Water was used to dilute
the digest to 10 mL. Similarly, about 0.25 g of biodiesel was added
to 7 mL of concentrated nitric acid (HNO3) and 1 mL of hydrogen
peroxide (H2O2) for digestion in the microwave for 25 min. In this
case, the volume of the digest was diluted to 25 mL with water.