Different types of tree nuts samples were ground and digested
in pressurized Teflon vessels using microwave heating. In this
study, four different acid mixtures were employed to digest the
samples in order to obtain complete sample dissolution. The
mixture of acids and/or oxidizing reagents tested were HNO3:
H2O2:HCl; HNO3:H2O2; HCl:HNO3; and HNO3. As a pre-digestion
step, samples were sonicated with the reagents in an ultrasonic
water bath. The procedures allowed the digestion of 0.5 g of sample
in safe conditions. After the digestion of samples in the microwave
oven, the use of the HNO3:H2O2 mixture and that of just pure HNO3
were selected, because, in the case of employing HCl, the samples
were not totally dissolved.