Pub Date : 2018-02-05DOI: 10.1590/S0100-46702008000200007
O. Fatibello‐Filho, H. Vieira
A spectrophotometric flow injection method for the determination of paracetamol in pharmaceutical formulations is proposed. The procedure was based on the oxidation of paracetamol by sodium hypochloride and the determination of the excess of this oxidant using o-tolidine dichloride as chromogenic reagent at 430 nm. The analytical curve was linear in the paracetamol concentration range from 8.50 x 10-6 to 2.51 x 10-4 mol L-1 with a detection limit of 5.0 x 10-6 mol L-1. The relative standard deviation was smaller than 1.2% for 1.20 x 10-4 mol L-1 paracetamol solution (n = 10). The results obtained for paracetamol in pharmaceutical formulations using the proposed flow injection method and those obtained using a USP Pharmacopoeia method are in agreement at the 95% confidence level.
{"title":"Spectrophotometric flow injection procedure to indirect determination of paracetamol in pharmaceutical formulations using o-tolidine as reagent","authors":"O. Fatibello‐Filho, H. Vieira","doi":"10.1590/S0100-46702008000200007","DOIUrl":"https://doi.org/10.1590/S0100-46702008000200007","url":null,"abstract":"A spectrophotometric flow injection method for the determination of paracetamol in pharmaceutical formulations is proposed. The procedure was based on the oxidation of paracetamol by sodium hypochloride and the determination of the excess of this oxidant using o-tolidine dichloride as chromogenic reagent at 430 nm. The analytical curve was linear in the paracetamol concentration range from 8.50 x 10-6 to 2.51 x 10-4 mol L-1 with a detection limit of 5.0 x 10-6 mol L-1. The relative standard deviation was smaller than 1.2% for 1.20 x 10-4 mol L-1 paracetamol solution (n = 10). The results obtained for paracetamol in pharmaceutical formulations using the proposed flow injection method and those obtained using a USP Pharmacopoeia method are in agreement at the 95% confidence level.","PeriodicalId":35894,"journal":{"name":"Ecletica Quimica","volume":"33 1","pages":"47-53"},"PeriodicalIF":0.0,"publicationDate":"2018-02-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48996094","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2018-02-05DOI: 10.1590/S0100-46702008000200003
K. Basavaiah, O. Z. Devi
Two sensitive spectrophotometric methods are described for the determination of simvastatin (SMT) in bulk drug and in tablets. The methods are based on the oxidation of SMT by a measured excess of cerium (IV) in acid medium followed by determination of unreacted oxidant by two different reaction schemes. In one procedure (method A), the residual cerium (IV) is reacted with a fixed concentration of fer- roin and the increase in absorbance is measured at 510 nm. The second approach (method B) involves the reduction of the unreacted cerium (IV) with a fixed quantity of iron (II), and the resulting iron (III) is com- plexed with thiocyanate and the absorbance measured at 470 nm. In both methods, the amount of cerium (IV) reacted corresponds to SMT concentration. The experimental conditions for both methods were opti- mized. In method A, the absorbance is found to increase linearly with SMT concentration (r = 0.9995) whereas in method B, the same decreased (r = -0.9943). The systems obey Beer's law for 0.6-7.5 and 0.5- 5.0 µg mL-1 for method A and method B, respectively. The calculated molar absorptivity values are 2.7 X 104 and 1.06 X 105 Lmol-1 cm-1, respectively; and the corresponding sandel sensitivity values are 0.0153 and 0.0039µg cm-2, respectively. The limit of detection (LOD) and quantification (LOQ) are reported for both methods. Intra-day and inter-day precision, and accuracy of the methods were established as per the current ICH guidelines. The methods were successfully applied to the determination of SMT in tablets and the results were statistically compared with those of the reference method by applying the Student's t-test and F-test. No interference was observed from the common excipients added to tablets. The accuracy and validity of the methods were further ascertained by performing recovery experiments via standard addition procedure.
