Back to Main
1. 2-5 g of dry plant sample material is weighed into a Teflon-tube (2a) or Kjeldahl's flask (2b). The exact mass of the sample is recorded.
2a. The sample is digested with MARS5TM-microwave machine according the introductions given in the manual. 20 ml of aqua regia (3:1 conc. HCl - HNO3
) and 0.2-0.5 Bq of 209
Po tracer solution (t½ = 103
a) is added to the tube and left to stand for overnight. Write down the activity concentration and the volume of the tracer. After digestion the sample is moved into a decanter glass and the teflon-tube is rinsed with 3 x 2 ml of conc. HCl. Add 15 ml of conc. HCl and evaporate to 2-3 ml and leave cool down.
2b. Alternatively the digestion can be carried out in 500 ml Kjeldahl's flask in concentrated HNO3
and HCl. First add 50 ml of conc. HNO3
and start heating carefully, because vigorous foaming may appear in the beginning. The digestion is continued until the HNO3
solution is evaporated to 10 ml. (If there still is unburned fat etc. HNO3
can be added and the digestion continued.) Let the flask cool well and add 20 ml of conc. HCl and evaporate HNO3
away (brown gases disappear). The sample is evaporated to 2-3 ml and left to cool down.