The direct analysis of fuel ethanol by ICP-MS using a flow injection system coupled to an ultrasonic nebulizer for sample introduction

In this work, a method for the analysis of fuel ethanol by ICP-MS is proposed. The direct introduction of a 10% v/v ethanol solution through an ultrasonic nebulizer formed carbon deposits on the cones. Therefore, a flow injection system was used to introduce 250 mu L of the diluted sample or calibration solution. The optimized operational conditions were 1200 W RF power, 0.7 L min(-1) nebulizer gas flow rate and 140 degrees C and -3 degrees C heating and cooling temperatures of the USN desolvation system. External calibration against aqueous solutions, matrix matching and isotope dilution (ID) were compared. The limits of detection were, in mu g L(-1), Ag: 0.08, Cd: 0.12, Co: 0.04, Cu: 0.4, Fe: 27, Mn: 0.7, Ni: 0.4 and Pb: 0.2, with calibration against aqueous solutions, and Ag: 0.02, Cd: 0.02, Cu: 0.2 and Pb: 0.04, with isotope dilution. Matrix matching was not recommended because of the carbon deposits formation. Both ID and calibration with aqueous solutions promoted speed, good precision, sensitivity and agreement with the results obtained by ETV-ICP-MS.