Determination of benzene and total aromatics in commercial gasolines using packed column GC and NMR techniques

A simple, accurate and rapid method has been developed for the estimation of benzene and total aromatics (0.5-50% w/w) including heavier aromatics (C₈, C₉, and C₁₀) in commercial gasoline using packed column GC and NMR techniques. The benzene content can be estimated as low as 0.1% w/w. The response of a flame ionisation detector (FID) to each major aromatic group in gasoline was calculated using internal standard. The results have been compared with the NMR and standard ASTM D5580 methods. The limitations of NMR and GC techniques for the estimation of total aromatics particularly in reformulated gasoline containing oxygenates have been discussed and attempts have been made to overcome problems associated with the analysis. The results obtained by both the techniques for a number of commercial gasoline samples containing olefins or free of olefins received from different refineries processing variety of crudes using different refining technologies have shown excellent correlation. The ¹H NMR method has a wider scope, convenient and fast, and also applicable to heavier naphtha. The method can routinely be adopted for the quality control of commercial gasoline at refinery as well as marketing terminals for monitoring benzene and total aromatic content. The time consumption for single run using gas chromatographic technique is approximately 35 min.