Formation of phosgene during welding activities in an atmosphere containing chlorinated hydrocarbons.

The formation of phosgene During welding activities in an atmosphere containing chlorinated hydrocarbons was investigated. Four different chlorinated hydrocarbons were studied under laboratory conditions. Results are presented as time-averaged phosgene concentration in a total volume of 250 L of air being purged through a 52-L reaction vessel during 20 min. It was found that the formation of phosgene was in the order dichloromethane < Freon-22 < carbon tetrachloride << trichoroethylene. Local concentrations may be higher depending on dispersion phenomena. The interpretation in terms of occupational health was rather difficult because of the interaction with smoke particles and because of possible nonhomogeneous dispersion of phosgene around the workers. In the case of dichloromethane and carbon tetrachloride the short-term maximum allowable concentration (MAC) of phosgene was not attained at the respective MAC values of the chlorinated hydrocarbons themselves. In the case of trichloroethylene and Freon-22, however, the short-term MAC-value of phosgene was attained even when the concentration was still much below the respective MAC-values.

Detection of staphylococcal enterotoxin B employing a piezoelectric crystal immunosensor.

This paper reports on a study concerning the development of a biochemical sensor for Staphylococcal Enterotoxin B (SEB), a substance within the bracket of biological warfare. A 20 MHz piezoelectric quartz crystal sensor device was employed in a flow injection system. The assay for SEB is based on a competition scheme using polyclonal antibodies (anti-SEB). Three parameters, i.e. the flow rate in the flow cell, the incubation time and the anti-SEB concentration, were optimized. A detection limit of 0.1 microgram/ml was obtained, whereas at concentrations of SEB of 10 micrograms/ml or higher the sensor response was completely inhibited. The results were compared with a competition enzyme linked immunosorbent assay.

Development of a surface acoustic wave gas sensor for organophosphorus nerve agents employing lanthanide compounds as the chemical interface.

The results of a study dealing with surface acoustic wave gas sensors for organophosphorus compounds such as nerve agents are described. Several lanthanum coordination compounds were applied as the chemical interface. The various sensors prepared were challenged with both the nerve agent sarin and the simulant dimethyl methylphosphonate. Many aspects were studied, such as sensitivity, selectivity, reversibility and response rate as well as the effect of temperature and structural features. Detection limits down to 0.1 ppm were found. Response rates require further improvement. Degradation phenomena were observed which in some cases yielded irreversible responses. The selectivity for organophosphorus compounds was found to be promising.

Various means for the detection of organophosphorous compounds.

Several reaction principles can be used for the detection of organophosphorous compounds. E.g. the "molybdenum blue" method, the colorimetric and fluorimetric variants of the Schoenemann reaction, electrochemical detection of cyanides upon reaction with certain oximes, photoemission of exitated HPO molecules in a hydrogen rich flame and the well known enzymatic detection of cholinesterase inhibiting compounds. Various detection systems have been developed varying from simple, manually operated devices to more sophisticated and continuous functioning detectors. These well established detection principles and some new emerging techniques, like microsensors using the surface acoustic wave technique, will be discussed.