Muhammad Makshoof Athar

Electrochemical determination of inorganic mercury and arsenic—A review

Inorganic mercury and arsenic encompasses a term which includes As(III), As(V) and Hg(II) species. These metal ions have been extensively studied due to their toxicity related issues. Different analytical methods are used to monitor inorganic mercury and arsenic in a variety of samples at trace level. The present study reviews various analytical techniques available for detection of inorganic mercury and arsenic with particular emphasis on electrochemical methods especially stripping voltammetry. A detailed critical evaluation of methods, advantages of electrochemical methods over other analytical methods, and various electrode materials available for mercury and arsenic analysis is presented in this review study. Modified carbon paste electrode provides better determination due to better deposition with linear and improved response under studied set of conditions. Biological materials may be the potent and economical alternative as compared to macro-electrodes and chemically modified carbon paste electrodes in stripping analysis of inorganic mercury and arsenic.

Molecularly Imprinted Nanomaterials for Sensor Applications

Molecular imprinting is a well-established technology to mimic antibody-antigen interaction in a synthetic platform. Molecularly imprinted polymers and nanomaterials usually possess outstanding recognition capabilities. Imprinted nanostructured materials are characterized by their small sizes, large reactive surface area and, most importantly, with rapid and specific analysis of analytes due to the formation of template driven recognition cavities within the matrix. The excellent recognition and selectivity offered by this class of materials towards a target analyte have found applications in many areas, such as separation science, analysis of organic pollutants in water, environmental analysis of trace gases, chemical or biological sensors, biochemical assays, fabricating artificial receptors, nanotechnology, etc. We present here a concise overview and recent developments in nanostructured imprinted materials with respect to various sensor systems, e.g., electrochemical, optical and mass sensitive, etc. Finally, in light of recent studies, we conclude the article with future perspectives and foreseen applications of imprinted nanomaterials in chemical sensors.

Injectable biopolymer based hydrogels for drug delivery applications.

Biopolymer based pH-sensitive hydrogels were prepared using chitosan (CS) with polyethylene glycol (PEG) of different molecular weights in the presence of silane crosslinker. The incorporated components remain undissolved in different swelling media as they are connected by siloxane linkage which was confirmed by Fourier transform infrared spectroscopy. The swelling in water was enhanced by the addition of higher molecular weight PEG. The swelling behaviour of the hydrogels against pH showed high swelling in acidic and basic pH, whereas, low swelling was examined at pH 6 and 7. This characteristic pH responsive behaviour at neutral pH made them suitable for injectable controlled drug delivery. The controlled release analysis of Cefixime (CFX) (model drug) loaded CS/PEG hydrogel exhibited that the entire drug was released in 30 min in simulated gastric fluid (SGF) while in simulated intestinal fluid (SIF), 85% of drug was released in controlled manner within 80 min. This inferred that the developed hydrogels can be an attractive biomaterial for injectable drug delivery with physiological pH and other biomedical applications.

Glucoxylan-mediated green synthesis of gold and silver nanoparticles and their phyto-toxicity study

A green synthesis of gold and silver nanoparticles having exceptional high stability is reported. The synthesis involves the use of glucoxylans isolated from seeds of Mimosa pudica and excludes the use of conventional reducing and capping agents. The average particle sizes were 40 and 6 nm for gold and silver, respectively. The size of gold particles obtained in this work is suitable for drug delivery as they are non-cytotoxic. In phyto-toxicity tests the gold and silver nanoparticles did not show any significant effect on germination of radish seeds, whereas in radish seedling root growth assay the two particles behaved differently. The silver nanoparticles exhibited a concentration-dependent stimulatory effect on root length, whereas the gold nanoparticles had no significant effect in this test. The likely mechanism of these effects is discussed.

Functionalized diamond nanopowder for phosphopeptides enrichment from complex biological fluids.

Diamond is known for its high affinity and biocompatibility towards biomolecules and is used exclusively in separation sciences and life science research. In present study, diamond nanopowder is derivatized as Immobilized Metal Ion Affinity Chromatographic (IMAC) material for the phosphopeptides enrichment and as Reversed Phase (C-18) media for the desalting of complex mixtures and human serum profiling through MALDI-TOF-MS. Functionalized diamond nanopowder is characterized by Fourier transform infrared (FT-IR) spectroscopy, scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) spectroscopy. Diamond-IMAC is applied to the standard protein (β-casein), spiked human serum, egg yolk and non-fat milk for the phosphopeptides enrichment. Results show the selectivity of synthesized IMAC-diamond immobilized with Fe(3+) and La(3+) ions. To comprehend the elaborated use, diamond-IMAC is also applied to the serum samples from gall bladder carcinoma for the potential biomarkers. Database search is carried out by the Mascot program (www.matrixscience.com) for the assignment of phosphorylation sites. Diamond nanopowder is thus a separation media with multifunctional use and can be applied to cancer protein profiling for the diagnosis and biomarker identification.

