SILICA-BASED METAL CHELATE AFFINITY SORBENTS .1. PREPARATION AND CHARACTERIZATION OF IMINODIACETIC ACID AFFINITY SORBENTS PREPARED VIA DIFFERENT IMMOBILIZATION TECHNIQUES

Iminodiacetic Acid (IDA) was immobilised on silica supports using eith er activated chromatographic supports or silanes carrying IDA in omega -position to silicium. Through reaction of IDA with glycidoxypropyltri methoxysilane (GLYMO) before immobilization, a new and simple method i s introduced which provides a metal chelate affinity sorbent of both h igh capacity for Cu(II) (28 mu mol/ml) and almost identical chromatogr aphic characteristics to soft gel metal chelate affinity sorbents. By immobilization of IDA through n-alkyl spacers exclusive of an epoxy gr oup a different chemical neighborhood to the chelator is obtained. The se metal chelate sorbents demonstrated higher capacities for Cu(II) (3 9 mu mol/ml). The selectivity for lysine was higher, for histidine low er, compared to epoxy-immobilized IDA chelates. It is concluded that t he beta-hydroxyl group, evolved during reaction with epoxy groups, is integrated with the metal chelate, thus forming a N-(hydroxyethyl)imin odiacetic acid (HEIDA). The most distinct chromatographic behaviour wa s observed with CDI-immobilised IDA chelates, which displayed higher s electivity for acidic amino acids than common IDA chelates.