Amino-calix[4]arene modified graphite as an electrochemical interface for mercury(II) quantification

A new simple amino-calix[4]arene modified graphitic composite electrode have been prepared and employed in the form of thin film on glassy carbon electrode (GCE) surface as a sensing probe for the measurement of mercury(II) ions. In order to decipher the complexing ability of the modifier towards the metal ions analytical techniques such as cyclic voltammetry and differential pulse anodic stripping voltammetric are used

Anthraquinone functionalized carbon composite electrode: Application to ammonia sensing

A simple strategy has been used to covalently modify the glassy carbon spheres with anthraquinone moieties through the diazonium salt reduction. The derivatized glassy carbon spheres were used to modify the basal plane pyrolytic graphite electrode by immobilizing them on its surface and examining its electrochemical behaviour. The composite electrode has been used to detect trace level ammonia in the concentration range 5 à 10-8 to 3 à 10-5 M and it was successfully applied to detect low levels of ammonia present in natural samples like urine and soil. © 2011 Elsevier B.V. All rights reserved

Determination of nitrogen dioxide, sulfur dioxide, ozone, and ammonia in ambient air using the passive sampling method associated with ion chromatographic and potentiometric analyses

Concentrations of nitrogen dioxide (NO2), sulfur dioxide (SO2), ozone (O3), and ammonia (NH3) were determined in the ambient air of Al-Ain city over a year using the passive sampling method associated with ion chromatographic and potentiometric detections. IVL samplers were used for collecting nitrogen and sulfur dioxides whereas Ogawa samplers were used for collecting ozone and ammonia. Five sites representing the industrial, traffic, commercial, residential, and background regions of the city were monitored in the course of this investigation. Year average concentrations of ≤59.26, 15.15, 17.03, and 11.88 μg/m3 were obtained for NO2, SO2, O3, and NH3, respectively. These values are lower than the maxima recommended for ambient air quality standards by the local environmental agency and the world health organization. Results obtained were correlated with the three meteorological parameters: humidity, wind speed, and temperature recorded during the same period of time using the paired t test, probability p values, and correlation coefficients. Humidity and wind speed showed insignificant effects on NO2, SO2, O3, and NH3 concentrations at 95% confidence level. Temperature showed insignificant effects on the concentrations of NO2 and NH3 while significant effects on SO2 and O3 were observed. Nonlinear correlations (R2 ≤ 0.722) were obtained for the changes in measured concentrations with changes in the three meteorological parameters. Passive samplers were shown to be not only precise (RSD ≤ 13.57) but also of low cost, low technical demand, and expediency in monitoring different locations

Chemical amplification method for the determination of hydrogen sulphide in air at trace level

A sensitive spectrophotometric method for the determination of trace amounts of hydrogen sulphide after fixing it in triethanolamine-zinc acetate-sodium hydroxide absorbing solution is described. The method is based on the reaction of hydrogen sulphide with iodine to form iodide and after the extraction of unreacted iodine, the iodide was oxidised to iodate by bromine. After the removal of excess bromine, the generated iodate is utilised to oxidise hydroxylamine to nitrite which produces an azo dye in the presence of p-nitroaniline and N-(1-naphthyl)ethylenediamine dihydrochloride NEDA in acidic medium with maximum absorption at 545 nm. The colour system obeys Beer's law over the concentration range 0-3 μm of H2 S (n=10). The interference of common air pollutants like SO2, NO2 and HCHO were suitably overcome by the proper reaction conditions. The proposed method has been applied to the determination of low levels of H2S generated using permeation devices and residual hydrogen sulfide in a laboratory fume hood. Copyright © Enviromedia

Hydrothermal Synthesis of Zr-Amino Terephthalate and its Composite with MWCNTs as a Novel Electrode Material in Nitrite Quantification

A simple and greener electrochemical sensing platform towards nitrite measurement using amine modified Zr-terephthalate and MWCNTs has been demonstrated. The characterization of the composite material has been carried out using spectroscopic and voltammetric techniques. The composite material overcomes the inherent drawbacks of MOFs like lower conductivity and stability in aqueous medium. The MWCNTs/Zr-ATA composite modified electrode showed better electrocatalytic activity in nitrite quantification with good linearity in the concentration range 2–440 μM with detection limit 0.22 μM and sensitivity of 0.657 μA μM-1 cm-2. The fabricated electrode has been applied to quantify nitrite from root nodule samples

Microwave-assisted functionalization of glassy carbon spheres: Electrochemical and mechanistic studies

Functionalization of glassy carbon spheres have been carried out by microwave irradiation in the presence of modifier molecules through oxidation followed by amidation reaction. The glassy carbon spheres were initially catalyzed by treating with concentrated nitric acid to introduce surface-bound carboxylic groups, and its subsequent amidation reaction in the presence of p-nitroaniline yields p-nitroanilide-functionalized substrate materials. These derivatized glassy carbon spheres have been electrochemically characterized by immobilizing them on bppg electrode and studying its voltammetric behavior. X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy studies have revealed that the modifying molecules are surface bound and covalently attached on the carbon substrate. © Springer-Verlag 2009

