Analysis of bioethanol samples through Inductively Coupled Plasma Mass Spectrometry with a total sample consumption system

Abstract Bioethanol real samples have been directly analyzed through ICP-MS by means of the so called High Temperature Torch Integrated Sample Introduction System (hTISIS). Because bioethanol samples may contain water, experiments have been carried out in order to determine the effect of ethanol concentration on the ICP-MS response. The ethanol content studied went from 0 to 50%, because higher alcohol concentrations led to carbon deposits on the ICP-MS interface. The spectrometer default spray chamber (double pass) equipped with a glass concentric pneumatic micronebulizer has been taken as the reference system. Two flow regimes have been evaluated: continuous sample aspiration at 25 μL min − 1 and 5 μL air-segmented sample injection. hTISIS temperature has been shown to be critical, in fact ICP-MS sensitivity increased with this variable up to 100–200 °C depending on the solution tested. Higher chamber temperatures led to either a drop in signal or a plateau. Compared with the reference system, the hTISIS improved the sensitivities by a factor included within the 4 to 8 range while average detection limits were 6 times lower for the latter device. Regarding the influence of the ethanol concentration on sensitivity, it has been observed that an increase in the temperature was not enough to eliminate the interferences. It was also necessary to modify the torch position with respect to the ICP-MS interface to overcome them. This fact was likely due to the different extent of ion plasma radial diffusion encountered as a function of the matrix when working at high chamber temperatures. When the torch was moved 1 mm plasma down axis, ethanolic and aqueous solutions provided statistically equal sensitivities. A preconcentration procedure has been applied in order to validate the methodology. It has been found that, under optimum conditions from the point of view of matrix effects, recoveries for spiked samples were close to 100%. Furthermore, analytical concentrations for real samples following the preconcentration method and the direct determination were not significantly different. The quantification method was finally based on external calibration with standards containing 50% (v/v) ethanol content.