Direct determination of calcium in milk by atomic absorption spectrometry using flow-injection analysis
Carregando...
Data
2007-01-01
Autores
Petrovich, M. B. [UNESP]
Filho, V. R. A. [UNESP]
Gomes Neto, José Anchieta [UNESP]
Título da Revista
ISSN da Revista
Título de Volume
Editor
Editora Unesp
Resumo
Um sistema de injeção em fluxo envolvendo a adição de amostra e reagente por zonas coalescentes sincronizadas é proposto para a determinação de cálcio em leites por FAAS. Um planejamento fatorial com ponto central auxiliou na seleção dos principais parâmetros experimentais, sendo as condições ótimas estabelecidas em: solução de lantânio 2,5% (m/v), vazão do transportador 8 mL min-1, comprimento da bobina de reação 20 cm e volume de amostra injetado 250 ìL. Quatro procedimentos de preparo de amostra foram avaliados: diluição em ácido nítrico diluído e em água, decomposição em forno de microondas empregando ácidos concentrados e diluídos. O sistema de análise por injeção em fluxo desenvolvido foi aplicado na determinação de cálcio em onze amostras de leite comerciais e em dois materiais de referência padrão diluídos em água. Teores similares de cálcio foram encontrados comparando-se os resultados obtidos pelo método proposto (diluição em água) com aqueles obtidos nos digeridos. As concentrações de cálcio determinadas nos dois materiais de referência padrão foram concordantes a um nível de 95% de confiança com seus valores certificados. Recuperações entre 93% a 116% foram obtidas. O desvio padrão relativo (n = 12) foi < 5,4% e a freqüência analítica equivalente a 150 medidas por hora, correspondendo a um consumo de 250 ìL de amostra e 6,25 mg de lantânio por determinação.
A flow-injection system with sample and reagent addition by the synchronous merging zones approach for calcium determination in milk by flame AAS is proposed. Main parameters were optimized using a factorial design with central point. The optimum conditions were 2.5% (m/v) for La concentration, 8 mL min-1 for the carrier flow-rate, 20 cm for coiled reactor and 250 ìL for sample volume. Different sample preparation procedures were evaluated such as dilution in water or acid and microwave-assisted decomposition using concentrated or diluted acids. The optimized flow system was applied to determine Ca in eleven commercial milk samples and two standard reference materials diluted in water. Similar calcium levels were encountered comparing the results obtained by the proposed method (dilution in water) with those obtained using microwave-oven digestion. Results obtained in two standard reference materials were in agreement at 95% confidence level with those certified. Recoveries of spiked samples were in the 93% - 116% range. Relative standard deviation (n = 12) was < 5.4% and the sample throughput was 150 measurements per hour, corresponding to a consumption of 250 µL of sample and 6.25 mg La per determination.
A flow-injection system with sample and reagent addition by the synchronous merging zones approach for calcium determination in milk by flame AAS is proposed. Main parameters were optimized using a factorial design with central point. The optimum conditions were 2.5% (m/v) for La concentration, 8 mL min-1 for the carrier flow-rate, 20 cm for coiled reactor and 250 ìL for sample volume. Different sample preparation procedures were evaluated such as dilution in water or acid and microwave-assisted decomposition using concentrated or diluted acids. The optimized flow system was applied to determine Ca in eleven commercial milk samples and two standard reference materials diluted in water. Similar calcium levels were encountered comparing the results obtained by the proposed method (dilution in water) with those obtained using microwave-oven digestion. Results obtained in two standard reference materials were in agreement at 95% confidence level with those certified. Recoveries of spiked samples were in the 93% - 116% range. Relative standard deviation (n = 12) was < 5.4% and the sample throughput was 150 measurements per hour, corresponding to a consumption of 250 µL of sample and 6.25 mg La per determination.
Descrição
Palavras-chave
cálcio, leite, espectrometria de absorção atômica em chama, análise por injeção em fluxo, Calcium, milk, flame atomic absorption spectrometry, flow-injection analysis
Como citar
Eclética Química. Fundação Editora da Universidade Estadual Paulista Júlio de Mesquita Filho - UNESP, v. 32, n. 3, p. 25-30, 2007.