Silver nanospheres (AgNS) with SPR band ∼417 nm was synthesized by Green synthesis, using a pre‐hydrolysed liquor (PHL) of Nilgiri wood without any pretreatment. The synthesis was carried out at room temperature and was complete within three hours. The reduction and stabilization of silver is brought about by hemicelluloses present in the pre‐hydrolysed liquor. Electrochemical oxidation of nitrite on glassy carbon electrode (GCE) modified with the AgNS in 0.1 M phosphate buffer solution (PBS) of pH 7.0 was found to occur at 0.86 V with respect to Ag/AgCl. Electrochemical sensing experiments with AgNS/GCE showed a linear range of detection between 0.1 to 8 μM, with detection limit of 0.031 μM and a sensitivity of 580 μA mM−1cm−2.
Summaw. Penicillins are determined by means of ion-pair formation with azure B and extraction into chloroform:the absorbance of the extract is stable for several days. The apparent molar absorptivities for sodium penicillin G and potassium penicillin V at 634 nm are 3.91 x 10' and 1.25 x 10' 1 mol-' cm-', respectively_ Calibration graphs are linear over the range 60-950 pg of sodium penicillin G and 40-600 pg of potassium penicillk V in 10 ml. The method is successfully applied to pharmaceutical preparations.
Hydrogeochemical investigations with emphasis on groundwater fluoride concentrations were carried out in the Shivani watershed area, Karnataka, South India. This drought-prone watershed is characterised by poor groundwater potential and is composed of different lithounits like gneisses, migmatites, tonalites, mafics-ultramafics, conglomerates and quartzites. Analysis of spatial variation of groundwater fluoride concentration through the use of GIS technology software platforms like ArcView 3.2a and MapInfo Professional 8.5 has enabled the identification of low-fluoride and high-fluoride areas within the watershed. Geochemical data indicates that 38% of groundwater samples have excessive fluoride concentration which poses a health risk to the population of the area. Correlation studies indicate that higher groundwater alkalinity activates leaching of fluoride resulting in elevated concentrations of fluoride. No other significant geochemical interrelationship could be identified between fluoride and rest of the physico-chemical parameters owing to the lack of any significant correlation coefficients. This holds good in the case of both low-fluoride (\1.5 mg/L) and high-fluoride ([1.5 mg/L) groundwaters of the watershed. However, differential or non-uniform type (positive or negative) of coefficient of correlation is observed between fluoride at different levels and other physico-chemical parameters. Among the different lithounits of the study area, gneisses house comparatively more number of high-fluoride groundwaters. Fluoride-bearing minerals biotite, hornblende and apatite are the probable natural sources of groundwater fluoride.
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