Mercury compounds protocols

It is recommended, as a minimum, that permanent employees working with mercury or mercury compounds be provided with periodic physical examinations with a test protocol selected specifically for mercury poisoning. Women who may be pregnant should be especially careful and encouraged to participate in the medical surveillance program if they cannot avoid exposure entirely. 

Improvements have been made recently for the preconcentration of gaseous methylmercury in air by preconcentration in mist chambers and subsequent determination by aqueous-phase ethylation, precollection on carbotrap columns, separation by GC, and detection by cold vapor atomic fluorescence spectrometry (CV-AFS). In order to understand the behavior and fate of mercury compounds in the atmosphere and their role in environmental mercury cycling, there is an urgent need for further development of analytical methods to afford identification of mercury species in the atmosphere by compound-specific analytical methods (as opposed to operationally defined protocols). 

Suzuki-type coupling protocols were also evaluated as a method to prepare some related tetrahedral stilbenoid molecules and the optimal yields were achieved when using Pd(dppf)Cl2 as the catalyst. The cruciform materials prepared using this strategy are shown in Scheme 3.3. Compounds 5a and b were obtained as a mixture of cis and trans isomers as identified by high-performance liquid chromatographic (HPLC) analysis. Nevertheless, the mixtures were readily converted into the all-trans isomers by irradiating the dissolved samples with a mercury lamp. 

Deficiencies in many of the studies make it difficult to fully evaluate the quality of the data reported. General problems include the following (1) many details of experimental protocols were omitted, thereby prohibiting an evaluation of the study s adequacy (2) very often, only one dose was used, so an analysis of any possible dose-response relationships was not possible, and the possibility that certain observed effects were not compound-related cannot be excluded (3) control data often were not presented and (4) the results were frequently described in subjective terms, and no attempt was made to quantitate the data. Despite these limitations, animal studies do provide irrefutable evidence that the central and peripheral nervous systems are target organs for organic mercury-induced toxicity. 

Collection and handling of aqueous samples for low-level determination of mercury must address factors such as whether the sample is representative of the system sampled, possible interconversion processes, contamination, as well as preservation and storage of the sample before analysis. The measurement (sampling and analysis) protocol must be even more carefully designed if speciation of mercury forms in aqueous samples is intended. There have been remarkable improvements in sampling and analytical techniques that have resulted in a dramatic increase in the reliability of data for mercury levels in water samples over the past 15 years. The stability of mercury in solution is affected by many factors. These include (1) the concentration of mercury and its compounds, (2) the type of water sample, (3) the type of containers used, (4) the cleaning and pretreatment of the containers, and (5) the preservative added. 

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