Electrochemical determination of thiols at single-wall carbon nanotubes and PQQ modified electrodes.
The electrocatalytic oxidation of thiols has been observed at a glassy carbon (GC) electrode coated with a single-wall carbon nanotube (SWNT) film. Fourteen thiols including L-cysteine (CySH) and glutathione were tested using the SWNT/GC electrode, and the cyclic voltammetry (CV) showed that each thiol was oxidized at much less positive potential than those at other electrodes such as bare GC and diamond electrodes. The SWNT/GC electrode was also modified with pyrroloquinoline quinone (PQQ) which showed a further improvement of the catalytic behavior of the SWNT/GC electrode: e.g. the oxidation peak current of CySH was observed at 0.27 V vs. Ag/AgCl in pH 7.5 phosphate buffer. The amperometic responses at these electrodes showed a linear relationship with the substrate concentration in a 10(-6)-10(-3) M range and 10(-6)-10(-7) M detection limits for several thiols including CySH, L-homocysteine, N-acetyl-L-cysteine, L-penicillamine and glutathione. These electrodes show a response time of 2-3 s and storage stabilities over 3 weeks. A PQQ/SWNT/GC electrode has been successfully applied for the assay of both L-cysteine and N-acetyl-L-cysteine in the dietary supplement.
Han
Heyou
H
Department of Chemistry, Jackson State university, 1400 J. R. Lynch Street, Jackson, MS 39217, USA.
Tachikawa
Hiroyasu
H
D003545:Cysteine / Q000032:analysis*; D004563:Electrochemistry / Q000379:methods*; D004566:Electrodes; D008956:Models, Chemical; D037742:Nanotubes, Carbon; D045542:PQQ Cofactor / Q000737:chemistry*; D013438:Sulfhydryl Compounds / Q000032:analysis* / Q000737:chemistry
D037742:Nanotubes, Carbon; D013438:Sulfhydryl Compounds; D045542:PQQ Cofactor; D003545:Cysteine