If I am to determine the concentration of Lead in gunshot residue using Flame Atomic Absorption Spectroscopy by thoroughly rubbing a cotton swab on the target and placing the swab into a vial and add 2 mL/ of 5% nitric acid and place test tubes containing the removed cotton from GSR samples in an oven set at approximately 80 °C to dry for one hour.... what is the purpose of putting sample/standards in the oven?