A novel method for the determination of carbonyl groups in cellulosics by fluorescence labeling. 1. Method development.

A novel method to accurately determine the carbonyl content in cellulosic materials by fluorescence labeling with carbazole-9-carboxylic acid [2-(2-aminooxyethoxy)ethoxy]amide has been developed. The procedure can readily be incorporated into a gel permeation chromatography (GPC) system with refractive index and multiple-angle laser light scattering detection. Both a homogeneous procedure, working in DMAc/LiCl (2.5%, w/v), and a heterogeneous derivatization approach, using aqueous buffer pH 4.0, for determination of carbonyls in pulps have been optimized with regard to reaction conditions, presence of catalysts, reproducibility, and completeness of conversion. The homogeneous labeling requires prolonged reaction times and removal of excess marker prior to GPC analysis by a time-consuming precipitation-washing-redissolution sequence, which is not needed in the heterogeneous approach. The heterogeneous procedure offers the additional advantages of higher efficiency, shortened analysis times, increased simplicity, and widest applicability.