| Visual_Elements__Mercury Image, general and physical information, source, uses, key isotopes, and ionisation energies. |
| WebElements__Mercury Contains extensive information about Mercury, as well as pictures and videos that show its physical appearance and how it reacts with certain chemicals. |
| Why_is_Mercury_liquid_at_room_temperature? Explores the question of why Mercury is liquid at room temperature. It also provides some links to other sites regarding this chemistry quandary. |
| Why_Worry_About_Mercury____Chemical_Properties Gives some chemical properties of mercury, as well as hazard precautions when dealing with mercury. |
| Wikipedia__Mercury Properties of the element, including its history, applications, and characteristics. |
| Radiochemistry_of_Mercury Full text of the monograph by Josef Roesmer (Westinghouse Astronuclear Laboratory, Pittsburgh, Pennsylvania). [PDF] (September, 1970) |
| Chronology_of_Mars_Exploration Overviews of every mission to Mars since 1960, including planned future missions. |
| Deep_Space_2 NASA's official site for the microprobe mission, launched with the Mars Polar Lander in January 1999. Contact was lost in December 1999. |
| Deep_Space_2 Spacecraft and mission profile from the National Space Science Data Center. |
| Mars_96 Overview of the Russian mission launched in 1996 that failed to reach earth orbit. |
| Mars_96_Orbiter Spacecraft and mission profile from the National Space Science Data Center. |
| Mars_Exploration Information on the Red Planet and links to the homepages of NASA's Mars exploration projects. |
| Mars_Observer Spacecraft and mission profile from the National Space Science Data Center. |
| On_Mars__Exploration_of_the_Red_Planet_1958-1978 A NASA history book on the Viking and Mariner missions. Discusses the motives for these programs and the evolution of hardware. Includes information on the search for life on Mars, spacecraft assembly |
| Zond_2 Spacecraft and mission profile from the National Space Science Data Center. |
| Zond_3 Spacecraft and mission profile from the National Space Science Data Center. |
| Center_for_Complex_Systems_&_Brain_Sciences,_Florida_University . Multidisciplinary since its inception, the Center involves the cooperative efforts of neuroscientists, psychologists, mathematicians, physicists, computer scientists, and engineers.Founded in 1985 |
| Center_for_Complex_Systems_Research,_University_of_Illinois_at_Urbana_Champaign Research group which studies phenomena of multivariante systems with a large flow, such as turbulence, lightenings, and information flow on the internet. |
| The_Center_for_Connected_Learning_and_Computer-Based_Modeling Connected Mathematics: Making Sense of Complex Phenomena Through Building Object-Based Parallel Models |
| Center_for_Nonlinear_Studies Group studying fundamentals and applications of nonlinear phenomena and complex systems. Located at Los Alamos National Laboratory. |
| Center_for_the_Study_of_Complex_Systems,_Michigan seminars, workshops, education and research |
| Centre_For_Nonlinear_Studies (UK) University of Leeds, Meetings, publications. |
| Complex_Systems_and_Networks CSN is a self-organized network of people spanning various academic units at Indiana University, interested in the broad areas of complex systems, network science, modeling, simulation, artificial lif |
| Complex_Systems_goroup_at_Academy_of_Finland complex system is a collective consisting of a large number of individual components that interact in a strongly nonlinear fashion |
| Complex_Systems_in_Argentina,_Buenos_AIRES Applications to economics, Links to other universities and resources |
| Complex_Systems_Modeling,_LANL,_USA The study of the dynamics of networks of agents at a US national laboratory. |
| Complex_Systems_Research_Center_at_New_Hampshire,_USA Part of Institute for the Study of Earth, Oceans, and Space (EOS), investigates the effects of human disturbance on the Earth's biogeochemical processes. Part of Geo-Web ring. |
| Complexity_Lab At the Niels Bohr Institute and the Danish Technical University. Working on biophysics, turbulence, self-organised criticality and other complex systems. |
| Complexity_Research_Programme At the London School of Economics, UK. |
| CSCO_-_Complex_Systems_Computation_Group,_Finland Computational study of collection of simple interacting agents, ... |
| Duke_Center_for_Nonlinear_and_Complex_Systems Interdisciplinary research at Duke University on nonlinear dynamics and emergent phenomona in complex systems. |
| Glushkov_Cybernetic_Centre,_Kiev,_Ukraine GMDH for prediction, optimization, clustering, data mining ... |
| Group_of_Nonlinear_Dynamics_and_Synergetics,_Slovenia Applications to the cardiovascular system |
| Instituto_Gulbenkian_de_Ciencia_-_Portugal Development and evolution of complex systems in an organism centered approach. |
| NESCI New England Complex Systems Institute |
| Nonlinear_and_Complex_Systems_Lab__Korea Resources on Nonlinear Dynamics and Complex Systems NCSL, |
| Organizational_theory_of_social_networks,_human_social_organizations Home page of Douglas R. White, Anthropologist, at UC Irwine |
| The_Plexus_Institute Application of Complex Systems to health care. Bibliography, news. |
| Santa_Fe_Institute Private, non-profit, multidisciplinary research and education center. New kind of scientific research community, pursuing emerging |
| Systems_Analysis,_Modelling_and_Prediction_Group SAMP is an interdisciplinary research group based at Oxford, studying the modelling, development and application of complex dynamical systems in a wide class of real-world domains. |
Mercury (Hg) is well known as an
environmental contaminant. Its high toxicity and penchant for bioaccumulation
make it of particular concern among heavy metals. There are several ways of
determining total mercury in environmental samples. Speciation of mercury,
however, is more difficult. It is known that Hg species metabolically convert
to methylmercury (MeHg+), a highly toxic
form which can accumulate in tissues.
