Analytical Comparison of Two Quantitative HSQC Methods for the Absolute Quantitation of Metabolites

Multiple 2D HSQC NMR methods have been developed for the absolute quantitation of metabolites in complex mixtures without need for external calibration or standard additions. However, analytical comparison between these methods is lacking. This study aims at comparing the performance of two "intrinsically quantitative" heteronuclear methods for the targeted quantitation of metabolite mixtures: HSQC₀ and Q QUIPU HSQC. Each method was applied on a model metabolite mixture in the same total experiment time. Both methods were accelerated with non-uniform sampling (NUS), then further accelerated by combining NUS with variation of the pulse sequence repetition time (VRT). Multiple analytical metrics were evaluated and compared for quantitation, including trueness, repeatability, and sensitivity. Globally, accelerated versions of the pulse sequences, using NUS and VRT, performed better than NUS-only acquisitions. On the one hand, provided enough sensitivity is achieved, better performance was observed for HSQC₀, which also appears as a more user-friendly technique. On the other hand, Q QUIPU HSQC was shown to be more repeatable and more sensitive.