Submicrogram quantities of organic phosphorous compounds in air were monitored by frustrated multiple internal reflectance (FMIR) spectroscopy. Vapor detection at these concentrations required the use of adsorptive films on the germanium FMIR cells. Of the various materials tried, platinum films gave the highest sensitivity. The effects of film thickness, temperature and organophosphorus compound concentrations were investigated. Adsorption was found to be reversible, permitting repeated use of detector probes. At optimum thickness and temperature 0.1 μg of dimethylmethylphosphonate per liter of air is detectable in 30 sec.
