Screen-printed carbon electrode modified with poly-L-histidine applied to gold(III) determination

Abstract

O presente trabalho reporta o desenvolvimento de um novo método voltamétrico para análise de íons ouro(III) usando eletrodo de carbono impresso modificado com poli-L-histidina. O procedimento é baseado no acúmulo do complexo [AuCl 4 ] − , na superfície do eletrodo sob potencial de circuito aberto e tempo de acúmulo controlado. Parâmetros que influenciam na resposta, tais como: preparação do filme, pH, potencial de acúmulo e tempo de acúmulo, foram otimizados e curvas analíticas para os íons ouro foram construídas usando voltametria de varredura linear (LSV), pulso diferencial (DPV), e onda quadrada (SWV). Limites de detecção de 6,0 × 10 −6 mol L -1 , 1,7 × 10 −6 mol L -1 e 4,0 × 10 −6 mol L -1 foram obtidos para LSV, DPV e SWV, respectivamente. O método foi aplicado para a determinação de íons ouro em amostras de urina humana.A sensitive voltammetric method for trace measurements of gold(III) ions using a screen-printed carbon electrode modified with poly-L-histidine is described. The new procedure is based on the accumulation of the tetrachloroaurates complex at the electrode surface under an open circuit potential condition, followed by a cathodic stripping scan of potential. Parameters such as film preparation, pH, accumulation potential and deposition time have been optimized to obtain the best voltammetric response. Using optimal experimental conditions, analytical curves for gold ions were obtained using a linear sweep (LSV), differential pulse (DPV), and square wave voltammetry (SWV). Limits of detection of 6.0 × 10 −6 mol L -1 , 1.7 × 10 -6 mol L -1 and 4.0 × 10 -6 mol L -1 were estimated for the LSV, DPV and SWV, respectively. The method was successfully applied to the determination of gold ions in human urine samples.Keywords: screen-printed electrode, poly-L-histidine, gold ions, stripping voltammetry IntroductionVo l t a m m e t r i c s t r i p p i n g m e t h o d s i nvo l v i n g preconcentration steps are generally very sensitive when used for metal-ion determination. The combination of chemically modified electrodes with stripping methods can offer an excellent alternative for electrochemical analysis of metals at trace levels, 1 increasing not only the sensitivity but also selectivity of the analysis. A common approach to increasing selectivity is to attach host molecules, which selectively interact with specific guest molecules. The properties of polyaminoacids as host molecules for metal ions have been widely explored. [2][3][4][5] Despite poly-L-lysine having received particular attention as a simple, efficient and rapid supporting material for several applications, polyaminoacids such as poly-L-histidine (PH) have also been described in literature to catalyze the reduction/ oxidation of some biological compounds. [6][7][8][9][10] Poli-L-histidine ( Figure 1) is a synthetic poliaminoacid with an imidazole group (pK a = 6.0) 11 that can be strongly adsorbed onto the surface of silver metal by covalent bonding and it can be employed to facilitate both the Vol. 20, No. 1, 2009 reduction an...

Recent Advances in the Fabrication and Application of Screen-Printed Electrochemical (Bio)Sensors Based on Carbon Materials for Biomedical, Agri-Food and Environmental Analyses

“…The determination of Au in human urine [105] by cathodic stripping voltammetry in 0.1 M KCl (pH 1.0) following open circuit accumulation has been reported at a poly- l -histidine modified SPCE. The stripping voltammetric determination of the accumulated Au was investigated by linear sweep (LSV), differential pulse (DPV), and square wave voltammetry (SWV).…”

Immobilization of biomolecules on nanostructured films for biosensing

“…Electrochemical sensors are interesting due to the versatility in size, geometry, selection of components, method of detection and surface chosen according to the analyte properties. Several electrochemical techniques are used in signal transducing, including cyclic voltammetry (Mohadesi et al, 2008), pulse voltammetry (conventional and differential) (Bergamini et al, 2009;Dos Reis et al, 2008), square-wave voltammetry (Sartori et al, 2009;Bergamini et al, 2009), stripping voltammetry (Mohadesi et al, 2008) and potentiometry (Santini et al, 2009), and amperometry Karimi-Maleh et al, 2009;Dos Reis et al, 2008;Cervini and Cavalheiro, 2008). With electrochemical cells, measurements can be made of the electrode potential, cell current and cell resistance as a function of the analyte at the electrode surface or at the electrochemical interfaces.…”

Screen-printed Electrochemical Sensors and Biosensors for Monitoring Metal Pollutants

“…Concentrations of Au in human urine have been quantified at a poly-L-histidine modified SPCE [86]. It was found possible to complex Au, present as tetrachloroaurates, at the modified electrode surface under open circuit conditions.…”