Adsorption of di-2-pyridylketone salicyloylhydrazone (DPKSH) on resin IRA 402: use in spectrophotometric determination of Cu(II) ions by FIA after separation and pre-concentration in solid phase / Adsorção da di-2-piridil cetona saliciloilhidrazona (DPKSH) em resina ira 402: aplicação na determinação espectrofotométrica de íons Cu(ii) por análise por injeção em fluxo (FIA) após separação e pré-concentração em fase sólida

AUTOR(ES)
FONTE

IBICT - Instituto Brasileiro de Informação em Ciência e Tecnologia

DATA DE PUBLICAÇÃO

25/09/2009

RESUMO

Pre-concentration in solid phase provides advantages such as simplicity, automation easiness, improvement in detection limits, possibilities to combine it with Flow Injection Analysis (FIA), integration of reaction and retention phases, lower consumption of reagents and increase in selectivity. This process requires the development and characterization of new solid phases. In this context, this paper is aimed to propose a study on the interaction of DPKSH (di-2-pyridylketone salicyloylhydrazone) with Amberlite IRA 402 ion-exchange resin. Studies carried out comprised the application of both kinetic (pseudo-first- and second-order conditions, and intraparticle diffusion) and adsorption isotherm models (Langmuir, Freundlich e Dubinin-Radushkevich) to experimental data gathered from pH 1.0, 4.7 and 12 values, in a 3% ethanol medium. For studies comprising kinetics, it was possible to notice that adsorption increases within contact time and a higher quantity of DPKSH is adsorbed in pH 12. It was also possible to notice an excellent adjustment of experimental data to pseudo-second-order kinetics. The study with adsorption isotherm models (in pH 4.7 and 12 values) demonstrated that the capacity for adsorption is 1.5-fold in pH 12 value. The Freundlich constant (KF) is approximately 30 times higher in pH 12 value, indicating that in the pH value DPKSH is more strongly linked to IRA 402. The n parameter higher 1, in both cases, indicates that the adsorption sites are energetically heterogeneous. Adsorption average energy (E) is an evidence that adsorption is physical for both cases. Desorption of DPKSH, previously retained in resin, in batch, was evaluated in water medium and solutions of HNO3 (0.01, 0.1 and 1) x 10-2 mol L-1. The highest percentage of desorption (26.3%) was seen in HNO3 1 x 10-2 mol L-1 medium. Thus, a flow spectrophotometric method was developed by using a mini-column filled with IRA 402 resin modified with DPKSH. To do so, the chemical parameters that are inherent to the flow system were tested. Based on the optimized method, the following were determined: detection limit estimated 5.22 μg L-1, 55 samples per hour and enrichment of 10.5. An analytical curve was obtained with a linear range of (0.31-1.26) x 10-6 mol L-1 of Cu(II) and molar absorptivity 2.48 x 105 L mol-1 cm-1. The minicolumn was used for at least 288 sampling cycles without significant variation in the analytical response. Finally, the method developed was applied in mineral water and ethanol fuel samples. It was then observed a good sequence by comparing the results reached, for the ethanol fuel, to the Flame Atomic Absorption Spectrometry (FAAS) method.

ASSUNTO(S)

cobre quimica analitica pré-concentração em fase sólida ira 402 dpksh análise por injeção em fluxo adsorção determinação espectrofotométrica álcool etílico combustível dpksh, ira 402, adsorption, solid phase pre-concentration, copper, ethanol fuel.

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