Investigation of amine and polyol functionality in extracts of polyurethane wound management dressings using MALDI-MS

Polyurethane (PU) foams used in wound management are produced by a reaction between aromatic diisocyanates and polyether polyols. There is concern that residues of these starting materials, which may contain aromatic amine functionality, may leach from the finished polymer during in vivo applications. Furthermore, oligomers and additives may be leached from the PU system after the polymerization process is complete. Finished polymers have, therefore, been extracted with a range of solvents, such as water, diethyl ether and dilute HCl. The extracts were subjected to MALDI-MS (matrix-assisted laser desorption ionization mass spectrometry) analysis in an attempt to determine the amine and polyol functionality. Direct MALDI-MS analysis of the wound dressing extracts indicated the presence of the polyol used in the formulation of the foam. The spacing between the peaks identified the base monomer used in the polyol. MALDI-MS analysis of the fluorescamine derivatives of model amine compounds has demonstrated the anticipated increase in mass (278 for monoamines and 278 and 556 for diamines). Similar results were obtained from the derivatization of model polyols with phenyl isocyanate, where the mass shift (n × 119) was a direct measure of the number of active hydroxyl groups. Fluorescamine labelling of PU foam extracts shows the colour change indicative of the presence of an amine, but the subsequent MALDI-MS analysis was unable to demonstrate the anticipated increase in mass.