The utility of a W-Ir permanent chemical modifier for the determination of Ni and V in emulsified fuel oils and naphtha by transverse heated electrothermal atomic absorption spectrometer

A 'water in oil' emulsification procedure has been applied to a transverse heated electrothermal atomic absorption spectrometer (TH-ETAAS) for direct determination of Ni and V in petroleum products such as naphtha, NIST SRM 1618 Residual Oil and NIST SRM 1634c Residual Fuel Oil. The utility of permanent chemical modifiers such as W, W-Rh and W-Ir, has been examined in determining these elements. The furnace with an integrated platform coated with W and Ir was found to provide 25-30% improved sensitivity than other coatings for Ni. In the case of V, a pyrocoated tube with an integrated platform was found to give the best results. The W-Ir coated tube could be used for nearly 400 firings. The limit of detection for naphtha emulsion was 0.002 and 0.006 mug g(-1) for Ni and V, respectively, indicating that the method is well suited for matrices containing very low concentration of trace elements. The method can also be applied to dense matrices such as SRMs Residual Oil and Residual Fuel Oil. In this case, the limit of detection was 0.1 mug g(-1) for Ni and 0.5 mug g(-1) for V with a precision of less than 5%.