Hilal Ahmad

Graphene Oxide Sheets Immobilized Polystyrene for Column Preconcentration and Sensitive Determination of Lead by Flame Atomic Absorption Spectrometry

A novel solid-phase extractant was synthesized by coupling graphene oxide (GO) on chloromethylated polystyrene through an ethylenediamine spacer unit to develop a column method for the preconcentration/separation of lead prior to its determination by flame atomic absorption spectrometry. It was characterized by Fourier transform infrared spectroscopy, far-infrared spectroscopy, thermogravimetric analysis/differential thermal analysis, scanning electron microscopy, energy-dispersive spectrometry, and transmission electron microscopy. The abundant oxygen-containing surface functional groups form a strong complex with lead, resulting in higher sorption capacity (227.92 mg g(-1)) than other nanosorbents used for sorption studies of the column method. Using the column procedure here is an alternative to the direct use of GO, which restricts irreversible aggregation of GO and its escape into the ecosystem, making it an environmentally sustainable method. The column method was optimized by varying experimental variables such as pH, flow rate for sorption/desorption, and elution condition and was observed to exhibit a high preconcentration factor (400) with a low preconcentration limit (2.5 ppb) and a high degree of tolerance for matrix ions. The accuracy of the proposed method was verified by determining the Pb content in the standard reference materials and by recovery experiments. The method showed good precision with a relative standard deviation <5%. The proposed method was successfully applied for the determination of lead in tap water, electroplating wastewater, river water, and food samples after preconcentration.

SPE coupled to AAS trace determination of Cd(II) and Zn(II) in food samples using amine functionalized GMA-MMA-EGDMA terpolymer: Isotherm and kinetic studies.

An ethylenediamine functionalized glycidyl methacrylate (GMA) based terpolymeric chelating resin was synthesized for the separation and preconcentration of Cd(II) and Zn(II) by SPE from bread, rice and fruit juice prior to FAAS determination. The resin was characterized by FT-IR, TGA/DTA, SEM, BET analysis and EDS. Synthesized resin shows a good capacity of 53.96mgg(-1) for Cd(II) and 24.19mgg(-1) for Zn(II) at pH 8.0. Five isotherm equilibrium models were studied to explain the sorption phenomenon out of which Langmuir, Dubinin-Radushkevich, Scatchard and Temkin models were found to be the best fitted. The limit of detection (LOD) and limit of quantification (LOQ) were observed to be 1.5 and 5.1μgL(-1) for Cd and 1.2 and 4.1μgL(-1) for Zn. The reliability of the method was investigated by the analysis of SRM and the recovery of analytes from various spiked food samples.

Efficacy of dihydroxy-mercaptopyrimidine functionalized polymeric resin for the trace determination of Cd by SPE coupled flame atomic absorption spectrometry

A novel 2-thiobarbituric acid functionalized polystyrene resin has been explored for its efficacy and applicability in solid phase preconcentration coupled atomic absorption spectrometric determination of trace cadmium. The prepared resin was characterized by infrared spectroscopy, scanning electron microscopy, energy dispersive X-ray analysis, and thermogravimetry. The maximum static sorption capacity of the prepared resin was 131.58 mg Cd g−1 resin with a low preconcentration limit of 2.5 μg L−1. The experimental parameters affecting the solid phase extraction of cadmium including sample pH, sorption time, flow rate for sorption and desorption, volume and concentration of the eluent, sample volume and concomitant ions were investigated. Under the optimized conditions, 96% recovery.

Biological control of soil-pathogenic nematodes infecting mungbean using Pseudomonas fluorescens

The addition of organic matters to soil has been explored as an alternative means of nematode control under field conditions. Several oil-seed cakes of neem (Azadirachta indica), castor (Ricinus communis), groundnut (Arachis hypogeae), linseed (Linum usitatissimum) and sunflower (Helianthus annuus) were found to be highly effective in reducing the multiplication of soil-pathogenic nematodes Meloidogyne incognita, Rotylenchulus reniformis, Tylenchorhynchus brassicae, etc. The plant growth parameters such as plant weight, per cent pollen fertility, number of pods per plant, root-nodulation and chlorophyll content of mungbean increased significantly. The multiplication rate of nematodes and number of root-galls were less in the presence of Pseudomonas fluorescens as compared to its absence. Damage caused by the nematodes was further reduced when P. fluorescens was added along with the oil-seed cakes. Neem cake was found most effective in combination with P. fluorescens.

Copper selective self-sorting polymeric resin with mixed-mode functionality for column preconcentration and atomic absorption spectrometric determination

A new approach for the synthesis of a highly Cu(II) selective mixed-mode solid phase extractant is proposed. In aqueous medium triethylenetetramine (trien) reacts with Dowex 50 resin and forms a self assembled product. The self-sorting trien molecules get attached by forming a hydrogen bond with the sulfonic acid groups of the resin, where nitrogen-containing functional groups flexibly change their orientation in order to selectively coordinate with Cu(II) in a square-planar geometry. This enables the solid phase to behave in a manner similar to a free monomeric ligand in a liquid–liquid system. A column procedure for preconcentration/separation of Cu(II) was developed optimizing various experimental variables which exhibits a low preconcentration limit (3.3 μg L−1) and high sorption capacity (101.6 mg g−1 of resin). An analytical method coupling column preconcentration procedure with flame atomic absorption spectrometry (FAAS) was validated analyzing standard reference materials and recovery of the spiked analyte. The proposed method was successfully applied for the preconcentration and determination of Cu(II) in tap water, river waters, electroplating wastewater, and a tea sample.