Stepwise injection spectrophotometric determination of cysteine in biologically active supplements and fodders

Solid-Phase Spectrometric Determination of Organic Thiols Using a Nanocomposite Based on Silver Triangular Nanoplates and Polyurethane Foam

Adsorption of silver nanoparticles on polymers may affect the processes in which they participate, adjusting the analytical characteristics of methods for the quantitation of various substances. In the present study, a composite material based on silver triangular nanoplates (AgTNPs) and polyurethane foam was proposed for chemical analysis. The prospects of its application for the solid-phase/colorimetric determination of organic thiols were substantiated. It was found that aggregation of AgTNPs upon the action of thiols is manifested by a decrease in the AgTNPs' localized surface plasmon resonance band and its significant broadening. Spectral changes accompanying the process can be registered using household color-recording devices and even visually. Four thiols differing in their functional groups were tested. It was found that their limits of detection increase in the series cysteamine < 2-mercaptoethanol < cysteine = 3-mercaptopropionic acid and come to 50, 160, 500, and 500 nM, respectively. The applicability of the developed approach was demonstrated during the analysis of pharmaceuticals and food products.

A novel and cost effective isatin based Schiff base fluorophore: a highly efficient “turn-off” fluorescence sensor for the selective detection of cysteine in an aqueous medium

We designed an efficient, sensitive, and selective chemosensor for the fluorimetric determination of cysteine.

Self-cascade reaction catalyzed by CuO nanoparticle-based dual-functional enzyme mimics

It is desirable but challenging to assemble various biomimetic properties into a functional catalytic cascade system. In this work, cupric oxide nanoparticles were investigated as oxidase mimics for the aerobic oxidation of cysteine to cystine with the generation of hydrogen peroxide. Coupling this property with the peroxidase-like activity of CuO nanoparticles, we constructed a self-organized cascade reaction system based on a single-component nanozyme, which includes the oxidation of cysteine to yield cystine and hydrogen peroxide and the hydrogen peroxide-mediated oxidation of terephthalic acid to produce a fluorescence change. Based on this artificial enzymatic cascade reaction system, a fluorometric assay method with a low detection limit of 6.6nM was established for cysteine determination. This platform was then applied for the detection of cysteine in pharmaceutical products and human plasma, which yielded satisfactory results. Our investigations open up a new route and holds promise for the development and applications of multifunctional nanomaterials as enzyme mimics.

A Miniaturized Stepwise Injection Spectrophotometric Analyzer

A novel micro-stepwise injection analyzer (μSWIA) has been developed for the automation and miniaturization of spectrophotometric analysis. The main unit of this device is a mixing chamber (MC) connected to the atmosphere. This part of the μSWIA provides rapid and effective homogenization of the reaction mixture components and completion of the reaction by means of gas bubbling. The μSWIA contained a rectangular labyrinth channel designed in way allowing one to eliminate bubbles by moving a solution from the MC to an optical channel. The light-emitting diode (LED) was used as a light emitter and the analytical signal was measured by a portable spectrophotometer. Fluid movement was attained via the use of a computer-controlled syringe pump. The μSWIA was successfully used for the spectrophotometric determination of cysteine in biologically active supplements and fodder by using 18-molybdo-2-phosphate heteropoly anion (18-MPA) as the reagent.