I do organic matter (OM) combustion in my sediment samples on a regular basis.
We heat Cu wires (Fisher Chemicals) for 6 hrs at 900C in covered porcelian
crucibles and add 2g of CuO + 1 g of Cu granules to the sample (80-100mg for
sand (TOC <0.5%) and 10-50 mg for clays/silts (TOC 2-30%)). The samples are
evacuated in quartz tubes and combusted for 2 hrs at 900C and 2 hrs at 600C.
Place all tubes inside ceramic jackets when you stick them into the oven. All
samples are treated w/ 10% HCl and washed w/ milli-Q water to get rid of
carbonates. Blanks obtained are low.
If you have very low TOC content in your samples and sample size is very small
you could use this alternative suggested to us by Dr. Marilyn Fogel. We are
using this method for our DOC samples. Use pre-treated CuO as before but combust
them in evacuated quartz tubes and store them like that. Also combust the Cu
granules (Alpha Resources) in quartz tubes as they too are a source of
contamination. (Cu granules have a thin coating of oil). I usually take 1-2g of
CuO and about 10g of Cu granules in evacuated tubes and heat it for 2 hrs at
900C. Break the seals and use CuO and Cu granules for combustion (as above) only
when everything is ready to go. Blanks obtained by this method are very low.
Combusted CuO/Cu granules stored otherwise for long periods of time tends to
give higher blank. If you have any questions e-mail me.
Department of Geology and Geophysics
Texas A&M University
College Station, TX 77843