Organic palladium and palladium-magnesium chemical modifiers in direct determination of lead in fractions from distillation of crude oil by electrothermal atomic absorption analysis

Platinum reforming catalysts are easily poisoned by increased levels of lead, therefore a sensitive atomic absorption spectrometric procedure for lead determination in fractions from crude oil distillation was developed. Lead was present in organic form in the samples analysed therefore the behaviour of various lead compounds (Pb-alkylarylsulphonate, Pb-4-cyclohexanobutyrate, tetraethyllead, Pb in fuel oil) was studied. The best procedure for the determination of lead in different petroleum products, including those containing asphaltenes includes a pretreatment with iodine and methyltrioctylammonium chloride, followed by the use of an organic Pd-Mg modifier. Under these conditions an effective matrix removal is possible at a pyrolysis temperature up to approximately 1100 degrees C and the behaviour of lead present in different forms is unified. The characteristic mass is 11-12 pg Pb, corresponding to a detection limit of 0.25 ng g(-1) for 20 mu 1 sample solution. This can be lowered by multiple injection. (C) 1999 Elsevier Science B.V. All rights reserved.