Covalent modification of glassy carbon spheres through ball milling under solvent free conditions: A novel electrochemical interface for mercury(II) quantification

A simple and green chemistry protocol has been proposed based on the covalent anchoring of benzamide molecule on glassy carbon spheres through ball milling under solvent free condition. The modification proceeds through the formation of an amide bond between carboxylic group of glassy carbon spheres and the amino group of modifier molecule. The formation of covalent bond was ascertained using X-ray photoelectron spectroscopy. Scanning electron microscopy was used to study the surface morphology of milled glassy carbon spheres. The aqueous colloidal solution of modified glassy carbon spheres was used in the preparation of thin film electrodes and subsequently used as a novel electrochemical interface in the quantification of mercury at trace level using a differential pulse anodic stripping voltammetric technique. The modified electrode showed good sensitivity and selectivity towards mercury with a detection limit of 1 nM with least interference from most of the ions. The analytical utility of the proposed electrode has been validated by determining the mercury levels in number of sample matrices. © 2014 Elsevier B.V

Synthesis and characterization of cobalt nitroprusside nano particles: Application to sulfite sensing in food and water samples

A new protocol toward the synthesis of cobalt nitroprusside (CoNP) coordination nanoparticles has been described based on drop-by-drop (DbD) method without using any additives. It was also prepared by sonication as well as bulk mixing methods for comparison purpose. The prepared complex was characterized by Infrared spectroscopy (FTIR), XRD and cyclicvoltammetry (CV) techniques. The CoNP complexes prepared by different synthetic approaches were used as modifier molecules to fabricate carbon paste electrodes (CPE's) toward electrochemical oxidation of sulfite. The experimental results revealed that the cobalt nitroprusside nanoparticles (n-CoNP) prepared by drop-by-drop method showed a considerable enhancement in the electrocatalytic activity when compared to its counterparts prepared by other approaches. Electrochemical behavior of the n-CoNP CPE was studied and used as an electrochemical sensor for the quantification of sulfite at trace level. It showed a linear response over the concentration range 1–5.9 × 10−5 M and 2–8 × 10−3 M of sulfite. The limit of detection and limit of quantification were found to be 0.4 × 10−5 M and 2.29 × 10−5 M respectively. The interference of various organic acids and inorganic ions commonly present in different food and water sample matrices were studied. The n-CoNP modified electrode was used for the quantification of sulfite in different food samples and the results were in good agreement with those obtained by the standard iodometric protocol

Diazonium functionalized exfoliated graphitic carbon as a binderless and covalently modified electrochemical interface for mercury sensing

A sensitive and selective electrochemical sensing platform for mercury quantification at picomolar level has been described. The interface was constructed using exfoliated graphitic carbon covalently functionalized with mercaptobenzothiozole (MBT) as a selective indicator species in mercury determination. It was characterized using Fourier transform infrared spectroscopy (FTIR), cyclic voltammetry (CV) techniques and subsequently used in the fabrication of surface renewable binderless bulk modified robust pellet electrode. The fabricated electrode was used in the measurement of mercury in alkaline medium using differential pulse anodic stripping voltammetry (DPASV). The developed interface showed linearity in the concentration range 1-20 pM with a detection limit of 1 pM. The analytical utility of the proposed interface has been validated by determining the mercury levels from various water and industrial effluent samples with least interference from commonly encountered cations and anions that are generally present in industrial effluents. The storage stability of the proposed interface has been studied over a period of 6 months and the results were found to be highly reproducible with a relative standard deviation of ±6. © 2013 Elsevier B.V

A binderless, covalently bulk modified electrochemical sensor: Application to simultaneous determination of lead and cadmium at trace level

A new type of covalent binderless bulk modified electrode has been fabricated and used in the simultaneous determination of lead and cadmium ions at nanomolar level. The modification of graphitic carbon with 4-amino salicylic acid was carried out under microwave irradiation through the amide bond formation. The electrochemical behavior of the fabricated electrode has been carried out to decipher the interacting ability of the functional moieties present on the modifier molecules toward the simultaneous determination of Pb 2+ and Cd 2+ ions using cyclic and differential pulse anodic stripping voltammetry. The possible mode of interaction of functional groups with metal ions is proposed based on the pKa values of the modifier functionalities present on the surface of graphitic carbon particles. The analytical utility of the proposed sensor has been validated by measuring the lead and cadmium content from pretreated waste water samples of lead acid batteries. © 2012 Elsevier B.V

2,7-dichlorofluorescein hydrazide as a new fluorescent probe for mercury quantification: Application to industrial effluents and polluted water samples

A new fluorescent probe 2,7-dichlorofluorescein hydrazide for mercury quantification in aqueous medium has been described. It is based on the spirolactam ring opening of colorless and nonfluorescent 2,7-dichlorofluorescein hydrazide induced by Hg2+ ions through the hydrolytic cleavage of amide bond to produce green-colored highly fluorescent dichlorofluorescein in alkaline medium. The significant color change of this reagent in the presence of mercury ions can be used as a sensitive naked-eye detector. The working range, limit of detection, and relative standard deviations were found to be 0.2-20 ngmL-1, 0.042 ngmL-1, and 0.69 respectively. The proposed method is free from most of the common interfering ions present in the environmental samples. The developed method has been successfully applied to determine trace level mercury from water, soil, and industrial effluents. © 2013 Sureshkumar Kempahanumakkagari et al

