Quantitative Quadrupolar NMR (qQNMR) via nitrogen-14 for the accurate control of L-carnitine in food supplements

A qQNMR methodology using nitrogen-14 as the quadrupolar nucleus of choice has been introduced for the first time as a robust and validated method to determine and quantify L-carnitine in food supplements. The quantification has been carried out by the alternative use of a calibration curve or by addition of ammonium chloride as internal standard. The method was validated at seven concentration levels in the range of 5.58-99.26 mM, affording intra-and inter day accuracies lower than 6.84% (expressed in CV), robustness towards temperature and recycle delay, limit of detection (LOD) of 2.48 mM, limit of quantification (LOQ) of 5.58 mM and remarkably with absence of matrix effect. (C) 2021 Elsevier B.V. All rights reserved.

Automated summary

A qQNMR methodology using nitrogen-14 as the quadrupolar nucleus has been introduced for the determination and quantification of L-carnitine in food supplements. The method was validated at seven concentration levels with high precision and robustness, showing low limits of detection and quantification. The absence of matrix effect is a notable feature of this method.