Cobalt hexacyanoferrate electrodeposited on electrode with the assistance of laponite: The enhanced electrochemical sensing of captopril

EDTA derived graphene supported porous cobalt hexacyanoferrate nanospheres as a highly electroactive nanocomposite for hydrogen peroxide sensing

Developed a highly electroactive graphene and porous cobalt hexacyanoferrate nanosphere (Gr/P-CoHCF-NSPs) composite for H2O2 sensing by using EDTA chelation strategy.

Recent Progress in the Analysis of Captopril Using Electrochemical Methods: A Review

Background:

Captopril is the synthetic dipeptide used as an angiotensin converting enzyme inhibitor. Captopril is used to treat hypertension as well as for the treatment of moderate heart failure. Analytical instrumentation and methodology plays an important role in pharmaceutical analysis.

Methods:

This review presents some important applications of electrochemical modes used for the analysis of captopril. So far captopril has been analyzed by using different bare and modified working electrodes with a variety of modifiers from organic and inorganic materials to various types of nano particles/materials.

Results:

This paper presents some of the methods which have been published in the last few years i.e. from 2003 to 2016. This review highlights the role of the analytical instrumentation, particularly electrochemical methods in assessing captopril using various working electrodes.

Conclusion:

A large number of studies on voltammetry noted by means of various bare and modified electrodes. Among all of the published voltammetric methods, DPV, SWV, CV and miscellaneous modes were trendy techniques used to analyze captopril in pharmaceutical formulations as well as biological samples. Electrodes modified with nanomaterials are promising sensing tools as this showed high sensitivity, good accuracy with precision as well as selectivity. In comparison to chromatographic methods, the main advantages of electrochemical methods are its cheaper instrumentation, lower detection limit and minimal or no sample preparation.

Preparation, characterization and application in cobalt ion adsorption using nanoparticle films of hybrid copper-nickel hexacyanoferrate

Different mole ratios (n Cu : n Ni = x : y) of hybrid copper-nickel metal hexacyanoferrates (Cu x Ni y HCFs) were prepared to explore their morphologies, structure, electrochemical properties and the feasibility of electrochemical adsorption of cobalt ions. Cyclic voltammetry (CV), field emission scanning electron microscopy (FE-SEM), Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD) indicated that the x : y ratio of Cu x Ni y HCF nanoparticles can be easily controlled as designed using a wet chemical coprecipitation method. The crystallite size and formal potential of Cu x Ni y HCF films showed an insignificant change when 0 ≤ x : y < 0.3. Given the shape of the CV curves, this might be due to Cu2+ ions being inserted into the NiHCF framework as countercations to maintain the electrical neutrality of the structure. On the other hand, crystallite size depended linearly on the x : y ratio when x : y > 0.3. This is because Cu tended to replace Ni sites in the lattice structure at higher molar ratios of x : y. Cu x Ni y HCF films inherited good electrochemical reversibility from the CuHCFs, in view of the cyclic voltammograms; in particular, Cu1Ni2HCF exhibited long-term cycling stability and high surface coverage. The adsorption of Co2+ fitted the Langmuir isotherm model well, and the kinetic data can be well described by a pseudo-second order model, which may imply that Co2+ adsorption is controlled by chemical adsorption. The diffusion process was dominated by both intraparticle diffusion and surface diffusion.

The structure-property relationship in LAPONITE® materials: from Wigner glasses to strong self-healing hydrogels formed by non-covalent interactions

Rheology, small-angle X-ray scattering (SAXS), and dynamic light scattering (DLS) analysis, zeta potential measurement, scanning electron microscopy (SEM), and micro-FTIR and absorbance spectroscopy were used to enlighten the controversial literature about LAPONITE® materials. Our data suggest that pristine LAPONITE® in water does not form hydrogels induced by the so-called "house of cards" assembly, but rather forms Wigner glasses governed by repulsive forces. Ionic interactions between anisotropic LAPONITE® nanodiscs, sodium polyacrylate and inorganic salts afforded hydrogels that were transparent, self-standing, moldable, strong, and biocompatible with shear-thinning and self-healing behavior. An extensive study on the role of salts in the gelification process dictates a trend that relates the valence of cations with the viscoelastic properties of the bulk material (G' values follow the trend, monovalent < divalent < trivalent). These hydrogels present G' values up to 5.1 × 104 Pa, which are considered high values for non-covalent hydrogels. Hydrogels crosslinked with sodium phosphate salts are biocompatible, and might be valid candidates for injectable drug delivery systems due to their shear-thinning behavior with rapid self-healing after injection.

High-capacity and selective ammonium removal from water using sodium cobalt hexacyanoferrate

A new NH₄⁺ adsorbent with high capacity and selectivity, sodium cobalt(ii) hexacyanoferrate(ii) (NaCoHCF, Na_yCo(ii) [Fe²⁺(CN)₆]_x·zH₂O), was prepared. The adsorption performance was investigated by varying the mixing ratio of [Fe(CN)₆]⁴⁻ to Co²⁺ during synthesis, R_mix. The ammonia capacity was found to be proportional to R_mix, indicating that the NH₄⁺ capacity can be increased by increasing the Na⁺-ion content in NaCoHCF. To conduct a detailed study, we prepared homogeneous nanoparticles by flow synthesis using a micromixer with R_mix = 1.00. Even on the addition of a saline solution (NaCl) with an Na⁺-ion concentration of 9350 mg L⁻¹, the capacity was maintained: q_max = 4.28 mol kg⁻¹. Using Markham–Benton analysis, the selectivity factor, defined by the ratio of equilibrium constants for NH₄⁺ to that for Na⁺, was calculated to be α = 96.2, and 4.36 mol kg⁻¹ was found to be the maximum capacity. The high selectivity of NaCoHCF results in good NH₄⁺-adsorption performance, even from seawater. In comparison with other adsorbents under the same conditions and even for a NH₄Cl solution, NaCoHCF showed the highest capacity. Moreover, the coexisting Na⁺ caused no interference with the adsorption of ammonium by NaCoHCF, whereas the other adsorbents adsorbed ammonia only slightly from the saline solution. We also found that the pores for NH₄⁺ adsorption changed their sizes and shapes after adsorption.

High capacity and selectivity of NH₄ adsorption achieved by the crystal structure optimization.