Comparison of UOP-326, voltammetric and gas chromatographic/mass spectrometric methods for the determination of conjugated dienes in Brazilian Naphtha

The content of conjugated dienes is one of the most important factors in determining the quality of gasoline. Owing to their easy polymerization, the presence of these compounds decreases the quality of the product. Although the Brazilian Petroleum Industry still uses the UOP-326 method to determine the content of conjugated dienes, this method has some disadvantages such as long analysis time, incomplete reaction with some conjugated dienes and the interference of primary alcohols. The main objective of this work is to compare and evaluate the three methods (UOP-326, voltammetric and gas chromatographic/mass spectrometric) used for the determination of the conjugated dienes values in naphtha samples. Our results show that the voltammetric and gas chromatographic/mass spectrometric methods can be applied for the determination of conjugated dienes in naphtha samples. However, the voltammetric method is recommended for daily routine analysis because, in addition to being faster and more precise than the UOP-326 method, it is less expensive if compared to the gas chromatographic/mass spectrometric.