Hi Annalisa,

Depending which radionuclides you are after and what detection limit you want to achieve there is a number of options.

The easiest I think is to start with sample ignition - slowly ramping the temperature up to 450 C. For bitumen samples the mass you can take will be quite limited-perhaps to a single gram or two. Keep the samples in the oven until you get rid of all residual carbon - you may want to take your sample out of the furnace and give it a bit of a stir with a glass rod. This step should remove all the organic compounds leaving you with mineral matrix which you can attack with acids (HF, Aqua Regia, HNO3...) or use fusion technique (melting with an appropriate flux) to achieve total sample dissolution.

Some beta emitters (I-131, I-129, Cl-36, Tc-99...) could suffer some losses during the ignition and/or acid attack. In this case I would start with NaOH sinter at 450 C followed by water leach to produce an alkaline solution.

Regards,

Pawel

 Though difficult, but may be useful the dissolution of bitumen in organic solvents

To dissolve the bitumen, microwave assisted acid digestion can be used with :

- HNO3 (9 ml) + HF (0.5 ml) + HCl (2 ml) ,Temperature 180 ° C, Pressure 23 atm, Time 25 min,

- or H2SO4 (10 ml) HNO3 (0.5 mL) + H2O2 (10 mL), 5 mL of concentrated H2SO4: 5 min at 60 W. After, more 5 mL of concentrated H2SO4 were added: 10 min at 120 W and 10 min at 150 W. Then, 4 mL of concentrated HNO3: 10 min at 210 W. In order to complete the digestion cycle, 10 mL of H2O2 were added and the mixture was irradiated for more 5 min.

Some beta transmitters should be lost: H-3, C-14, C-36, I-129, I-131, Tc-99.

Best regrads,

Marcel