Applicable to the determination of lead, cadmium, zinc, copper, and iron in food by dry ashing and flame atomic absorption spec trometry(GFAAS), flame and graphite furnace pro See Ta ble39 11A for the results of the interlaboratory study supporting the acceptance of the method.] Caution: Always gently add acid to water. Avoid environmental contamination by Pb. Store quartz crucibles in 20% HNO, and rinse with deionized water before use. When neces- sary, crucibles may be boiled with 20% HNO, before use. Heat plati num crucibles until red hot and boil with 50% (vlv)HCl prior to use.