CTAB allowed the increase in the mass loading of MnO2 in the nanocomposites. In the presence of CTAB, the highest value of 654 F g−1 at a scan rate of 10 mV s−1 has been obtained for MnO2/C that has the mass loading of 0.570 mg cm−2. This result confirmed a good performance of the prepared MnO2/C nanocomposites as the electrode material for supercapacitors.
物理科学与技术中心，3 Saulïtekio Avenue，10257 Vilnius，立陶宛，通过应用不同浓度的阳离子表面活性剂-十六烷基三甲基溴化铵（CTAB），使用简单的一步微波加热方法制备了MnO2/C纳米复合材料。利用X射线光电子能谱（XPS）、场发射扫描电子显微镜（FE-SEM）、透射电子显微镜（TEM）和电感耦合等离子体发射光谱（ICP-OES）研究了制备的MnO2/C纳米复合材料的形貌和组成。用循环伏安法分析了制备的纳米复合材料的电化学性能。研究发现，对于质量负载为0.140 mg cm−2的MnO2/C纳米复合材料，在没有CTAB的情况下合成的，在1M Na2SO4溶液中以10 mV s−1的扫描速率获得了742 F g−1的高比电容（Cs）。同时，CTAB的应用使纳米复合材料中MnO2的质量负载增加。在存在CTAB的情况下，质量负载为0.570 mg cm−2的MnO2/C在10 mV s−1的扫描速率下获得了654 F g−1的最高值。这一结果证实了所制备的MnO2/C纳米复合材料作为超级电容器的电极材料具有良好的性能。
{"title":"Surfactant-assisted microwave synthesis of carbon supported MnO2 nanocomposites and their application for electrochemical supercapacitors","authors":"J. Jablonskienė, D. Šimkūnaitė, J. Vaičiūnienė, A. Selskis, Audrius Drabavičius, V. Jasulaitienė, L. Tamašauskaitė-Tamašiūnaitė, E. Norkus","doi":"10.6001/chemija.v31i1.4168","DOIUrl":"https://doi.org/10.6001/chemija.v31i1.4168","url":null,"abstract":"Center for Physical Sciences and Technology, 3 Saulėtekio Avenue, 10257 Vilnius, Lithuania MnO2/C nanocomposites have been prepared using a simple onestep microwave heating method by applying different concentrations of cationic surfactant – cetyl trimethylammonium bromide (CTAB). The morphology and composition of the prepared MnO2/C nanocomposites have been investigated using X-ray photoelectron spectroscopy (XPS), field-emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), and inductively coupled plasma optical emission spectroscopy (ICP-OES). The electrochemical performance of the prepared nanocomposites has been analysed using cyclic voltammetry. It was found that a high specific capacitance (Cs) of 742 F g −1 at a scan rate of 10 mV s−1 in a 1 M Na2SO4 solution has been obtained for the MnO2/C nanocomposite that has the mass loading of 0.140 mg cm−2 and has been synthesized in the absence of CTAB. Meanwhile, the application of CTAB allowed the increase in the mass loading of MnO2 in the nanocomposites. In the presence of CTAB, the highest value of 654 F g−1 at a scan rate of 10 mV s−1 has been obtained for MnO2/C that has the mass loading of 0.570 mg cm−2. This result confirmed a good performance of the prepared MnO2/C nanocomposites as the electrode material for supercapacitors.","PeriodicalId":9720,"journal":{"name":"Chemija","volume":" ","pages":""},"PeriodicalIF":0.6,"publicationDate":"2020-02-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45635607","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 : 2020-02-26DOI: 10.6001/chemija.v31i1.4167
Z. Sukackienė, K. Antanavičiūtė, J. Vaičiūnienė, L. Tamašauskaitė-Tamašiūnaitė, A. Naujokaitis, E. Norkus
Department of Catalysis, Center for Physical Sciences and Technology, 3 Saulėtekio Avenue, 10257 Vilnius, Lithuania Nickel boron (NiB) coatings were deposited onto copper using a nickelglycine (Ni-Gly) plating solution and morpholine borane (MB) as a reducing agent. It has been determined that using MB as a reducing agent in the Ni-Gly plating solution produces NiB coatings, which exhibit typical cauliflower-like textures. The deposition rate of the NiB coatings and their composition depend on the concentrations of the reducing agent (MB) and the ligand (Gly), in addition to the pH and temperature of the plating solution. The highest deposition rate (3.42 mg cm–2 h–1) of the NiB coating was obtained when the plating bath was operated at pH 5 and 60°C temperature. Using this method, NiB coatings containing 10–20 at.% of boron can be obtained.
