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Köln, Germany

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Köln, Germany
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Monakhova Y.B.,Chernyshevsky Saratov State University | Goryacheva I.Y.,Spectral Service | Goryacheva I.Y.,Saint Petersburg State University
TrAC - Trends in Analytical Chemistry | Year: 2016

Due to diverse favorable physicochemical properties, luminescent quantum dots (QD) are widely used as labels or nanosensors for various analytical purposes. However, to the best of our knowledge there are not many reports applying chemometric approaches in nanoscience despite wide utilization of these methods in other research areas. The review addresses the usage of multivariate methods to resolve strongly overlapping signals for exploring different properties of QDs, as well as environmental characteristics. In particular, we discuss chemonetric applications for investigation of evolving luminescence signals of passive QD-based labels and active QD-based nanosensors, excitation-emission matrix (EEM) spectroscopic data and in vivo imaging of QD systems. Our review has shown that chemometrics plays an important role in the processing of luminescent nanoparticles signals and their role will definitely increase in the future. © 2016 Elsevier B.V.


PubMed | Spectral Service, Bavarian Health and Food Safety Authority, University of Würzburg and Chemical and Veterinary Investigation Laboratory
Type: Evaluation Studies | Journal: Journal of agricultural and food chemistry | Year: 2015

Because the basic suitability of proton nuclear magnetic resonance spectroscopy ((1)H NMR) to differentiate organic versus conventional tomatoes was recently proven, the approach to optimize (1)H NMR classification models (comprising overall 205 authentic tomato samples) by including additional data of isotope ratio mass spectrometry (IRMS, (13)C, (15)N, and (18)O) and mid-infrared (MIR) spectroscopy was assessed. Both individual and combined analytical methods ((1)H NMR + MIR, (1)H NMR + IRMS, MIR + IRMS, and (1)H NMR + MIR + IRMS) were examined using principal component analysis (PCA), partial least squares discriminant analysis (PLS-DA), linear discriminant analysis (LDA), and common components and specific weight analysis (ComDim). With regard to classification abilities, fused data of (1)H NMR + MIR + IRMS yielded better validation results (ranging between 95.0 and 100.0%) than individual methods ((1)H NMR, 91.3-100%; MIR, 75.6-91.7%), suggesting that the combined examination of analytical profiles enhances authentication of organically produced tomatoes.


Hohmann M.,University of Würzburg | Hohmann M.,Bavarian Health and Food Safety Authority | Koospal V.,Bavarian Health and Food Safety Authority | Bauer-Christoph C.,Bavarian Health and Food Safety Authority | And 4 more authors.
Journal of Agricultural and Food Chemistry | Year: 2015

Analyzing egg liqueurs for compliance with legal requirements means several different time-consuming preparations and analytical processes. In this paper, we describe the approach to use quantitative 1H NMR spectroscopy as an accurate alternative technique. 1H NMR analysis comprised two different rapid sample preparations for water-soluble or nonpolar ingredients. Fifteen egg liqueurs were analyzed for alcoholic strength and content of total sugar and egg yolk (estimated by cholesterol as a marker substance) with both classical methods and quantitative 1H NMR spectroscopy. The results of both methods showed excellent correlations for alcoholic strength (R = 0.996, p < 0.001) and content of total sugar (R = 0.989, p < 0.001) and cholesterol (R = 0.995, p < 0.001). Besides, NMR spectra revealed further information: a signal of phosphatidylcholine at about δ = 3.20 ppm served as a second marker for the egg yolk content, and characteristic signals of lactose at δ = 4.46 ppm and butyric acid at δ = 0.97 ppm indicated the use of milk products, which has to be declared for lactose-intolerant consumers. © 2015 American Chemical Society.


Monakhova Y.B.,Chemisches und Veterinaruntersuchungsamt CVUA Karlsruhe | Monakhova Y.B.,Bruker Biospin Gmbh | Monakhova Y.B.,Chernyshevsky Saratov State University | Ruge W.,Chemisches und Veterinaruntersuchungsamt CVUA Karlsruhe | And 6 more authors.
Food Chemistry | Year: 2015

NMR spectroscopy was used to verify the presence of Arabica and Robusta species in coffee. Lipophilic extracts of authentic roasted and green coffees showed the presence of established markers for Robusta (16-O-methylcafestol (16-OMC)) and for Arabica (kahweol). The integration of the 16-OMC signal (δ 3.165 ppm) was used to estimate the amount of Robusta in coffee blends with an approximate limit of detection of 1-3%. The method was successfully applied for the analysis of 77 commercial coffee samples (coffee pods, coffee capsules, and coffee beans). Furthermore, principal component analysis (PCA) was applied to the spectra of lipophilic and aqueous extracts of 20 monovarietal authentic samples. Clusters of the two species were observed. NMR spectroscopy can be used as a rapid prescreening tool to discriminate Arabica and Robusta coffee species before the confirmation applying the official method. © 2015 Elsevier Ltd. All rights reserved.


PubMed | Chemisches und Veterinaruntersuchungsamt CVUA Karlsruhe, Bruker Biospin Gmbh, Eurofins and Spectral Service
Type: | Journal: Food chemistry | Year: 2015

NMR spectroscopy was used to verify the presence of Arabica and Robusta species in coffee. Lipophilic extracts of authentic roasted and green coffees showed the presence of established markers for Robusta (16-O-methylcafestol (16-OMC)) and for Arabica (kahweol). The integration of the 16-OMC signal ( 3.165 ppm) was used to estimate the amount of Robusta in coffee blends with an approximate limit of detection of 1-3%. The method was successfully applied for the analysis of 77 commercial coffee samples (coffee pods, coffee capsules, and coffee beans). Furthermore, principal component analysis (PCA) was applied to the spectra of lipophilic and aqueous extracts of 20 monovarietal authentic samples. Clusters of the two species were observed. NMR spectroscopy can be used as a rapid prescreening tool to discriminate Arabica and Robusta coffee species before the confirmation applying the official method.


