This method is for determining nickel, vanadium, iron, lead and copper in gas oils by graphite furnance electrothermal Atomic Absorption Spectrophotometry (GFAAS) at levels below 2000 ng/mL (approximating mass-ppb). For determination of higher levels, see UOP 800. Sodium content, expressed as g/g (mass-ppm), is determined directly by flame AAS. The lower limit of detection for all metals, including sodium, ranges from about 2 to 20 ppb depending on the element sought.