Determination of Tetramethyllead and Tetraethyllead in the Atmosphere by a Two-Step Enrichment Method and Gas Chromatographic-Mass Spectrometric Isotope Dilution Analysis

The development of a specific and sensitive technique for determining tetramethyllead (TML) in air is described. The method has been tested in different areas under differing meteorological conditions to determine the atmospheric content of TML and tetraethyllead (TEL). The advantages and limitations of the method are critically discussed.

The tetraalkyllead compounds are collected on Porapak QS or N at ambient temperature, desorbed, re-collected at -80°C on a small column containing 4% Apiezon M on Chromosorb PAW-DCMS, and analysed by gas chromatography—mass spectrometry with single ion monitoring. The isotope dilution technique is used by adding known amounts of d12-TML and d20-TEL to the sampling columns in advance.

This makes it possible to correct for decomposition during the sampling and/or during the analytical procedure. The detection limit for TML is 20 pg m-3.