A Comparison of Photoionisation Detection Gas Chromatography with a Tenax GC Sampling Tube Procedure for the Measurement of Aromatic Hydrocarbons in Ambient Air

Photoionisation detector/gas chromatography (PID/GC) provides an opportunity for direct measurement of aromatic hydrocarbons in ambient air at ppb levels without preconcentration. The use of a portable PID/GC instrument has been evaluated and compared with a Tenax GC sampling tube method. The minimum detectable concentration using PID/GC was determined to be 0.3 ppb for benzene and toluene and 1.0ppb for C8-alkylbenzenes. At high concentrations (1ppm), were found using the Tenax GC preconcentration method. On-site measurement of aromatic hydrocarbons at a busy urban road-side location was undertaken using the two techniques. Measured concentrations of benzene and toluene compared favourably although the PID/GC technique was found to be inconsistent in the detection of low ambient concentrations of higher alkylbenzenes. However it is evident that rapid and direct measurement of a wide range of concentrations can be achieved using the PID/GC techniques which complement and in some cases supercede existing preconcentration techniques.