Place 2 digestion tablets into a digestion tube. Weigh approximately 1 g of sample (to a
precision of 2 decimal places) using a weighing boat. Quantitatively transfer the sample into the
digestion tube using 12 mL of concentrated sulphuric acid.
Warning: Check the bottom of the digestion tubes for star cracks prior to adding the sample and
reagents. Only handle the concentrated sulphuric acid in a dedicated fume hood; wearing
protective gloves and a face shield. First pour the acid into a beaker. Then measure 12 mL from the
beaker into a cylinder. Transfer the sample to the digestion tube such that the walls stay clean.
Rinse off any remains of the sample using sulphuric acid from the cylinder.
After shaking it in a circular fashion, place the tube in a digestion stand. Attach a vapour exhauster,
switch a water vacuum aspirator on and set the recommended digestion temperature (i.e. 420 oC).
After the required temperature is reached (approx. 15 minutes), digest the sample for 40 minutes.
Switch the digestion unit off and let the stand with the digestion tubes cool down in a separate place
(approx. 20 minutes).
Warning: Only the instructor may put the digestion tubes in the digestion unit, or take them out.
Only the instructor may switch the digestion unit on/off.
Note: Digestion was shortened for the purpose of this exercise. To enable the digestion of resistant
compounds (Lysin, Tyrosin) an additional 60 minutes of digestion would be necessary after clearing
up the tube´s contents.