Organic carbon samples are combusted at high temperature to produce CO2 in our Sample Prep Lab. But first, depending on the sample, these also can require special labor-intensive pretreatment steps.
Plant/wood and charcoal samples undergo a series of acid-base-acid leaches to remove inorganic carbon and mobile organic acid phases. This process necessarily removes some sample mass. Sediment samples undergo the acid pretreatment only. If neither pretreatment is required, the sample is considered "ready to burn" and the fee is less accordingly.
Inorganic carbon samples, or carbonate minerals, are directly acidified with strong acid, H3PO4, to convert the carbon in the sample to CO2.
Dissolved inorganic carbon is "stripped" in an automated system in our Sample Prep Lab using acidification and sparging with nitrogen to "strip" the evolving CO2 from the water.
Dissolved organic carbon is oxidized in an automated system in our Sample Prep Lab using ultraviolet light to oxidize the dissolved organic carbon and sparging to "strip" the evolving CO2 from the water.
Samples submitted as ampoules of CO2 are cracked, quantified, split (if required), and transferred to a reaction tube for reduction to pure carbon. The CO2 is reduced with use of a catalayst (Fe or Co) in the presence of excess hydrogen
CO2 + 2H2 = C(graphite) + 2H2O
Samples submitted as solid carbon (graphite) require pressing into target cartridges for loading into the AMS.
Samples submitted as solid carbon, pressed into targets, require only AMS and data analysis
Samples submitted on quartz or glass filters. Methods are aimed to prevent sample cross-contamination. All procedures are carried out in a dedicated separate laboratory.