Correction for Irrelevant Absorption in Multicomponent Spectrophotometric Assay of Riboflavin, Formylmethylflavin, and Degradation Products: Kinetic Applications

Abstract

Abstract. In the spectrophotometric assay of multicomponent systems involved in drug degradation studies, some minor or unknown degradation products may be present. These products may interfere in the assay and thus invalidate the results due to their absorption in the range of analytical wavelengths. This interference may be eliminated by the application of an appropriate correction procedure to obtain reliable data for kinetic treatment. The present study is based on the application of linear and non-linear irrelevant absorption corrections in the multicomponent spectrophotometric assay of riboflavin and formylmethylflavin during the photolysis and hydrolysis studies. The correction procedures take into account the interference caused by minor or unknown products and have shown considerable improvement in the assay data in terms of the molar balance. The treatment of the corrected data has led to more accurate kinetic results in degradation studies.

Photo, thermal and chemical degradation of riboflavin

“…It is hydrolyzed to LC and LF [18–19 22–33] and is oxidized to CMF [20,27,32]. Both LC and LF are also sensitive to light, with LC having relatively better stability [36].…”

“…It has been suggested that the formation of the β-keto acid and the flavo-violet type compounds takes place through a 1,2-dihydro-1-methyl-2-oxo-quinoxaline-3-carboxyureide intermediate in the reaction [164]. The presence of similar compounds in the hydrolytic degradation of formylmethylflavin in alkaline media has been reported [33]. Earlier studies on the alkaline hydrolysis of FMF showed the formation of LC and LF by the cleavage of the formyl side chain [19,22].…”

“…It shows strong absorption at 223, 267, 373 and 444 nm in the UV and visible regions in aqueous solution and is degraded into various photoproducts on exposure to light [ 1 ]. These products include formylmethylflavin (FMF), lumichrome (LC), lumiflavin (LF), carboxymethylflavin (CMF), 2,3-butanedione, a β-keto acid and a diketo compound [ 14 – 33 ]. Some of the products reported earlier [ 14 , 20 , 34 ] still need to be identified.…”

“…FMF is an intermediate in the photodegradation of RF and is more sensitive to light than RF [ 15 – 17 27 , 32 – 33 ]. It is hydrolyzed to LC and LF [ 18 – 19 22 – 33 ] and is oxidized to CMF [ 20 , 27 , 32 ]. Both LC and LF are also sensitive to light, with LC having relatively better stability [ 36 ].…”