{"title":"Electroless deposition of nickel boron coatings using morpholine borane as a reducing agent","authors":"Z. Sukackienė, K. Antanavičiūtė, J. Vaičiūnienė, L. Tamašauskaitė-Tamašiūnaitė, A. Naujokaitis, E. Norkus","doi":"10.6001/chemija.v31i1.4167","DOIUrl":"https://doi.org/10.6001/chemija.v31i1.4167","url":null,"abstract":"Department of Catalysis, Center for Physical Sciences and Technology, 3 Saulėtekio Avenue, 10257 Vilnius, Lithuania Nickel boron (NiB) coatings were deposited onto copper using a nickelglycine (Ni-Gly) plating solution and morpholine borane (MB) as a reducing agent. It has been determined that using MB as a reducing agent in the Ni-Gly plating solution produces NiB coatings, which exhibit typical cauliflower-like textures. The deposition rate of the NiB coatings and their composition depend on the concentrations of the reducing agent (MB) and the ligand (Gly), in addition to the pH and temperature of the plating solution. The highest deposition rate (3.42 mg cm–2 h–1) of the NiB coating was obtained when the plating bath was operated at pH 5 and 60°C temperature. Using this method, NiB coatings containing 10–20 at.% of boron can be obtained.","PeriodicalId":9720,"journal":{"name":"Chemija","volume":" ","pages":""},"PeriodicalIF":0.6,"publicationDate":"2020-02-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43801279","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 : 2020-02-26DOI: 10.6001/chemija.v31i1.4171
S. Saunoriūtė, O. Ragažinskienė, L. Ivanauskas, M. Marksa
3 Department of Analytical and Toxicological Chemistry, Lithuanian University of Health Science, 13 Sukilėlių Street, 50162 Kaunas, Lithuania Artemisia abrotanum L. was introduced in the Middle of Lithuania Collection of Spice–Melliferous Plants of the Scientific Sector of Medicinal and Aromatic Plants of the Botanical Garden ex situ at Vytautas Magnus University since 1980. The object of investigation was Artemisiae abrotani herba of Artemisia abrotanum L. All samples were collected at different vegetation stages: growth and leaf production, flower bud development, the beginning of flowering, massive flowering and the end of flowering. Essential oils were obtained by hydrodistillation. The chemical composition of the essential oils of Artemisiae abrotani herba was studied by GC/MS in the Department of Analytical and Toxicological Chemistry at the Lithuanian University of Health Science in 2018–2019. Fifty-six compounds of the oil were identified, of which (+)-piperitone was the major component (20.38–38.48%). The data in this study showed a remarkable quantitative variation of constituents in the essential oils. The highest content and diversity of compounds was determined during the flower bud development stage. Sixty identified compounds in this stage reached 76.6% of the identified oil content. The highest concentration of this compound (38.48%) was detected at the end of the flowering vegetation stage and the lowest amount (20.38%) was found during the growth and leaf production. Among the other major compounds were (+)-piperitone, 1,4-cineole, lavandulyl butyrate, aromandendrene and isogermacrene D.
