Srikant Sahoo

Uranium and other heavy toxic elements distribution in the drinking water samples of SW-Punjab, India

Abstract In the present investigations, Laser Fluorimetry technique has been used for the microanalysis of uranium content in drinking water samples collected from different sources like the hand pumps, tube wells of various depths from wide range of locations in the four districts of SW-Punjab, India. The purpose of this study was to investigate the uranium concentration levels of ground water being used for drinking purposes and to determine its health effects, if any, to the local population of this region. Corresponding radiological and chemical risks have also been calculated for the uranium concentrations in ground water samples. Some other heavy elements have also been analysed using the Atomic Absorption Spectrometry. In this region, uranium concentration in 498 drinking water samples has been found to vary between 0.5–579 μgl−1with an average of 73.5 μgl−1. Data analysis revealed that 338 of 498 samples had uranium concentration higher than recommended safe limit of 30 μgl−1 (WHO, 2011) while 216 samples exceeded the threshold of 60 μgl−1 recommended by AERB, DAE, India, 2004.

Electrodeposited Bi-Au nanocomposite modified carbon paste electrode for the simultaneous determination of copper and mercury

Composites of bismuth and gold nanoparticles (Bi–AuNPs) were prepared on a carbon paste electrode (CPE) by an electrochemical deposition method. The electrochemical parameters were optimized for the effective deposition of Bi–AuNP composite materials. Microscopic examination revealed that nanoparticle clusters of gold were embedded well within the bismuth films (Bi films) over the surface of the CPE. An analytical anodic stripping voltammetry method has been developed for the simultaneous determination of copper and mercury at ultratrace levels using the Bi–AuNP modified CPE. It was possible to observe well separated stripping peaks of the two metal ions and the modified electrode was successfully applied for simultaneous determination of Cu and Hg. The limits of detection using the optimized analytical procedure were observed as 0.16 μg L−1 and 0.28 μg L−1 for Cu and Hg respectively. Interference effects of some of the commonly occurring metal ions were investigated and the method was applied for the determination of Cu and Hg in two ground water and two soil samples collected from different places.

Bi-Film on a carbon paste electrode modified with nafion film embedded with multiwall carbon nano tubes for the determination of heavy metals

Bi-film was deposited on the carbon paste electrode and used as the modified electrode in stripping voltammetry. Bi deposition was carried out ex-situ in acetate buffer solution of pH 4.5 under mild stirring conditions. The deposition potential, deposition time and the Bi-concentration in the deposition solution were optimized and the corresponding values are −0.8 V (SCE), 300 s and 0.3 mM Bi-nitrate solution respectively. A substantial enhancement of an order of magnitude in the sensitivity has been observed when carbon paste electrode was modified with nafion coated carbon nano tube on which Bi-film was deposited. This enhanced sensitivity was attributed to the increased active surface area and also the enhanced charge transfer processes which increased the deposition processes and so the stripping current. Effect of different surfactants on the stripping peak of the heavy metal ions is investigated with and without modification by nafion. Detection limits using Bi-film electrode was obtained for Zn, Cd and Pb as 17.3, 16.9, 11.9 μg L−1, respectively, using Bi-film electrode. Analysis result of two water samples and two ayurvedic medicines are reported.

Electrochemical and spectroelectrochemical investigations of quercetin on unmodified and DNA-modified carbon paste electrode and its determination using voltammetry

The electrochemistry of quercetin on a carbon paste electrode in non aqueous and aqueous media has been investigated. Cyclic voltammetric experiments were carried out and the basic electrochemical parameters such as diffusion coefficient, exchange current density and the anodic Tafel slopes were determined. A differential pulse voltammetric procedure was proposed for the determination of quercetin in aqueous solution using a carbon paste electrode, and the detection limit was obtained as 38.5 nM L−1. The electrochemical properties of quercetin were studied using a DNA-modified carbon paste electrode using electrochemical impedance measurements. From spectroelectrochemical measurements it was evident that the hydroxyl groups at the 3′ and 4′ positions were oxidized in the presence of Cu(II) and are responsible for DNA damage. Impedance measurements supported the intercalation of quercetin into the DNA strands.

Modification of gold electrode by self-assembled 2-mercapto benzothiazole for the determination of Hg2+

An electrochemical method was developed for the determination of mercury using polycrystalline gold electrode modified by self-assembled monolayers (SAMs) of 2-mercaptobenzothiazole (MBTH). Morphological and electrochemical characterisation of the self-assembled structure of MBTH was performed using atomic force microscopy (AFM) and electrochemical impedance spectroscopy (EIS) measurements. The monolayer of MBTH has shown high affinity for Hg2+. The limit of detection for the determination of Hg2+ using the MBTH SAMs modified gold electrode was obtained as 0.421 μg L−1. The pre-concentration of Hg2+ at open circuit potential is beneficial for the onsite monitoring of mercury concentration in water samples.

Electrochemically deposited gold nanoparticles on a carbon paste electrode surface for the determination of mercury.

An electrochemical method was developed for the determination of Hg at ultratrace levels using an Au nanoparticle (AuNP) array modified carbon paste electrode (CPE) by anodic stripping voltammetry. Scanning electron microscopy measurements imaged the size and shape of AuNPs on the CPE substrate; it was possible to tune the size and the NP density by changing the deposition time and medium. Electrochemical characterization of the AuNP modified CPE was carried out using cyclic voltammetry and electrochemical impedance measurements. Interferences due to some commonly occurring metal ions and surfactants on the stripping peak of Hg were also investigated. The 3σ detection limit for Hg using the AuNP modified electrode was as 0.24 μg/L. This method was applied to determine Hg in soil samples.