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Relevant academic research and scientific papers

Liquid phase determination of isuprel in pharmaceutical and biological samples using a nanostructure modified carbon paste electrode

The electrochemical behavior of isuprel (ISP) on the ionic liquid of 1,3-dipropylimidazolium bromide NiO nanoparticle (NiO/NPs) modified carbon paste electrode (IL/NiO/NPs/CPE) was studied in this paper and further used for ISP detection. ISP showed a diffusion oxidation process on the IL/NiO/NPs/CPE with the oxidation peak potential located at 0.62 V (vs. Ag/AgCl/KClsat) in a pH 5.0. Compared with that on the traditional carbon paste electrode, small shift of the oxidation peak potentials appeared but with a great increment of the oxidation peak current on the IL/NiO/NPs/CPE, which was due to the presence of ionic liquid and NiO/NPs in the modified electrode. The diffusion coefficient (D) was also determined using electrochemical approaches. The linear response range and detection limit were found to be 0.4-500 μmol L- 1 and 0.1 μmol L-1, respectively. Other physiological species did not interfere in the determination of ISP at the surface of the proposed sensor in the optimum condition. The proposed sensor was successfully applied for the determination of ISP in real samples.

Stereospecificity of mushroom tyrosinase immobilized on a chiral and a nonchiral support

Mushroom tyrosinase was immobilized from an extract onto glass beads covered with the cross-linked totally cinnamoylated derivates of D-sorbitol (sorbitol cinnamate) and glycerine (glycerine cinnamate). The enzyme was immobilized onto the support by direct adsorption, and the quantity of immobilized tyrosinase was higher for sorbitol cinnamate, the support with the higher number of esterified hydroxyls per unit of monosacharide, than for glycerine cinnamate. The results obtained from the stereospecificity study of the monophenolase and diphenolase activity of immobilized mushroom tyrosinase are reported. The enantiomers L-tyrosine, DL-tyrosine, D-tyrosine, L-dopa, DL-dopa, D-dopa, L-α-methyldopa, DL-α-methyldopa, L-isoprenaline, DL-isoprenaline, L-adrenaline, DL-adrenaline, L-noradrenaline, and D-noradrenaline were assayed with tyrosinase immobilized on a chiral support (sorbitol cinnamate), whereas L-tyrosine, DL-tyrosine, D-tyrosine, L-dopa, DL-dopa, D-dopa, L-α-methyldopa, and DL-α-methyldopa were assayed with tyrosinase immobilized on a nonchiral support (glycerine cinnamate). The same Vmaxapp values for each series of enantiomers were obtained. However, the Kmapp values were different, the L isomers showing lower values than the DL isomers, whereas the highest K mapp value was obtained with D isomers. No difference was observed in the stereospecificity of tyrosinase immobilized on a chiral (sorbitol cinnamate) or nonchiral (glycerine cinnamate) support.