{"title":"Cerimetric determination of simvastatin in pharmaceuticals based on redox and complex formation reactions","authors":"K. Basavaiah, O. Z. Devi","doi":"10.1590/S0100-46702008000200003","DOIUrl":"https://doi.org/10.1590/S0100-46702008000200003","url":null,"abstract":"Two sensitive spectrophotometric methods are described for the determination of simvastatin (SMT) in bulk drug and in tablets. The methods are based on the oxidation of SMT by a measured excess of cerium (IV) in acid medium followed by determination of unreacted oxidant by two different reaction schemes. In one procedure (method A), the residual cerium (IV) is reacted with a fixed concentration of fer- roin and the increase in absorbance is measured at 510 nm. The second approach (method B) involves the reduction of the unreacted cerium (IV) with a fixed quantity of iron (II), and the resulting iron (III) is com- plexed with thiocyanate and the absorbance measured at 470 nm. In both methods, the amount of cerium (IV) reacted corresponds to SMT concentration. The experimental conditions for both methods were opti- mized. In method A, the absorbance is found to increase linearly with SMT concentration (r = 0.9995) whereas in method B, the same decreased (r = -0.9943). The systems obey Beer's law for 0.6-7.5 and 0.5- 5.0 µg mL-1 for method A and method B, respectively. The calculated molar absorptivity values are 2.7 X 104 and 1.06 X 105 Lmol-1 cm-1, respectively; and the corresponding sandel sensitivity values are 0.0153 and 0.0039µg cm-2, respectively. The limit of detection (LOD) and quantification (LOQ) are reported for both methods. Intra-day and inter-day precision, and accuracy of the methods were established as per the current ICH guidelines. The methods were successfully applied to the determination of SMT in tablets and the results were statistically compared with those of the reference method by applying the Student's t-test and F-test. No interference was observed from the common excipients added to tablets. The accuracy and validity of the methods were further ascertained by performing recovery experiments via standard addition procedure.","PeriodicalId":35894,"journal":{"name":"Ecletica Quimica","volume":"33 1","pages":"21-28"},"PeriodicalIF":0.0,"publicationDate":"2018-02-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44833965","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2018-02-05DOI: 10.1590/S0100-46702008000200004
F. Khan, Afroza Khanam
Voltammetric technique was used to study the binary and ternary complexes of cadmium with L-amino acids and vitamin-C (L-ascorbic acid) at pH =7.30 ± 0.01, µ = 1.0M KNO3 at 25oC and 35oC. Cd (II) formed 1:1:1, 1:1:2 and 1:2:1 complexes with L-lysine, L-ornithine, L-threonine, L-serine, L-phenylglycine, L-phenylalanine, L-glutamic acid and L-aspartic acid used as primary ligands and L-ascorbic acid used as secondary ligand. The trend of stability constant of complexes was L-lysine < L-ornithine < L-threonine < L-serine < L-phenylglycine < L-phenylalanine < L-glutamic acid < L-aspartic acid which can be explained on the basis of size, basicity and steric hindrance of ligands. The values of stability constant (log β) varied from 2.23 to11.33 confirm that these drugs i.e. L-amino acids or in combination with L-ascorbic acid or their complexes could be used against Cd (II) toxicity. The study has been carried out at 35oC also to determine the thermodynamic parameters such as enthalpy change (ΔH), Free energy change (ΔG) and entropy change (ΔS) respectively.
