Extraction induced by emulsion breaking for simultaneous determination of Co, Fe and Ni in petroleum asphalt cement by high-resolution continuum source atomic absorption spectrometry

This paper reports, for the first time, the simultaneous determination of Co, Fe and Ni in petroleum asphalt cement by high-resolution continuum source atomic absorption spectrometry after extraction induced by the emulsion breaking method. The variables that could influence the sample preparation were evaluated, like sample dilution with toluene and mineral oil, extraction time, HNO3 and Triton X-100 concentration in the aqueous extractant solution. M optimized conditions, 0.08 g of the sample was dissolved with 1.5 mL of toluene and 3.5 mL of mineral oil and vigorous mixed with the extractant solution containing 40% (v/v) of HNO3 and 40% (v/v) of Triton-X-100. The emulsions were broken by heating just after their formation and the aqueous extracts were collected for analysis. Simultaneous determination was carried out at the secondary lines of Co (352.685 nm), Fe (352.604 nm) and Ni (352.454 nm). For this purpose, the best pyrolysis and atomization temperatures were 700 and 2400 degrees C, respectively. Calibration was performed with standard aqueous solutions and no matrix effects were observed. The limit of detection was 0.003 mg L-1 for Co, 0.018 mg L-1 for Fe and 0.027 mg L-1 for Ni. Method accuracy was confirmed by comparing the results obtained by the proposed extraction method with those obtained after samples acid digestion. Recoveries ranged from 100 to 107%, 103 to 109% and 95.5 to 98.9% were obtained for Co, Fe and Ni, respectively.