¹⁷O Quantitative Nuclear Magnetic Resonance Spectroscopy of Gasoline and Oxygenated Additives

Abstract

17O Nuclear magnetic resonance (NMR) spectroscopy allows exclusive detection and direct quantification of oxygenates in gasoline unaffected by its hydrocarbon content, using the internal standard quantitative NMR (QNMR) method. Chemical shifts of 24 oxygen-containing compounds as potential additives and contaminants have been measured in gasoline and corrected values of deltaO 18.1 and 3.9 determined for neat methyl tert-butyl ether (MTBE) and neat di-n-butyl ether, respectively. Quantification of ethanol in gasoline can be readily achieved by 17O QNMR with dimethyl sulfone as an internal standard reference material, at the levels currently used in retail gasolines (1-20%). In addition, the simultaneous detection and quantification of the oxygenates methanol, ethanol, 2-propanol, tert-butyl alcohol, and MTBE in gasoline has been established to further demonstrate the specificity of the method. 17O NMR has distinct advantages over 1H and 13C QNMR methods, and although it cannot reliably differentiate 1-propanol, 1-butanol, 1-pentanol, and isopentyl alcohol, 17O NMR does allow the rapid and unambiguous identification of unexpected oxygenates such as acetates and ketones found as contaminants in some retail gasoline.

Analytical Methods for Determining Automotive Fuel Composition

“…Infrared spectroscopy has been reported for quantitative analysis of ethanol and methanol in fuels by using attenuated total reflectance (ATR) (Battiste, 1981) and Fourier transform near infrared (FT-NIR) (Fernandes et al, 2008). 17 O nuclear magnetic resonance spectroscopy ( 17 O NMR) was used for the quantification of oxygenated additives in gasoline (Lonnon & Hook, 2003). Although these methods are reliable they need trained professionals and costly equipments and cannot be performed in loco.…”

Fast and Ultrafast Quantitative 2D NMR

“…Since then, 1 H NMR has continuously been used for quantitative measurements in a wide range of domains, including but not limited to pharmaceutical analysis (Kwakye, 1985), natural products (Pauli, Jaki, & Lankin, 2005), in vivo spectroscopy (Podo et al, 1998) and metabolomics (Wishart, 2008). Quantitative studies relying on other nuclei have also been reported, such as 15 N (Levy, Pehk, & Srinivasan, 1980), 31 P (Dais & Spyros, 2007) or 17 O (Lonnon & Hook, 2003). In particular, quantitative 13 C NMR has been widely described (Cookson & Smith, 1984;Mareci & Scott, 1977;Shoolery, 1977) and applied in a variety of fields, from food science (Mavromoustakos et al, 1997;Vlahov, 1999) or metabolic studies (Aursand, Jorgensen, & Grasdalen, 1995) to the isotopic analysis of natural or synthetic molecules (Bussy et al, 2011;Caytan, Remaud, Tenailleau, & Akoka, 2007;Tenailleau et al, 2004).…”

Characterization of siloxane copolymers by solution 17O NMR spectroscopy

“…However, poor resolution due to broadened signals was observed when higher polymeric condensation products of tetramethoxysilane were monitored by 17 O NMR in solution [7]. Even the linewidths of short aliphatic n-alcohols range from 90 to 200 Hz [24]. Solid state MAS 17 O NMR spectroscopy of polydimethylsiloxane hybrid materials provided larger linewidths of approximately 2000 Hz [16,17].…”