Digestion of Hair Samples For each of the hair samples, 3 g was weighed into a clean crucible. It was dried in the oven to partial dryness to avoid explosion. The dried hair samples were digested with 10ml of 6:1 mixture of concentrated nitric acid and perchloric acid, the mixture were heated until complete evaporation to obtain a water clear solution. Each digested samples were transferred into a 100 mL volumetric flask and made up to the mark with distilled water.