Spectrophotometric determination of chromium(VI) in soil and steel samples using methdilazine hydrochloride^†

659-661Methdilazine hydrochloride has been used as a sensitive and selective reagent for the rapid spectrophotometric determination of chromium(VI). The reagent gives a red coloured species instantaneously on reaction with chromium(VI) in phosphoric acid medium and exhibits maximum absorbance at 512 nm with Sandell's sensitivity of 3.1ng cm-2. Beer's law is obeyed over the concentration range of 0.1-1.8 ppm; the optimum concentration range is 0.2-1.6 ppm. The method has been successfully applied to the analysis of chromium(VI) in steels and soil samples

Spectrophotometric determination of trace amounts of vanadium(V) with isothipendyl hydrochloride

465-467Isothipendyl hydrochloride is proposed as a selective and sensitive reagent for the rapid spectrophotometric determination of vanadium(V). The reagent instantaneously forms a red coloured species with vanadium(V) in phosphoric acid medium which exhibits maximum absorbance at 500 nm with Sandell's sensitivity of 6.55 ng cm-2. Beer's law is valid over the concentration range of 0.2-4.8 ppm with an optimum concentration range of 0.4-4.5 ppm. The method has been successfully applied to the analysis of vanadium steels and minerals

Spectrophotometric determination of vanadium(V) using methdilazine hydrochloride in minerals and steel samples

1107-1109Methdilazine hydrochloride has been used as a sensitive and selective reagent for the rapid spectrophotometric determination of vanadium(V). The reagent gives instantaneously a red coloured species on reaction with vanadium(V) in phosphoric acid medium and exhibits maximum absorbance at 512 nm with Sandell's sensitivity of 6.72 ng cm-2. Beer's law is obeyed over the concentration range 0.2-5.4 ppm; the optimum concentration range is 0.5-5.0 ppm. The method has been successfully applied to the analysis of vanadium steels and minerals

Spectroscopic studies on the interaction of riboflavin with bovine serum albumin

173-178The mechanism of interaction of riboflavin (RF) with bovine serum albumin (BSA) using fluorometric and circular dichroism (CD) methods has been reported. The association constant (K) for RF-BSA binding shows that the interaction is non-covalent in nature. Stern-Volmer analysis of fluorescence quenching data shows that the fraction of fluorophore (BSA) accessible to the quencher (RF) is close to unity, indicating that both tryptophan residues of BSA are involved in the interaction. The high magnitude of rate constant for quenching kq (1013 M-1s-1) indicates that RF binding site is in close proximity to tryptophan residue of BSA. Thermodynamic parameters obtained from data at different temperatures showed that the binding of RF to BSA predominantly involves the formation of hydrophobic bonds. Binding studies in the presence of a hydrophobic probe 8-anilino-1-naphthalene sulphonic acid, sodium salt (ANS) showed that RF and ANS do not share common sites in BSA. The small decrease in critical micellar concentration of anionic surfactant, sodium dodecyl sulphate in the presence of RF shows that ionic character of RF also contributes to binding and is not solubilized inside the micelle. Significant decrease in concentration of free RF has been observed in the presence of paracetamol. The CD spectrum shows the binding of RF leads to a change in the α helical structure of BSA

Spectrophotometric determination of iron(III) in ore, pharmaceutical formulations, plant material and foodstuff using piroxicam

576-578Piroxicam (PR) has been proposed as a sensitive and selective reagent for the spectrophotometric determination of Fe(III) in ore, pharmaceutical formulations, plant material and foodstuff. The method is based on the formation of a chloroform-soluble red coloured 1:1 complex by the reaction of Fe(III) with PR in Walpole buffer. Beer's law is valid over the concentration range of 0.4-6.4 ppm. The coloured complex exhibits an absorption maximum at 510 nm with molar absorptivity of 1.82×104 l mol-1 cm-1 and Sandell's sensitivity of 17.32 ng cm-2. The absorbances are found to increase linearly with increase in concentration of iron, which are corroborated by the calculated correlation coefficient value (0.9992). The effects of foreign ions in the determination of Fe(III) have been studied. Statistical comparison of the results with those of direct AAS method shows good agreement and indicates no significant difference in precision