( a ) Pre-treatment .—Homogenize product if necessary, using noncontaminating equipment. Check for leaching metals if the ap- paratus consists of metal parts. ( b ) Drying .—In a crucible, weigh 10–20 g test portion to nearest 0.01 g. Dry in a drying oven, on a water-bath, or a hot plate at 100°C, if there is a risk of heavy boiling in the ashing step. Proceed according to type of furnace. ( c ) Ashing .—( 1 ) Ashing in a programmable furnace .—Place dish infurnaceatinitialtemperaturenothigherthan100°C.Increase temperature at a maximum rate of 50°C/h to 450°C. Let dish stand for at least8hor overnight. Continue according to ( e ). ( 2 ) Ashing in a muffle furnace with thermostat following drying and pre-ashing in apparatus described in B ( d )–( h ).—See Figure 999.11 . Place cruci- ble with the test portion covered with the glass cover on the ceramic plate, and let purified air coming through a glass tube sweep over the product. Put IR lamp down at the cover. Pre-ash product sample by increasing temperature slowly with IR lamp by gradually increasing temperature on hot plate to maximum. Final temperature on ceramic plate should then be about 300°C. Time required for pre-ashing var- ies with product. Put crucible in muffle furnace at 200–250°C and slowly raise temperature to 450°C at a rate of no more than 50°C/h. Let stand for at least 8 h or overnight. Take crucible out of furnace and let cool. Wet ash with 1–3 mL water and evaporate on wa- ter-bath or hot plate. Put crucible back in furnace at no more than