Application of 13C Quantitative NMR Spectroscopy to Isotopic Analyses for Vanillin Authentication Source

Abstract

The carbon stable isotope ratio (δ13C) is a valuable chemical parameter in the investigation of the geographic origin, quality, and authenticity of foods. The aim of this study is the evaluation of the feasibility of 13C-NMR (Nuclear Magnetic Resonance) spectroscopy to determine the carbon stable isotope ratio, at natural abundance, of small organic molecules, such as vanillin, without the use of IRMS (Isotope Ratio Mass Spectrometry). The determination of vanillin origin is an active task of research, and differentiating between its natural and artificial forms is important to guarantee the quality of food products. To reach our goal, nine vanillin samples were analyzed using both 13C quantitative NMR spectroscopy (under optimized experimental conditions) and IRMS, and the obtained δ13C values were compared using statistical analysis (linear regression, Bland–Altman plot, and ANOVA (analysis of variance)). The results of our study show that 13C-NMR spectroscopy can be used as a valuable alternative methodology to determine the bulk carbon isotope ratio and to identify the origin of vanillin. This makes it attractive for the analysis in the same experiment of site-specific and total isotope effects for testing authenticity, quality, and typicality of food samples. Moreover, the improvement of NMR spectroscopy makes it possible to avoid the influence of additives on carbon stable isotope ratio analysis and to clearly identify fraud and falsification in commercial samples.

NMR in forensics

“…[ 21 ] NMR is well suited for the analysis of complex mixtures and food products as it is an information rich spectroscopic method with relatively minimal sample preparation requirements, excellent reproducibility, and an intrinsic quantitative response across a diversity of analytes that permits quantification with both internal and external calibration. The publication record in this area using NMR methods is extensive and numerous examples can be found in the literature in the last few years across a variety of product types including edible oils, [ 22 ] wine and beer, [ 23 ] herbs and spices, [ 23f,24 ] honey, [ 25 ] milk and dairy, [ 26 ] and herbal/botanical products. [ 27 ] Most of these articles represent demonstrations of the utility of NMR in the analysis of this diverse range of products.…”

Monitoring of the concentration of particulate matter, volatile organic compounds and nitrogen dioxide in the Vesuvius National Park

“…The ambient air pollutants (e.g., CO2, NOx, SOx, PM and VOCs) have a potential adverse impact on buildings, artifacts and biochemical parameters, which further leads, for example, to a reduction in plant growth and development [2][3][4]. Moreover, a high concentration of specific pollutants can pose risks to human health [5][6][7][8]. In recent years, urban air pollution represents one of the greatest environmental challenges in the 21st century [9,10].…”

Development of an analytical methodology based on stable isotope ratios for air quality assessment in cultural heritage

“…Carbon stable isotope ratio, expressed as δ 13 C, is a useful tool for the identification and classification of the origin of a sample [27][28][29][30][31][32], including CO2 sources [26]. In fact, carbon stable isotope ratio permitted to discriminate between anthropogenic (e.g., vehicular traffic) and biogenic origin of CO2 in urban environments [26].…”