Enhancing benchtop NMR spectroscopy by means of sample shifting

Abstract

Benchtop NMR spectrometers have become widely available over the last decade. They are now used successfully in various branches of chemistry. Their popularity continues to grow due to their low price and almost zero running costs. However, benchtop spectrometers suffer from low resolution and sensitivity compared to the high-field spectrometers used in NMR labs for several decades. In this article we present a solution for boosting the sensitivity of benchtop NMR spectrometers in a multi-scan experiment and improving their capabilities in quantitative measurement. Our solution involves the synchronized shifting of a sample to preserve its high nuclear polarization during the measurement. We performed several experiments using different samples to confirm this improved performance: an ¹H NMR experiment for 4,4-dimethoxy-2-butanone, and ¹³C NMR experiments for benzyl salicylate, the liquid pharmaceutical product Acerin (skin solution), and a mixture of m-anisaldehyde and (R)-(+)-limonene.