Search results for "Reagent"
showing 10 items of 699 documents
Toward an understanding of the 1,3-dipolar cycloaddition between diphenylnitrone and a maleimide:bisamide complex. A DFT analysis of the reactivity o…
2007
Abstract The 1,3-dipolar cycloaddition between diphenylnitrone and a maleimide:bisamide complex has been studied using density functional theory (DFT) methods at the B3LYP/6-31G∗ level. The molecular recognition of the bisamide receptor to maleimide favors the formation of the complex through three hydrogen bonds. However, they are not able to produce an efficient acceleration of the cycloaddition because the symmetric substitution of the dipolarophile sites. This poor capability is discussed in base of the transition state structures and the analysis of the reactivity indexes of the reagents.
Triazole-Containing [FeFe] Hydrogenase Mimics: Synthesis and Electrocatalytic Behavior
2019
Through a Cu-catalyzed Huisgen cycloaddition between terminal alkynes and azides (CuAAC) reaction, azide [(μ-SCH2)2N(4-N3C6H4)Fe2(CO)6] has demonstrated to be a robust and versatile reagent able to...
Towards chemical communication between gated nanoparticles.
2014
The design of comparatively simple and modularly configurable artificial systems able to communicate through the exchange of chemical messengers is, to the best of our knowledge, an unexplored field. As a proof-of-concept, we present here a family of nanoparticles that have been designed to communicate with one another in a hierarchical manner. The concept involves the use of capped mesoporous silica supports in which the messenger delivered by a first type of gated nanoparticle is used to open a second type of nanoparticle, which delivers another messenger that opens a third group of gated nanoobjects.We believe that the conceptual idea that nanodevices can be designed to communicate with …
Optical chemosensors and reagents to detect explosives
2012
[EN] This critical review is focused on examples reported from 1947 to 2010 related to the design of chromo-fluorogenic chemosensors and reagents for explosives (141 references). © 2012 The Royal Society of Chemistry.
Acetic acid compared with i-scan imaging for detecting Barrett's esophagus: a randomized, comparative trial.
2013
Background Traditional surveillance in patients with Barrett's esophagus (BE) has relied on random biopsies. Targeted biopsies that use advanced imaging modalities may significantly improve detection of specialized columnar epithelium (SCE). Objective We compared the efficacy of targeted biopsies that used i -scan or acetic acid to random biopsies in the detection of SCE. Design Patients with visible columnar lined epithelium or known BE were randomized at a 1:1 ratio to undergo acetic acid application or i -scan with targeted biopsies. Setting Targeted biopsies were performed based on surface architecture according to the Guelrud classification followed by 4-quadrant biopsies. Patients A t…
Influence of ligand density on the properties of metal-chelate affinity supports.
1993
A new procedure has been developed to immobilize iminodiacetic acid (IDA) onto the surface of silica supports, such as LiChrospher Si-1000 and 1.5-microns nonporous silica, for use in high-performance immobilized metal affinity chromatography (HPIMAC) of proteins. This IDA immobilization method has been achieved through the synthesis of a new silylation reagent, 1-(iminodiacetic acid di-tert-butylester)-3-glycidoxy-propyltrimethoxysilane (IDA-silane). Various modified silicas of different ligand densities have been prepared by using mixtures between 1 and 100% of the IDA-silane diluted with the corresponding 3-glycidoxy-propyltrimethoxysilane (GLYMO-silane). Frontal analysis was used with t…
A passive solid sensor for in-situ colorimetric estimation of the presence of ketamine in illicit drug samples
2017
Abstract A colorimetric sensor has been developed for the presumptive detection of ketamine in illicit drug samples. The sensor has been prepared by immobilized the reagent Co(SCN) 2 into polydimethylsiloxane (PDMS). When exposed to solutions of ketamine at a basic pH, the sensor color changes from brown to blue-purple due to the diffusion of the analyte molecules to the polymeric matrix and subsequent interaction with the reagent particles. The sensor enables the visual identification of amounts of drug as low as 30 μg in a few minutes. Quantification of ketamine is also possible through the measurement of the absorbance in diffuse reflectance mode. Under the proposed conditions, linear re…
NQS-Doped PDMS Solid Sensor: From Water Matrix to Urine Enzymatic Application
2021
The development of in situ analytical devices has gained outstanding scientific interest. A solid sensing membrane composed of 1,2-naphthoquinone-4-sulfonate (NQS) derivatizing reagent embedded into a polymeric polydimethylsiloxane (PDMS) composite was proposed for in situ ammonium (NH4+) and urea (NH2CONH2) analysis in water and urine samples, respectively. Satisfactory strategies were also applied for urease-catalyzed hydrolysis of urea, either in solution or glass-supported urease immobilization. Using diffuse reflectance measurements combined with digital image processing of color intensity (RGB coordinates), qualitative and quantitative analyte detection was assessed after the colorime…
Cotton swabs supported in-situ assay for quaternary ammonium compounds residues in effluents and surfaces
2018
Abstract Cellulose paper and cotton swabs have been tested as sampling, reaction and measurement media for quaternary ammonium compounds (QACs) using the reagent Chromo Azurol S in the presence of aluminum cations (CAS-Al). On the basis of the results obtained a new method is proposed for the analysis of QACs in water samples which only entails the successive immersion of swabs into 1 mL of the samples, 1 mL of a solution of CAS-Al for the formation of a ternary blue complex, and 1 mL of water to remove the excess of reagent. The method can be used for the visual on site detection of QACs in effluents, as well as for their quantification within the 3.62–36.2 mg/L range through the direct me…
‘In situ’ preparation of nitrous acid solutions by photoreduction in a flow assembly for analysis of pharmaceuticals
2003
The solutions of nitrite ion, or nitrous acid, are frequently used as reagent in different analytical procedures and in pharmaceutical analysis. The low stability of the aqueous solutions of this reagent implies the tedious work of freshly prepared solutions every day and being kept in the refrigerator. In this paper, a photoreactor formed by a low pressure mercury lamp and nesting in a continuous-flow manifold is studied, tested, and proposed for the in situ reduction of nitrate solution into nitrite. The conversion into nitrite is reproducible and it has been successfully applied to determination of different drugs, mostly from the sulphonamide family, in an FIA assembly.