Facile photometric quantification of aldehyde content in oxidized starches using 2-aminobenzamide oxime as an aldehyde selective reagent

Abstract

The oxidation of starch to aldehyde starch or dialdehyde starch introduces aldehyde groups to the starch core structure. This functionalization enables a wide range of further derivatization, e.g., oxidation to the corresponding carboxylic acid or functionalization to the corresponding amine via imine formation and reduction, which can be used for cross-linking. Herein, we report a novel method for efficiently quantifying these aldehyde groups based on the selective adduct formation of 2-aminobenzamide oxime (ABAO) and aldehydes. We initially implemented this photometric assay for C6-oxidized aldehyde starch using a plate reader, enabling parallel analysis of multiple samples in a fraction of the time and consistent with the conventional titration methods. Complementing this stream-lined analytical approach, we present an abbreviated workflow for faster downstream processing of reaction samples toward analysis. All of this was performed at a very small scale, cutting costs for (expensive) reagents and solvents, as well as drastically reducing working time. Finally, we also demonstrate our assay's applicability for quantifying the two aldehyde groups formed in dialdehyde starch derived from NaIO4 oxidation.