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ISO/IEC 17025 is the worldwide quality standard for testing and calibration laboratories. It is the basis for accreditation by an accreditation body. The current version was published in 2018.
Implementing ISO/IEC 17025 as part of laboratory quality initiatives offers both laboratory and business benefits, such as expanding the potential customer base for testing and/or calibration, increasing the reputation and image of the laboratory at national and international level, continuous improvement of the data quality and the effectiveness of the laboratory or creation of a good basis for most other quality systems in the laboratory sector, such as GxP. The main difference between a proper approach to analysis and a formal accreditation is shown in a targeted documentation, especially on the qualification of the personnel, the test equipment and the validation of the analytical methods.
Using quantitative NMR spectroscopy as an example, it is shown how accreditation can be carried out and what documentation is required. In our case, we have described the procedure in an SOP ("Determination of the quantitative composition of simple mixtures of structurally known compounds with 1H-NMR spectroscopy") and supported it with a modular system of organizational and equipment SOPs. The special feature is that the accredited method is independent for the choice of the analyte and the matrix and therefore it is possible to operate with a single validated method. In our case, we have proposed three quality levels ("leagues") with different levels of analytical effort, which differ in their measurement uncertainty, in order to simplify the workflow and analysis design.
Introduction
NMR spectroscopy is one of the most important analytical methods in organic chemistry. While most analyses are carried out qualitatively with the aim of substance identification and structure elucidation, quantitative NMR spectroscopy (qNMR) is increasingly gaining importance in research and industry. qNMR provides the most universally applicable form of direct purity determination without need for reference materials of impurities or the calculation of response factors but only exhibiting suitable NMR properties.
Methods
One of the most attractive features of quantitative NMR spectroscopy is that the NMR peak areas can be used directly for concentration quantification without further calibration. Another advantage of NMR spectroscopy is that the method has a high linearity between absolute signal area and sample concentration, which makes it an absolute analytical comparison method that is independent of the matrix. This enables automated robust data evaluation strategies that can be used for online applications of qNMR spectroscopy.
Jancke et al. proposed NMR spectroscopy as a relative primary analytical method because it can be fully described by mathematical equations from which a complete uncertainty budget can be derived, allowing it to be used at the highest metrological level. Weber et al. discussed in detail important aspects of the procedure that enable the realisation of low measurement uncertainties in qNMR measurements. Since certification of CRM requires expanded mea¬sure¬ment uncertainties of less than 0.5 % (relative), the work of Weber et al. demonstrated for the first time that qNMR can fulfil this criterion.
Results
To date, further comparative studies have been carried out in metrology and industry, demonstrating the performance of quantitative NMR spectroscopy and further reducing measurement uncertainties. The development of validation concepts and the commercial availability of suitable certified reference materials facilitate the application, especially in the usually highly regulated industrial environment. Users can thus accelerate the development of analytical methods. The talk will cover a wide range of topics from current metrological activities to new challenges for qNMR spectroscopy and also deals with aspects such as validation and accreditation.
Innovative aspects
• qNMR provides the most universally applicable form of direct purity determination
• Expanded measurement uncertainties lower than 0.15 % (relative) possible
• Benchtop NMR instruments increasingly used for qNMR spectroscopy
qNMR - The handbook
(2023)
Quantitative NMR (qNMR) has been around for a long time, but also has great potential to solve future problems in any quantitative analysis. As a primary method, it differs fundamentally from chromatographic methods: it is better described as a quantum mechanical balance. Succesful implementation of qNMR requires certain attention to detail. "qNMR - the handbook" is intended to be a guide for analysts to help understand the fundamental principles of NMR and the significant points relating to its implementation for quantitation. Regulatory considerations of qNMR adoption are explained. NMR fundamentals are explained to provide understanding. Together with many useful examples, the book is a compelling addition to the laboratory's reference library, providing all the tools that any practitioner should know to successfully implement qNMR.
The authors are qNMR pioneers and come from a variety of backgrounds including business, government and academia.
