@article{BlockMayWetzeletal.2023,
  author    = {Block, Franziska and May, Alexander and Wetzel, Katharina and Adels, Klaudia and Elbers, Gereon and Schulze, Margit and Monakhova, Yulia},
  title     = {What is the best spectroscopic method for simultaneous analysis of organic acids and (poly)saccharides in biological matrices: Example of Aloe vera extracts?},
  series = {Talanta Open},
  volume    = {7},
  journal   = {Talanta Open},
  number    = {Art. No. 100220},
  publisher = {Elsevier},
  address   = {Amsterdam},
  issn      = {2666-8319},
  doi       = {10.1016/j.talo.2023.100220},
  pages     = {1 -- 9},
  year      = {2023},
  abstract  = {Several species of (poly)saccharides and organic acids can be found often simultaneously in various biological matrices, e.g., fruits, plant materials, and biological fluids. The analysis of such matrices sometimes represents a challenging task. Using Aloe vera (A. vera) plant materials as an example, the performance of several spectro-scopic methods (80 MHz benchtop NMR, NIR, ATR-FTIR and UV-vis) for the simultaneous analysis of quality parameters of this plant material was compared. The determined parameters include (poly)saccharides such as aloverose, fructose and glucose as well as organic acids (malic, lactic, citric, isocitric, acetic, fumaric, benzoic and sorbic acids). 500 MHz NMR and high-performance liquid chromatography (HPLC) were used as the reference methods. UV-vis data can be used only for identification of added preservatives (benzoic and sorbic acids) and drying agent (maltodextrin) and semiquantitative analysis of malic acid. NIR and MIR spectroscopies combined with multivariate regression can deliver more informative overview of A. vera extracts being able to additionally quantify glucose, aloverose, citric, isocitric, malic, lactic acids and fructose. Low-field NMR measurements can be used for the quantification of aloverose, glucose, malic, lactic, acetic, and benzoic acids. The benchtop NMR method was successfully validated in terms of robustness, stability, precision, reproducibility and limit of detection (LOD) and quantification (LOQ), respectively. All spectroscopic techniques are useful for the screening of (poly)saccharides and organic acids in plant extracts and should be applied according to its availability as well as information and confidence required for the specific analytical goal. Benchtop NMR spectroscopy seems to be the most feasible solution for quality control of A. vera products.},
  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}
}
@article{AdelsMonakhova2024,
  author    = {Adels, Klaudia and Monakhova, Yulia},
  title     = {Low-field NMR spectroscopic study of e-cigarettes: Is determination of only nicotine and organic carrier solvents possible?},
  series = {Microchemical Journal},
  volume    = {203},
  journal   = {Microchemical Journal},
  publisher = {Elsevier},
  address   = {Amsterdam},
  issn      = {1095-9149},
  doi       = {10.1016/j.microc.2024.110859},
  pages     = {9 Seiten},
  year      = {2024},
  abstract  = {Electronic cigarettes (e-cigarettes) have become popular worldwide with the market growing exponentially in some countries. The absence of product standards and safety regulations requires urgent development of analytical methodologies for the holistic control of the growing diversity of such products. An approach based on low-field nuclear magnetic resonance (LF-NMR) at 80 MHz is presented for the simultaneous determination of key parameters: carrier solvents (vegetable glycerine (VG), propylene glycol (PG) and water), total nicotine as well as free-base nicotine fraction. Moreover, qualitative and quantitative determination of fourteen weak organic acids deliberately added to enhance sensory characteristics of e-cigarettes was possible. In most cases these parameters can be rapidly and conveniently determined without using any sample manipulation such as dilution, extraction or derivatization steps. The method was applied for 37 authentic e-cigarettes samples. In particular, eight different organic acids with the content up to 56 mg/mL were detected. Due to its simplicity, the method can be used in routine regulatory control as well as to study release behaviour of nicotine and other e-cigarettes constituents in different products.},
  language  = {en}
}