采用伏安法研究了在pH =7.30±0.01，µ= 1.0M KNO3, 25℃和35℃条件下镉与l -氨基酸和维生素c (l -抗坏血酸)的二元和三元配合物。Cd (II)以l -赖氨酸、l -鸟氨酸、l -苏氨酸、l -丝氨酸、l -苯甘氨酸、l -苯丙氨酸、l -谷氨酸和l -天冬氨酸为一级配体，l -抗坏血酸为二级配体，形成1:1:1、1:1:2和1:2:1的配合物。配合物稳定性常数的变化趋势为l -赖氨酸< l -鸟氨酸< l -苏氨酸< l -丝氨酸< l -苯甘氨酸< l -苯丙氨酸< l -谷氨酸< l -天冬氨酸，这与配体的大小、碱度和位阻有关。稳定性常数(log β)在2.23 ~ 11.33之间变化，证实l -氨基酸或与l -抗坏血酸或它们的配合物联合使用可用于抗Cd (II)毒性。在35℃下进行了研究，并分别确定了焓变(ΔH)、自由能变化(ΔG)和熵变(ΔS)等热力学参数。
{"title":"Study of complexes of cadmium with some L-amino acids and vitamin-C by voltammetric technique","authors":"F. Khan, Afroza Khanam","doi":"10.1590/S0100-46702008000200004","DOIUrl":"https://doi.org/10.1590/S0100-46702008000200004","url":null,"abstract":"Voltammetric technique was used to study the binary and ternary complexes of cadmium with L-amino acids and vitamin-C (L-ascorbic acid) at pH =7.30 ± 0.01, µ = 1.0M KNO3 at 25oC and 35oC. Cd (II) formed 1:1:1, 1:1:2 and 1:2:1 complexes with L-lysine, L-ornithine, L-threonine, L-serine, L-phenylglycine, L-phenylalanine, L-glutamic acid and L-aspartic acid used as primary ligands and L-ascorbic acid used as secondary ligand. The trend of stability constant of complexes was L-lysine < L-ornithine < L-threonine < L-serine < L-phenylglycine < L-phenylalanine < L-glutamic acid < L-aspartic acid which can be explained on the basis of size, basicity and steric hindrance of ligands. The values of stability constant (log β) varied from 2.23 to11.33 confirm that these drugs i.e. L-amino acids or in combination with L-ascorbic acid or their complexes could be used against Cd (II) toxicity. The study has been carried out at 35oC also to determine the thermodynamic parameters such as enthalpy change (ΔH), Free energy change (ΔG) and entropy change (ΔS) respectively.","PeriodicalId":35894,"journal":{"name":"Ecletica Quimica","volume":"33 1","pages":"29-36"},"PeriodicalIF":0.0,"publicationDate":"2018-02-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1590/S0100-46702008000200004","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47084058","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2018-02-01DOI: 10.1590/S0100-46702008000100005
A. R. Nascimento, Roberta Lourenço Ziolli, J. T. Ararun, Carolina de Souza Pires, T. B. Silva
This work deals with an optimization of TPH (Total Petroleum Hydrocarbon) analysis methodology for samples of contaminated sands, validating the infrared detection technique through the use of Infracal TOG/TPH equipment. Tests were validated using Marine Fuel 380 oil, density 0.987 g cm-3 and viscosity 5313 cP at 20 oC. This oil sample was kindly supplied by Petrobras Research Centre (CENPES), and is the same oil that leaked from a pipeline in REDUC Refinery on January 2000, contaminating several beaches in Guanabara Bay, including Anil and Maua. The validation results suggested that the methodology performance was adequate for this application. Amongst the metrological parameters obtained from this work, the detection limit, 4.06 mg L-1, was a plus; since it was far below to the concentration range obtained from this samples.
