Electrochemical analytical methods lead analysis

Reversed-phase high-performance liquid chromatography (RP-HPLC) is the usual method of choice for the separation of anthocyanins combined with an ultraviolet-visible (UV-Vis) or diode-array detector (DAD)(Hebrero et al., 1988 Hong et ah, 1990). With reversed-phase columns the elution pattern of anthocyanins is mainly dependent on the partition coefficients between the mobile phase and the Cjg stationary phase, and on the polarity of the analytes. The mobile phase consists normally of an aqueous solvent (water/carboxylic acid) and an organic solvent (methanol or acetonitrile/carboxylic acid). Typically the amount of carboxylic acid has been up to 10%, but with the addition of a mass spectrometer as a detector, the amount of acid has been decreased to as low as 1 % with a shift from trifluoroacetic acid to formic acid to prevent quenching of the ionization process that may occur with trifluoroacetic acid. The acidic media allows for the complete displacement of the equilibrium to the fiavylium cation, resulting in better resolution and a characteristic absorbance between 515 and 540 nm. HPLC separation methods, combined with electrochemical or DAD, are effective tools for anthocyanin analysis. The weakness of these detection methods is a lack of structural information and some nonspecificity leading to misattribution of peaks, particularly with electrochemical... 

A final class of materials is the optically transparent electrodes based on metal oxides (e.g., indium-tin oxide, ITO). These materials are very popular in the field of energy conversion, as a support for Dye-Sensitive Solar Cells, but the group of Heinemann developed at the end of the 1990s a spectroelectrochemical sensing method based on such transparent electrodes. The method is defined as the coupling of an electrochemical detection with a spectroscopic analysis." " This approach allows for multimode selectivity and is usually applied in the presence of surface modification for preconcentration of the analyte. More recently, porous and optically transparent electrodes have been prepared and applied for combined spectroscopic and electrochemical analysis" " which should lead in a near future to further developments in analytical sciences applied to the environment. 

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