engleski

Indirect method for spectrophotometric determination of ascorbic acid in pharmaceutical preparations with 2, 4, 6-tripyridyl-s-triazine by flow-injection analysis

A flow-injection indirect spectrophotometric method for the determination of ascorbic acid (AA) in pharmaceutical preparations is proposed. The method is based on the reduction of iron(III) to iron(II) by the AA, and by the subsequent reaction of the produced iron(II) with 2, 4, 6-tripyridyl-s-triazine (TPTZ) in buffered medium (pH = 3.6) to form a coloured complex (max = 593 nm). The three-line manifold with one reaction coil was used. The linear range of the method is from 0.08 to 10 M of ascorbic acid, with the detection limit 24 nM of AA. The proposed method is simple, rapid (sampling rate of 180 samples per hour), sensitive and reproducible (RSD 0.8%, n = 100). The proposed method is very selective, because only the reducing substances with standard (formal) potentials lower than 0.6 V would have the thermodynamic predisposition to interfere in the proposed method. Tested reducing substances (thiol compounds) did not give serious errors when present at the same concentrations as the ascorbic acid. The proposed method can be applied for the determination of AA in pharmaceutical preparations, down to picomolar quantity.

ascorbic acid; flow injection analysis; indirect spectrometric determination; coupled redox-complexation reaction; 2; 4; 6-tripyridyl-s-triazine

Jedan od odabranih adova prezentiranih na skupu The 17th ICFIA, održanom 2011.g., Krakovw, Poljska.