A simple method for the estimation of amino groups on insoluble matrix beads

A method for the determination of free amino groups on solid supports is proposed. The method is based on the reaction of the matrix with excess 2,4,6-trinitrobenzenesulfonic acid (TNBS) and subsequent quantitative determination of unreacted TNBS by reaction with glycine. The method is simple and reproducible and does not require the solubilization of the matrix, therefore proving suitable even for crosslinked insoluble supports.