Speciation of organolead compounds

C. Concentration and Speciation of Organolead Compounds in the Natural Environment... 

Heisterkamp, M., DeSmaele, T., Candelone, J.E, Moens, L., Dams, R. and Adam, F.C. (1997) Inductively coupled plasma mass spectrometry hyphenated to capillary gas chromatography as a detection system for the speciation of organolead compounds in environmental waters./. Anal. At. Spectrom., 12, 1077-1081. 

Leal-Granadillo, I. A., Garcfa Alonso, J. I., and Sanz-Medel, A. (2000) Determination of the speciation of organolead compounds in airborne particulate matter by gas chromatography-inductively coupled plasma mass spectrometry. Anal. Chim. Acta, 432, 21-9. 

Bergmann, K. andNeidhart, B. (1996) Speciation of organolead compounds in water samples by GC-AAS after in-situ butylation with tetrabutylammonium tetrabutylborate. Fresenius J. Anal Chem., 356, 57 61. 

Lobinski, R., Boutron, C.F., Candelone, J.P., Hong, S.M., Szpunarlobinska, J. and Adams, F.C. (1993) Speciation analysis of organolead compounds in Greenland snow at the femtogram-per-gram level by capillary gas chromatography/atomic emission spectrometry. Anal. Chem., 65, 2509-2515. 

Lobinski, R., Dirkx, W.M.R., Szpunar-Lobinska, J. and Adams, F.C. (1996) Speciation analysis of organolead compounds. Status and future projects. In Quality Assurance for Environmental Analysis (eds Quevauviller, Ph., Maier, E.A. and Griepink, B.), Vol. 14. Elsevier, Amsterdam, 320 pp. 

Investigations of lead speciation in various environmental samples have relied upon gas and liquid chromatographic separations coupled to mass spectrometric and atomic absorption spectrometric detectors. The combination of atomic absorption spectrometry with gas chromatography (GC-AAS) has proved to be the most widely applied technique. Sample types have included air, surface water, air particulates, sediments, grass, and clinical materials such as blood. A review of speciation analyses of organolead compounds by GC-AAS, with emphasis on environmental materials, was published (Lobinski et al., 1994). 

The concentrations of organolead compounds found in the different environmental compartments are often in the pgm, ngl , and ng per g levels for air, water, and sediment and biological tissues, respectively. However, inorganic lead forms can simultaneously be present in the same samples at a 1000-fold higher level. For this reason, the instrumentation necessary to carry out lead speciation analysis in real samples requires the isolation, separation, and sensitive detection of the individual organolead species in the presence of thousands of... 

Atomic absorption spectrometry (AAS) was established as the most popular gas chromatography (GC) detection technique for lead speciation analysis in the first years of speciation studies. The increase of the residence time of the species in the flame using a ceramic tube inside the flame and, later, the use of electrically heated tubes, made out of graphite or quartz where electrothermal atomization was achieved, provided lower detection limits but still not sufficiently low. Later, the boom of plasma detectors, mainly microwave induced plasma atomic emission (MIP-AES) and, above all, inductively coupled plasma atomic emission and mass spectrometry (ICP-AES and ICP-MS, respectively) allowed the sensitivity requirements for reliable organolead speciation analysis in environmental and biological samples (typically subfemtogram levels) to be achieved. These sensitivity requirements makes speciation analysis of organolead compounds by molecular detection techniques such as electrospray mass spectrometry (ES-MS) a very difficult task and, therefore, the number of applications in the literature is very limited. 

Chau et al pointed out that as the authenticity of the compounds to be analyzed must be preserved, any of the digestion methods with acids or alkalis are not suitable, and that extraction seemed to be the method of choice for removing these compounds from samples. For this traction, they adopted benzene as recommended by Sirota and Uthe for the quantitative extraction of tetramethyllead and tetraethyllead from fish homogenates suspended in aqueous EDTA solution. Although ionic forms of lead such as Pb(II), diethyllead dichloride, and trimethyllead acetate do not extract in the benzene phase, any lead compounds that distribute into the benzene phase as tetraalkyllead will be determined. Chau et al421 found that environmental samples can contain other forms of organolead compounds that are extractable into benzene but which are not volatile enough to be analyzed by the GC-AAS technique, hence the need for a speciation specific analytical system. 

Heisterkamp M. and Adams F. C. (2001) Gas chromatography-induc-tively coupled plasma-time-of-flight mass spectrometry for the speciation analysis of organolead compounds in environmental water samples, Frese-nius J. Anal. Chem. 370 597-605. 

Schubert, P., E. Rosenberg, and M. Grasserbauer. 2000. Comparison of sodium tetraethylborate and sodium tetra(n-propyl)borate as derivatization reagent for the speciation of organotin and organolead compounds in water samples. Fresenius J. Anal. Chem. 366 356-360. 

Methylmercury species in sediment samples were speciated in a study by Hintelman et al. [89]. Detection limits were 1 pg (as Hg) in dry sediment samples. Organomercury compounds, along with organotin and organolead compounds, were also separated in another study by Prange and Jantzen [90]. Detection limits were three orders of magnitude lower than those reported previously in the literature. A quartz transfer line was used in this study. 

Salih, B. Speciation of inorganic and organolead compounds by gas chromatography-atomic absorption spectrometry and the determination of lead species after pre-concentration onto diphenylthiocarbazone-anchored polymeric microbeads. Spectrochim. Acta B 55, 1117-1127 (2000)... 

Several efforts have been carried out to develop a new aqueous derivatization reagent. Phenylation with sodium tetraphenylborate is a promising procedure for the speciation of several metals. Its application for organomercury analysis has been comprehensively studied [10]. Sodium tetrapropylborate is another reagent that has been investigated for determining organolead, tin, and mercury compounds [1]. However, its application is limited because it is not commercially available. 

Differences in the volatility of the elements and their compounds may also be used for speciation work. Accordingly, it is possible, for example, to determine different organolead compounds such as Pb(CH3)4 and Pb(C2Hs)4 directly by furnace AAS (see e.g. Refs. [284, 285]) or after on-line coupling with chromatographic separations. This approach can be used for other species as well but must be developed carefully for each special case. 

In this overview, we have limited our discussion to the speciation of four important organometals, each presenting specific analytical features, in environmental samples organomer-cury, organoarsenical, organotin, and organolead compounds. Their uses, presence in the environment, toxicity and threat to human health are also briefly discussed. 

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