Amperometric detectors electrode arrays

An assay for NE, E, L-DOPA, DA, 3-nitrotyrosine, m-,o-, and p-tyrosine compared an amperometric detector with a CoulArray detector. A CoulArray detector has the sensitivity of a coulometric detector applied to eight different electrodes to give an array of applied voltages. A C18 column with a mobile phase consisting of an acetate buffer (pH 4.75) and sodium citrate in methanol was used. The assay was... 

Many published articles on HPLC-ECD refer to the use of one of three voltammetric detectors (amperometric, coulometric, or polarographic). More detailed information on principles and techniques of various electrochemical detection modes can be obtained from the recent book, Coulometric Electrode Array Detectors for HPLC (34). There are also two electrode array detectors, the coulometric electrode array system and the CoulArray detector, currently available. Both detectors offer the qualitative data of PDA and the extreme sensitivity of ECD (34). The... 

The information that can be obtained with electrochemical detectors is not restricted to quantification. Instead of the conventional use of electrochemical detectors in amperometric mode at fixed potential, electrode arrays with each electrode held at different values of fixed potential can be used, in order to build up chronovoltammograms, three-dimensional current-voltage-time profiles. A 32-microband electrode array has been described for this purpose and applied to phenolic compounds [17] and which permits studying the electrode reaction mechanism at the same time as identification and quantification are carried out. Alternatively, fast voltammetric techniques such as fast-scan cyclic voltammetry or square wave voltammetry can be used to create chronovoltammograms of the eluted components. 

Iodide in urine [39] and catecholamines [40,41] are example of analytes recently detected electrochemically and studied under IPC conditions. Pulsed amperometric detection on a gold electrode was used to detect etimicin [42] and gentamicin [43] in commercial samples, thus avoiding tedious pre-column derivatization. Heterocyclic aromatic amines in soup cubes [44] were determined by a coulometric electrode array detector, and the coulometric detection of a quinone-bearing drug candidate [45] allowed the study of electrochemical properties. 

Carbon fibers have been used for array construction because they are more rigid than gold. The construction of carbon fiber arrays consisting of five layers of 20 electrodes was introduced by Caudill et al. (29) and used as a flow rate independent amperometric detector. Sleszynski et al. (25) reported the design of ensembles based on reticulate vitreous carbon embedded in epoxy resin. 

Fig. 4. Amperometric array response to various nitroaromatic explosives at a flow detector with four electrodes coated with different films. LP, lipid BR, bare NF, Nafion PP, polyphenol.

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