Abstract
Since a couple of years, low-field (LF) nuclear magnetic resonance (NMR) spectrometers (40-100 MHz) have re-entered the market. They are used for various purposes including analyses of natural products. Similar to high-field instruments (300-1200 MHz), modern LF instruments can measure multiple nuclei and record two-dimensional (2D) NMR spectra. To review the commercial availability as well as applications, advantages, limitations, and prospects of LF-NMR spectrometers for the purpose of natural products analysis. Commercial LF instruments were compared. A literature search was performed for articles using and discussing modern LF-NMR. Next, the articles relevant to natural products were read and summarised. Seventy articles were reviewed. Most appeared in 2018 and 2019. Low costs and ease of operation are most often mentioned as reasons for using LF-NMR. As the spectral resolution of LF instruments is limited, they are not used for structure elucidation of new natural products but rather applied for quality control (QC), forensics, food and health research, process control and teaching. Chemometric data handling is valuable. LF-NMR is a rapidly developing niche and new instruments keep being introduced.
Highlights
Since a couple of years, low-field (LF) nuclear magnetic resonance (NMR) spectrometers (40–100 MHz) have re-entered the market
Until 1960, structure elucidation of natural products was tedious and of ultraviolet (UV), infrared (IR), mass spectrometry (MS) and nuclear time-consuming requiring skill and persistence. It relied almost exclu- magnetic resonance (NMR), this all changed and nowadays a new sively on degradative chemistry and elemental analysis requiring structure is solved within days or weeks instead of a century
Its appearance is timely as in 2019 many more LFNMR articles appeared than ever before and in 2019 there were many exciting hardware introductions: an autosampler (Magritek), first 100 MHz instrument (Nanalysis), first broadband instrument (Oxford Instruments), < 0.2 Hz line width instrument (Magritek) and a new vendor entering the market (Bruker). This information might act as an eye-opener for the Phytochemical Analysis readership regarding the application niche of LF-NMR
Summary
Passed between the first isolation and the final correct structure, examples being morphine, strychnine and patchoulol. Until 1960, structure elucidation of natural products was tedious and of ultraviolet (UV), infrared (IR), mass spectrometry (MS) and nuclear time-consuming requiring skill and persistence It relied almost exclu- magnetic resonance (NMR), this all changed and nowadays a new sively on degradative chemistry and elemental analysis requiring structure is solved within days or weeks instead of a century. Its appearance is timely as in 2019 many more LFNMR articles appeared than ever before and in 2019 there were many exciting hardware introductions: an autosampler (Magritek), first 100 MHz instrument (Nanalysis), first broadband instrument (Oxford Instruments), < 0.2 Hz line width instrument (Magritek) and a new vendor entering the market (Bruker) Combined, this information might act as an eye-opener for the Phytochemical Analysis readership regarding the application niche of LF-NMR. The Magritek 43 MHz is by far the most popular
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