@article{MonakhovaDiehl2021,
  author    = {Monakhova, Yulia and Diehl, Bernd W.K.},
  title     = {Novel approach of qNMR workflow by standardization using 2H integral: Application to any intrinsic calibration standard},
  series = {Talanta},
  volume    = {222},
  journal   = {Talanta},
  number    = {Article number: 121504},
  publisher = {Elsevier},
  isbn      = {0039-9140},
  doi       = {10.1016/j.talanta.2020.121504},
  year      = {2021},
  abstract  = {Quantitative nuclear magnetic resonance (qNMR) is routinely performed by the internal or external standardization. The manuscript describes a simple alternative to these common workflows by using NMR signal of another active nuclei of calibration compound. For example, for any arbitrary compound quantification by NMR can be based on the use of an indirect concentration referencing that relies on a solvent having both 1H and 2H signals. To perform high-quality quantification, the deuteration level of the utilized deuterated solvent has to be estimated. In this contribution the new method was applied to the determination of deuteration levels in different deuterated solvents (MeOD, ACN, CDCl3, acetone, benzene, DMSO-d6). Isopropanol-d6, which contains a defined number of deuterons and protons, was used for standardization. Validation characteristics (precision, accuracy, robustness) were calculated and the results showed that the method can be used in routine practice. Uncertainty budget was also evaluated. In general, this novel approach, using standardization by 2H integral, benefits from reduced sample preparation steps and uncertainties, and can be applied in different application areas (purity determination, forensics, pharmaceutical analysis, etc.).},
  language  = {en}
}
@article{MonakhovaDiehl2022,
  author    = {Monakhova, Yulia and Diehl, Bernd W.K.},
  title     = {Multinuclear NMR screening of pharmaceuticals using standardization by 2H integral of a deuterated solvent},
  series = {Journal of Pharmaceutical and Biomedical Analysis},
  volume    = {209},
  journal   = {Journal of Pharmaceutical and Biomedical Analysis},
  number    = {Article number: 114530},
  publisher = {Elsevier},
  isbn      = {0731-7085},
  doi       = {10.1016/j.jpba.2021.114530},
  year      = {2022},
  abstract  = {NMR standardization approach that uses the 2H integral of deuterated solvent for quantitative multinuclear analysis of pharmaceuticals is described. As a proof of principle, the existing NMR procedure for the analysis of heparin products according to US Pharmacopeia monograph is extended to the determination of Na+ and Cl- content in this matrix. Quantification is performed based on the ratio of a 23Na (35Cl) NMR integral and 2H NMR signal of deuterated solvent, D2O, acquired using the specific spectrometer hardware. As an alternative, the possibility of 133Cs standardization using the addition of Cs2CO3 stock solution is shown. Validation characteristics (linearity, repeatability, sensitivity) are evaluated. A holistic NMR profiling of heparin products can now also be used for the quantitative determination of inorganic compounds in a single analytical run using a single sample. In general, the new standardization methodology provides an appealing alternative for the NMR screening of inorganic and organic components in pharmaceutical products.},
  language  = {en}
}