Micellar-mediated extractive spectrophotometric determination of hydrogen sulfide/sulfide through prussian blue reaction: Application to environmental samples

A sensitive surfactant-mediated extractive spectrophotometric method has been developed, based on the reaction of ferric iron with sulfide to form ferrous iron and its subsequent reaction with ferricyanide to form Prussian Blue, to quantify trace levels of hydrogen sulfide/sulfide in environmental samples. The method obeys Beer's law in the concentration range 2 - 10 μg of sulfide in 25 mL of aqueous phase with molar absorptivity (ε) of 3.92 à 104 L mol-1 cm-1. The colored species has been extracted into isoamyl acetate in the presence of a cationic surfactant i.e. cetylpyridinium chloride, to enhance the sensitivity of the method with ε value 5.2 à 104 L mol-1 cm-1. The relative standard deviation has been found to be 0.69 for 10 determinations at 4 μg of sulfide and the limit of detection was 0.009 μg mL-1. The interference from common anions and cations has been studied. The proposed method has been applied to the determination of residual hydrogen sulfide in the laboratory fume hood as well as ambient atmospheric hydrogen sulfide in the vicinity of open sewer lines after fixing the analyte in ionic form using suitable trapping medium. 2010 © The Japan Society for Analytical Chemistry

Derivatization and characterization of functionalized carbon powder via diazonium salt reduction

Chemical reduction of 4-chloro-2-nitrobenzenediazonium chloride salt in the presence of hypophosphorous acid and carbon powder results in functionalized carbon powder with chloronitrophenyl groups attached on carbon particle surface. This type of bulk derivatization protocol is very useful and most inexpensive compared to widely used electrochemically assisted derivatization protocol. The derivatized carbon powder has been characterized by studying its Fourier transform infrared spectroscopy (FTIR) and cyclic voltammetric studies. The surface functionalized moieties have been examined electrochemically by immobilizing them onto the surface of basal plane pyrolytic graphite electrode and studying its cyclic voltammetry. The effect of pH, scan rate (v), and the peak potentials (E p) as a function of pH has revealed that the species are surface bound in nature and covalently attached on the carbon surface. The FTIR studies of the derivatized carbon powder have revealed that the modifying molecule is covalently attached on the carbon particle surface. © 2007 Springer-Verlag

Nitrite/nitrate speciation through arsenomolybdenum blue complex at trace level: Application to biological and environmental samples

A novel and simple method has been proposed for the estimation of nitrite/nitrate based on the reduction of arsenomolybdic acid to arsenomolybdenum blue using ascorbic acid. The obtained arsenomolybdenum blue complex has been oxidized by the addition of nitrite and the decrease in the absorbance of blue color is directly proportional to the nitrite quantity. The absorbance of the arsenomolybdenum blue complex has been measured at 840 nm. All the reaction variables have been optimized and Beer's law has been obeyed in the concentration range 2-10 μg in 25 mL of aqueous phase with a molar absorptivity 4.37 à 104 L mol-1 cm-1. The relative standard deviation of the method has been found to be 1.7 for five measurements with a detection limit of 0.003 μg mL-1. The method has been applied to determine nitrite/nitrate levels in biological samples as well as environmental samples. © The Royal Society of Chemistry 2011

Aminophenyl benzimidazole as a new reagent for the estimation of NO2/nitrite/nitrate at trace level: Application to environmental samples

A simple and sensitive spectrophotometric method for the determination of nitrogen dioxide in ambient air and nitrite/nitrate in water and soil samples has been developed. Nitrogen dioxide in air has been fixed as nitrite ion using alkaline sodium arsenite as absorbing medium. The method is based on the reaction of nitrite with aminophenyl benzimidazole in acid medium to form diazonium ion, which is coupled with N-(1-naphthyl)ethylenediamine dihydrochloride to form an azo dye with an absorption maximum at 555 nm in aqueous phase. The method obeys Beer's law in the concentration range 0-10 μg of nitrite in 25 ml solution. The molar absorptivity has been found to be 6.3�104 l mol-1 cm-1. The dye can be extracted quantitatively into isoamyl alcohol under alkaline condition and the addition of methanolic hydrochloric acid restores the original dye colour. Beer's law is obeyed in the concentration range 0-2 μg of nitrite with a detection limit of 0.009 μg. The effect of interfering species has been studied and the developed method has been applied to determine trace levels of nitrogen dioxide in ambient air and the results have been compared with the standard method. It is also applied to measure the nitrite/nitrate levels of surface and ground water samples collected from lakes, tube wells as well as soil samples. Copyright © Taylor & Francis Group, LLC