Liquid chromatography with rapid scanning electrochemical detection at carbon electrodes

Abstract

An interpretation of eq 24 is that the slope of In with respect to xA is (0aí + /3AcXc); i.e., the "effect" of depends upon XC. Similarly, in eq 25 the slope of In with respect to xc is (ß + /3AcXa); •6•, the "effect" of xc depends upon .Substituting an estimated parameter value for, say, aniline gives (1.356 + 0.651xc) for the xA effect, and (-0.996 + 0.651 ) for the xc effect; similar effects are seen for the other solutes. In each case, the presence of one surfactant already adsorbed on the surface appears to cause a greater increase (or a lesser decrease) in In ft¡ when the other surfactant becomes adsorbed. However, as seen in Figures 1 and 2, increased adsorption of one surfactant is usually accompanied by decreased adsorption of the other surfactant. Thus, there seems to be a type of "self regulatory feedback" associated with this parameter. The possibility exists that the net effect of the 3ac parameter is zero and that it may be removed from the model.Elimination of the /3Ac term from the model expressed by eq 23 gives a total sum of squares of residuals only slightly larger than before (0.358 vs. 0.304). The values of the remaining parameter estimsites change only slightly (35% in the worst case). Thus, whatever the real phenomenological interpretation of the parameter ß it does not appear to be a necessary parameter to adequately model the systems described in this study.Registry No. Sodium octanesulfonate, 5324-84-5; octylamine, 111-86-4; aniline, 62-53-3; phenylethylamine, 64-04-0; benzenesulfonic acid, 98-11-3; chromotropic acid, 148-25-4.

Monitoring the Stimulated Release of Dopamine with In Vivo Voltammetry. I: Characterization of the Response Observed in the Caudate Nucleus of the Rat

“…The separated compounds were detected amperometrically at the oxidized basal plane of pressure-annealed pyrolytic graphite at +0.6 V vs. SCE. The above conditions allowed for the simultaneous determination of DOPAC, DA, 3-methoxybenzylamine, 3-methoxytyramine (3-MT), and 5-hydroxytryptamine within 30 min (Caudill et al, 1983). 3-Methoxybenzylamine was used as the internal standard.…”

Combination of Flow Injection Analysis and Fast Scan Differential Pulse Voltammetry for the Determination of Antioxidants

“…Alternatively, traditional single electrode systems can be also used to achieve multivariate signals in the so‐called fast‐scan voltammetry technique, where the electrode potential is quickly raised and lowered in a triangular wave fashion to allow the rapid acquisition of voltammograms within several milliseconds and ensures high temporal resolution. This approach was tested several times in the past, first on traditional glassy carbon electrodes and on microelectrode arrays , later particularly on microelectrodes due to the better suppression of the capacitance current . Besides the combination with HPLC and flow injection analysis (FIA), the technique was also applied in capillary zone electrophoresis .…”

“…Besides the combination with HPLC and flow injection analysis (FIA), the technique was also applied in capillary zone electrophoresis . Selected potential programs were compared, including normal pulse voltammetry, staircase voltammetry , cyclic voltammetry , and square‐wave voltammetry . The studies were generally aimed to the determination of neurotransmitters, hormones, and metabolites in biological systems.…”

Electrochemical determination of 6‐Mercaptopurine at silver microdisk electrodes

“…1−4 Also of importance is the possibility of introducing an extra domain for resolution of analytes by recording consecutive voltammograms as the solution containing the electroactive species moves past the electrode. 5,6 This can only be attained at scan rates fast enough, justifying the need for using microelectrodes since problems associated with both background increase and distortion in the wave shape are minimised. Another approach consists of using an assembly of independent microelectrodes parallel to the flowing solution, all of them held at a different potential by means of a multipotentiostat.…”