@article{MonakhovaDiehl2021,
  author    = {Monakhova, Yulia and Diehl, Bernd W. K.},
  title     = {Simplification of NMR Workflows by Standardization Using 2H Integral of Deuterated Solvent as Applied to Aloe vera Preparations},
  series = {Applied Magnetic Resonance},
  volume    = {52},
  journal   = {Applied Magnetic Resonance},
  number    = {11},
  publisher = {Springer},
  address   = {Cham},
  issn      = {1613-7507},
  doi       = {10.1007/s00723-021-01393-4},
  pages     = {1591 -- 1600},
  year      = {2021},
  abstract  = {In this study, a recently proposed NMR standardization approach by 2H integral of deuterated solvent for quantitative multicomponent analysis of complex mixtures is presented. As a proof of principle, the existing NMR routine for the analysis of Aloe vera products was modified. Instead of using absolute integrals of targeted compounds and internal standard (nicotinamide) from 1H-NMR spectra, quantification was performed based on the ratio of a particular 1H-NMR compound integral and 2H-NMR signal of deuterated solvent D2O. Validation characteristics (linearity, repeatability, accuracy) were evaluated and the results showed that the method has the same precision as internal standardization in case of multicomponent screening. Moreover, a dehydration process by freeze drying is not necessary for the new routine. Now, our NMR profiling of A. vera products needs only limited sample preparation and data processing. The new standardization methodology provides an appealing alternative for multicomponent NMR screening. In general, this novel approach, using standardization by 2H integral, benefits from reduced sample preparation steps and uncertainties, and is recommended in different application areas (purity determination, forensics, pharmaceutical analysis, etc.).},
  language  = {en}
}
@article{AdelsElbersDiehletal.2023,
  author    = {Adels, Klaudia and Elbers, Gereon and Diehl, Bernd and Monakhova, Yulia},
  title     = {Multicomponent analysis of dietary supplements containing glucosamine and chondroitin: comparative low- and high-field NMR spectroscopic study},
  series = {Analytical Sciences},
  volume    = {2023},
  journal   = {Analytical Sciences},
  publisher = {Springer Verlag},
  address   = {Cham},
  issn      = {1348-2246 (Online)},
  doi       = {10.1007/s44211-023-00433-2},
  pages     = {13 Seiten},
  year      = {2023},
  abstract  = {With the prevalence of glucosamine- and chondroitin-containing dietary supplements for people with osteoarthritis in the marketplace, it is important to have an accurate and reproducible analytical method for the quantitation of these compounds in finished products. NMR spectroscopic method based both on low- (80 MHz) and high- (500-600 MHz) field NMR instrumentation was established, compared and validated for the determination of chondroitin sulfate and glucosamine in dietary supplements. The proposed method was applied for analysis of 20 different dietary supplements. In the majority of cases, quantification results obtained on the low-field NMR spectrometer are similar to those obtained with high-field 500-600 MHz NMR devices. Validation results in terms of accuracy, precision, reproducibility, limit of detection and recovery demonstrated that the developed method is fit for purpose for the marketed products. The NMR method was extended to the analysis of methylsulfonylmethane, adulterant maltodextrin, acetate and inorganic ions. Low-field NMR can be a quicker and cheaper alternative to more expensive high-field NMR measurements for quality control of the investigated dietary supplements. High-field NMR instrumentation can be more favorable for samples with complex composition due to better resolution, simultaneously giving the possibility of analysis of inorganic species such as potassium and chloride.},
  language  = {en}
}