Determination of Cr, Ni, Pb and V in gasoline and ethanol fuel by microwave plasma optical emission spectrometry

Simple procedures for the determination of Cr, Ni, Pb and V in gasoline and ethanol fuel by microwave plasma optical emission spectrometry (MIP OES) are described. Ethanol fuel samples were simply diluted in an aqueous 1% v/v HNO3 solution. For gasoline, microemulsions in n-propanol were prepared. The MIP OES instrument requires no separate gas source since a N-2 gas generator coupled to a simple air compressor is sufficient to maintain the microwave-induced plasma. An external gas control module (EGCM) is used to inject air into the plasma in order to minimize background emissions and avoid carbon deposition on the torch and on the pre-optical window. The Flow Blurring Nebulizer (FBN) technology was also employed to ensure more efficient and homogeneous sample aerosols, which contributes to plasma stability and lower limits of detection (LODs). Nebulizer gas pressure and plasma viewing position were optimized separately for each analyte. Gasoline and ethanol fuel samples were analyzed and the calculated LODs were in the range of 0.3-60 mu g L-1 or 4-1700 mu g kg(-1) for all analytes. The accuracy was checked by spike experiments and recoveries between 84 and 123% were obtained.