Abstract
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.
Highlights
An inter-laboratory comparison (ILC) was organized with the aim to set up quality control indicators suitable for multi component quantitative analysis by nuclear magnetic resonance (NMR) spectroscopy. 36 NMR data sets were produced by 30 participants using 34 NMR spectrometers
Among the quantification approaches available for NMR spectroscopy,[4] the calibration line method was chosen in this work as it allows for identification of a theoretical line to be taken as reference in performance assessment
It is apparent that changing the processing conditions of the NMR spectra, from “one operator – all NMR data sets” to “one operator – one NMR data set”, has a little impact on the final result in terms of mean value
Summary
An inter-laboratory comparison (ILC) was organized with the aim to set up quality control indicators suitable for multi component quantitative analysis by nuclear magnetic resonance (NMR) spectroscopy. 36 NMR data sets (corresponding to 1260 NMR spectra) were produced by 30 participants using 34 NMR spectrometers. The reproducibility of a single pulse experiment preceded by pre-saturation of the solvent signal has been evaluated by application of Principal Component Analysis (PCA) to 1H NMR data in the framework of two inter-laboratory comparisons.[32,33] PCA offers the advantage to estimate measurement reproducibility by easy visual inspection of the scores plot, but quality control indexes to be used as general reference parameters for quality assessment of NMR spectra are still lacking.
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