Trimethyllead in artificial rainwater and urban dust

Following a feasibility study, it was found that trimethyllead (TML) would be of sufficient stability for the purpose of interlaboratory studies and possibly certifications of RMs whereas dialkyllead species and triethyllead were not stable enough. Interlaboratory studies were performed in 1992-1994 on TML in artificial rainwater and urban dust and enabled a significant improvement of the state-of-the-art to be achieved (Quevauviller et al., 1995b). These exercises were followed by a certification campaign aiming to certify TML in candidate RMs of artificial rainwater and urban dust. The between-laboratory agreement obtained was very satisfactory and both materials were proposed for certification. 

The artificial rainwater (RM 604) was proposed to be certified at the level of 55.2 (3.5) ng kg-1 (as TML). While the stability of the material was demonstrated at +20°C for a period of 12 months, storage conditions above this temperature (as tested at +40°C) would degrade its long-term stability. Additional checks made after 37 months, storage at +20°C showed a clear decay (around 20%) of TML and the candidate artificial rainwater material could hence not be considered as a CRM (Quevauviller et al., 1998b). 

The urban dust RM (CRM 605) was successfully certified (Table 6.1). The stability of the material at +20°C was verified over 37 months and was found to be suitable for certification an instability was, however, noted at +40°C which justified the recommendation to store the material at +4°C in the dark (Quevauviller etai, 1999b). 

The techniques used were based on solvent extraction (e.g. with pentane), complexation (e.g. with diethyldithiocarbamate, EDTA), derivatisation (e.g. hydride generation, propylation or ethylation), and capillary GC separation followed by a range of detection techniques (e.g. QFAAS, ICPMS, MIP-AES, MS) DPASV has also been successfully used. In the frame of this project, two new techniques were also developed and successfully applied, namely supercritical fluid extraction followed by CGC/MS and isotope dilution ICPMS after ethylation and CGC separation. A full description of the techniques is given elsewhere (Quevauviller, 1998b). 

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The project to improve the quality control of lead speciation analysis was started in 1990 by a feasibility study on the stability of alkyllead species in solution [118], and was concluded in 1991. The first interlaboratory study was conducted in 1992 [119] and was followed by a second exercise carried out in 1993 [120]. The certification campaign of trimethyllead in artificial rainwater and urban dust was conducted in 1995-96. 

Techniques used in the interlaboratory studies and in the certification campaigns on trimethyllead in artificial rainwater and urban dust are described below. 

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