Anodic stripping voltammetric determination of silver ion at a carbon paste electrode modified with carbon nanotubes

Anthracene benzene conjugate (ABC): An asymmetric Schiff base for the selective detection of Ag+ ion using fluorimetry and its applications

Anthracene based chemosensor ABC has been synthesized and characterized through ¹H, ¹³C NMR, mass spectral studies. UV absorption and emission studies performed to identify the sensing behavior of chemosensor ABC. The probe ABC, originally bright fluorescent, selectively sense Ag⁺ ion by the quenching the fluorescence intensity through a "Switch On-off" process and quench the fluorescence due to the heavy atom effect interaction with the free chemosensor. The binding constant of the probe ABC with Ag⁺ was calculated as 5.4 × 10⁴ M^-1 and the limit of detection upto 1.4 nM level. The practical utilization of the probe ABC was demonstrated by applying to the real water and soil sample analysis, latent finger print, and the sensor as a fluorescent ink.

Elucidation of Selectivity for Silver Ion Based on Metal-Induced H-Type Aggregation of Fluorescent Receptor

In present work, a new substituted phthalonitrile derivative was prepared by the nucleophilic displacement reaction and then highly soluble zinc phthalocyanine (ZnPc) with four peripheral 1-hydroxyhexan-3-ylthio groups was synthesized by cyclotetramerization and characterized by FTIR, ¹H and ¹³C NMRs spectroscopies, fluorescence and UV-vis measurements. The optical property and quantum yield of ZnPc were elucidated in mixed solvent of ethanol/water with varying compositions. The pH-dependent fluorescence and absorbance spectra of ZnPc in the absence and presence of Ag⁺ ions were obtained to elucidate the optimum pH value that is convenient for stable complex formation in predetermined mixture. A comparative study for recognition of Ag⁺ ion has been carried out to evaluate the effect of the solution parameters on selective sensing ability of ZnPc as a fluorescent receptor. Interference effect was investigated by spectrofluorometric titration based on fluorescence quenching of ZnPc upon addition of Ag⁺ ion in the presence of foreign metal ions. Stepwise complexation/decomplexation cycles with Na₂S-titration by fluorescence quenching/enhancement were investigated to establish the reversible response rate and reusability of ZnPc toward Ag⁺ ions. Graphical Abstract Selective determination of silver ion based on H-type aggregation of zinc phthalocyanine.

Determination of Au(III) and Ag(I) in Carbonaceous Shales and Pyrites by Stripping Voltammetry

Techniques of stripping voltammetry (SV) determination of silver and gold in pyrites and carbonaceous matter are developed. The problem of quantitative transfer of the analytes into the solution is solved. For this purpose, the ore matrix of carbonaceous shales was decomposed by mineral acids in autoclaves at high pressures. The element to be determined from the sample matrix was separated by extraction. Ag(I) ions from the solutions were extracted in the form of a dithizonate complex in CCl4. Au(III) ions were extracted by diethyl ether. The extracts were decomposed thermally. The dry residue was dissolved in the background electrolyte, and the element was determined by the SV method. The graphite electrode (GE) impregnated with polyethylene was used as a working electrode in the SV determination of silver. The SV determination of gold was carried out using a GE modified by bismuth. The limits of detection (LOD) of Ag(I) and Au(III) contents were equal to 0.016 mg L−1 and 0.0086 mg L−1, respectively. The results of SV determination of gold and silver in standard samples, pyrites, and carbonaceous shales were presented. The silver content in the pyrite was 13.6 g t−1, and in carbon shale it was 0.34 g t−1. The concentration of gold in the pyrite of the Kirovsko–Kryklinskaya ore zone was 1.15 g t−1, while in carbonaceous shales it was 2.66 g t−1. The obtained data were consistent with the data of atomic emission spectroscopy (AES) and inductively-coupled plasma mass spectrometry (ICP–MS). The error of determination of elements by stripping voltammetry was calculated as ranging from 10 to 6 g t−1 (less than 12%) in pyrite and carbonaceous material when determining the silver content, and from 1 to 3 g t−1 (less than 22%) when determining the gold content in pyrite and carbonaceous matter.

Design of dual working electrodes for concentration process in metalloimmunoassay

Electrochemical immunosensing, particularly through a metalloimmunoassay, is a promising approach for development of point-of-care (POC) diagnostics devices. This study investigated the structure of dual working electrodes (W1 and W2), used in a silver nanoparticles-labeled sandwich-type immunoassay and silver concentration process, paying special attention to the position of W1 relative to W2. The new structures of the dual working electrodes were fabricated for efficient silver concentration and evaluated experimentally, which showed that the duration of prereduction before current measurement decreased from 480 s to 300 s by transforming the position of W1 from 1 line to 2 lines or 6 parts. The experimental results were also compared with numerical simulations based on three-dimensional diffusion, and the prereduction step almost followed the three-dimensional diffusion equation. Using numerical simulations, the ideal structures of dual working electrodes were designed based on relationships between the structures and duration of prereduction or the LOD. In the case of 36 lines at an area ratio of W1 to W1 + W2 of 1 to 10, the prereduction duration decreased to 96 s. The dual working electrodes designed in this study promise to shorten the total analysis time and lower the LOD for POC diagnostics.

Silver ion imprinted polymer nanobeads based on a aza-thioether crown containing a 1,10-phenanthroline subunit for solid phase extraction and for voltammetric and potentiometric silver sensors

A new nano-sized silver(I) ion-imprinted polymer (IIP) was prepared via precipitation copolymerization using ethyleneglycol dimethacrylate, as a cross-linking agent in the presence of Ag(+) and an aza-thioether crown containing a 1,10-phenanthroline subunit as a highly selective complexing agent. The imprint silver(I) ion was removed from the polymeric matrix using a 1.0M HNO3 solution. The resulting powder material was characterized using IR spectroscopy and scanning electron microscopy. The SEM micrographs showed colloidal nanoparticles of about 52 nm and 75 nm in diameter and slightly irregular in shape for leached and unleached IIPs, respectively. The optimal pH for quantitative enrichment was 6.0 and maximum sorbent capacity of the prepared IIP for Ag(+) was 18.08 μmol g(-1). The relative standard deviation and limit of detection (LOD=3Sb/m) for flame atomic absorption spectrometric determination of silver(I) ion, after its selective extraction by the prepared IIP nanobeads, were evaluated as 2.42% and 2.2×10(-8) M, respectively. The new Ag(+)-IIP was also applied as a suitable sensing element to the preparation of highly selective and sensitive voltammetric and potentiometric sensors for ultra trace detection of silver(I) ion in water samples, with limits of detection of 9.0×10(-10) and 1.2×10(-9) M, respectively.

Modified carbon nanotube paste electrode for voltammetric determination of carbidopa, folic Acid, and tryptophan

A simple and convenient method is described for voltammetric determination of carbidopa (CD), based on its electrochemical oxidation at a modified multiwall carbon nanotube paste electrode. Under optimized conditions, the proposed method exhibited acceptable analytical performances in terms of linearity (over the concentration range from 0.1 to 700.0 μM), detection limit (65.0 nM), and reproducibility (RSD = 2.5%) for a solution containing CD. Also, square wave voltammetry (SWV) was used for simultaneous determination of CD, folic acid (FA), and tryptophan (TRP) at the modified electrode. To further validate its possible application, the method was used for the quantification of CD, FA, and TRP in urine samples.