Determination of trace elements in crude oil by ICP-OES using ultrasound-assisted acid extraction

The determination of Cr, Mo, Ti, V, Cd, Fe, Mn, Ni and Zn in crude oil by ICP-OES using ultrasound-assisted acid extraction is proposed. The crude oil was treated with concentrated nitric acid and heated at 85 degrees C for 30 min. Then, the mixture was placed in an ultrasonic bath for 15 min in order to obtain total extraction of trace elements from the oil sample into the acid solution, which was directly aspirated into the ICP to be quantified using analytical curves constructed with inorganic standards. Principal component analysis (PCA) and factor analysis (FA) were used to evaluate the effect and importance of the experimental variables in this sample preparation procedure. The proposed method was tested using NIST 1634c (Trace Elements in Residual Fuel Oil) and two petroleum samples. Recoveries between 90 and 105% were achieved. Limits of quanti. cation in the sample ranged from 0.008 to 0.62 mu g g(-1), depending on the analyte.