NMR spectroscopy has recently been utilized to determine the absolute amounts of organic molecules with metrological traceability since signal intensity is directly proportional to the number of each nucleus in a molecule. The NMR methodology that uses hydrogen nucleus ( 1 H) to quantify chemicals is called quantitative 1 H-NMR ( 1 H qNMR). The quantitative method using 1 H qNMR for determining the purity or content of chemicals has been adopted into some compendial guidelines and official standards. However, there are still few reports in the literature regarding validation of 1 H qNMR methodology. Here, we coordinated an international collaborative study to validate a 1 H qNMR based on the use of an internal calibration methodology. Thirteen laboratories participated in this study, and the purities of three samples were individually measured using 1 H qNMR method. The three samples were all certified via conventional primary methods of measurement, such as butyl p-hydroxybenzoate Japanese Pharmacopeia (JP) reference standard certified by mass balance; benzoic acid certified reference material (CRM) certified by coulometric titration; fludioxonil CRM certified by a combination of freezing point depression method and 1 H qNMR. For each sample, 1 H qNMR experiments were optimized before quantitative analysis. The results showed that the measured values of each sample were equivalent to the corresponding reference labeled value. Furthermore, assessment of these 1 H qNMR data using the normalized error, E n -value, concluded that statistically 1 H qNMR has the competence to obtain the same quantification performance and accuracy as the conventional primary methods of measurement.
A high-resolution 31 P NMR method for determining the concentration of phospholipid (PL) species in krill oil was proficiency tested using an international interlaboratory study. Fourteen laboratories from five countries tested five different krill oil samples providing 17 datasets. Krill oil samples were prepared by the organizer using liquid-liquid extraction and sent to the participants who ran the nuclear magnetic resonance (NMR) analysis and evaluated the spectra. The relative standard deviation (RSD) among all the results provided by the participants varied between 2.1% and 3.3% for the phosphatidylcholine (PtdCho) content and between 2.8% and 12.3% for the sum of other PL. Afterward, an automated procedure was applied to all collected NMR data, which significantly improved the RSD values and provided reliable quantitative results for specific PL (PtdCho, 1-lysophosphatidylcholine [LPC], 2-LPS, PtdEtn, acylphosphatidylethanolamine [APE], and lysophosphatidylethanolamine [LPE]). The RSD varied between 1.6% and 2.7% for PtdCho and between 1.6% and 2.9% for the total phosphorus. Higher but acceptable values were obtained for 1-LPC (5.1% to 8.9%), PtdEtn (7.0% to 10.5%), and LPE (5.7% to 16.5%) due to their small concentrations. The influence of different magnetic field strengths (400-600 MHz), probes, and slight differences in acquisition parameters was assessed as nonsignificant. PtdCho hydrolysis during 14 weeks before measurements was the major factor that affects the result distribution. This method was submitted to the AOCS to become an official AOCS method for krill oil analysis.
A proton (1H) NMR spectroscopic method was established for the quality assessment of vegetable oils. To date, several research studies have been published demonstrating the high potential of the NMR technique in lipid analysis. An interlaboratory comparison was organized with the following main objectives: (1) to evaluate an alternative analysis of edible oils by using 1H NMR spectroscopy; and (2) to determine the robustness and reproducibility of the method. Five different edible oil samples were analyzed by evaluating 15 signals (free fatty acids, peroxides, aldehydes, double bonds, and linoleic and linolenic acids) in each spectrum. A total of 21 NMR data sets were obtained from 17 international participant laboratories. The performance of each laboratory was assessed by their z-scores. The test was successfully passed by 90.5% of the participants. Results showed that NMR spectroscopy is a robust alternative method for edible oil analysis.
Blood species identification is an important challenge in forensic science. Conventional methods used for blood species analysis are destructive and associated with time-consuming sample preparation steps. Nuclear magnetic resonance (NMR) spectroscopy is known for its nondestructive properties and fast results. This research study presents a proton (H) NMR method to discriminate blood species including human, cat, dog, elephant, and bison. Characteristic signals acting as markers are observed for each species. Moreover, the data are evaluated by principle component analysis (PCA) and support vector machines (SVM). A 100% correct species recognition between human and nonhuman species is achieved using radial basis kernel function (RBF) and standardized data. The research study shows that H NMR spectroscopy is a powerful tool for differentiating human and nonhuman blood showing a great significance to forensic science.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.