Development of Colorimetric Method for the Detection of Amines Bound to Solid Support

Abstract

4-N,N′-Dimethylaminoazobenzene-4′-isothiocyanate (DABITC), malachite green isothiocyanate (MGI) and 2,3-indolinedione (isatin) have been evaluated for the detection of primary aromatic and secondary aliphatic/aromatic amines bound to polystyrene resins. Isatin was found to be an ideal reagent for the derivatisation of resine bound compounds containing a proline residue. Both DABITC and MGI reacted with primary and a secondary resin bound amines. However, MGI was found to be the more useful reagent because reaction with this dye gives distinctly coloured polystyrene beads. Beads containing bound aniline turned from brown to green and those containing bound proline or piperazine turned from white to deep-blue in colour. The sensitivity of the colorimetric assay was tested by treating a resin containing partially derivatised (approximately 11% unreacted amine) piperazine with MGI. The resin turned from white to deep-blue in colour, demonstrating the presence of unreacted piperazine.