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Carbonates are reaction products (salts, esters) of carbonic acid and play an important role, especially in environmental research. They occur everywhere in nature, mostly in the form of minerals (aragonite, calcite, dolomite, etc.) or in dissolved form in waters such as rivers, lakes and seas. Organisms use dissolved and undissolved carbonates as scaffolding substance (bones, shells). As minerals they are rock-forming or frequently found in sediments. Stalagmites and stalactites are carbonate precipitates found in caves and play an important role in climate research. Limestone precipitates such as loess or gypsum are often found in sediments, which are washed out of the sediment by the interaction with groundwater. Carbonates are also used as building materials in the form of admixtures to mortar (lime as a binder in lime mortar).

Sample properties

Depending on the material and analysis method, exchange products in the carbonate are to be expected, especially in the case of apatite, an exchange with carbon from the environment often occurs. In the case of dissolved carbonates in water samples, it may be necessary to stop any further change in the dissolved carbonate by adding suitable chemicals (see Water). The sample quantity for dissolved carbonates should be selected larger, as the concentration is lower than for solid carbonates.


For radiocarbon dating of solid carbonates, such as mussels or speleothems, 50 – 100 mg are required, since still adhering contamination have to be removed and this type of carbonate contains only about 10% carbon. For dissolved carbonates (DIC) in water a quantity of 250 ml is desirable. Please contact the laboratory for much smaller sample quantities.

Carbon and oxygen isotope analyses

For carbon and oxygen isotope analyses on pure carbonates, a few micrograms of sample material are sufficient. However, the size of the samples to be submitted must be large enough to allow for appropriate handling during sampling and weighing. In particular, for serial analyses, e.g. on stalactites or for the analysis of water samples, please contact us prior to sample submission.