Determination of organic lead in soils and waters by hydride generation inductively coupled plasma atomic emission spectrometry

Abstract

This paper describes a simple and rapid method for the determination of the sum of tetraalkyllead (TAL) compounds (Me₄Pb, Et₄Pb) and their intermediate decomposition products, the trialkyllead (Me₃Pb⁺, Et₃Pb⁺) and dialkyllead (Me₂Pb²⁺, Et₂Pb²⁺) species.

The lead species in solution are transformed into the corresponding hydrides by sodium tetrahydroborate and directly introduced into the ICP torch. Hydride generation takes place in a continuous flow hydride generator and the products are fed into an inductively coupled plasma atomic emission spectrometer. This arrangement avoids the necessity for solvent extraction and sample transfer.

The reaction conditions (argon flow rate, concentration of acid and concentration of sodium borohydride) have been optimized. The acid is decisive for obtaining strongly different sensitivities for organic lead and inorganic lead; 2.0% (m/v) citric acid suppresses the signal of inorganic lead and this offers the possibility to determine the organolead compounds in the presence of excess amounts of inorganic lead, thus characterizing the method as a screening method.

Linear calibration for six organolead compounds of varying polarity (neutral and ionic species) was established over the concentration range of 0.1 to 100

µg l^–1. Spiked natural water and soil samples were analyzed by this method with recoveries of 71–107%. Best extraction efficiences were found for a mixture of 5 ml of 1% ammonical methanol and 5 ml of 0.2 M sodium acetate. The optimized method was tested for soil samples with varying matrices and a wide range of concentrations of alkyllead obtained from an old industrial production site.