Use of Doehlert design for optimizing the digestion of beans for multi-element determination by inductively coupled plasma optical emission spectrometry

Abstract

Neste trabalho a otimização de um procedimento rápido e de baixo custo para digestão ácida de feijão foi desenvolvida. Elementos essenciais (Ca, Cu, Fe, K, Mg, Mn, Ni, P, Zn) e não essenciais (Al, Ba, Sr) foram determinados por espectrometria de emissão óptica com plasma indutivamente acoplado (ICP OES). Foi utilizado planejamento fatorial de dois níveis fracionário com cinco fatores (volumes de HNO 3 e H 2 O 2 , tempo, temperatura do bloco e tamanho de partícula). O fator temperatura foi o parâmetro mais importante e o planejamento Doehlert foi aplicado para determinar as condições ótimas, que foram obtidas quando se utiliza 3,5 mL de HNO 3 concentrado e o tempo de 45 min. A exatidão foi demonstrada usando um material de referência certificado (folhas de espinafre NIST 1570a) e método oficial recomendado. Os resultados obtidos para todos os analitos foram concordantes com os valores certificados de acordo com o teste-t pareado para um nível de confiança de 95%. In this work, the optimization of a fast and inexpensive acid wet digestion procedure for beans was developed. Essential (Ca, Cu, Fe, K, Mg, Mn, Ni, P, Zn) and non-essential (Al, Ba, Sr) elements were determined in beans degestates by inductively coupled plasma optical emission spectrometry (ICP OES). Experimental designs for five factors (HNO 3 and H 2 O 2 volume, digestion time, block temperature and particle size) were used for optimization of the digestion procedure, adopting a factorial experiment with 2 5-1 design. The factor block temperature was found to be the most important parameter and Doehlert designs were applied in order to determine the optimum conditions. Decomposition conditions were attained using 3.5 mL of concentrated HNO 3 and lasts 45 min. The accuracy of the results was demonstrated using one certified reference material (spinach leaves NIST 1570a) and comparison with recommended official method. A paired t-test showed a good agreement for all analytes at 95% confidence values.

Chemometrics in Practical Applications

“…al., 2008). The aim was to optimize the recovery percentage of several elements with respect to the temperature and the volume of concentrated nitric acid from which we take only the recovery percentage of manganese (for details, see (Dos Santos et. al., 2008).…”

Sample Preparation for Determination of Bioaccessibility of Essential and Toxic Elements in Legumes

“…However, it is necessary to mention the possible presence of inorganic contaminants in plants, which, although generally inferior to foods of animal origin, should also be investigated, since it poses an imminent risk to health maintenance [18]. In recent work, concentrations of Pb in samples of carioca beans varied between 4.6 and 6.2 μg g −1 [19]. These concentrations are above the maximum tolerance limit (LMT) recommended by the Brazilian legislation for legumes in natura or industrialized (0.50 μg g −1 ) [20].…”