NEUBA®: A Multicolumn, Multidetector Liquid Chromatograph with Electrochemical Detection for Use in the Identification and Determination of Neurochemicals and Related Species
The widespread utilization of liquid chromatography with electrochemical detection to the determination of neurochemicals began to prominently appear in the literature following the initial utilization of a thin-layer electrochemical cell (Refshauge et al., 1974). The initial utilization of rather large diameter particles as the packing material for the liquid chromatograph led to what is now considered poor resolution. At best, the original systems accomplished the separation of only 3–4 compounds in 15–20 minutes. Rapid improvements in the area of liquid chromatography led to the development of columns having packings with particles of only 3μ in diameter. These systems have provided the separation of up to 18 compounds in 51/2–71/2 minutes (Lin et al., 1984). This represents a substantial advance in the capabilities of neuroscientists to examine the neurochemical mode of action of a variety of behavioral, psychological, and pharmacological events. However, one would certainly like to obtain even further amounts of information concerning such events at the neurochemical level. A hint at a possible route to obtain such further information was provided in a paper we published in 1976 (Blank, 1976). In this paper, we described a dual amperometric electrochemical detector which could be used in a serial arrangement. This detector, employing different potentials at the two electrodes, allowed for some expanded qualitative information concerning eluting components from a liquid chromatograph. This idea has been expanded upon somewhat and, more recently, many investigators have now used multiple electrochemical detectors in both parallel and series configurations to enhance the qualitative information derived from their chromatograms (Roston and Kissinger, 1982). Similar investigations employing multiple coulometric detectors have been reported by Matson and co-workers (Matson et al., 1984; Matson et al., 1987). Employing an initial screen electrode, the coulometric approach relies upon a series arrangement of flow-through carbon detectors which are placed at a variety of potentials. These potentials can be selectively oxidizing followed by oxidation and reduction aimed for particular chemical species, or can be arranged in a straightforward mathematical array to simply provide an on-line hydrodynamic voltammogram for the eluting species. The resultant output from such a multielectrode system is necessarily three-dimensional in character, since it contains information concerning the time, the current, and the applied potential. As expected, the qualitative information contained in such an approach is considerably enhanced over that one can receive from a simple single electrode, single column LCEC setup.
KeywordsQualitative Information Amperometric Detector Liquid Chromatography System Bypass Line Performance Liquid Chromatographic Analysis
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