Organomercury compounds, derivatization

If derivatization of the native species is carried out, derivatization yields should also be assessed. In aqueous samples these yields are relatively easy to assess when a derivatized standard similar to the derivatized organomercury compound is available. Use of the standard addition method allows the derivatization yield to be determined. 

Monsalud, S. Determination of organomercury compounds in environmental and biological samples by using derivatization and gas chromatographic detection M.S. Thesis, Florida International University, 1999. 

De Smaele, T., L. Moens, R. Dams, R Sandra, J. Van de Eycken, and J. Vandyck. 1998. Sodium tetra( -propyl)borate A novel aqueous in situ derivatization reagent for the simultaneous determination of organomercury, lead- and tin-compounds with capillary gas chromatography-inductively coupled plasma mass spectrometry. J. Chromatogr. A 793 99-106. 

Figure 2 shows an example of separating organomercury using supercritical CO2. A 10-m X 50- tm-in-ner diameter SB-Methyl 100 column was used for the separation. Due to their poor solubility in supercritical carbon dioxide, monoorganomercury compounds were derivatized by diethyldithiocarbamate. An interface for a system consisting of SFC and atomic fluorescence spectrometry was developed for the detection of organomercurials. 

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. 

In general, methods are classified according to the isolation technique and the detection system. Most methods for the isolation/separation of organomer-cury compounds have been based on solvent extraction, differential reduction, difference calculations between total and ionic mercury, derivatization, or with paper- and thin-layer chromatography (TLC). The most common approaches to organomercury separation and detection are schematically presented in Figure 1. 

Among organomercury species currently of interest, ethylmercury (EtHg) is a compound that requires further attention as it is still used in Thiomersal for preservation of vaccines. It is important to analyze ethylmercury in vaccines, in wastewater from waste treatment plants in industries using ethylmercury, as well biological samples in order to understand ethylmercury uptake, distribution, excretion, and effects. In principle, methods developed for methylmercury can also be used for ethylmercury, except in the protocols using derivatization by ethylation. In such cases propylation is recommended. 

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