Selenomethionine-catalyzed nickel ion reduction at a mercury electrode: applications in the analysis of nutritional supplements
Journal article, Peer reviewed
MetadataVis full innførsel
- Institutt for kjemi 
Selenomethionine (SeMet) is a catalyst for Ni(II) reduction at a mercury electrode in a borax buffer at pH around 9 and gives rise to a differential pulse voltammetric peak, A, at -0.74 V vs. the Ag|AgCl, (3 M KCl) reference electrode. Peak current is directly proportional to SeMet over the concentration range 0.4–10 µM. Alkali and alkali-earth ions depress to some extent the sensitivity but the current-concentration relationships remains linear even under these conditions. Differential pulse cathodic stripping voltammetry (DPCSV) in 0.01 M borax results in two partially overlapped peaks. The more negative (A, at about -0.74 V) is similar to that recorded with no deposition and is due to the catalysis by non-adsorbed SeMet, whereas the more positive one (B, at about –0.60 V) results from the catalysis by adsorbed SeMet. Only the DPCSV peak A appears if 0.1 M KNO3 is also present along with 0.01 M borax. Stearic acid, which is present in nutritional supplement tablets, improves the separation of the DPCSV peaks. Consequently, the peak B recorded with 0.01 M borax buffer allows determining SeMet in nutritional supplement tablets by the standard addition method.