A simplified apparatus for ambient formaldehyde detection via GC-pHID

An apparatus has been developed for the direct determination of ambient, atmospheric formaldehyde using gas chromatography. A loop sample of 1–6 ml is transferred onto the column and the formaldehyde is focused with a cold trap. Following separation, formaldehyde is detected with an argon doped, pulsed discharge helium ionization detector. Absolute values are obtained via calibration with a permeation source. A detection limit of 42 pptv is calculated. The relatively high duty cycle ( 11 h−1) allows measurements to be taken on timescales that are short compared to the atmospheric lifetime of formaldehyde. The reliability of the apparatus has been investigated via a 4-week field campaign at an urban site in Leeds, UK. Diurnal profiles are observed with evidence for both primary emissions from traffic and secondary, photochemical production. A decrease in formaldehyde concentrations was observed during rain events.