Systematic Neutron Activation Technique for the Determination of Trace Metals in Petroleum

A systematic neutron activation technique, based on a series of consecutive irradiations and analyses of individual activities was applied to the determination of trace metals in crude oils, distillation fractions, asphalts, and related substances. Analytical procedures are described that allow the determination of traces of V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Mo, Sb, and Au in petroleum products, even when only samples of about 1 gram are available to the laboratory. A detailed description of the experimental method is given, and the data obtained in the analysis of several Italian oils and asphalts are reported. The method does not require ashing of samples under analysis: some metals, such as V, Cr, Mn, Cu, and Sb, are determined directly on irradiated samples, while the other metals are counted after low temperature coking and chemical separation of activities. Serious losses of volatile metal-organic complexes are thus prevented. The different sources of error are discussed. The accuracy of the method is in the order of plus or minus 10%. (auth)