The Royal Society of Chemistry NMR Discussion Group and Molecular Spectroscopy Group would like to invite you to the 2017 Spring Meeting, which will be held at GlaxoSmithKline (GSK), Stevenage. The theme for the meeting is “Low level detection and quantification by NMR” and different NMR technologies, including solution state NMR, solid state NMR and benchtop/low field NMR will be discussed. The presentations will cover a range of NMR related disciplines, including conventional low level detection and quantification, the use of cryoprobes, quantification of polymorphism using ssNMR and also methods for spectral simplification. Recent developments and applications of hyperpolarisation techniques, within both solution state and solid state NMR, will be presented in conjunction with the effect these sensitivity enhancements have with respect to quantification and limits of detection.
Resolving overlapping peaks of multiple components. Relative primary analytical method - Fundamental relationship of qNMR.
qNMR provides the most universally applicable form of direct purity determination without need for reference materials of impurities or the calculation of response factors but only exhibiting suitable NMR properties. The development of CRMs addressing qNMR specific measurement issues will give analysts compounds ideally suited for the analytical method and also provide full characterisation of qNMR related parameters to enable more realistic uncertainty budgets. These materials will give users the tools to exploit qNMR more easily and enable them to speed up analytical method development and reduce the time and financial burden of multiple analytical testing.
Due to recent advances in technical developments of NMR instruments such as acquisition electronics and probe design, detection limits of components in liquid mixtures were improved into the lower ppm range (approx. 5–10 ppm amount of substance). This showed that modern NMR equipment is also suitable for the observation of hydrocarbon samples in the expanded fluid phase or gas phase. Since Quantitative NMR spectroscopy (qNMR) is a direct ratio method of analysis without the need of calibration it was used to determine impurities in appropriate liquid and liquefied hydrocarbon isomers up to C6, which are used for preparation of primary gas standards, e.g., natural gas or exhaust gas standards. At the same time it is possible to yield structural information with a minimum of sample preparation. Thus, cross contaminations between different isomers of the observed hydrocarbons and their (NMR-active) impurities can be identified and quantified.
In general, most quantitative organic chemical measurements rely on the availability of highly purified compounds to act as calibration standards. The traceability and providence of these standards is an essential component of any measurement uncertainty budget and provides the final link of the result to the units of measurement, ideally the SI. The more recent increase in the use of qNMR for the direct assessment of chemical purity however can potentially improve the traceability and reduce the uncertainty of the measured chemical purity at a reduced cost and with less material. For example the method has beneficially been used by National Measurement institutes for recent CCQM comparisons including the CCQM–K55 series of purity studies.
Traditional ‘indirect’ methods of purity analysis require that all impurities are identified and quantified, leading to a minimum of 4 individual analytical methods (organic impurities, water, solvents, inorganic residue). These multiple technique approaches measure an array of different chemical impurities normally present in purified organic chemical compounds. As many analytical methodologies have compound-specific response factors, the accuracy and traceability of the purity assessment is dependent on the availability of reference materials of the impurities being available.
qNMR provides the most universally applicable form of direct purity determination without need for reference materials of impurities or the calculation of response factors but only exhibiting suitable NMR properties. The development of CRMs addressing qNMR specific measurement issues will give analysts compounds ideally suited for the analytical method and also provide full characterisation of qNMR related parameters to enable more realistic uncertainty budgets. These materials will give users the tools to exploit qNMR more easily and enable them to speed up analytical method development and reduce the time and financial burden of multiple analytical testing.
Quantitative NMR Spectroscopy (qNMR) provides the most universally applicable form of direct purity determination without need for reference materials of impurities or the calculation of response factors but only exhibiting suitable NMR properties. Broadly accepted validation methods of qNMR spectroscopy will give users the tools to exploit qNMR more easily and enable them to speed up analytical method development and reduce the time and financial burden.
The first initiative towards a worldwide agreement goes back to a panel discussion at PANIC 2014 (Practical Applications of NMR in Industry Conference) in Chicago. Since that, the Validation Workshop takes place following the PANIC Conference each year, last in 2017 with a turnout of over 50 people. The group aims at identifying a network of NMR people concerned with validation that can ultimately assist each other through the validation process, harmonize the terminology and a standard approach for NMR validations and position the guidelines produced by consensus of the NMR community so that accreditation agencies can use this process.