A sampling and analytical method for airborne m-phenylenediamine (MPDA) and 4,4'-methylenedianiline (MDA)

A method has been developed and validated for monitoring worker exposure to airborne m-phenylenediamine (MPDA) and 4,4'-methylenedianiline (MDA) in an epoxy resin manufacturing operation. Aerosol and vapor MPDA and MDA are collected on an acid-coated, glass-fiber filter to stabilize them as their amine salts. The amines are extracted from the filter with a mixture of acetonitrile in aqueous base and then treated with acetic anhydride to form the diacetamide derivatives. Studies were performed on the acetylation reaction to establish sample work-up conditions. The derivatives are analyzed by high performance liquid chromatography with UV detection. The method was tested for precision and accuracy using the National Institute for Occupational Safety and Health (NIOSH) criteria for a valid industrial hygiene method. The method may be used with confidence to measure from 0.90 to 755 micrograms of MPDA and/or 0.36 to 55 micrograms of MDA in a total air volume of 200 to 630 L, sampling at a rate of 1.5 to 2.0 L/min. Collected samples remain stable on filters for at least 1 week before analysis. The method will not suffer from interference from high relative humidity or other process volatiles, including diglycidyl ether of bisphenyl A and bis(2,3-epoxycyclopentyl) ether. Test atmospheres of the process materials were prepared in the laboratory for validation of the overall sampling and analytical method. This method can be applied to most aromatic amines and is recommended for monitoring both ambient and workplace air.