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Electrochemical behavior of L-cysteine and its detection at ordered mesoporous carbon-modified glassy carbon electrode.

Authors
  • Zhou, Ming
  • Ding, Jie
  • Guo, Li-ping
  • Shang, Qing-kun
Type
Published Article
Journal
Analytical chemistry
Publication Date
Jul 15, 2007
Volume
79
Issue
14
Pages
5328–5335
Identifiers
PMID: 17555298
Source
Medline
License
Unknown

Abstract

In this paper, the electrochemical behavior of L-cysteine (CySH) was investigated thoroughly at an ordered mesoporous carbon-modified glassy carbon (OMC/GC) electrode. The voltammetric studies showed there were three anodic peaks for the electrooxidation of CySH in the pH range of 2.00-5.00; however, one peak disappeared above pH 5.00. This behavior has never been reported before. Through the studies of the effect of pH on the distribution fractions (delta) of the four chemical species of CySH, we conclude only CySH2+ (H3A+) and CyS- (HA-) are the electroactive substances and should be responsible for the electrooxidation of CySH. And for the first time, we successfully established the exact and systemic mechanisms based on the electroactive species to explain CySH oxidation at different pH values. On the other hand, a sensitive CySH sensor was developed based on an OMC/GC electrode, which shows a large determination range (18-2500 micromol L(-1)), a high sensitivity (23.6 microA mmol L(-1)), and a remarkably low detection limit (2.0 nmol L(-1), which is the lowest value ever reported for direct CySH determination on the electrodes) at pH 2.00. At pH 7.00, the modified electrode can be still used to readily detect CySH in the range of the physiological levels. These make OMC/GC electrode a promising candidate for efficient electrochemical sensors for the detection of CySH.

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