Ionization chamber as a gas sensor: organophosphorus compound detection

It is experimentally proved that a simple AC mode ionization chamber with an internal radiation source could be successfully used as a sensor for organophosphorus compounds (ca. 0.2 mg m−3) in the vapour phase. By adjusting the applied voltage and frequency, the chamber is brought to the proper operating region. At that point, the greatest change in the total current is obtained after formation of less mobile product ions. The chamber is calibrated for various organophosphorus compounds. The results are in a good agreement with predicted theoretical values. The response is fast and reversible. Partial selectivity is due to high proton affinity of organophosphorus compounds. The signal to noise ratio and different waveforms of applied voltage are also discussed.