Methode zur Bestimmung der Emission von Diphenylmethan-4,4′-diisocyanat (MDI) aus isocyanatgebundenen Holzwerkstoffen

A method for the determination of 4,4′-diphenylmethane diisocyanate (MDI) and 4,4′-methylenedianiline (MDA) in air is presented. The air sample is drawn through an impinger containing diluted hydrochloric acid as absorption solution. MDI hydrolyzes quantitatively to MDA and is determined together with MDA absorbed from the air by high performance liquid chromatography after derivatization with 2,4-dinitro-1-fluorobenzene. MDA was included in the analysis because of its carcenogenic potency and to avoid an eventual loss of MDI due to hydrolysis during exposure and sampling. The method is sensitive (detection limit ca. 0.5 μg MDI/MDA/m³) and specific; other diisocyanates as tolylene-2,4-diisocyanate (2,4-TDI), tolylene-2,6-diisocyanate (2,6-TDI), 1,6-diisocyanatohexane (HDI) and isophorone diisocyanate (IPDI), respectively the corresponding diamines, do not interfere. MDI-bonded particleboard and a polymeric MDI adhesive were exposed in a test chamber under worst case-conditions (particleboard: high surface/air volume ratio (2 m²/m³) without air exchange; adhesive: large open surface in a small test chamber (0.16 m²/0.01 m³), thick adhesive layer (600 g/m²) and sampling start immediately after spreading). No MDI/MDA-emission was found in the case of particleboard. During the first two hours of exposure the adhesive emitted a very low amount of MDI/MDA near the detection limit.