这项工作对污染沙样品的TPH（总石油碳氢化合物）分析方法进行了优化，通过使用红外TOG/TPH设备验证了红外检测技术。使用密度为0.987 g cm-3、粘度为5313 cP的船用燃料380油在20℃下对试验进行了验证。该石油样本由巴西国家石油公司研究中心（CENPES）提供，与2000年1月REDUCRefinery管道泄漏的石油相同，污染了Guanabara湾的几个海滩，包括Anil和Maua。验证结果表明，该方法的性能适合该应用。在从这项工作中获得的计量参数中，检测限为4.06 mg L-1，为正；因为它远低于从该样品获得的浓度范围。
{"title":"Avaliação do desempenho analítico do método de determinação de TPH (Total Petroleum Hydrocarbon) por detecção no infravermelho","authors":"A. R. Nascimento, Roberta Lourenço Ziolli, J. T. Ararun, Carolina de Souza Pires, T. B. Silva","doi":"10.1590/S0100-46702008000100005","DOIUrl":"https://doi.org/10.1590/S0100-46702008000100005","url":null,"abstract":"This work deals with an optimization of TPH (Total Petroleum Hydrocarbon) analysis methodology for samples of contaminated sands, validating the infrared detection technique through the use of Infracal TOG/TPH equipment. Tests were validated using Marine Fuel 380 oil, density 0.987 g cm-3 and viscosity 5313 cP at 20 oC. This oil sample was kindly supplied by Petrobras Research Centre (CENPES), and is the same oil that leaked from a pipeline in REDUC Refinery on January 2000, contaminating several beaches in Guanabara Bay, including Anil and Maua. The validation results suggested that the methodology performance was adequate for this application. Amongst the metrological parameters obtained from this work, the detection limit, 4.06 mg L-1, was a plus; since it was far below to the concentration range obtained from this samples.","PeriodicalId":35894,"journal":{"name":"Ecletica Quimica","volume":"33 1","pages":"35-42"},"PeriodicalIF":0.0,"publicationDate":"2018-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1590/S0100-46702008000100005","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45909084","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2018-02-01DOI: 10.1590/S0100-46702008000100002
Zhen‐Xing Tang, Lu-E. Shi
MgO is an important inorganic material, which can be used in many aspects, such as cata- lyst, toxic-waste remediation agent, adsorbent, and others. In order to make use of MgO, nano-MgO was prepared by ultrasonic method using Mg (CH3COO)2.2H2O as precursor, NaOH aqueous solution as precipitant in this paper. Effect factors on MgO nano-particle size were investigated. Characteristics of samples were measured by TGA, XRD, TEM, and others techniques. The results showed that the size of nano-MgO about 4 nm could be obtained under the following conditions (ultrasonic time 20 min, ultrasonic power 250 W, titration rate of NaOH 0.25 mL/min, NaOH concentration 0.48 mol/L, calcinations temperature 410 °C, calcination time 1.5 h, heating rate of calcination 5 °C/min). It was a very simple and effective method to prepare nano-MgO. Keyword: MgO; nano-particle size; ultrasonic method.
{"title":"Preparation of nano-MgO using ultrasonic method and its characteristics","authors":"Zhen‐Xing Tang, Lu-E. Shi","doi":"10.1590/S0100-46702008000100002","DOIUrl":"https://doi.org/10.1590/S0100-46702008000100002","url":null,"abstract":"MgO is an important inorganic material, which can be used in many aspects, such as cata- lyst, toxic-waste remediation agent, adsorbent, and others. In order to make use of MgO, nano-MgO was prepared by ultrasonic method using Mg (CH3COO)2.2H2O as precursor, NaOH aqueous solution as precipitant in this paper. Effect factors on MgO nano-particle size were investigated. Characteristics of samples were measured by TGA, XRD, TEM, and others techniques. The results showed that the size of nano-MgO about 4 nm could be obtained under the following conditions (ultrasonic time 20 min, ultrasonic power 250 W, titration rate of NaOH 0.25 mL/min, NaOH concentration 0.48 mol/L, calcinations temperature 410 °C, calcination time 1.5 h, heating rate of calcination 5 °C/min). It was a very simple and effective method to prepare nano-MgO. Keyword: MgO; nano-particle size; ultrasonic method.","PeriodicalId":35894,"journal":{"name":"Ecletica Quimica","volume":"33 1","pages":"15-20"},"PeriodicalIF":0.0,"publicationDate":"2018-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1590/S0100-46702008000100002","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41830373","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2018-02-01DOI: 10.1590/S0100-46702008000100003
M. Ibrahim, H. Elhaes, A. Hameed, A. H. Essa
Semiempirical calculations at the level of PM3 of theory were carried out to study the struc- tural and electronic properties of C 80 and some of its doped derivatives with the elements of group III and V at the level of PM3 of theory. We have selected these elements to be substituted in the fullerene- C80 cage in order to show the effect of such structural change on the electronic properties of the mol- ecules studied. The theoretical IR spectra, some of physical and chemical properties of the molecules studied are obtained and discussed.
