Abstract
Three different methods—a high performance liquid chromatographic (HPLC) method, a colorimetric method and a continuous tape monitoring method—were utilized to determine the concentrations of diphenylmethane diisocyanate (MDI) in the air of different environments. The determinations were made of two industrial work atmospheres and in a laboratory exposure chamber. Comparison of the methods showed that neither the colorimetric nor the tape monitoring method are sensitive enough to determine trace concentrations of MDI (< 0.2·10-2 and < 1·10-2 mg/m3 respectively). Determinations made with the liquid chromatographic method at different rates of sampling yielded similar results on simultaneous sampling even at a concentration level of about 0.2·10 2 mg/m3, which indicates that HPLC is a fairly precise method as to both sampling and analysis. The volumes during sampling varied from about 5 L to 150 L. The recommended flow rate chosen was 2.5–3.0 L/min. The analysis showed that the use of one bubbler when samples were taken was satisfactory. The concentration of MDI in the atmospheres of the studied workplaces were all well below the current threshold limit value of 0.2 mg/m3.