Characterization of low-molecular-weight metal species in plant extracts by using HPLC with pulsed amperometric detection and cyclic voltammetry |
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Authors: | G Weber F Alt and J Messerschmidt |
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Institution: | (1) Institut für Spektrochemie und Angewandte Spektroskopie, Bunsen-Kirchhoff-Strasse 11, D-44139 Dortmund, Germany, DE |
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Abstract: | An analytical separation scheme is presented for the isolation of low-molecular-weight metal species (< 10 kDa) in plants.
After ultrafiltration of the aqueous plant extracts isotachophoresis or gel chromatography is used for pre-separation and
HPLC at a cyclodextrin-phase for further separation of metal containing fractions. Trace metals are detected off-line by using
either adsorptive stripping voltammetry for platinum or AAS for zinc and magnesium. It is shown that platinum and zinc detection
closely correlate with pulsed amperometric detection (PAD), while magnesium behaves differently. PAD is carried out after
post-column addition of sodium hydroxide, thus enabling a sensitive and selective detection of carbohydrates. It is demonstrated
that cyclic voltammetry is a useful tool for further characterization of the PAD-detectable metal species. By comparison of
the cyclic voltammograms of carbohydrate standards, including carbohydrate-metal species, with the respective voltammograms
obtained from HPLC fractions, carbohydrate species isolated from the samples can be considered as being either partly oxidized
sugars (sugar alcohols or sugar acids) or glycosidically bound sugars.
Received: 26 January 1998 / Revised: 19 June 1998 / Accepted: 24 June 1998 |
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