Skiera C.,University of Würzburg | Steliopoulos P.,Chemisches und Veterinaruntersuchungsamt Karlsruhe | Kuballa T.,Chemisches und Veterinaruntersuchungsamt Karlsruhe | Diehl B.,Spectral Service | Holzgrabe U.,University of Würzburg
Journal of Pharmaceutical and Biomedical Analysis | Year: 2014

Indices like acid value, peroxide value, and saponification value play an important role in quality control and identification of lipids. Requirements on these parameters are given by the monographs of the European pharmacopeia. 1H NMR spectroscopy provides a fast and simple alternative to these classical approaches. In the present work a new 1H NMR approach to determine the acid value is described. The method was validated using a statistical approach based on a variance components model. The performance under repeatability and in-house reproducibility conditions was assessed. We applied this 1H NMR assay to a wide range of different fatty oils. A total of 305 oil and fat samples were examined by both the classical and the NMR method. Except for hard fat, the data obtained by the two methods were in good agreement. The 1H NMR method was adapted to analyse waxes and oleyloleat. Furthermore, the effect of solvent and in the case of castor oil the effect of the oil matrix on line broadening and chemical shift of the carboxyl group signal are discussed. © 2013 Elsevier B.V.


Skiera C.,University of Würzburg | Steliopoulos P.,Chemisches und Veterinaruntersuchungsamt Karlsruhe | Kuballa T.,Chemisches und Veterinaruntersuchungsamt Karlsruhe | Holzgrabe U.,University of Würzburg | Diehl B.,Spectral Service
Lipid Technology | Year: 2012

Here we describe a novel 1H NMR assay for the determination of FFAs in edible oils. The analytical performance of the NMR assay is similar to that of the commonly used acid value (AV) method. A total of 120 edible oil samples were analysed by both approaches. Except for pumpkin seed oil, showing slight deviations, there was a good compliance between the results obtained from the two methods. © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.


Skiera C.,University of Würzburg | Steliopoulos P.,Chemisches und Veterinaruntersuchungsamt Karlsruhe | Kuballa T.,Chemisches und Veterinaruntersuchungsamt Karlsruhe | Holzgrabe U.,University of Würzburg | Diehl B.,Spectral Service
European Food Research and Technology | Year: 2012

Aldehydes, formed as secondary oxidation products during the autoxidation process of oils and fats, are analytical markers used to assess the lipid deterioration status. Generally, the level of aldehydes is expressed as the p-anisidine value (AV). This deterioration index is based on the reaction of the carbonyl group with p-anisidine leading to the formation of an intensively coloured Schiff base which is determined spectroscopically (UV/ViS). 1H NMR provides an alternative approach by enabling the quantification of individual aldehydes like n-alkanals, 2-alkenals or (E,E)-2,4-alkadienals. This work illustrates that the AV can be modelled as a linear combination of the NMR integrals of aldehydes. A functional relationship was derived on the basis of calibration experiments. The suitability of the model is shown by comparing the NMR-determined AVs with the classical AVs of 79 commercially available edible oils of different oil types. © 2012 Springer-Verlag Berlin Heidelberg.


Skiera C.,University of Würzburg | Steliopoulos P.,Chemisches und Veterinaruntersuchungsamt Karlsruhe | Kuballa T.,Chemisches und Veterinaruntersuchungsamt Karlsruhe | Holzgrabe U.,University of Würzburg | Diehl B.,Spectral Service
JAOCS, Journal of the American Oil Chemists' Society | Year: 2012

Within the course of lipid peroxidation, hydroperoxides are formed as primary products. They can be used as analytical markers to assess the deterioration status of oils and fats. Here a new 1H-NMR assay to determine the hydroperoxide amount in edible oils is presented. We were able to show that the analytical performance of the method is similar to that of the commonly used peroxide value (PV) according to Wheeler. A total of 290 edible oil samples were analyzed using both methods. For some oil varieties considerable discrepancies were found between the results obtained. In the case of black seed and olive oil, two substances could be identified that cause positive (black seed oil) and negative (olive oils) deviations from the theoretical PV expected from the NMR values. © 2012 AOCS.


Beyer T.,University of Würzburg | Diehl B.,Spectral Service | Holzgrabe U.,University of Würzburg
Bioanalytical Reviews | Year: 2010

Biologically active ingredients and excipients are the essentials of a drug formulation, such as a tablet, dragee, solution, etc. Quality control of such substances thus plays a pivotal role in the production process of pharmaceutical drugs. Since these agents often exhibit complex structures, consist of multiple components, or lack of a chromophore, traditional means of characterization are often not feasible. Furthermore, substances of small molecular weight or strong polar character generally exhibit poor chromatographic properties, thus, conventional procedures such as high-performance liquid chromatography are often not applicable. Instead, quantitative nuclear magnetic resonance (qNMR) spectroscopy has emerged as an alternative or orthogonal method in drug analysis. In this review, we elaborate on the application of qNMR to three important classes of biological substances, namely polysaccharides, amino acids, and lipids, and demonstrate the benefits of this modern tool in contrast to traditional techniques. © 2010 Springer-Verlag.

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