Analytical methods for mercury speciation in several matrixes: a review

Mercury is one of the hazardous contaminants that may be present in the environment. Moreover, its toxicological effects are strongly dependent on the chemical form of the element, being the organic species the most toxic. In spite of this, the determination of mercury compounds in environmental samples, such as water, soils, sediments and biological matrixes, is of great importance. This review examines the current state of the sample treatments that have been developed, during the last 18 years (1990-2007),previous to separation and detection of mercury compounds, namely acid lixiviation, distillation,alkaline digestion and supercritical fluid extraction, as well as of the chromatographic techniques (gas chromatography and high performance liquid chromatography) used in order to separate mercury compounds and detection techniques usually coupled with them. The detection limits and the linear range achieved coupling both separation techniques with different detectors are presented, as well as the advantages and disadvantages of each one. Finally, a brief discussion over the most used detection systems is also presented

Microwave-assisted extraction for methylmercury determination in sediments by high performance liquid chromatography-cold vapour-atomic fluorescence spectrometry

A simple and rapid procedure for methylmercury extraction from sediments based on microwave-assisted alkaline digestion with methanolic potassium hydroxide was optimized on parameters such as microwave power, extraction time and sample size. Organomercury species were extracted with dichloromethane in hydrochloric acid medium and back-extracted into ultra-pure water. The sediment extracts were injected into an analytical system composed of high-performance liquid chromatography-ultraviolet-post-column oxidation-cold vapour-atomic fluorescence spectrometry (HPLC-UV-PCO-CV-AFS) for methylmercury determination. Quantitative methylmercury recoveries were obtained when 0.15 g of sediment were suspended into 6 mi of 25% m/v methanolic potassium hydroxide and the slurry was exposed to microwave irradiation at 84 W for 2 min. The detection limit of proposed method was 12 ng g(-1) while the relative standard deviation was less than 5%. The method was validated by the analysis of two sediment certified reference materials and the methylmercury concentrations found were in good agreement (95% confidence level) with the certified values

Simple methodology for methylmercury and inorganic mercury determinations by high-performance liquid chromatography-cold vapour atomic fluorescence spectrometry

An analytical methodology was developed to separate and quantify methylmercury (MeHg) and inorganic mercury by high-performance liquid chromatography (HPLC)-cold vapour atomic fluorescence spectrometry (CV-AFS). The use of UV oxidation of the organic forms of mercury, the tin(II) chloride reduction in acidic medium of mercury and the introduction of a water vapour trap based on H2SO4/CaCl2 resulted in a low detection limit (DL) (10 +/- 2 pg, mean value +/- S.D.). The apparatus was operationally optimised through the modified simplex method leading to an increase of the signal by a factor of 2. The method performance has been tested by determining the MeHg concentration in a sediment certified reference material (CRM) and the results were statistically indistinguishable from the certificate value (alpha = 0.05) both for the mean value and S.D