Reproducibility mercury speciation

Garcia-Monco Carra et al. [296] have described a hybrid mercury film electrode for the voltammetric analysis of copper (and lead) in acidified seawater. Mercury plating conditions for preparing a consistently reproducible mercury film electrode on a glassy carbon substrate in acid media are evaluated. It is found that a hybrid electrode , i.e., one preplated with mercury and then replated with mercury in situ with the sample, gives very reproducible results in the analysis of copper in seawater. Consistently reproducible electrode performance allows for the calculation of a cell constant and prediction of the slopes of standard addition plots, useful parameters in the study of copper speciation in seawater. 

Fig. 4.23. Manifolds used for speciation analysis of solid samples. (A) Mercury speciation (as Hg- and PhHgH). (B) Nitrogen speciation (as ammonia and urea). GLS gas-liquid separator, MWS microwave system, ISE ammonia-selective electrode, RE reference electrode, WB water bath thermostat. Other abbreviations as in previous figures. (Reproduced with permission of Elsevier.)...

Figure 7 Letkeman (1996) used chemical speciation calculations to estimate the major complexes for lead and mercury as a function of pH in a fluid having overall plasma composition. The results show that most metal complexes with low-molecular-weight organic ligands such as amino acids diminish in importance with decreasing pH (such as in the gastric fluids) due to the increased protonation of the organic ligands. Cl—chloride Cy—cysteinate Ct—citrate Glut— glutathione (reproduced by permission of the Division of Chemical Education Inc. from J. Chem. Educat.

---