Amperometric flow-injection method for the assay of l-ascorbic acid based on the photochemical reduction of Methylene Blue

Ascorbic acid (AA) is determined by amperometric detection based on the photochemical reduction of Methylene Blue (MB +) in 0.1 M phthalate buffer at pH 3.8. In this medium, MB + using flow-injection analysis. The carrier stream is 1 mM MB + is reduced quasi-reversibly at a glassy carbon electrode a...

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Veröffentlicht in:Talanta (Oxford) 1996-08, Vol.43 (8), p.1275-1279
1. Verfasser: LEON, L. E
Format: Artikel
Sprache:eng
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Zusammenfassung:Ascorbic acid (AA) is determined by amperometric detection based on the photochemical reduction of Methylene Blue (MB +) in 0.1 M phthalate buffer at pH 3.8. In this medium, MB + using flow-injection analysis. The carrier stream is 1 mM MB + is reduced quasi-reversibly at a glassy carbon electrode at −0.34 V vs. Ag/AgCl, while AA is oxidized irreversibly at about 0.3 V. The reactor is irradiated with a 500 W halogen lamp to facilitate the development of the photochemical reaction. A laboratory-built wall-jet electrode system was used. The Leucomethylene Blue formed in the reaction is detected at +0.050 V. At 2.2 ml min −1 and using a sample loop of 43 μl, the method allows the determination of AA in the range 5.0–90.0 μg ml −1, with a relative standard deviation of 1.3–4.8%, a detection limit of 1.9 μg ml −1 and a sampling frequency of 45–50 h −1.
ISSN:0039-9140
1873-3573
DOI:10.1016/0039-9140(96)01846-2