Enhancement of the detection sensitivity for volatile organic compounds by using an annular type photoionization detector and a pre-concentration system

Photoionization detector (PID) was developed for a sensitive on-site detection of trace amounts of volatile organic compounds (VOCs) based on an annular type ion collection electrode assembly. An ion collector with an annular geometry could detect more stable ion signals in the PID system when compared to the other types of ion collectors when an UV lamp of 10.6 eV was used as an ionization source. In order to enhance the detection sensitivity, a pre-concentration system, which was developed by adopting a ceramic heater packed with rod shaped molecular sieves, was adopted for a detection of VOCs. The adopted ceramic heaters had a resistance of 10–20 Ohm, and the temperature of the heater was optimized by controlling the heating time of the resistor. The enhancement of the detection sensitivity was found to be 8–10 times with the PID system when compared to the signals measured without a pre-concentrator. The overall detection sensitivity of the developed PID system was estimated as 10 ppb or better.