2.4. Sample digestions
An exact amount of 3.0 mL of milk and doogh and/or 3.0 g of
yoghurt and cheese samples were transferred into a beaker. Then
4.0 mL of HNO3 (65% w/w) was added to each sample and heated
to dryness. After that, 1.0 mL of H2SO4 (95% w/w) was added to
each sample and heated to be completely dried. 1.0 mL of H2O2
(30% v/v) was added to the residue and heated until the sample
turned colorless and dried. Finally the residues were dissolved
and made up to 1.0 mL using triple distilled water.