{"title":"Spectroscopic analysis of C80 doping with group III and group V elements using semiempirical PM3 molecular modelling technique","authors":"M. Ibrahim, H. Elhaes, A. Hameed, A. H. Essa","doi":"10.1590/S0100-46702008000100003","DOIUrl":"https://doi.org/10.1590/S0100-46702008000100003","url":null,"abstract":"Semiempirical calculations at the level of PM3 of theory were carried out to study the struc- tural and electronic properties of C 80 and some of its doped derivatives with the elements of group III and V at the level of PM3 of theory. We have selected these elements to be substituted in the fullerene- C80 cage in order to show the effect of such structural change on the electronic properties of the mol- ecules studied. The theoretical IR spectra, some of physical and chemical properties of the molecules studied are obtained and discussed.","PeriodicalId":35894,"journal":{"name":"Ecletica Quimica","volume":"33 1","pages":"21-27"},"PeriodicalIF":0.0,"publicationDate":"2018-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1590/S0100-46702008000100003","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48990154","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2018-02-01DOI: 10.1590/S0100-46702008000100001
W. Ferenc, M. Bernat, J. Sarzyński, B. Paszkowska
The complexes of 4-chlorophenoxyacetates of Mn(II), Co(II), Ni(II) and Cu(II) have been synthesized as polycrystalline solids, and characterized by elemental analysis, spectroscopy, magnetic studies and also by X-ray diffraction and thermogravimetric measurements. The analysed complexes have the following colours: pink for Co(II), green for Ni(II), blue for Cu(II) and a pale pink for Mn(II) compounds. The carboxylate group binds as monodentate and bidentate ligands. On heating to 1173K in air the complexes decompose in several steps. At first, they dehydrate in one step to anhydrous salts, that next decompose to the oxides of respective metals. Their magnetic moments were determined in the range of 76-303K. The results reveal them to be high-spin complexes of weak ligand fields.
{"title":"The physico-chemical properties of 4-chlorophenoxyacetates of Mn(II), Co(II), Ni(II) and Cu(II)","authors":"W. Ferenc, M. Bernat, J. Sarzyński, B. Paszkowska","doi":"10.1590/S0100-46702008000100001","DOIUrl":"https://doi.org/10.1590/S0100-46702008000100001","url":null,"abstract":"The complexes of 4-chlorophenoxyacetates of Mn(II), Co(II), Ni(II) and Cu(II) have been synthesized as polycrystalline solids, and characterized by elemental analysis, spectroscopy, magnetic studies and also by X-ray diffraction and thermogravimetric measurements. The analysed complexes have the following colours: pink for Co(II), green for Ni(II), blue for Cu(II) and a pale pink for Mn(II) compounds. The carboxylate group binds as monodentate and bidentate ligands. On heating to 1173K in air the complexes decompose in several steps. At first, they dehydrate in one step to anhydrous salts, that next decompose to the oxides of respective metals. Their magnetic moments were determined in the range of 76-303K. The results reveal them to be high-spin complexes of weak ligand fields.","PeriodicalId":35894,"journal":{"name":"Ecletica Quimica","volume":"33 1","pages":"7-14"},"PeriodicalIF":0.0,"publicationDate":"2018-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1590/S0100-46702008000100001","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46841301","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2018-02-01DOI: 10.1590/S0100-46702008000100004
M. S. Parihar, F. Khan
Stability constant (log `) and thermodynamic parameters of Cd 2+ complexes with sulfon- amide and cephapirin were determined by Polarographic technique at pH = 7.30 ± 0.01 and µ = 1.0 M KNO 3 at 250°C. The sulfonamides were sulfadiazine, sulfisoxazole, sulfamethaxazole, sulfamet- hazine, sulfathiazole, sulfacetamide and sulfanilamide used as primary ligands and cephapirin as sec- ondary ligand. Cd 2+ formed 1:1:1, 1:2:1 and 1:1:2 complexes. The nature of electrode processes were reversible and diffusion controlled. The stability constants and thermodynamic parameters (® G,® H and® S) were determined. The formation of the metal complexes has been found to be spontaneous, exothermic in nature, and entropically unfavourable at higher temperature. Keyword: polarography; stability constant; sulfonamide; cephapirin; thermodynamics.
