Polarographic Determination of 5 Heavy Metals in Oil with Ashing Digestion of Sample

Five heavy metals,i.e.,cadmium,lead,copper,nickel and cobalt,were determined by polarography.The oil sample was pretreated by burning,ashing and finally igniting at 600 ℃.Cadmium(Ⅱ),lead(Ⅱ) and copper(Ⅱ) were determined in an acetate buffer of pH 4.6 and nickel(Ⅱ) as well as cobalt(Ⅱ) were determined in an ammoniacal solution of pH 9.5 containing phosphate and sulfosalicylate.Detection limits of the 5 elements were in range of 1.3×10-4-9.8×10-4g·L-1.Their values of RSD′s were found in the range of 0.22%-3.16%,and values of recovery were in the range of 90%-106%.