Development of a method for extraction and determination of 4,4′-methylenedianiline in soils by solid-phase extraction and UPLC-MS-MS

The 4,4′-methylenedianiline (MDA) substance is an important chemical intermediate which is produced in very large tonnages, the majority of which is consumed in its conversion to 4,4′-methylenediphenyl diisocyanate (MDI). The MDA substance has known adverse effects which can be associated with human and environmental exposure. The growing number and volume of applications of polyurethane formulations containing MDI in the open environment and in agriculture has led to increased concern about indirect exposure to MDA in the environment, where it may occur as a potential degradation product of these polyurethane materials. This method employs ultra performance liquid chromatography coupled to tandem mass spectrometry. A recovery of (101.1 ± 5.2) % of MDA was demonstrated for samples prepared by spiking known amounts of MDA to a representative sandy loam surface soil. The overall method was adjusted to a deliver a dynamic MDA detection range from 5 to 250 μg/kg MDA load (dry wt.) in soils. The accuracy of the method was evaluated at 87%, while intra- and inter-day precision were 9% and 8%, respectively. When coupled with an integrated soil sampling strategy and a solid-liquid extraction protocol validated across a wide variety of soil types, the developed method will prove a powerful tool for definitively quantifying the occurrence (or absence) of MDA in both targeted and exploratory soil monitoring programs.