Studies on phase and morphological evolution of silver vanadium oxides as a function of pH: Evaluation of electrochemical behavior towards quantification of Pb2+ and Cd2+ ions

The effect of pH on morphological and phase evolution of silver vanadium oxide nanostructures are investigated under hydrothermal process. The results of powder x-ray diffraction (PXRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) disclosed that the morphological evolution of nanobelts into nanoring structures occurs at pH in between 4 and 5 with Ag2V4O11 phase and nanobelt morphologies at pH from 6 to 7 with β-AgVO3 phase. The prepared Ag2V4O11 and β-AgVO3 have been evaluated for the simultaneous quantification of Pb2+ and Cd2+ ions in aqueous solution using differential pulse anodic stripping voltammetry. The results reveal that Ag2V4O11 shows better quantification result compared to β-AgVO3. © 2017 IOP Publishing Ltd

Calixarene bulk modified screen-printed electrodes (SPCCEs) as a one-shot disposable sensor for the simultaneous detection of lead(II), copper(II) and mercury(II) ions: Application to environmental samples

Calixarene bulk modified screen-printed electrodes (SPCCEs) have been designed, fabricated and utilized as one-shot disposable electrochemical sensors towards the simultaneous measurement of toxic metal ions lead(II), copper(II) and mercury(II) within environmental samples. These SPCCEs have been fabricated upon polyester strips, which have been modified over a range of different calixarene compositions. These bespoke sensors have been utilized as disposable electrochemical sensors and quantified in model aqueous solution of 0.1 M HCl giving rise to the simultaneous sensing of lead(II), copper(II) and mercury(II) using cyclic voltammetry and differential pulse anodic stripping voltammetry techniques. These SPCCEs have additionally been applied for the sensing of lead(II), copper(II) and mercury(II) within industrial and environmental samples such as industrial effluents and wastewater samples, furthermore the presented method has been subjected to a comprehensive interference study and further validated with an atomic absorption spectrometric method. © 2017 Elsevier B.V

Surfactant mediated sulfide estimation at trace level: Application to environmental samples

A simple spectrophotometric method has been developed for the quantification of dissolved sulfide based on its reaction with ferric iron and the subsequent reaction of ferrous iron with 1-nitroso-2-naphthol in alkaline medium. The insoluble iron(II)-ligand complex has been solubilized in micellar medium using neutral surfactant which facilitates the non extraction step. The method obeys Beer’s law in the concentration range 0.5–8 μg in 10 mL of aqueous phase. The complex showed an absorption maximum at 710 nm with ε value of 4.11 × 104 L/mol cm. The detection limit has been found to be 0.0036 μg/mL. The interference of common cations and anions has been studied and the proposed method has been successfully applied to determine the sulfide in different sewage water sample

Graphene–platinum nanocomposite as a sensitive and selective voltammetric sensor for trace level arsenic quantification

A simple protocol for the chemical modification of graphene with platinum nanoparticles and its subsequent electroanalytical application toward sensitive and selective determination of arsenic has been described. Chemical modification was carried out by the simultaneous and sequential chemical reduction of graphene oxide and hexachloroplatinic acid in the presence of ethylene glycol as a mild reducing agent. The synthesized graphene–platinum nanocomposite (Gr–nPt) has been characterized through infrared spectroscopy, x-ray diffraction study, field emission scanning electron microscopy and cyclic voltammetry (CV) techniques. CV and square-wave anodic stripping voltammetry have been used to quantify arsenic. The proposed nanostructure showed linearity in the concentration range 10–100 nM with a detection limit of 1.1 nM. The proposed sensor has been successfully applied to measure trace levels of arsenic present in natural sample matrices like borewell water, polluted lake water, agricultural soil, tomato and spinach leaves

Covalent anchoring of cobalt hexacyanoferrate particles on graphitic carbon: A simple and renewable robust pellet electrode as an electrochemical interface for amperometric quantification of sulfite

A simple strategy has been proposed for the covalent anchoring of cobalt hexacyanoferrate (CoHCF) particles on graphitic carbon substrate using p-phenylenediamine as a linker molecule. The covalent anchoring was confirmed by X-ray diffraction, Fourier transform infrared spectroscopy and electrochemical studies. A robust pellet electrode was fabricated using CoHCF particles modified graphitic carbon and it has been applied in the electrocatalytic oxidation of sulfite. The proposed sensor showed a linearity in the concentration range 4�128 μM of sulfite with a limit of detection (LOD) 1.7 μM and limit of quantification (LOQ) 5.8 μM. Proposed sensor has been successfully applied to measure sulfite levels from a variety of food sample matrices. The results obtained by the proposed electrochemical sensor have been compared with the iodimetric method. © 2017 Elsevier Lt