Abstract
A new dry ashing method using an aluminium foil cup as a vessel is proposed. Commercially available aluminium foil was cut and formed into a shape of cup. Cups were doubled and heated in a muffle furnace at 600°C for 23h. After the sample was ashed in the muffle furnace at 550°C, the inner cup was removed out and the bottom of the cup was destroyed with a glass rod so the ash dropped into a conical beaker, the inside of the cup was then washed with 1% hydrochloric acid. The washing solution was evaporated on a hot plate, and 5ml of 20% hydrochloric acid was added and subsequently evaporated on a hot plate. The residue was dried at 110°C oven for 1h and then dissolved with 1% hydrochloric acid. This method was applied to NBS SRM Oyster Tissue, Wheat Flour, Rice Flour, Orchard Leaves and Citrus Leaves. Potassium, magnesium, calcium, zinc, manganese, copper and iron were determined by AAS, and phosphorus was determined by the vanadomolybdate spectrophotometric method. The results obtained using this method agreed with the certified values and those obtained using platinum dish dry ashing method. The dry ashing method for pretreatment of a large number of samples can be performed economically by using the aluminium foil cup.
