Quantitative determination of aliphatic hydrocarbon compounds by 2D NMR

Abstract

Quantitative analysis of complex mixtures by NMR is often hampered by heavily overlapping signals in 1D1 H or 13 C spectra. To resolve the overlap problem, we have been looking at the possibilities of using heteronuclear correlated 2D NMR methods for quantification. In this work, we applied 2D INEPT to analyze mixtures of tetradecane and squalane, which represent typical substructures of lube oil fractions. The factors affecting correlation peak volumes, namely the polarization transfer delays within pulse sequence, multiplicity of CH n group and the magnitude of 1 J .C,H/ couplings were taken into account by product operator formalism calculations. The results indicate that if absolute precision in quantification is not essential, the current approach can be used for the quantitative analysis of the molecular composition of complex mixtures when conventional 1D NMR methods fail.

Some aspects of quantitative 2D NMR

“…When the availability of substance is not an issue, X-nuclei detection can provide good resolution in the F 2 dimension, while resonances can be further discriminated by the proton chemical shift on the F 1 dimension [3,4]. This kind of approach, and some matters which have an influence on quantitativity, have been discussed in literature [5,6]. However, usually the amount of sample is restricted, so one has to rely on more sensitive methods, which exploit inverse detection.…”

Quantitative 2D liquid‐state NMR

“…However, the use of 2D NMR for quantitative analysis has been expanding only over the last decade . There are two main reasons explaining this late development.…”

Fast and Ultrafast Quantitative 2D NMR

“…The HSQC spectrum presented in Fig. Even though early works reported the application of DQF-COSY (Alonso, Arus, Westler, & Markley, 1989) or TOCSY (Morvan, Demidem, Papon, & Madelmont, 2003) for measuring relative concentrations in complex samples, the number of papers on quantitative 2D NMR has really only taken off in the past 7 years, thanks to the works of Koskela et al (Koskela, 2009;Koskela et al, 2005;Koskela & Väänänen, 2002), Zhang et al (Zhang & Gellerstedt, 2007), Massou et al (Massou et al, 2007a, 2007b, Markley et al (Lewis et al, 2010(Lewis et al, , 2007, ourselves Martineau et al, 2011Martineau et al, , 2012 and others. The spectrum exhibits more resonances than its homo-nuclear counterpart, and these resonances are better separated.…”