Concentration Of OCl Research Articles

A rapid and sensitive colorimetric sensor for hypochlorite detection based on polyvinylpyrrolidone-stabilized gold nanoparticles.

It is important to develop simple and effective approaches for hypochlorite (OCl-) detection at trace levels due to its widespread use as a disinfectant especially for water treatments including drinking water. In this work, a simple, facile colorimetric sensor for the sensitive determination of hypochlorite was developed based on the oxidation of cysteine by OCl-, a process that prohibits the cysteine-triggered aggregation of Au nanoparticles (AuNPs) stabilized by polyvinylpyrrolidone. With this strategy, the concentration of OCl- could be detected with the naked eye and/or ultraviolet-visible spectroscopy, and the limit of detection for OCl- was 1.0 μM and 250 nM, respectively. Additionally, the proposed method shows excellent anti-interference capability against many other interfering ions and real water sample applicability.

Managing microbes

Managing microbes

Oclacitinib induces Foxp3 expression in CD4+ T cells under activation conditions

Abstract Oclacitinib (OCL) is a novel immunosuppressive agent approved for dogs that controls inflammation in allergic disease via the inhibition of the JAK/STAT pathway. The present study attempts to shed light on the involvement of Foxp3-expressing regulatory CD4+ T (Treg) cells and inducible type 1 regulatory T (Tr1) cells in the anti-inflammatory and anti-allergic actions of OCL. Our previous study demonstrated that exposure of unstimulated canine lymphocytes to OCL did not affect Foxp3 expression in T cells. This study investigates the effect of OCL on Foxp3 expression by canine CD4+ T cells in the course of in vitro activation. Effect of OCL on generation of Tr1 (i.e. CD223+CD49b+CD4+) cells was studied using murine lymphocytes due to the lack of appropriate antibodies for the induction and detection of these cells in dogs. The exposure of canine lymphocytes to both concentration of OCL, with a concomitant stimulation, led to a significant increase in the percentage of Foxp3-expressing cells within the CD4+ T cell subset. In the light of our previous results, it can be suggested that the effect of OCL on Foxp3 expression in CD4+ T cells may depend on T cell activation status. The mean percentage of CD3/CD28-induced CD223+CD49b+CD4+ T cells was approximately 6- and 2-fold lower in the cultures exposed to OCL 10−6 and 10−7M, respectively, compared to untreated cells. Thus, the results strongly suggest that the generation of inducible Foxp3-expressing CD4+ T cells may constitute one of mechanisms responsible for the production of anti-inflammatory and anti-allergic effects of OCL. These effects are not mediated by generation of Tr1 cells. What is more, the present results indicate that OCL may counteract the induction of these cells.

A fluorescence ratiometric sensor for hypochlorite based on a novel dual-fluorophore response approach

A fluorescence ratiometric sensor for OCl− has been developed based on a novel dual fluorophore response approach. The sensor molecule contains a coumarin fluorophore and a rhodamine fluorophore, and the two fluorophores are directly linked to an OCl− recognition group. The structure of the sensor was characterized by ESI-MS, NMR, and X-ray crystallographic analysis. Upon treatment with OCl−, both fluorophores in the sensor responded simultaneously at two separate optical windows, with large enhancement of the fluorescence ratio (I578/I501) from 0.01 to 39.55. The fluorescence ratios for the sensor showed a good linearity with the concentration of OCl− in the range of 0.2–40μM and the detection limits is 0.024μM (SN−1=3). Investigation of reaction products indicated that the sensor reaction with OCl− produced two new fluorescent molecules, which were responsible for the fluorescence changes in two optical windows. In addition, the sensor showed high selectivity to OCl− over other reactive oxygen species, reactive nitrogen species, cations, and anions. The sensor has also been successfully applied to detection of OCl− in natural water samples with satisfactory recovery.

The Mode of Action of Sodium Hypochlorite in the Decolorization of Azo Dye Orange II in Aqueous Solution

The effect of sodium hypochlorite (NaOCl) on the decolorization of azo dye orange II (4-[(2-hydroxy-1-naphthalenyl) azo]-benzenesulfonic acid, monosodium salt) in aqueous solution was studied as a function of pH. The first-order rate constant of color reduction (k) was evaluated from the curve of color reduction in the initial stage of decolorization. The k values increased with increasing the pH from 5.4 to 9.3 and the NaOCl concentration from 2.82 × 10(-4) M to 1.13 × 10(-3) M. It was found that k depended on the concentration of OCl(-), but not on HOCl. On the other hand, k decreased markedly at pHs more than 10, depending on pH. This suggested that the reactivity of the orange II molecule with OCl(-) decreased probably due to the competitive action of the hydroxide ion under alkaline conditions. It could be concluded that controlling the solution pH and the OCl(-) concentration was indeed a key factor determining the rate of decolorization of orange II in aqueous solution.

