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Made available in DSpace on 2022-04-28T22:37:19Z (GMT). No. of bitstreams: 0 Previous issue date: 2011-03-01 The usefulness of the side pixel registration approach and molecular absorption was investigated for the determination of phosphorus (P) and potassium (K) in liquid fertilizers by highresolution continuum source flame atomic absorption spectrometry. The phosphorus oxide (PO) lines at 246.400 nm, 247.620 nm, 247.780 nm, 324.616 nm, and 327.040 nm were evaluated. The influence of side pixel registration to extend the linear working range was also investigated by measuring at wings (404.402 nm, 404.406 nm, 404.410 nm, 404.418 nm, 404.422 nm and 404.426 nm) of the secondary line for K at 404.414 nm. For the lines 327.040 nm and 404.422 nm, analytical curves in the 100-5000 mg L.1 P and 50-1000 mg L-1 K ranges were obtained with linear correlations better than 0.999 and 0.995, respectively. The proposed method was applied to six liquid fertilizer samples. The found concentrations for K and P were in agreement with those obtained by inductively coupled plasma optical emission spectrometry (ICP-OES), spectrophotometry, and flame atomic emission spectrometry at the 95% confidence level. UNESP University Estadual Paulista Analytical Chemistry Department, Rua Prof. Francisco Degni, s/n, 14801-970, Araraquara - SP UNESP University Estadual Paulista Analytical Chemistry Department, Rua Prof. Francisco Degni, s/n, 14801-970, Araraquara - SP

A sensor based on graphite electrode modified with palladium-platinum-palladium film is proposed for phosphite determination by flow-injection amperometry. The modified electrode was prepared by a sequential cathodic deposition of Pd, Pt and Pd on a graphite electrode from 0.5% m/v PdCl2+28% m/v NH4OH and 2% m/v H2PtCl6+10% v/v H2SO4 solutions. After suitable conditioning, the electrode showed catalytic activity for phosphite oxidation when 0.15 V was applied. The proposed system handles approximately 50 samples per hour (0.01–0.05 mol L−1 Na2HPO3; R2=0.9997), consuming ca. 70 μL of sample per determination. The limit of detection and amperometric sensibility were 5×10−4 mol L−1 and 1.5 mA L mol−1, respectively. The proposed method was applied to analysis of fertilizer samples without pre-treatment. Results are in agreement with those obtained by spectrophotometry and titrimetry at 95% confidence level and good recoveries (96–109%) of spiked samples were found. Relative standard deviation (n= 12) of a 0.01 mol L−1 Na2HPO3 sample was 2%. The useful lifetime of modified electrode was around 220 determinations. For routine purposes it means that this electrode can be continuously used for 5 hours.

Submitted by Guilherme Lemeszenski (guilherme@nead.unesp.br) on 2013-08-22T18:49:20Z No. of bitstreams: 1 S0100-46702008000100007.pdf: 275088 bytes, checksum: 6fb8b86692a8058fd3922577bf026744 (MD5) Made available in DSpace on 2013-08-22T18:49:20Z (GMT). No. of bitstreams: 1 S0100-46702008000100007.pdf: 275088 bytes, checksum: 6fb8b86692a8058fd3922577bf026744 (MD5) Previous issue date: 2008-01-01 Made available in DSpace on 2013-09-30T19:09:36Z (GMT). No. of bitstreams: 2 S0100-46702008000100007.pdf: 275088 bytes, checksum: 6fb8b86692a8058fd3922577bf026744 (MD5) S0100-46702008000100007.pdf.txt: 16840 bytes, checksum: 71bbeddf59cacae8236590585a5a6fba (MD5) Previous issue date: 2008-01-01 Submitted by Vitor Silverio Rodrigues (vitorsrodrigues@reitoria.unesp.br) on 2014-05-20T14:19:52Z No. of bitstreams: 2 S0100-46702008000100007.pdf: 275088 bytes, checksum: 6fb8b86692a8058fd3922577bf026744 (MD5) S0100-46702008000100007.pdf.txt: 16840 bytes, checksum: 71bbeddf59cacae8236590585a5a6fba (MD5) Made available in DSpace on 2014-05-20T14:19:52Z (GMT). No. of bitstreams: 2 S0100-46702008000100007.pdf: 275088 bytes, checksum: 6fb8b86692a8058fd3922577bf026744 (MD5) S0100-46702008000100007.pdf.txt: 16840 bytes, checksum: 71bbeddf59cacae8236590585a5a6fba (MD5) Previous issue date: 2008-01-01 Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) De acordo com a Resolução nº 54 da Agência Nacional de Vigilância Sanitária (ANVISA), os limites máximos permitidos para níquel e chumbo em água mineral natural e água natural são 20 µg L-1 e 10 µg L-1, respectivamente. O presente trabalho apresenta o potencial de uso da técnica de espectrometria de absorção atômica em chama com fonte contínua e de alta resolução (HR-CS FAAS) na determinação seqüencial rápida de níquel e chumbo para fins de análise classificatória de água mineral de acordo com a ANVISA. Duas linhas de absorção atômica foram empregadas para níquel (232,003 nm - principal e 341,477 nm - secundária) e chumbo (217,0005 nm - principal e 283,306 nm - secundária) e diferentes volumes de linha (número de pixels). em geral, a sensibilidade melhorou com o aumento do número de pixels e com a soma das absorbâncias das linhas atômicas estudadas. As principais figuras de mérito obtidas com a técnica HR-CS FAAS foram comparadas com a espectrometria de absorção atômica em chama com fonte de linhas (LS FAAS). As amostras de água mineral foram evaporadas antes de serem analisadas de modo a obter um fator de pré-concentração de aproximadamente cinco vezes. As recuperações de Pb variaram significativamente com o aumento do volume das linhas. As melhores recuperações foram observadas na linha principal (92-93%) e na somatória de ambas (90-92%). No caso do Ni, esta influência foi pouco relevante, sendo que a recuperação variou de 92-104%. National Health Surveillance Agency (ANVISA) established in the decree number 54 maximum allowed levels for Ni and Pb in mineral and natural waters at 20 µg L-1 and 10 µg L-1, respectively. 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 associated 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 evaporation 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. Universidade Estadual Paulista Instituto de Química Departamento de Química Analítica Universidade Estadual Paulista Instituto de Química Departamento de Química Analítica

