NMR methods for the analysis of mixtures

Abstract

NMR spectroscopy is a powerful approach for the analysis of mixtures. This feature article describes a selection of methods that aim to address the complexity, the low concentrations, and the changing nature that mixtures can display.

Quantitative NMR spectroscopy of complex mixtures

“…40 The ability of NMR to quantify multiple species in a single experiment is particularly interesting for such analysis, but the multicomponent nature of such drugs makes 1 H NMR poorly suited to resolve and integrate signals from the individual components of complex polymers. Chemometric techniques based on 1 H NMR profiling can be used to tackle such complexity, and several papers demonstrated the utility of such methods to detect contaminated heparin samples. 41 It was recently shown that such chemometric methods can also be applied to diffusion-ordered spectroscopy (DOSY) datasets, allowing to predict the molecular weight of heparin samples.…”

“…Fig. 1A shows how 1 H NMR provides an opportunity to identify and quantify an impurity (kaempferol) present in a sample of quercetin (a flavonoid used as a food supplement). 30 While the mixture contains only two compounds, it can already be considered as ''complex'' because the two molecules have very similar structures.…”

“…In particular the initial pure-shift methods were hampered by artefacts due to the data chunking mode applied during data acquisition. However, this limitation was recently circumvented by methods capable of delivering clean 1D pure-shift 1 H spectra with a repeatability that enabled their application into metabolomics workflows. Several studies were subsequently published, including the differentiation of fruit extracts from different Andean ecosystems, 71 or the detection of adulteration of food samples.…”

“…While many complementary analytical methods are used for the analysis of complex mixtures, nuclear magnetic resonance (NMR) spectroscopy has unique advantages. 1 First, it is a nondestructive method that can provide both structural and…”

“…While many complementary analytical methods are used for the analysis of complex mixtures, nuclear magnetic resonance (NMR) spectroscopy has unique advantages. 1 First, it is a non-destructive method that can provide both structural and quantitative information at the same time. Second, the level of accuracy that can be achieved with NMR gives a very high degree of confidence in the quantitative results obtained.…”