Quantitative Nuclear Magnetic Resonance Applications in Analytical Chemistry

Quantitative nuclear magnetic resonance (qNMR) has emerged as a gold‐standard tool in analytical chemistry, owing to its inherent direct proportionality between signal intensity and number of nuclear spins. This non-destructive methodology offers rapid and precise determinations of compound purity, concentration and structural integrity without the need for reference standards of the analyte itself. Applications span pharmaceutical quality control, natural product quantification, metabolomics in food science and the certification of organic reference materials. Advances in pulse sequence design, including one- and two-dimensional experiments, have extended the capabilities of qNMR to complex mixtures by resolving overlapping resonances and minimising systematic bias. Metrological frameworks have been established to achieve SI traceability, utilising internal or external calibration strategies such as PULCON and ERETIC. The technique’s high reproducibility and low uncertainty have underpinned its adoption for regulatory compliance and standardisation across global laboratories. Emerging trends include benchtop NMR instruments for in-field analyses, hybrid chromatographic coupling and real-time reaction monitoring, further broadening the impact of qNMR in both research and industrial settings.

Research from Nature Portfolio

Recent work has applied qNMR to the absolute quantification and stability assessment of vitamin D metabolites used as calibrators in diagnostic assays. By deploying tailored one- and two-dimensional pulse sequences, researchers identified spin systems for 25-hydroxyvitamin D2/D3 and 24R,25-dihydroxyvitamin D2, quantifying these non-certified compounds directly against SI-traceable standards. This study revealed significant isomerisation phenomena in borderline-polar solvents over time, offering critical insights for accurate calibration of hyphenated techniques. The approach emphasises the atom-based quantification advantage of qNMR, enhancing the reliability of analytical workflows in clinical chemistry and reference material development.

Quantitative Nuclear Magnetic Resonance Applications in Analytical Chemistry publication trend

The graph below shows the total number of articles in quantitative nuclear magnetic resonance applications in analytical chemistry across all publications each year (not limited to Nature Index journals).

Technical terms

Quantitative NMR (qNMR): An NMR technique in which signal integrals are used to determine absolute concentrations or purities based on the direct proportionality between resonance intensity and number of nuclei.

Internal standard method: A calibration strategy employing a compound of known concentration added to the sample, against which the analyte’s signal is compared for quantification.

External standard method (PULCON/ERETIC): Calibration approaches using electronically generated or separately measured standards to establish a reference signal, eliminating the need for added internal compounds.

Spin system: A set of coupled nuclear spins within a molecule that give rise to characteristic resonance patterns, crucial for selecting appropriate signals for quantitation.

Relaxation delay: The time interval between successive NMR pulses allowing nuclear spins to return to thermal equilibrium, essential for accurate signal integration and quantification.

SI traceability: The property of a measurement result whereby it can be related to the International System of Units through an unbroken chain of calibrations, ensuring comparability and standardisation.

References

1. A new single-reference quantitative method using liquid chromatography with relative molar sensitivity based on 1H-qNMR for khellactone esters from Peucedanum japonicum root extract. Food Chemistry (2023).
2. Quantitation of L-cystine in Food Supplements and Additives Using 1H qNMR: Method Development and Application. Foods (2023).
3. Quantitative NMR (qNMR) spectroscopy based investigation of the absolute content, stability and isomerization of 25-hydroxyvitamin D2/D3 and 24(R),25-dihydroxyvitamin D2 in solution phase. Scientific Reports (2022).
4. Quantitative Nuclear Magnetic Resonance Spectroscopy Based on PULCON Methodology: Application to Quantification of Invaluable Marine Toxin, Okadaic Acid. Toxins (2016).
5. Using high-performance quantitative NMR (HP-qNMR®) for certifying traceable and highly accurate purity values of organic reference materials with uncertainties. Accreditation and Quality Assurance (2013).