Electrochemical characterization of tenoxicam using a bare carbon paste electrode under stagnant and forced convection conditions

Spectro-electrochemical characterization and quantification of Rutin in aqueous media

From UV-Vis spectrophotometric measurements the acidity constants of Rutin in aqueous media, at 25 °C and 0.1 M ionic strength, were determined as: pK₁ = 4.392 ± 0.167, pK₂ = 7.130 ± 0.050, pK₃ = 8.661 ± 0.042 and pK₄ = 12.354 ± 0.020 and the molar absorptivity coefficients of all the Rutin pH-dependent species were reported as a function of wavelength. Furthermore, the electrochemical behavior of Rutin at neutral pH was investigated using a bare carbon paste electrode, CPE. It was found that both: Rutin electrochemical oxidation and reduction are reversible, adsorption-controlled processes, involving 2 electron transfers. Moreover, the bare CPE was used for the electrochemical quantification of Rutin in neutral aqueous media, displaying the following features: (1.078 ± 0.440) μM, (3.594 ± 0.400) μM and (0.308 ± 0.014) μA μM^-1 for the detection and quantification limits and sensitivity, respectively, within the 1-11 μM linear range. Meanwhile the spectrophotometric method displayed the following analytical features: (3.385 ± 1.318) μM, (11.283 ± 3.114) μM and (0.0120 ± 0.0001) AU μM^-1 for the detection and quantification limits and sensitivity, respectively within the 11-110 μM linear range. In like manner, the bare CPE is also shown as a robust electrochemical sensor that allows Rutin quantification even in the presence of ascorbic acid, commonly found in Rutin samples.

Laccase immobilization on the electrode surface to design a biosensor for the detection of phenolic compound such as catechol

Biosensors based on the coupling of a biological entity with a suitable transducer offer an effective route to detect phenolic compounds. Phenol and phenolic compounds are among the most toxic environmental pollutants. Laccases are multi-copper oxidases that can oxide phenol and phenolic compounds. A method is described for construction of an electrochemical biosensor to detect phenolic compounds based on covalent immobilization of laccase (Lac) onto polyaniline (PANI) electrodeposited onto a glassy carbon (GC) electrode via glutaraldehyde coupling. The modified electrode was characterized by voltammetry, Fourier transform infrared (FTIR) spectroscopy and atomic force microscopy (AFM) techniques. The results indicated that laccase was immobilized onto modified GC electrode by the covalent interaction between laccase and terminal functional groups of the glutaraldehyde. The laccase immobilized modified electrode showed a direct electron transfer reaction between laccase and the electrode. Linear range, sensitivity, and detection limit for this biosensor were 3.2 × 10(-6) to 19.6 × 10(-6)M, 706.7 mAL mol(-1), 2.07 × 10(-6)M, respectively.