Validating nmr methods for fingerprinting and simultaneous multicomponent quantitative analysis

The goal of this work was to set up validation procedures and new quality control parameters suitable for performance assessment in simultaneous multi component quantitative NMR analysis and NMR fingerprinting methods. In order to achieve the goal, three inter-laboratory comparisons (ILCs) were organized. The first one [1,2]consisted in the analysis of wheat and flours aqueous extracts (4 samples) and was aimed to ascertain the statistical equivalence of the scaled NMR spectra. Seven signals were submitted to univariate internationally agreed statistics typically applied in performance assessment of ILC participants. The second ILC [3]regarded a model mixture made up of five compounds. In particular, a model mixture made up of five compounds [Aldicarb, Methamidophos, Oxadixyl, Pirimicarb and 3-(trimethylsilyl)-2,2,3,3-tetradeutero-propionic acid sodium salt (TSP)] dissolved in deuterated water was submitted to NMR analyses. The analytical target of the second ILC was the quantification of analytes by the calibration line method. Such a method was chosen as it allows for identification of a theoretical line to be taken as reference in performance assessment. The third ILC consisted in the analysis of wine grape juice (7 samples) and was aimed to confirm the statistical equivalence of the scaled NMR spectra and to quantify several metabolites by standard addition method. Results show that quantitative NMR is a robust quantification tool. Performance assessment was carried out on single component quantification, by the popular and traditional z-score, and on multi-component analyses 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. Qp-score is a parameter suitable for harmonization of fingerprinting protocols and simultaneous quantitative multi component analysis. Such parameter, that was designed considering consolidated internationally agreed statistics, represents an unbiased evaluation tools for NMR method validations.