Determination of Hydrocarbons Types and Oxygenates in Motor Gasoline: A Comparative Study by Different Analytical Techniques

Various standard and published methods based on chromatographic and spectroscopic techniques are routinely used for hydrocarbon types (aromatics, olefins, oxygenates, etc.) in gasoline range fuel products for the assessment of product quality monitoring (PQM). The precision of data obtained by different techniques is of great significance in the PQM accomplished by various refining processes. The present work describes systematic studies for the statistical correlation of the results of total aromatics, olefins, and oxygenates (MTBE and ethanol) in motor gasoline (MS) obtained by the standard and published methods based on gas chromatography (GC, ASTM-D-5580, ASTM-D-4815), nuclear magnetic resonance (NMR) spectroscopy, and fluorescence indicator analysis (FIA, ASTM-D-1319). Results of a large number of samples from different sources were obtained by using these methods and treated statistically including two tests of significance—the Student t test and the analysis of variance (ANOVA)—in order to establish differences or similarities between the results obtained by these methods. The comparative study has proved that methods based on the 1H NMR spectroscopic technique for the estimation of aromatics, olefins, and oxygenates are comparable with the standard ASTM methods in terms of repeatability and accuracy. Results have indicated very good correlation between NMR, FIA, and GC based methods. The utility of NMR spectroscopic methods in real quality control situations is discussed in this paper.