Sample introduction and atomization of volatile alkyllead compounds in flame atomic absorption spectrometry

Abstract

Flame atomic absorption spectrometric (FAAS) analysis of organic liquids containing volatile organometallic compounds is discussed. Isobutyl acetate, acetone and a light hydrocarbon mixture (gasoline) were used as solvents and tetramethyllead (TML) and tetraethyllead (TEL) served as model compounds. Detailed analysis of the sample introduction process revealed that the analyte reaches the flame mostly as a vapour. The amount and composition of the vapour change significantly with the uptake rate. At low uptake rates the sample completely evaporates, whereas the composition of the vapour phase gradually approaches the value determined by the actual liquid–vapour equilibrium at higher uptake rates. The differences in efficiency of sample introduction, and hence in the analytical signals of different lead compounds, can be explained by their relative volatilities. The behaviour of volatile lead compounds in the nebulizer and the atomizer allowed a rapid and accurate FAAS method to be developed for the determination of total lead content and the concentrations of TML and TEL in light hydrocarbon mixtures.