Abstract
The performance of a carbon paste electrode (CPE) modified with SBA-15 nanostructured silica organofunctionalised with 2-benzothiazolethiol in the determination of Cd(II) ions in natural water is described, based in a DPASV procedure. The Cd(II) oxidation peak was observed around -0.85 V (vs. SCE) in phosphate buffer (pH 3.0). The best results were obtained under the following optimised conditions: 100 mV pulse amplitude, 2 min accumulation time, 10 mV s-1 scan rate in phosphate buffer pH 3.0. Using such parameters a linear dynamic range from 1.00 to 10.0 <FONT FACE=Symbol>´</FONT> 10-6 mol L-1 Cd(II) was observed with limit of detection 4.5 <FONT FACE=Symbol>´</FONT> 10-7 mol L-1. Cd(II) spiked in a natural water sample was determined with 96.4% mean recovery at µmol L-1 level. The results indicate that this electrode is sensitive for determination of Cd(II). Interference of some divalent cations were also evaluated.
Highlights
The discovery of micelle templated silicas like MCM41, MCM-48 and SBA-15 first reported in the early 1990 ́s has lead to a whole new class of materials with high thermal and mechanical stability.[1,2] The continuing development of mesoporous silica make the studies on silica-supported nanocomposites very active
Effect of scan rate and pulse amplitude The anodic peak currents for cadmium in Differential Pulse Anodic Stripping Voltammetry (DPASV) were evaluated as a function of scan rate between 5 and 50 mV s-1 and pulse amplitudes from 15 to 100 mV. For this purpose pre-concentration of Cd(II) from a 3.85 × 10-5 mol L-1 solution in 0.1 mol L-1 phosphate buffer pH 4.0 were performed for 10 s, potential interval –1.10 to –0.60 V and a carbon-paste composition of 15% (m/m) modified SBA-15 silica, 60% (m/m) graphite and 25% (m/m) mineral oil
When the accumulation process was carried out for 120 s at –1.10 V in a solution containing 3.85 × 10-5 mol L-1Cd(II), at the unmodified carbon paste electrode, the Cd(II) oxidation peak appears at –0.81 V, the SBA-15-Modified carbon paste electrodes (MCPE) exhibits an anodic peak at –0.82 V and the BTPSBA-MCPE the Cd(II) oxidation peak appears at –0.85 V, with higher intensity of the anodic current in comparison to that observed at another electrodes
Summary
The discovery of micelle templated silicas like MCM41, MCM-48 and SBA-15 first reported in the early 1990 ́s has lead to a whole new class of materials with high thermal and mechanical stability.[1,2] The continuing development of mesoporous silica make the studies on silica-supported nanocomposites very active. The use of organofunctionalised SBA-15 silica with 2- benzothiazolethiol in the preparation of carbon paste electrodes is described.
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