Application of simplex optimization in the development of an automated online preconcentration system for manganese determination

Abstract

Um procedimento automatizado foi desenvolvido para determinação de quantidades traços de manganês provenientes de folhas de vegetais e águas de rio utilizando espectrometria de absorção atômica com chama (FAAS) após a pré-concentração em linha deste metal usando uma minicoluna de Amberlite XAD-4 modificada com 2-aminotiofenol. O sistema de pré-concentração baseia-se na extração em fase sólida do metal na minicoluna e eluição com ácido clorídrico 0,30 mol L -1 , seguido de sua determinação. As variáveis associadas ao desempenho do sistema de pré-concentração, tais como, pH, vazão de amostragem e concentração do eluente foram otimizadas utilizando um simplex básico como técnica multivariada. O método desenvolvido gerou um fator de enriquecimento de 14 vezes atingindo um limite de detecção (3 s B ) de 2,0 mg L -1 e precisão expressa como desvio padrão relativo de 2,2% (%RSD, n = 10; 30,00 mg L -1 ). O procedimento foi aplicado para a determinação de manganês em águas de rio coletada na área urbana de Jequié/Bahia. A exatidão do procedimento foi verificada usando-se materiais de referência certificados (folhas de macieira, NIST 1515 e folhas de espinafre, NIST 1570). O procedimento desenvolvido foi aplicado para a determinação de manganês em folhas de vegetais (cebolinha, espinafre, couve-flor e repolho).An automated procedure was developed to determine trace amounts of manganese from vegetal leaves and river waters using flame atomic absorption spectrometry (FAAS) after online preconcentration of this metal using an Amberlite XAD-4 minicolumn modified with 2-aminothiophenol. The preconcentration system is based on the solid-phase extraction of the metal into the minicolumn and elution with 0.30 mol L -1 hydrochloric acid, followed by its determination. Variables associated with the preconcentration system performance, such as pH, sampling flow rate and eluent concentration were optimized using a basic simplex as multivariate technique. The developed method provides an improvement factor of 14 along with limit of detection (3s B ) of 2.0 µg L -1 , and precision expressed as a 2.2% relative standard deviation (RSD%, n = 10, 30.0 µg L -1 ). The procedure was applied to determine manganese in river waters collected from urban area of Jequié/Bahia. The accuracy of the procedure was checked by analysis of two certified reference materials (apple leaves, NIST 1515 and spinach leaves, NIST 1570). The developed procedure has been applied for manganese determination in vegetal leaves (chive, spinach, cauliflower and cabbage).

Solid‐phase extraction of lead and copper on a polyhydroxybutyrate‐b‐polydimethyl siloxane (PHB‐b‐PDMS) block copolymer disc and flame atomic absorption spectrometric determination of them in water and food samples

“…pH is an important parameter on the solid‐phase extraction studies of metal ions for quantitative recoveries of them (Soylak et al ., , ; Ngeontae et al ., ; Elassar et al ., ; dos Santos et al ., ). The effect of pH on the extraction of copper(II) and lead(II) ions on PHB‐b‐PDMS disc was investigated in the pH range of 2.0–7.0.…”

Use of Arduino in the Development of a New and Fast Automated Online Preconcentration System Based on Double-Knotted Reactor for the Mn Determination in Tea Samples by Flame Atomic Absorption Spectrometry (F AAS)

“…38 This method was applied in the analysis of natural waters and certified reference materials such as rice flour. 38 Santos et al 39 have developed an automated flow injection system based on multicommutation principle aiming to the Mn determination in vegetal leaves (chive, spinach, cauliflower, cabbage and certified reference materials of apple and spinach leaves) and natural waters. Preconcentration was carried out using an Amberlite XAD-4 minicolumn modified with 2-aminothiophenol.…”

“…An improvement factor of 14 was found along with a limit of detection of 2.0 μg L -1 . 39 Tobiasz et al 40 have developed Vol. 31, No.…”

Simplex optimization: A tutorial approach and recent applications in analytical chemistry

“…In analytical chemistry, the simplex method has been applied in the optimization of instrumental parameters, such as in ICP OES, for example [19]. Santos et al [23] emphasized that the characteristics of the simplex method are quite proper for the optimization of automated analytical systems for the reason that the levels of the parameters can easily be varied. In addition, these kinds of systems can generate rapid responses-a demand of the simplex method.…”

“…Perhaps this is due to their disadvantages in relation to the modified algorithm, such as the need to determine the size of the original simplex risking not succeeding in the accurate location of the optimal point. Santos et al [23] developed an automated flow injection method to determine trace amounts of manganese from vegetal leaves and river waters using flame atomic absorption spectrometry (FAAS) after online preconcentration of this metal using an Amberlite XAD-4 minicolumn modified with 2-aminothiophenol. Variables associated with the preconcentration system performance, such as pH, sampling flow rate and eluent concentration were optimized using a basic simplex.…”