LIQUID-CHROMATOGRAPHIC DETERMINATION OF RESIDUAL ISOCYANATE MONOMERS IN PLASTICS INTENDED FOR FOOD CONTACT USE

A liquid chromatographic (LC) method was developed for the analysis of 10 isocyanates in polyurethane articles and laminates intended for fo od use. Residual isocyanates are extracted by dichloromethane with con current derivatization by 9-(methylaminomethyl)anthracene. The resulta nt derivatives are analyzed by reversed-phase LC with fluorescence det ection. Separation of the isocyanates was studied and optimized. Quant itation uses 1-naphthyl isocyanate as internal standard and standard a ddition to the food package. Validation demonstrated the method to hav e good precision (+/- 2-5%) and recovery (83-95%) for samples spiked w ith isocyanates at 0.1 mg/kg. The limit of detection was 0.03 mg/kg. A nalysis of 19 commercial polyurethane or laminate food packages demons trated that the method was not prone to interferences. Residues of dip henylmethane-4,4'-diisocyanate were detected in 5 packages and ranged from 0.14 to 1.08 mg/kg.