Voltammetric detection of As(III) with Porphyridium cruentum based modified carbon paste electrode biosensor

A novel biosensor based on carbon paste electrode modified with Porphyridium cruentum biomass was developed for the determination of As(III) in contaminated water. As(III) was first biosorbed-accumulated on the electrode surface at open circuit potential and then stripped off by applying anodic scan range of -0.8 to +0.8 V using differential pulse anodic stripping voltammetric technique. The best result was obtained at pH 6.0 with 0.1M HNO3 solution as stripping medium, allowing biosorption-accumulation time of 8 min using 5% P. cruentum biomass in graphite-mineral oil paste. Linear range for As(III) detection with the modified electrode-biosensor was observed between 2.5 and 20 µg L(-1). The FTIR spectrum of P. cruentum biomass confirmed the presence of active functional groups that participate in the binding of As(III). Scanning Electron Microscopy (SEM) indulged the surface morphology of modified electrode-biosensor before and after As(III) adsorption. Similarly, Atomic Force Microscopy (AFM) showed that the average roughness of the modified electrode decreased indicating the successful incorporation of P. cruentum biomass. Efficiency of the biosensor in the presence of different interfering metal (Na(+), K(+), Ca(2+), and Mg(2+)) ions were also evaluated. The application of P. cruentum modified biosensor was successfully used for the detection of As(III) in the binary metal (Fe(3+), Mn(2+), Cd(2+), Cu(2+), Ni(2+), Hg(2+), and Pb(2+)) contaminated system. The accuracy of application of biosorption based biosensor for the detection of As(III) is as low as 2.5 µg L(-1).

Adsorption Optimization of Lead (II) Using Saccharum Bengalense as a Non-Conventional Low Cost Biosorbent: Isotherm and Thermodynamics Modeling

In the present study a novel biomass, derived from the pulp of Saccharum bengalense, was used as an adsorbent material for the removal of Pb (II) ions from aqueous solution. After 50 minutes contact time, almost 92% lead removal was possible at pH 6.0 under batch test conditions. The experimental data was analyzed using Langmuir, Freundlich, Timken and Dubinin-Radushkevich two parameters isotherm model, three parameters Redlich—Peterson, Sip and Toth models and four parameters Fritz Schlunder isotherm models. Langmuir, Redlich—Peterson and Fritz-Schlunder models were found to be the best fit models. Kinetic studies revealed that the sorption process was well explained with pseudo second-order kinetic model. Thermodynamic parameters including free energy change (ΔG°), enthalpy change (ΔH°) and entropy change (ΔS°) have been calculated and reveal the spontaneous, endothermic and feasible nature of the adsorption process. The thermodynamic parameters of activation (ΔG #, ΔH #and ΔS #) were calculated from the pseudo-second order rate constant by using the Eyring equation. Results showed that Pb (II) adsorption onto SB is an associated mechanism and the reorientation step is entropy controlled.

Biosorption of toxic congo red dye from aqueous solution by eco-friendly biosorbent Saccharum bengalense: kinetics and thermodynamics

Abstract In the present study, Saccharum bengalense (SB), a potential biosorbent, was investigated for the removal of toxic Congo red (CR) dye. The effect of various operating variables, viz. adsorbent dosage, pH, contact time, and temperature on the removal of dye has been studied. Almost 94% removal of dye is possible after 50 min at pH 2.0 under batch test conditions. It was found that a pseudo-second-order mechanism was predominant and the overall rate of the dye adsorption process appears to be controlled by more than one step. The intra-particle diffusion model was applied to investigate the rate determining step. Langmuir, Freundlich, and Dubinin–Radushkevich adsorption isotherm models were applied to describe the biosorption isotherm. The biosorption data were better represented by the Langmuir model and the biosorption capacity (q max) of SB for CR was achieved at 125 mg/g. Thermodynamic parameters such as standard free energy change (ΔG°), standard enthalpy change (ΔH°), and standard entropy cha...

N-(2-Methyl­phen­yl)-6-(1H-pyrazol-1-yl)pyridazin-3-amine

The title compound, C14H13N5, crystallizes with two crystallographically independent molecules in the unit cell. The two molecules form dimers through intermolecular N—H⋯N and C—H⋯N hydrogen bonds. The hydrogen-bonding motifs are R 2 2(8) for both the N—H⋯N and C—H⋯N interactions. The pyrazole and pyrimidine rings form dihedral angles of 6.2 (3) and 8.3 (3)° with each other and the dihedral angles between the pyrazole and benzene rings are 54.9 (2) and 58.6 (2)°. The benzene rings of neighbouring dimers also exhibit C—H⋯π interactions.

Dye removal using carbonized biomass, isotherm and kinetic studies

AbstractEffect of thermal treatment on green tea dredge, an abundant waste, for dye removal was investigated in the present study. Variable temperature (800 and 900°C) and residence time in furnace (10 min, 1 and 2 h) were used to prepare six adsorbents which were characterized for surface morphology. The adsorption study was carried out using methylene blue as a model molecule and the effect of shaking time, pH and concentration was determined. Adsorbents prepared at 900°C were found to be more effective than those prepared at 800°C while longer residence time in furnace yielded adsorbents with higher adsorption capacity. The maximum adsorption capacity achieved in this case study was 71.4 ± 4.6 mg/g which is better than many activated carbons derived from other materials. Langmuir model was a better fit in isotherm studies while the sorption process followed pseudo-second-order kinetics.