Acid fumigation - Preparing C-13 solid samples for organic analysis

 

TIPS FOR PREPARING LARGE BULK DIFFICULT COMBUSTION ¹³C & ¹⁵N SOLID SAMPLES – SOILS, SEDIMENTS, FILTERS, WOOD, AND CARBONATES

Removing carbonates from calcareous soils and sediments before organic ¹³C analysis

Inorganic C in the form of carbonates can interfere with the measurement of organic ¹³C in soils. Remove inorganic C by acid fumigation. Weigh soil samples into silver capsules (tin decomposes when exposed to acid) and arrange samples in a 96-well tray. Add a small amount of water to each open capsule to wet the soil. Place the whole 96-well tray in a desiccator containing a beaker of concentrated (12M) HCl. Carbonates are released as CO₂ in 6 to 8 hours. Dry the samples at 60°C and carefully crimp-seal the capsules. The capsules become brittle after drying, resulting in leaks; be careful not to lose material when crimping. We recommend placing the whole capsule into a new tin (Sn) capsule and crimp it closed. The additional tin capsule is an important combustion catalyst, so it is advantageous to use tin capsules for re-encapsulating leaking samples.

Reference:

Harris, D., Horwath, W. R., and van Kessel, C., 2001. Acid fumigation of soils to remove carbonates prior to total organic carbon or carbon-13 isotopic analysis. Soil Science Society of America Journal 65: 1853-1856.

Source : http://stableisotopefacility.ucdavis.edu/sample-weight-calculator.html

(Accessed 26 August 2015)