The Mode of Action of Sodium Hypochlorite in the Cleaning Process

The action of sodium hypochlorite (NaOCl) solution in the cleaning of alumina (Al2O3) particles fouled with bovine serum albumin (BSA) or pectin was studied as a function of pH. The efficacy of NaOCl in the cleaning process was evaluated in the pH region where OH- alone exerted no significant action on BSA or pectin removal. The efficiency and the rate of the removal of BSA or pectin increased with increasing available chlorine concentrations and pH. The pH dependence of the efficacy of NaOCl could be explained on the basis of the equilibrium between undissociated hypochiorous acid (HOCl) and dissociated hypochlorite ion (OCl-). The efficacy of NaOCl in the removal of BSA or pectin depended on the concentration of OCl-, but not on HOCl. Size-exclusion chromatographic analysis showed that BSA molecules were partially decomposed by the action of NaOCl, whereas no significant variation in the molecular weight of pectin molecules took place. The difference between the actions of OCl- in the removal of BSA and pectin could probably be ascribed to the reactivity of OCl- with their molecules. It could be concluded that the concentration of OCl- was a major factor determining the actual NaOCI concentration required for an efficient cleaning treatment.

Spectrophotometric Assay for Hypochlorite/Hypochlorous Acid Using Tris(2-carboxyethyl)phosphine

A simple spectrophotometric method for quantitative determination of hypochlorite (OCl − ) or hypochlorous acid (HOCl) is described. The OCl − or HOCl sample is first incubated with an excess amount of tris(2-carboxyethyl)phosphine (TCEP). The concentration of the residual TCEP is then measured as the amount of 2-nitro-5-thiobenzoate produced after reaction with 5,5′-dithiobis(2-nitrobenzoic acid). The concentration of OCl − or HOCl is equivalent to the amount of decrease in the concentration of TCEP because one molecule of TCEP is rapidly and irreversibly oxidized to TCEP oxide by one molecule of OCl − or HOCl. This method is more sensitive and convenient than the standard procedure of NaOCl assay which involves reaction with potassium iodide followed by titration of the liberated triiodide with thiosulfate.

Solution chemistry of iodide leaching of gold

The thermodynamic equilibria and kinetic aspects of gold dissolution in iodide electrolytes have been studied with emphasis on the effect of different oxidants on the system. In conjunction with kinetic measurements, the chemix computer program was used to predict the concentration profiles of the predominant species at equilibrium in different solution conditions for the systems Au-I −-I 2-H 2O and Au-I −-OCl −-H 2O. The thermodynamic study showed that I 3 − is the predominant oxidants species in both systems. However, if the concentrations of OCl − and I − are equal, solid iodine is formed. In these systems iodide (I −)_is used to form I 3 − (responsible for the gold oxidation) and more free iodide needed for the gold complexation is destroyed in the I −-OCl − system than the I −-I 2 system. The formation of solid AuI also explains the lower rate of gold dissolution determined for certain conditions in the kinetic study. The thermodynamic modelling supports the kinetic measurements which show that, although the I −-OCl − system has a higher oxidation capacity, it does not extract gold as well as the I −-I 2 system. In all cases there exist optimum oxidant/iodide ratios for achieving maximum gold extraction rates. A mixture which has the highest I 3 − and free I − concentration will attain the best gold extraction rate.

The oxidant hypochlorite (OCl −), a product of the myeloperoxidase system, degrades articular cartilage proteoglycan aggregate

The myeloperoxidase-derived oxidant, hyprochlorite (OCL −) was shown to be able to degrade proteogylcan aggregate prepared from bovine articular cartilage. Exposure of proteoglycan aggregate to OCl − concentrations less than 10 −4 resulted in a decrease in the size of the constituent proteoglycan monomers, which were unable to reaggregate with hyaluronate due to the loss of the hyaluronic acid binding region as indicated by immunoblotting using the monoclonal 1-C-6 antibody. Analysis of the [ 35S]-labeled core proteins by SDS / polyacrylamide electrophoresis and flurography indicated a decrease in the size of the core protein. These data suggest that concentrations of OCl − below 10 −3 M results in the cleavage of the proteoglycan core protein in or near the hyaluronic acid binding region. The physiological consequences of these data are discussed. Exposure to higher concentrations (>10 −3) of OCl − caused more extensive degradation of the core protein; however, there was no evidence to suggest that OCl − cleaves glycosaminoglycan (GAG) chains.