{"title":"Essential oil composition of Artemisia abrotanum L. during different vegetation stages in Lithuania","authors":"S. Saunoriūtė, O. Ragažinskienė, L. Ivanauskas, M. Marksa","doi":"10.6001/chemija.v31i1.4171","DOIUrl":"https://doi.org/10.6001/chemija.v31i1.4171","url":null,"abstract":"3 Department of Analytical and Toxicological Chemistry, Lithuanian University of Health Science, 13 Sukilėlių Street, 50162 Kaunas, Lithuania Artemisia abrotanum L. was introduced in the Middle of Lithuania Collection of Spice–Melliferous Plants of the Scientific Sector of Medicinal and Aromatic Plants of the Botanical Garden ex situ at Vytautas Magnus University since 1980. The object of investigation was Artemisiae abrotani herba of Artemisia abrotanum L. All samples were collected at different vegetation stages: growth and leaf production, flower bud development, the beginning of flowering, massive flowering and the end of flowering. Essential oils were obtained by hydrodistillation. The chemical composition of the essential oils of Artemisiae abrotani herba was studied by GC/MS in the Department of Analytical and Toxicological Chemistry at the Lithuanian University of Health Science in 2018–2019. Fifty-six compounds of the oil were identified, of which (+)-piperitone was the major component (20.38–38.48%). The data in this study showed a remarkable quantitative variation of constituents in the essential oils. The highest content and diversity of compounds was determined during the flower bud development stage. Sixty identified compounds in this stage reached 76.6% of the identified oil content. The highest concentration of this compound (38.48%) was detected at the end of the flowering vegetation stage and the lowest amount (20.38%) was found during the growth and leaf production. Among the other major compounds were (+)-piperitone, 1,4-cineole, lavandulyl butyrate, aromandendrene and isogermacrene D.","PeriodicalId":9720,"journal":{"name":"Chemija","volume":" ","pages":""},"PeriodicalIF":0.6,"publicationDate":"2020-02-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45266924","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 : 2019-12-04DOI: 10.6001/chemija.v30i4.4098
Kazimieras Mikulskis, S. Kanapeckaitė, A. Survila
2 Center for Physical Sciences and Technology, 3 Saulėtekio Avenue, 10222 Vilnius, Lithuania The distribution of species in Cu(II)-glycine solutions, containing sulfate or perchlorate as a supporting electrolyte, is considered. Substantial differences are observed at pH < 4.5, where the molar fraction of monoligand complex (associate) CuSO4 reaches up to 20 percent of the total Cu(II) concentration. Cu(I)-containing species are generated at the Cu|solution interface. These are Cu+ aqua-complexes (acid media) or monoand bidentate Cu(I)-glycine complexes (alkaline media). The addition of sulfate reduces the content of Cu+ ions, but practically does not affect the distribution of Cu(I) complexes. The study of acidbase equilibria involving Cu+ ions shows that the thermodynamic probability of Cu2O formation remains low in both perchlorate and sulfate media. HSO4 – ions formed in acid media should be treated as rather labile proton donors. This is quantitatively confirmed by experimental data, according to which the rate of hydrogen evolution increases correspondingly when perchlorate is replaced by sulfate in glycine solutions.
{"title":"Comparative study of equilibrium characteristics of Cu|Cu(II), Cu(I), glycine system containing sulfate or perchlorate as a supporting electrolyte","authors":"Kazimieras Mikulskis, S. Kanapeckaitė, A. Survila","doi":"10.6001/chemija.v30i4.4098","DOIUrl":"https://doi.org/10.6001/chemija.v30i4.4098","url":null,"abstract":"2 Center for Physical Sciences and Technology, 3 Saulėtekio Avenue, 10222 Vilnius, Lithuania The distribution of species in Cu(II)-glycine solutions, containing sulfate or perchlorate as a supporting electrolyte, is considered. Substantial differences are observed at pH < 4.5, where the molar fraction of monoligand complex (associate) CuSO4 reaches up to 20 percent of the total Cu(II) concentration. Cu(I)-containing species are generated at the Cu|solution interface. These are Cu+ aqua-complexes (acid media) or monoand bidentate Cu(I)-glycine complexes (alkaline media). The addition of sulfate reduces the content of Cu+ ions, but practically does not affect the distribution of Cu(I) complexes. The study of acidbase equilibria involving Cu+ ions shows that the thermodynamic probability of Cu2O formation remains low in both perchlorate and sulfate media. HSO4 – ions formed in acid media should be treated as rather labile proton donors. This is quantitatively confirmed by experimental data, according to which the rate of hydrogen evolution increases correspondingly when perchlorate is replaced by sulfate in glycine solutions.","PeriodicalId":9720,"journal":{"name":"Chemija","volume":"30 1","pages":""},"PeriodicalIF":0.6,"publicationDate":"2019-12-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41794174","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 : 2019-12-04DOI: 10.6001/chemija.v30i4.4097
