A sensitive, specific method for the determination of tetraalkyllead compounds in air by gas chromatography/atomic absorption spectrometry

Abstract

The development of a sensitive and specific method of determining individually the five tetraalkyllead compounds normally present in ambient air is described. The method is based on collection of the analytes on a porous polymer using a prefilter to destroy ozone and prevent decomposition of the sample during collection and storage. Two-stage thermal desorption, separation by gas chromatography and detection by modified flame atomic absorption spectrometry gives detection limits (3σ) of ca. 0.25 ng Pb m −3 for tetramethyllead and 0.37 ng Pb m −3 for tetraethyllead in an air sample of 80 dm 3 collected over a 3–24 h period. Environmental sampling by this method in paralle with a wet chemical (iodine monochloride) method was used to validate the method. During the comparative study, higher organic lead levels were consistently found by the iodine monochloride method; it is postulated that this indicates the presence of vapour-phase tri-(or di)-alkyllead in excess of 1 ng Pb m −3 in rural air. The versatility of the method is demonstrated by the results of atmospheric sampling at two locations, one rural and one at the kerbside in a city centre.