The development of an air sampling and analytic method for o-phenylenediamine in an industrial environment

A new method for monitoring o-phenylenediamine (OPD) in the industrial environment was developed. Some aromatic amines such as OPD are difficult to collect and analyze directly because they are sensitive to oxidation. The method developed overcomes this difficulty by derivatizing the OPD directly upon collection. The OPD vapor is drawn through a bubbler containing acetic anhydride to form the relatively stable 1,2-diacetamidobenzene. The acetic anhydride solution is analyzed by means of high performance liquid chromatography (HPLC), and the diacetamido derivative quantified. The analysis is linear for standard solutions in the range of 0.5 microgram/mL to over 0.5 mg/mL. Air concentrations of OPD were prepared by passing a metered stream of nitrogen through a class tube packed with OPD crystals and diluting the stream with a metered air stream to achieve the desired level. The collection efficiency and conversion of OPD to the derivative was found to approach 100% at vapor concentrations of 0.09 mg/m3 but was reduced to about 60% at 0.02 mg/m3. The poor recovery at low concentrations appeared to be at least in part due to wall adsorption. Moisture had little effect on sample collection and analysis. O-Toluenediamine, chemically similar to OPD, was found to interfere in the analysis.