Ewa M. Cukrowska Hermogne Nsengimana Luke Chimuka School of Chemistry, University of the Witwatersrand, Johannesburg, South Africa Original Paper Speciation of alkyllead in aqueous samples with application of liquid membrane probe for extraction and preconcentration Lead is known to be toxic, especially in its organic forms (organolead, OL). In the environment tetraalkyllead species are rapidly degraded by sunlight and atmo- spheric constituents like ozone or hydroxyl radicals. Such breakdown yields the soluble forms such as trialkyllead and dialkyllead and finally ionic lead species. The liquid membrane extraction probe (LMP) device has been developed and used as an extraction and preconcentration tool for the speciation analysis of organolead com- pounds by GC/MS. It allows analysis of OL species at low concentrations in compli- cated matrices of environmental samples. The effect of pH, stirring rate, and time that influence the extraction efficiency of OL extraction by the LMP method were optimized. The transformation of tetramethyllead in aqueous media at different concentrations of major ions K + , Na + , Ca 2+ , Mg 2+ , Cl – , SO 4 2– and the application of LMP to environmental samples are presented. It was found that degradation of tetra- methyllead takes between 24 and 37 days. The detection limit (LOD) of the method for all organolead species investigated is around 4.7 lg/L, with a limit of quantita- tion of 15 lg/L. Keywords: Liquid membrane extraction / Membrane probe / Organolead compounds speciation / Preconcentration / Water samples / Received: April 19, 2007; revised: May 21, 2007; accepted: June 18, 2007 DOI 10.1002/jssc.200700174 1 Introduction Organolead (OL), organotin (OT), and organomercury (OM) compounds are highly toxic [1, 2]. Their presence in environmental compartments is of great concern. A wealth of data has been reported from speciation studies of various heavy metal ions, far less on the organometal- lic forms of these metals. Organolead compounds are present in the environ- ment mostly as a result of tetraalkyllead compound used as antiknock additives in gasoline, but there are addi- tional sources of alkyllead provided by the natural meth- ylation of inorganic lead [1, 3]. Alkylleads enter the biosphere mainly in the form of tetraalkyllead which can undergo atmospheric break- down to form trialkylleads and dialkylleads. They can also spill into the terrestrial environment during trans- port and be directly scavenged from the atmosphere by rainfall ([1, 4, 5], see also The Lead Biogeochemical Cycle by R. Greenaway, 2005, www.mona.uwi.edu). Alkyllead species released into the atmosphere can be transported as free molecules or be adsorbed onto atmo- spheric particles and, therefore, enter into other environ- mental reservoirs via the hydrological cycle [5 – 7]. The toxicity of the various lead compounds depends upon several factors, including the solubility of the com- pound in body fluids and the molecular species to which they are chemically bonded [3]. Alkyllead compounds in the environment have more profound physiological effects than inorganic lead. The toxicity of alkyllead decreases in the sequence R 4 Pb A R 3 Pb + A R 2 Pb 2+ with R = – CH 3 or –C 2 H 5 , methylated lead species being less toxic than the ethylated compounds [6, 8]. Correspondence: Professor Ewa Cukrowska, School of Chemis- try, University of the Witwatersrand, P Bag 3, WITS, 2050 Johan- nesburg, South Africa E-mail: ewa.cukrowska@wits.ac.za Fax: +27-11-7176749 Abbreviations: ASV, anodic stripping voltammetry; DML, dime- thyllead; LMP, liquid membrane extraction probe; MAE, micro- wave assisted extraction; OL, organolead; OM, organomercury; OT, organotin; PLE, pressurized liquid extraction; TEL, tetra- ethyllead; TiEL, triethyllead; TiML, trimethyllead; TML, tetrame- thyllead i 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim www.jss-journal.com 2754 E. M. Cukrowska et al. J. Sep. Sci. 2007, 30, 2754 – 2759