A spectrophotometric assay for soluble and immobilized N-hydroxysuccinimide esters

A quantitative spectrophotometric assay for N-hydroxysuccinimide and its esters based on the formation of a chromophore upon titration with mild base has been developed. The maximum absorbance for the chromophore is at 260 nm with an extinction coefficient of 9700 m−1 cm−1. The method can be used for measuring the active esters on carriers and their interaction with amines during peptide synthesis.