Performance Assessment in Fingerprinting and Multi Component Quantitative NMR Analyses

An interlaboratory comparison (ILC) was organized with the aim to set up quality control indicators suitable for multicomponent quantitative analysis by nuclear magnetic resonance (NMR) spectroscopy. A total of 36 NMR data sets (corresponding to 1260 NMR spectra) were produced by 30 participants using 34 NMR spectrometers. The calibration line method was chosen for the quantification of a five-component model mixture. Results show that quantitative NMR is a robust quantification tool and that 26 out of 36 data sets resulted in statistically equivalent calibration lines for all considered NMR signals. The performance of each laboratory was assessed by means of a new performance index (named Qp-score) which is related to the difference between the experimental and the consensus values of the slope of the calibration lines. Laboratories endowed with a Qp-score falling within the suitable acceptability range are qualified to produce NMR spectra that can be considered statistically equivalent in terms of relative intensities of the signals. In addition, the specific response of nuclei to the experimental excitation/relaxation conditions was addressed by means of the parameter named NR. NR is related to the difference between the theoretical and the consensus slopes of the calibration lines and is specific for each signal produced by a well-defined set of acquisition parameters

A Contribution to the Harmonization of Non-targeted NMR Methods for Data-Driven Food Authenticity Assessment

Spectroscopic non-targeted methods are gaining ever-growing importance in quality control and authenticity assessment of food products because of their strong potential for identification of specific features of the products by data-driven classifiers. One of the factors hampering the diffusion of spectroscopic non-targeted methods and data-driven classifiers is the lack of harmonized guidelines for their development and validation. In particular, to date, neither conditions to directly compare spectra recorded by different spectrometers nor studies demonstrating the statistical equivalence of the spectra are available. Among the spectroscopic analytical techniques suitable for the development of non-targeted methods, nuclear magnetic resonance (NMR) offers the unique opportunity to generate statistically equivalent signals. In this paper, the feasibility of NMR spectroscopy to generate statistically equivalent NMR signals from a number of different spectrometers was demonstrated for complex mixtures (aqueous extracts of wheat and flour) by organizing an inter-laboratory comparison involving 36 NMR spectrometers. Univariate statistics along with multivariate analysis were exploited to establish unbiased criteria for assessing the statistical equivalence of the NMR signals. The aspects affecting the signal equivalence were investigated, and possible solutions to reduce the extent of the human error were proposed and applied with satisfactory results. This study furnishes the scientific community with an appropriate and easy procedure to validate non-targeted NMR methods and provides error values to be used as a reference for future studies

Depressive symptoms, vascular risk factors and mild cognitive impairment. The Italian longitudinal study on aging.

Aims: We evaluated the impact of depressive symptoms on the rate of incident mild cognitive impairment (MCI) after a 3.5-year follow-up, and we assessed the interaction between depressive symptoms and vascular risk factors for incident MCI. Methods: A total of 2,963 individuals from a sample of 5,632 65- to 84-year-old subjects were cognitively and functionally evaluated at the 1st and 2nd surveys of the Italian Longitudinal Study on Aging, a prospective cohort study with a 3.5-year follow-up. MCI and dementia were classified using current clinical criteria. Depressive symptoms were measured with the Geriatric Depression Scale. Results: Among the 2,963 participants, 139 prevalent MCI cases were diagnosed at the 1st survey. During the 3.5-year follow-up, 105 new events of MCI were diagnosed. We did not observe any significant association between depressive symptoms and incident MCI (RR = 1.25, 95% CI = 0.85–1.84, 2 = 1.30, p ! 0.25). No sociodemographic variables or vascular risk factors modified the relationship between depressive symptoms and incident MCI. Conclusion: In our population, depressive symptoms were not associated with the rate of incident MCI. Our findings did not support a role of sociodemographic variables or vascular risk factors in the link between depressive symptoms and incident MCI

A community-built calibration system: The case study of quantification of metabolites in grape juice by qNMR spectroscopy

Nuclear Magnetic Resonance (NMR) is an analytical technique extensively used in almost every chemical laboratory for structural identification. This technique provides statistically equivalent signals in spite of using spectrometer with different hardware features and is successfully used for the traceability and quantification of analytes in food samples. Nevertheless, to date only a few internationally agreed guidelines have been reported on the use of NMR for quantitative analysis. The main goal of the present study is to provide a methodological pipeline to assess the reproducibility of NMR data produced for a given matrix by spectrometers from different manufacturers, with different magnetic field strengths, age and hardware configurations. The results have been analyzed through a sequence of chemometric tests to generate a community-built calibration system which was used to verify the performance of the spectrometers and the reproducibility of the predicted sample concentrations