在pH = 7.30±0.01，µ= 1.0 M kno3, 250℃条件下，用极谱法测定了cd2 +与磺胺和头孢匹林配合物的稳定常数(log’)和热力学参数。以磺胺嘧啶、磺胺恶唑、磺胺甲恶唑、磺胺-亚胺、磺胺噻唑、磺胺乙酰胺和磺胺为一级配体，以头孢匹林为二级配体。cd2 +形成1:1:1,1:2:1和1:1:2的配合物。电极过程的性质是可逆的和扩散控制的。测定了稳定性常数和热力学参数(®G、®H和®S)。金属配合物的形成是自发的，本质上是放热的，在较高的温度下熵是不利的。关键字:极谱法;稳定常数;磺胺类药;cephapirin;热力学。
{"title":"Stability constants and thermodynamic parameters of cadmium complexes with sulfonamides and cephapirin","authors":"M. S. Parihar, F. Khan","doi":"10.1590/S0100-46702008000100004","DOIUrl":"https://doi.org/10.1590/S0100-46702008000100004","url":null,"abstract":"Stability constant (log `) and thermodynamic parameters of Cd 2+ complexes with sulfon- amide and cephapirin were determined by Polarographic technique at pH = 7.30 ± 0.01 and µ = 1.0 M KNO 3 at 250°C. The sulfonamides were sulfadiazine, sulfisoxazole, sulfamethaxazole, sulfamet- hazine, sulfathiazole, sulfacetamide and sulfanilamide used as primary ligands and cephapirin as sec- ondary ligand. Cd 2+ formed 1:1:1, 1:2:1 and 1:1:2 complexes. The nature of electrode processes were reversible and diffusion controlled. The stability constants and thermodynamic parameters (® G,® H and® S) were determined. The formation of the metal complexes has been found to be spontaneous, exothermic in nature, and entropically unfavourable at higher temperature. Keyword: polarography; stability constant; sulfonamide; cephapirin; thermodynamics.","PeriodicalId":35894,"journal":{"name":"Ecletica Quimica","volume":"33 1","pages":"29-34"},"PeriodicalIF":0.0,"publicationDate":"2018-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48541146","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2018-02-01DOI: 10.1590/S0100-46702008000100009
Ricardo Alexandre Hakime Silva, A. G. Magdalena, T. Carvalho
IntroducaoAs ligas Cu-Al apresentam boas pro-priedades mecânicas e dependendo da concen-tracao de aluminio uma boa estabilidade quimica.De acordo com o diagrama de equilibrio para osistema Cu-Al [1,2], a solubilidade do Al nocobre e completa ate em torno de 8,5% em massa,o que corresponde a regiao de existencia da fase?. As ligas com composicao nesta regiao sao bas-tante ducteis e apresentam estrutura semelhante ado cobre puro. Estas ligas nao sao susceptiveis amodificacao em suas propriedades atraves detratamentos termicos. A adicao de prata altera olimite de estabilidade de algumas fases presentesnas ligas do sistema Cu-Al [2-4], a dureza dasligas [5], sua resistividade eletrica [6] e a cineticade precipitacao [7]. Neste trabalho a reacao deprecipitacao de Ag na liga Cu-8%Al foi estudadausando medidas de variacao da microdureza coma temperatura e o tempo, difratometria de raios X(XRD), calorimetria exploratoria diferencial(DSC), microscopia eletronica de varredura(MEV) para discutir o mecanismo de formacaodos precipitados de Ag na liga Cu-8%Al-6%Ag.Material e metodosA liga Cu-8%Al-6%Ag foi preparada emum forno de inducao INDUCTOTHERM sobatmosfera de argonio, usando material de partidacom pureza em torno de 99,95% e cadinho degrafite. A analise quimica de amostras da liga indi-cou uma concentracao resultante bastante proximada nominal. A partir do tarugo obtido foram corta-dos discos com cerca de 2,0 mm de espessura, queforam laminados ate a deformacao de 50%, para seobter pequenas placas quadradas, com cerca de 20mm de lado e 1,0 mm de