Why Mercury Speciation Analysis?
Total mercury analysis alone cannot accuractely describe mercury chemistry in a sample. As shown in a study published in Science, knowing the distribution of different types of mercury can enhance and enable conclusions. For this reason, all current research recommends mercury speciation analysis instead of total mercury analysis. Mercury speciation has several advantages to total mercury analysis.
- Mercury speciation analysis provides much more
information than total mercury analysis alone. - Mercury speciation analysis determines proportions
of mercury types present in a sample. - Mercury speciation analysis can also predict mobility and
toxicity of mercury within a specific ecosystem’s food chain.
Different Forms, Inconsistent Proportions
The distribution, or proportion, of different species of mercury in a sample vary widely. Measuring only total mercury and using a conversion factor to determine mercury species can produce wildly inaccurate data. Ratios of methylmercury to inorganic mercury are sample and site specific. Directly measuring these species is the only way to really know how much of each is present in a sample.
In sediment, for example, methylmercury (also referred to as monomethylmercury or MeHg) may range from <0.001% to >>1% of the total mercury present. The remaining mercury will include inorganic mercury (mercuric mercury or HgII), and possibly other forms. In recent analyses of insects and macroinvertebrates, Quicksilver Scientific determined that methylmercury, as a percentage of total mercury, could vary more than 80 percentage points. Clearly bioaccumulation studies cannot rely on total mercury analysis alone.
Different Mobilities, Different Toxicities
Different forms of mercury move through systems and tissues differently and have different modes of toxicity. Only speciation analysis can determine which types of mercury are in a sample.
Methylmercury
Methylmercury (also referred to as monomethylmercury, MeHg) can move through tissues much more easily than inorganic mercury, which tends to stick to cell walls. Methylmercury’s mobility plays a big role in its ability to bioacuumulate. In the environment, methylmercury moves from sediments and water into living things, such as bacteria and plankton. Inorganic mercury, however, sticks onto the cells walls of bacteria and carapace of plankton. As predatory organisms consume smaller ones, the cell walls and carapace, which have inorganic mercury, get excreted. However, the inner parts along with the methylmercury get assimilated the predator’s tissues. This process continues along the food chain so that the larger the predatory species, the more methylmercury there is in it. This is called bioaccumulation. The dramatic effect of bioaccumulation is often seen in fish, which can have methylmercury concentrations 1 to 10 million times more than the water in which they swim.
In humans, methylmercury is equally as mobile. In fact, human intestines absorb about 95% of methylmercury that enters them. Once in the blood, methylmercury can easily cross the blood-brain barrier, which sets the scene for negative neurological effects. Methylmercury can move easily throughout the human body because methylmercury gets mistaken by amino acid transporters in the intestines and brain. This mistaken identity occurs because mercury binds with an amino acid, cistine.
Methylmercury has two opportunities to bind with cistine. The binding could occur in fish, or it may occur in the human intestines. In the human body, methylmercury binds with a protein that usually helps remove metals from the body called glutathione. However, when bound to methylmercury, glutathione breaksdown in the intestines and becomes cysteine. Once in this form, the bound methylmercury will not get excreted by the body.
Inorganic Mercury
Inorganic mercury is not as easily absorbed as methylmercury and thus does not bioaccumulate to the same degree. But when it does get absorbed in tissues, its toxic effects can pose an immediate threat.
In prey animals, including insects, high levels of inorganic mercury can cause toxic effects in animals that consume them. Potential toxic effects include gland and organ dysfunction, and in fact, recent studies show evidences that fish with high inorganic mercury loads suffer from liver toxicity.
What is Mercury Speciation Analysis?
Mercury speciation analysis is the process of separating and analyzing different types of mercury in a sample.
What is Mercury Speciation Analysis? (contd)
What Makes Quicksilver Scientific Technology Superior?
Quicksilver Scientific uses patented and uniquely licensed technology that allows us to conduct speciation analysis of the highest quality for the lowest price.