Cellulose extraction – first trials

NaOH treatment of wood samples

This week I started with a first -trial- cellulose extraction for my wood core stable isotope experiment. I have one plate to test the routine and look for possible flaws in the setup before ordering the final batch – money permitting. The setup has been running for a two days now. The picture in this posts shows the small wood samples submerged in NaOH to remove all resins, tannins etc. In a next step you add a strong acid to eat away the lignin and leave the cellulose behind.

The procedure is done in a hot water bath (60°C). I noticed that a lot of water evaporated, or more than I was used too when learning the procedure at GFZ Potsdam last October. Even with a small lid on it the water level decreased at a significant rate, with the possibility of not heating the reagents at the end of a treatment. After some thinking I found to culprit to be the laminary flow system on overdrive. Evaporation depends on the temperature of the water and the air, the evaporative surface area but also the velocity of the air mass above the surface. Given that all other parameters did not deviate significantly from the setup in Potsdam the more draughty laminary flow system in Ghent was an easy find. Opening the hood a bit more so the velocity of the air moving over the heated setup was less reduced the evaporation to within workable values. Covering the tray with a lid would reduce evaporation even further. Covering the water surface itself as with swimming pools, limiting the surface area from which you could evaporate water, would allow me to limit the refills after treatments even further. More on this later…