espessura. Essas amostrasforam inicialmente submetidas a um recozimentoprolongado durante 120 horas a 850 °C, para homo-geneizacao. Em seguida foram feitos tratamentostermicos nas amostras recozidas e submetidas atempera em agua gelada a partir de 850°C. Os trata-mentos termicos foram realizados em um fornoEDG 3P com controlador de temperatura. As medi-das de variacao da microdureza com a temperaturae o tempo foram efetuadas utilizando-se um micro-durimetro digital BURHLER MICROMET 2003.As curvas de DSC foram obtidas em um aparelhoDSC 2910 da TAInstruments com razao de aqueci-
{"title":"Reação de precipitação de Ag na liga Cu-8%Al-6%Ag","authors":"Ricardo Alexandre Hakime Silva, A. G. Magdalena, T. Carvalho","doi":"10.1590/S0100-46702008000100009","DOIUrl":"https://doi.org/10.1590/S0100-46702008000100009","url":null,"abstract":"IntroducaoAs ligas Cu-Al apresentam boas pro-priedades mecânicas e dependendo da concen-tracao de aluminio uma boa estabilidade quimica.De acordo com o diagrama de equilibrio para osistema Cu-Al [1,2], a solubilidade do Al nocobre e completa ate em torno de 8,5% em massa,o que corresponde a regiao de existencia da fase?. As ligas com composicao nesta regiao sao bas-tante ducteis e apresentam estrutura semelhante ado cobre puro. Estas ligas nao sao susceptiveis amodificacao em suas propriedades atraves detratamentos termicos. A adicao de prata altera olimite de estabilidade de algumas fases presentesnas ligas do sistema Cu-Al [2-4], a dureza dasligas [5], sua resistividade eletrica [6] e a cineticade precipitacao [7]. Neste trabalho a reacao deprecipitacao de Ag na liga Cu-8%Al foi estudadausando medidas de variacao da microdureza coma temperatura e o tempo, difratometria de raios X(XRD), calorimetria exploratoria diferencial(DSC), microscopia eletronica de varredura(MEV) para discutir o mecanismo de formacaodos precipitados de Ag na liga Cu-8%Al-6%Ag.Material e metodosA liga Cu-8%Al-6%Ag foi preparada emum forno de inducao INDUCTOTHERM sobatmosfera de argonio, usando material de partidacom pureza em torno de 99,95% e cadinho degrafite. A analise quimica de amostras da liga indi-cou uma concentracao resultante bastante proximada nominal. A partir do tarugo obtido foram corta-dos discos com cerca de 2,0 mm de espessura, queforam laminados ate a deformacao de 50%, para seobter pequenas placas quadradas, com cerca de 20mm de lado e 1,0 mm de espessura. Essas amostrasforam inicialmente submetidas a um recozimentoprolongado durante 120 horas a 850 °C, para homo-geneizacao. Em seguida foram feitos tratamentostermicos nas amostras recozidas e submetidas atempera em agua gelada a partir de 850°C. Os trata-mentos termicos foram realizados em um fornoEDG 3P com controlador de temperatura. As medi-das de variacao da microdureza com a temperaturae o tempo foram efetuadas utilizando-se um micro-durimetro digital BURHLER MICROMET 2003.As curvas de DSC foram obtidas em um aparelhoDSC 2910 da TAInstruments com razao de aqueci-","PeriodicalId":35894,"journal":{"name":"Ecletica Quimica","volume":"33 1","pages":"63-70"},"PeriodicalIF":0.0,"publicationDate":"2018-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46277927","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2018-02-01DOI: 10.1590/S0100-46702008000100007
V. R. A. Filho, V. P. Franzini, J. A. Neto