D. Kaušpėdienė, E. Zubrytė, A. Gefenienė, M. Jovaišaitė, V. Gefenas, R. Binkienė, R. Ragauskas, A. Selskienė, V. Pakštas
2 Vytautas Magnus University, 58 K. Donelaičio Street, 44248 Kaunas, Lithuania In this study, CuO nanoparticles have been synthesized via a simple sol– gel method and green synthesis using flower (Matricaria chamomilla) extract. XRD analysis of the synthesized CuO nanoparticles clearly indicated a crystalline nature with a monoclinic structure regardless of the method of synthesis, while SEM revealed that the used synthesis methods affected the morphology of the CuO nanoparticles. The oxidative degradation kinetics of the organic dye Methyl Orange (MO) in the presence of the synthesized catalyst CuO and H2O2 has been investigated and compared depending on the dye concentration, reaction time and temperature. The catalytic activity of CuO was studied by measuring the UV–visible spectrum of the MO dye solution treated with CuO and H2O2. It was determined that the MO degradation reaction kinetics followed the pseudo-first-order mechanism. Thermodynamic studies indicated an endothermic nature (∆H# = +73.03 kJ mol–1) and a decrease in randomness at the catalyst CuO/solution interface during the reaction (∆S# = –0.021 kJ mol–1 K–1). At the same conditions, the green synthesized CuO nanoparticles exhibit similar activity properties as CuO synthesized using the sol–gel method. Besides, the green synthesis of CuO nanoparticles is simple and uses a small number of chemicals. The obtained CuO may be a promising catalyst for the oxidative degradation of organics, especially used in medical procedures.
{"title":"Comparative investigation of oxidative degradation of organic dye in the presence of H2O2 and CuO nanoparticles synthesized by sol–gel method and green synthesis using flower (Matricaria chamomilla) extract","authors":"D. Kaušpėdienė, E. Zubrytė, A. Gefenienė, M. Jovaišaitė, V. Gefenas, R. Binkienė, R. Ragauskas, A. Selskienė, V. Pakštas","doi":"10.6001/chemija.v30i4.4097","DOIUrl":"https://doi.org/10.6001/chemija.v30i4.4097","url":null,"abstract":"2 Vytautas Magnus University, 58 K. Donelaičio Street, 44248 Kaunas, Lithuania In this study, CuO nanoparticles have been synthesized via a simple sol– gel method and green synthesis using flower (Matricaria chamomilla) extract. XRD analysis of the synthesized CuO nanoparticles clearly indicated a crystalline nature with a monoclinic structure regardless of the method of synthesis, while SEM revealed that the used synthesis methods affected the morphology of the CuO nanoparticles. The oxidative degradation kinetics of the organic dye Methyl Orange (MO) in the presence of the synthesized catalyst CuO and H2O2 has been investigated and compared depending on the dye concentration, reaction time and temperature. The catalytic activity of CuO was studied by measuring the UV–visible spectrum of the MO dye solution treated with CuO and H2O2. It was determined that the MO degradation reaction kinetics followed the pseudo-first-order mechanism. Thermodynamic studies indicated an endothermic nature (∆H# = +73.03 kJ mol–1) and a decrease in randomness at the catalyst CuO/solution interface during the reaction (∆S# = –0.021 kJ mol–1 K–1). At the same conditions, the green synthesized CuO nanoparticles exhibit similar activity properties as CuO synthesized using the sol–gel method. Besides, the green synthesis of CuO nanoparticles is simple and uses a small number of chemicals. The obtained CuO may be a promising catalyst for the oxidative degradation of organics, especially used in medical procedures.","PeriodicalId":9720,"journal":{"name":"Chemija","volume":" ","pages":""},"PeriodicalIF":0.6,"publicationDate":"2019-12-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45458200","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 : 2019-12-04DOI: 10.6001/chemija.v30i4.4099
R. Mažeikienė, G. Niaura, A. Malinauskas
Department of Organic Chemistry, Center for Physical Sciences and Technology, 3 Saulėtekio Avenue, 10257 Vilnius, Lithuania A layer of polyaniline has been deposited at a gold electrode and studied by differential multiwavelength Raman spectroelectrochemistry. A set of laser line excitation wavelengths was used, including blue (442 nm), green (532 nm), red (633 nm) and far red (785 nm). From the results obtained, the difference spectra between deprotonated (pH 9.0) and protonated (pH 1.0) forms of oxidized and reduced polyaniline were derived and analysed. The characteristic features for different forms of polyaniline were identified, and their dependence on the excitation wavelength was shown. In addition to the usual Raman spectroscopy, the differential spectroscopy enables one to analyse the increase or decrease of intensity for selected Raman bands upon a reversible deprotonation of this polymer.
