Quantification of nickel, vanadium and manganese in petroleum products and biofuels through inductively coupled plasma mass spectrometry equipped with a high temperature single pass spray chamber

Abstract

A heated Torch Integrated Sample Introduction System (hTISIS) has been applied to the analysis of petroleum products and biofuels through Inductively Coupled Plasma Mass Spectrometry (ICP-MS). Three elements have been determined because of their importance in the petroleum industry: V, Ni and Mn. Sample injection has been accomplished by means of the introduction of a low sample volume (2.5 μl) into an air carrier stream. A peak has been thus obtained. Two sets of samples have been selected: five solvents (xylene, kerosene, nonane, undecane and hexadecane) and five real samples (biodiesel, diesel, kerosene, superethanol and gasoline). The chamber temperature has been varied when introducing either solvents or real samples. In both cases it has been found that sensitivity peaked at 110 °C heating temperature. However, non-spectral interferences caused by differences in the matrix composition became less severe as this variable was increased and they were virtually eliminated at temperatures of 150 °C (alkanes) and 200 °C (real samples). When comparing with a default spray chamber (i.e., conical chamber with an impact bead) 3 to 6 times lower LODs were obtained. At 150 °C, this parameter has taken values of approximately 80 ng l⁻¹ for V and Ni to 140 ng l⁻¹ for Mn. At 200 °C heating temperature it has been possible to carry out accurate ICP-MS determinations by applying external calibration. Additional advantages of the present approach were that no oxygen was required to avoid soot deposition at the sampler cone and that nickel, instead of platinum cones, was used.