National Health Surveillance Agency (ANVISA) established in the decree number 54 max- imum allowed levels for Ni and Pb in mineral and natural waters at 20 µg L -1 and 10 µg L -1 , respec- tively. For screening analysis purposes, the high-resolution continuum source flame atomic absorption spectrometry technique (HR-CS FAAS) was evaluated for the fast-sequential determination of nickel and lead in mineral waters.Two atomic lines for Ni (232.003 nm - main and 341.477 nm - secondary) and Pb (217.0005 nm - main and 283.306 nm - secondary) at different wavelength integrated absorbance (number of pixels) were evaluated. Sensitivity enhanced with the increase of the number of pixels and with the summation of the atomic lines absorbances. The main figures of merit associat- ed to the HR-CS FAAS technique were compared with that obtained by line-source flame atomic absorption spectrometry (LS FAAS). Water samples were pre-concentrated about 5-fold by evapora- tion before analysis. Recoveries of Pb significantly varied with increased wavelength integrated absorbance. Better recoveries (92-93%) were observed for higher number of pixels at the main line or summating the atomic lines (90-92%). This influence was irrelevant for Ni, and recoveries in the 92- 104% range were obtained in all situations.
{"title":"Exploring potentialities of the HR-CS FAAS technique in the determination of Ni and Pb in mineral waters","authors":"V. R. A. Filho, V. P. Franzini, J. A. Neto","doi":"10.1590/S0100-46702008000100007","DOIUrl":"https://doi.org/10.1590/S0100-46702008000100007","url":null,"abstract":"National Health Surveillance Agency (ANVISA) established in the decree number 54 max- imum allowed levels for Ni and Pb in mineral and natural waters at 20 µg L -1 and 10 µg L -1 , respec- tively. For screening analysis purposes, the high-resolution continuum source flame atomic absorption spectrometry technique (HR-CS FAAS) was evaluated for the fast-sequential determination of nickel and lead in mineral waters.Two atomic lines for Ni (232.003 nm - main and 341.477 nm - secondary) and Pb (217.0005 nm - main and 283.306 nm - secondary) at different wavelength integrated absorbance (number of pixels) were evaluated. Sensitivity enhanced with the increase of the number of pixels and with the summation of the atomic lines absorbances. The main figures of merit associat- ed to the HR-CS FAAS technique were compared with that obtained by line-source flame atomic absorption spectrometry (LS FAAS). Water samples were pre-concentrated about 5-fold by evapora- tion before analysis. Recoveries of Pb significantly varied with increased wavelength integrated absorbance. Better recoveries (92-93%) were observed for higher number of pixels at the main line or summating the atomic lines (90-92%). This influence was irrelevant for Ni, and recoveries in the 92- 104% range were obtained in all situations.","PeriodicalId":35894,"journal":{"name":"Ecletica Quimica","volume":"33 1","pages":"49-56"},"PeriodicalIF":0.0,"publicationDate":"2018-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1590/S0100-46702008000100007","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44114372","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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