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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.

A flow injection spectrophotometric system is proposed for phosphite determination in fertilizers by the molybdenum blue method after the processing of each sample two times on-line without and with an oxidizing step. The flow system was designed to add sulfuric acid or permanganate solutions alternately into the system by simply displacing the injector-commutator from one resting position to another, allowing the determination of phosphate and total phosphate, respectively. The concentration of phosphite is obtained then by difference between the two measurents. The influence of flow rates, sample volume, and dimension of flow line connecting the injector-commutator to the main analytical channel was evaluated. The proposed method was applied to phosphite determination in commercial liquid fertilizers. Results obtained with the proposed FIA system were not statistically different from those obtained by titrimetry at the 95% confidence level. In addition, recoveries within 94 and 100% of spiked fertilizers were found. The relative standard deviation (n = 12) related to the phosphite-converted-phosphate peak alone was

Submitted by Guilherme Lemeszenski (guilherme@nead.unesp.br) on 2013-08-22T18:49:18Z No. of bitstreams: 1 S0100-46702007000100006.pdf: 100993 bytes, checksum: 61589360741e4147fbef4207ed39dd92 (MD5) Made available in DSpace on 2013-08-22T18:49:18Z (GMT). No. of bitstreams: 1 S0100-46702007000100006.pdf: 100993 bytes, checksum: 61589360741e4147fbef4207ed39dd92 (MD5) Previous issue date: 2007-01-01 Made available in DSpace on 2013-09-30T19:09:35Z (GMT). No. of bitstreams: 2 S0100-46702007000100006.pdf: 100993 bytes, checksum: 61589360741e4147fbef4207ed39dd92 (MD5) S0100-46702007000100006.pdf.txt: 23186 bytes, checksum: dbb035f44fa2e907940a2d8047b476b3 (MD5) Previous issue date: 2007-01-01 Submitted by Vitor Silverio Rodrigues (vitorsrodrigues@reitoria.unesp.br) on 2014-05-20T14:19:51Z No. of bitstreams: 2 S0100-46702007000100006.pdf: 100993 bytes, checksum: 61589360741e4147fbef4207ed39dd92 (MD5) S0100-46702007000100006.pdf.txt: 23186 bytes, checksum: dbb035f44fa2e907940a2d8047b476b3 (MD5) Made available in DSpace on 2014-05-20T14:19:51Z (GMT). No. of bitstreams: 2 S0100-46702007000100006.pdf: 100993 bytes, checksum: 61589360741e4147fbef4207ed39dd92 (MD5) S0100-46702007000100006.pdf.txt: 23186 bytes, checksum: dbb035f44fa2e907940a2d8047b476b3 (MD5) Previous issue date: 2007-01-01 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) Foi desenvolvido um método espectrofotométrico para a determinação de biureto em fertilizantes à base de uréia empregando Cu(OH)2(s) como reagente analítico. O método se baseia na reação entre biureto e Cu(OH)2(s) e formação do complexo Cu(C2N3O2H5)2 de coloração violeta cujo espectro apresenta máximo de absorção em 510 nm. Após o estabelecimento das melhores condições analíticas, o método proposto foi aplicado na determinação de biureto em duas amostras comerciais de uréia, uma para pecuária e outra para agricultura. Curvas analíticas construídas no intervalo de concentrações de 0,1 a 0,5% (m/v) em biureto produziram coeficientes de correlação típicos > 0,9990. Os resultados obtidos pelo método proposto foram concordantes ao nível de 95% de confiança com os obtidos por um método alternativo empregando espectrometria de absorção atômica. A exatidão do método foi também avaliada por meio de testes de adição e recuperação de padrão. Recuperações de 92 a 100% foram obtidas e o desvio padrão relativo calculado para 12 medidas sucessivas de uma amostra contendo 0,31% (m/v) foi 2%. A spectrophotometric method for the determination of biuret in urea-based fertilizers using Cu(OH)2(s) as analytical reagent is proposed. The principle of the method is the reaction between biuret and Cu(OH)2 (s) and formation of the purple complex Cu(C2N3O2H5)2 that presents absorption maximum at 510 nm. After establishment of analytical conditions, the method was applied to the determination of biuret in two commercial urea samples used as fertilizer and foodstuffs in agriculture. For analytical solutions prepared in the 0.1 - 0.5% (m/v) biuret, analytical curves with typical correlation coefficient of 0.9990 were always obtained. Results obtained by the proposed procedure were in agreement with those obtained by atomic absorption spectrometry at 95% confidence level. Accuracy was also evaluated by means of addition and recovery tests using spiked samples with biuret. Recoveries in the 92 - 100% were obtained and the calculated relative standard deviation of a sample containing 0.31% (m/v) biuret after twelve successive measurements was 2%. Universidade Estadual Paulista Instituto de Química Departamento de Química Analítica Universidade Estadual Paulista Instituto de Química Departamento de Química Analítica

Amperometric titration using two Pt microelectrodes for the determination of phosphite in fertilizers based on the oxidation of analyte by iodine is proposed. The influence of pH, buffer composition, temperature, and foreign species on the end point and titration time was investigated. For titrations carried out at 70 degrees C using the pH 6.8 phosphate buffer, samples containing ca. 0.4% (m/v) P(2)O(5) could be titrated with 0.050 mol L(-1) iodine titrant, and the end point determined by extrapolating the linear portions of the plot to their intersection coincided with the end point identified by spectrophotometry. Accuracy was checked for phosphite determination in five fertilizer samples. Results were in agreement at the 95% confidence level (paired t test) with spectrophotometry. Recoveries of phosphite added to fertilizer samples ranged from 97% to 102% regardless of the amount of spiking in several determinations. The relative standard deviation (n = 10) was 1.0% for a diluted sample containing 0.050 mol L(-1) Na(2)HPO(3).

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