| Room |
Carbon/Carbonate Laboratory
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| Location |
Rm. M3005,
3rd floor,
Bldg. 15 (McKelvey Bldg.)
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| Contact |
Michael E.
Torresan
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| Description |
Laboratory is outfitted for the determination of total carbon, inorganic carbon, and organic carbon in a variety of geological samples.
This laboratory houses a Coulometrics carbon analyzer, a fume hood, two ovens, counter top centrifuges, dessicators, labware, and microscope supplies.
The lab's labware can be applied for any purpose as the lab is not dedicated solely to carbon analysis and can be employed for other analytical procedures.
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Specialized
Equipment |
Two Coulometrics UIC Carbon/Carbonate Analyzers. Other equipment includes small counter-top centrifuges, a microscope and microscope supplies, a fume hood, dessicators and tools required to maintain and repair the laboratory and laboratory equipment. |
Equipment
and
Technique |
There is also substantial counter top and storage space such that other analyses or preparations can be conducted.
Laboratory expendables are also stored in this laboratory as are most dry chemicals used required for the various sedimentological procedures.
Storage under the fume hood accommodates liquids such as acids and some organics.
The common applications of the carbon analyzer include the determination of the percent total carbon, organic carbon, and mineral or carbonate carbon in water, soil, sediment, rock, and other geologic materials and substrates.
Other applications include the amount of dissolved carbon dioxide in water and carbon in steel.
Investigators use carbon analysis to study paleoclimate, environments of deposition, the geotechnical behavior of soils or sediment, and environmental studies having to do with monitoring pollution levels in soil, sediment, or water.
Carbon in samples exists in two forms, organic carbon and mineral or carbonate carbon.
In order to calculate the percentages of each type of carbon, the investigator must determine the total carbon and the carbonate carbon in the same sample.
Organic carbon is calculated as the difference between the total carbon and the carbonate carbon.
The high accuracy of the carbon analyzer provides very precise organic carbon values.
In some cases organic carbon can be directly determined in the total carbon apparatus by pretreating the sample with acid, which selectively removes carbonate carbon, thus leaving organic carbon as the only constituent of carbon.
The carbon analyzer has three major components:
- a carbon dioxide coulometer,
- a total carbon apparatus, and
- a carbonate carbon apparatus.
The carbon dioxide coulometer receives carbon dioxide gas from either the total carbon apparatus or the carbonate carbon apparatus (described below).
The carbon dioxide coulometer provides accurate, absolute determination of carbon dioxide introduced into the coulometer cell by a carrier gas.
Typical carrier gases include oxygen, carbon dioxide free air, nitrogen and helium.
The USGS uses carbon dioxide free air with the carbonate carbon apparatus and pure oxygen with the total carbon apparatus as the carrier gases.
The carbon dioxide delivered to the coulometer is absorbed in a special cell filled with a partially aqueous medium containing ethanolamine and a colorimetric indicator.
When gas is passed through the solution, carbon dioxide is quantitatively absorbed and is converted to a titratable acid by the ethanolamine, and the solution simultaneously changes color.
The coulometer electrically generates a current that converts the acid to a base and returns the indicator color to the starting point, automatically counting the number of micrograms of carbon converted, and gives the results in basic theoretical units.
Electronic scaling within the coulometer converts the number of coulombs to a digital readout of micrograms of carbon, and accuracy is 0.1% for samples containing over 1 mg carbon.
The total carbon apparatus is a high temperature induction furnace.
Samples in powder or liquid form are placed into the furnace, and the furnace uses high temperature (1000°C) combustion in pure dry oxygen to convert both organic and mineral carbon in the sample to carbon dioxide.
The carbon dioxide is carried to the coulometer (described above) for determination of % total carbon.
The carbonate carbon apparatus treats the sample with acid (perchloric or hydrochloric) and transfers the evolved carbon dioxide to the carbon dioxide coulometer.
The unit is self contained with an air pump and acid dispenser.
The ambient air that is used as a carrier gas is scrubbed prior to analysis in order to remove the carbon dioxide already present.
Like the total carbon apparatus, the carbon dioxide evolved from the reaction is carried through to the carbon dioxide coulometer.
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