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- Direct purity determination (2) (entfernen)
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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 for all samples exhibiting suitable NMR properties. Broadly accepted validation methods of qNMR spectroscopy gives users tools to exploit qNMR more easily and enables rapid analytical method development and reduce time and financial burdens.
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 time, the Validation Workshop takes place each year following the PANIC Conference, last in 2017 with a turnout of over 65 people. The group aims to 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.
The talk briefly summarises the outcome of the former PANIC Validation Workshops (2015, 2016, and 2017) as well as the recent satellite meetings including the qNMR meeting held at Spectral Service in Cologne, Germany (June 2016), a validation workshop at SMASH (La Jolla, USA, September 2016), the qNMR Summit with USP in Rockville, USA (October 2016), the qNMR Summit at BAM in Berlin, Germany (March 2017), and the qNMR Minisymposium at SMASH in Baveno, Italy (September 2017).
Upcoming activities will be a qNMR Summit held by JP and JEOL in Tokyo, Japan (January 29th-30th, 2018) and a qNMR Summit at the University of Würzburg, Germany (planned for October 2018). The next PANIC takes place March 4th-8th, 2018 in La Jolla (San Diego), CA, USA.
Further Information can be found under:
http://www.validnmr.com
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 Metrology Institutes for comparisons including comparisons on CCQM (Consultative Committee for Amount of Substance: Metrology in Chemistry and Biology, www.bipm.org). First comparisons started 1998 with CCQM-P3 (Organics in solution) or CCQM-P35 (2002, EtOH in solution), were underpinned by a broad range of polarity and molecular size (CCQM–K55 series of purity studies including Valine, Aldrin, or Folic acid) and were continued with the recent pilot studies CCQM-P150 (2014, purity of Dimethyl sulfone) or CCQM-P150b (2017, purity of Pyributicarb).
Traditional ‘indirect’ methods of purity analysis require that all impurities are identified and quantified, leading to a minimum of four 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.
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) qNMR studies increasingly attract broader interest.