A simple dilute-and-shoot procedure for Si determination in diesel and biodiesel by microwave-induced plasma optical emission spectrometry

In the present work, microwave-induced plasma optical emission spectrometry (MIP OES) and the flow blurring nebulizer (FBN) technology are used to determine silicon in diesel and biodiesel samples. A simple dilute-and-shoot procedure with ethanol is presented. Two additional sample preparation procedures are also evaluated for comparison: closed-vessel microwave-assisted acid digestion and microemulsion preparation in n-propanol. Limits of detection (LOD) vary from 5 to 20 mu g L-1 and relative standard deviations (RSD) are lower than 2% in all cases. Accuracy is evaluated by spike experiments, with recoveries between 80 and 103%. The influence of Ca, K, Mg and Na as concomitant ions on silicon determination by MIP OES is also investigated. Significant effects on Si emission signals are observed neither in single nor multiple concomitant experiments. Although good results are obtained with all sample preparation procedures evaluated, sample dilution in ethanol represents a simpler and faster strategy, which allows external calibration with inorganic standards and aqueous solutions. (C) 2012 Elsevier B.V. All rights reserved.