The Study Of The Irreversible Biamperometry And The Application On The Pharmaceuticals Analysis

In this paper, the application of the irreversible biamperometriemethod in different electrodes has been presented. For different analyticalobjects, several coupling electrode (such as gold-gold modified electrode,glassy carbon modified electrode, platinum- platium electrode andgold-platium electrode) were selected to esblish the irreversiblebiamperometric detection scheme. And the analytical mechanism of thismethod has been discussed simply.This paper includes the works in the following aspects:1. L-cysteine self-assembled monolayers modified electrode (L-Cys/AuSAMs) has been prepared on bare gold wire. The proposed method is basedon the electrochemical oxidation of acetaminophen at the L-cysteine goldmodified electrode and the reduction of permanganate at the bare goldelectrode to form an irreversible biamperometric detection system. Underthe external potential difference (AE) of 0V, acetaminophen can bedetermined over the range of 2.0×10^-7-2.0×10^-4mol/L (r=0.9986, n=13). Thedetection limit is 9.5×10^-8mol/L and the RSD for 20 replicate determination of 1.00×10^-4mol/L acetaminophen is 1.9%. This proposed method has theadvantage of wide linear range, high selectivity and sensitivity. The disposalmethod of the sample is simple, and it is suitable to online analysis.2. A new method for the determination of vitamine B6 using polymermodified electrode is described in this paper. In pH=6.80 phosphate buffersolution, the poly (L-glutamie acid) modified electrode was prepared byusing cyclic voltammetric method on the bare glassy carbon electrode. Thevoltammetric behavior of vitamine B6 at the poly (L-glutamic acid)modified electrode has been investigated, and flow injection irreversiblebiamperometry analysis method were studied. Vitamine B₆ can bedetermined over the range 4.0×10^-6-2.0×10^-3 mol/L (r=0.9935, n=10). Thedetection limit is 9.0×10^-7 mol/L and the RSD for 20 replicatedeterminations of 4.0×10^-4 moi/L vitamine B6 is 1.1%. The method has theadvantage of simple, rapid, high selectivity and sensitivity, large linearrange, and low detection limit. The method is applied to the determinationof vitamine B₆ in the drug with satisfactory results.3. A flow injection irreversible biamperometrie method for the directdetermination of chlorogenic acid is described. The proposed method isbased on the electrochemical oxidation of chlorogenic acid at one pretreatedplatinum electrode and the reduction of permanganate at another electrodeto form an irreversible biamperometrie detection. Chlorogenic acid can bedetermined over the range 0.8-120 mg/L and the detection limit is 0.18 mg/L. The proposed method exhibits satisfactory reproducibility with a relativestandard derivation (RSD) of 2.2% for 19 successive determinations of40 mg/L chlorogenic acid.4. Based on the electrocatalytic oxidation of levodopa at gold electrodeand the reduction of permanganate at platinum electrode, a novel flowinjection irreversible biamperometric method is developed for thedetermination of levodopa. The linear relationships between currents andthe concentrations of levodopa are obtained in the range from 0.04 mg/L to20 mg/L with the detection limit of 0.012 mg/L. The stability of the proposedmethod is shown by a RSD of 0.89% for 41 successive determinations of 1.5mg/L levodopa. The proposed method has applied to the determination oflevodopa in pharmaceutical preparations.