This is especially true
in fish. This makes measurement of methylmercury of vital importance in accurately
assessing risk. Previous methods of determining methylmercury involved the gas chromatographic
analysis of poorly behaved methylmercuric chloride (CH3HgCl). New
methods have been published which improve the analysis.
By LC-ICPMS (8/2002)
We've finally found a methylmercury method that we like. It is based on a method by Chiou, et al1.
Biological tissue samples are extracted into a mixture of L-cysteine
and 2-mercaptoethanol by microwave digestion. Mercury compounds are
separated on a C8-column using the same mixture of L-cysteine and
2-mercaptoethanol. An ICPMS system with conventional pneumatic
nebulization is used as the HPLC detector.
This method has been applied to the National Research Council of
Canada Reference Material DORM-1 Dogfish
Muscle. Concentrations of 0.70±0.03
µg/g methylmercury and 0.12±0.03 µg/g inorganic mercury have been
found in very good agreement with the certified value for total
mercury of 0.800±0.074 µg/g and a value of 0.721±0.033 µg/g for
methylmercury determined by Beauchemin, et al2.
Using this method a detection limit of about 0.3 µg/L for standard
solutions is achievable. Detection limits for tissue samples are about
30 µg/kg. The option of vapor generation might give better
detection limits by a factor of 10.
The chromatograms show a 10 µg/L standard and an extract of
DORM-1.
By GCMS
Another novel method employs alkylation and GCMS. The mercury compounds are
derivatized
using sodium tetraethylborate, which convert methylmercuric chloride to methylethylmercury and inorganic mercury [Hg(II)] to
diethylmercury.
These volatile species (and native dimethylmercury) can be effectively
purged from water with helium, analogous to EPA Method 8260.
The purged contaminants
are then determined using GCMS. The purge-and-trap technique cleanly
removes the target compounds from the matrix, leaving the interferences behind.
Click here for a Chromatogram
and a Mass Spectrum.
Unfortunately we've found this method difficult to perform
routinely at an appropriate cost.
References
For more information on methylmercury analysis:
1. Chiou et al., Spectrochim. Acta Part B 56, 1133 (2001).
2. Beauchemin, et al., Anal. Chem. 60, 2587 (1988).
3. Artifact formation of Methylmercury During Aqueous Distillation
and Alternative Techniques for the Extraction of Methylmercury for
Environmental Samples. N.S. Bloom, J.A. Colman, L. Barber, 1997,
Fres. J. Chem 358: 371
4. Determination of Picogram Levels of Methylmercury by Aqueous Phase
Ethylation, followed by Cryogenic Gas Chromatography with Cold Vapor Atomic
Fluorescence Detection, Can. J. Fish. Aquat. Sci., 46, 1131 (1989)
5. EPA Methods 245.7 and 1630,
and EPA Water
Quality Criteria
6. Method performance evaluation for methylmercury determination in
fish and sediment, P. Quevauviller, et al., Trends in Analytical Chemistry,
19, 157 (2000).
7. "Methylmercury Toxicology Probed", C&EN,
Jan 19, 2004.
8. Draft FDA/EPA Methylmercury
Consumer Advisory, Dec 2003.
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