{"title":"Study of deprotonation processes of polyaniline by differential multiwavelength Raman spectroscopy in an electrochemical system","authors":"R. Mažeikienė, G. Niaura, A. Malinauskas","doi":"10.6001/chemija.v30i4.4099","DOIUrl":"https://doi.org/10.6001/chemija.v30i4.4099","url":null,"abstract":"Department of Organic Chemistry, Center for Physical Sciences and Technology, 3 Saulėtekio Avenue, 10257 Vilnius, Lithuania A layer of polyaniline has been deposited at a gold electrode and studied by differential multiwavelength Raman spectroelectrochemistry. A set of laser line excitation wavelengths was used, including blue (442 nm), green (532 nm), red (633 nm) and far red (785 nm). From the results obtained, the difference spectra between deprotonated (pH 9.0) and protonated (pH 1.0) forms of oxidized and reduced polyaniline were derived and analysed. The characteristic features for different forms of polyaniline were identified, and their dependence on the excitation wavelength was shown. In addition to the usual Raman spectroscopy, the differential spectroscopy enables one to analyse the increase or decrease of intensity for selected Raman bands upon a reversible deprotonation of this polymer.","PeriodicalId":9720,"journal":{"name":"Chemija","volume":" ","pages":""},"PeriodicalIF":0.6,"publicationDate":"2019-12-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44893685","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 : 2019-12-04DOI: 10.6001/chemija.v30i4.4100
B. Bugelytė, Karolina Ilonina, Vilius Poškus, V. Vickackaite
Department of Analytical and Environmental Chemistry, Vilnius University, 24 Naugarduko Street, 03225 Vilnius, Lithuania Direct and headspace gas chromatographic analysis is compared for the determination of lactic, oxalic, succinic, malic and citric acids. For better chromatographic behaviour, prior to GC analysis carboxylic acids were derivatized using BSTFA as a silylation reagent. Three solvents – acetone, diethyl ether and dimethylformamide – were tested as a derivatization medium and DMF was considered as the best. Derivatization conditions were optimized and analytical characteristics of the direct gas chromatographic determination of analytes in solutions were determined. The method was applied for the determination of citric acid in food. For the analytes dissolved in DMF, the headspace gas chromatographic determination was not sensitive enough. Concentrations of the derivates in the headspace were very low, thus the limits of detection were high and the method was not of practical use. On the other hand, headspace gas chromatography can be applied for identifying of carboxylic acids in solid samples.
{"title":"Gas chromatographic determination of some carboxylic acids: comparison between solution and headspace analysis","authors":"B. Bugelytė, Karolina Ilonina, Vilius Poškus, V. Vickackaite","doi":"10.6001/chemija.v30i4.4100","DOIUrl":"https://doi.org/10.6001/chemija.v30i4.4100","url":null,"abstract":"Department of Analytical and Environmental Chemistry, Vilnius University, 24 Naugarduko Street, 03225 Vilnius, Lithuania Direct and headspace gas chromatographic analysis is compared for the determination of lactic, oxalic, succinic, malic and citric acids. For better chromatographic behaviour, prior to GC analysis carboxylic acids were derivatized using BSTFA as a silylation reagent. Three solvents – acetone, diethyl ether and dimethylformamide – were tested as a derivatization medium and DMF was considered as the best. Derivatization conditions were optimized and analytical characteristics of the direct gas chromatographic determination of analytes in solutions were determined. The method was applied for the determination of citric acid in food. For the analytes dissolved in DMF, the headspace gas chromatographic determination was not sensitive enough. Concentrations of the derivates in the headspace were very low, thus the limits of detection were high and the method was not of practical use. On the other hand, headspace gas chromatography can be applied for identifying of carboxylic acids in solid samples.","PeriodicalId":9720,"journal":{"name":"Chemija","volume":" ","pages":""},"PeriodicalIF":0.6,"publicationDate":"2019-12-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48770987","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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