No ambient air quality analysis is complete without an accurate quantitation of the toxic organic volatile hydrocarbons. The typical gas standard used in calibrating such an analysis is a mixture of paraffins/BTEX in nitrogen. This chromatogram illustrates how the detector's sensitivity to the air peak is suppressed when argon is added as a dopant. It also shows the PDD's remarkable sensitivity to a 30 ppb calibration mixture.

chromatogram of hydrocarbons

Courtesy of Scott-Marrin, Inc., John Marrin, president

Run conditions
Sample 250 µl of a 30 ppb paraffins/BTEX blend in nitrogen
Detector mode Argon photoionization
Discharge gas 1.5% Ar (mole) in helium, 30 mL/min
Dopant gas None
Detector temp 40°C
Column 100% dimethylpolysiloxane, 20m x 0.53mm
Column temp 30°C for 1 min to 110°C at 8°min
Attenuation 2 x 10-1