Submitted by Guilherme Lemeszenski (guilherme@nead.unesp.br) on 2013-08-22T18:48:39Z No. of bitstreams: 1 S0100-40422007000200013.pdf: 120271 bytes, checksum: fa39c21a219b4c88666ae6e17159f5dd (MD5) Made available in DSpace on 2013-08-22T18:48:39Z (GMT). No. of bitstreams: 1 S0100-40422007000200013.pdf: 120271 bytes, checksum: fa39c21a219b4c88666ae6e17159f5dd (MD5) Previous issue date: 2007-04-01 Made available in DSpace on 2013-09-30T19:09:14Z (GMT). No. of bitstreams: 2 S0100-40422007000200013.pdf: 120271 bytes, checksum: fa39c21a219b4c88666ae6e17159f5dd (MD5) S0100-40422007000200013.pdf.txt: 20765 bytes, checksum: 92868e938c2f1abfbe341daaafa371e4 (MD5) Previous issue date: 2007-04-01 Submitted by Vitor Silverio Rodrigues (vitorsrodrigues@reitoria.unesp.br) on 2014-05-20T14:19:35Z No. of bitstreams: 2 S0100-40422007000200013.pdf: 120271 bytes, checksum: fa39c21a219b4c88666ae6e17159f5dd (MD5) S0100-40422007000200013.pdf.txt: 20765 bytes, checksum: 92868e938c2f1abfbe341daaafa371e4 (MD5) Made available in DSpace on 2014-05-20T14:19:35Z (GMT). No. of bitstreams: 2 S0100-40422007000200013.pdf: 120271 bytes, checksum: fa39c21a219b4c88666ae6e17159f5dd (MD5) S0100-40422007000200013.pdf.txt: 20765 bytes, checksum: 92868e938c2f1abfbe341daaafa371e4 (MD5) Previous issue date: 2007-04-01 Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) A new titrimetric method for the determination of phosphite in fertilizer samples, based on reaction of H3PO3 with standard iodine solution in neutral media, is proposed. Diluted samples containing ca. 0.4% m/v P2O5 are heated and titrated with 0.05 mol L-1 iodine standard until the solution becomes faint yellow. Back titration is also feasible: a slight excess of titrant is added followed by starch indicator and titration is completed taking as the end point the change in color from blue to colorless. The influence of chemical composition and pH of buffers, temperature and foreign species on waiting time and end-point detection were investigated. For the Na2HPO4/NaH2PO4 buffer (pH 6.8) at 70 °C, the titration time was 10 min, corresponding to about 127 mg iodine, 200 mg KI and 174 mg Na2HPO4 and 176 mg NaH2PO4 consumed per determination. Accuracy was checked for phosphite determination in seven fertilizer samples. Results obtained by the proposed procedure were in agreement with those obtained by spectrophotometry at 95% confidence level. The R.S.D. (n=10) for direct and back titration was 0.4% and 1.3% respectively. Universidade Estadual Paulista Instituto de Química Departamento de Química Analítica Universidade Estadual Paulista Instituto de Química Departamento de Química Analítica