![]() ![]() All chemical shifts ( d) referred to an internal trimethylsilylpropane sulphonic acid (TMPS) reference.įor 2D DOSY 1H NMR, stimulated echo bipolar gradient pulse experiments were used with a pulse delay of 3 ms after each gradient, a pulse field gradient length of 1–2 ms depending on experiments and a diffusion delay of around 100–150 ms. The solvent used was a mixture of acetonitrile-d 3 (CD 3CN) : heavy water (D 2O) (80 : 20) for herbal medicines or dimethylsulphoxide-d 6 (DMSO-d6) for genuine and fake artesunate. Solutions for NMR analyses of medicines were prepared as follows: tablets were powdered or capsules emptied and the powder was resuspended in 5 mL of deuterated NMR solvent the suspension was then centrifuged and the supernatant analysed. The 1H NMR experiments were performed on a Bruker Avance 500 spectrometer operating at 500.13 MHz. This article outlines the use of the DOSY NMR method applied to drug analysis and screening for counterfeit drugs or fake herbal medicines. Diffusion measurement by NMR and especially the DOSY-type experiments are thus powerful analytical tools, which have so far been overlooked by most scientists. Based on the analysis of mono- and multi-exponential decays, spectra of mixture components can be separated depending on the value of their apparent diffusion coefficients. ![]() The DOSY method allows measuring the translational self-diffusion of molecules in a solution. One should also keep in mind the non-destructive nature of NMR spectroscopy. ![]() 1 Furthermore, DOSY experiments do not need complicated setups and the method can be easily standardised and automated. But there is indeed “a pure NMR” method that allows a precise analysis of a complex mixture without any prior separation of the different components: the Diffusion Ordered SpectroscopY (DOSY) method. LC-NMR, in which the NMR spectrometer acts as a high performance liquid chromatography (HPLC) detector, has been developed on this basis. For most scientists, the preferred methods for mixture analysis and/or trace detection are still the chromatographic methods, generally coupled with spectroscopic methods such as mass spectrometry or NMR. ![]() Nevertheless, technological advancements in the field of magnetic resonance have made significant strides in improving sensitivity levels, developing new acquisition/processing tools and implementing innovative NMR experiments/pulse sequences.įor a long time it has been preferred, when possible, to isolate each mixture component prior to its study by NMR rather than to analyse the whole mixture. Unfortunately, NMR has traditionally been sensitivity-limited compared with many other analytical techniques. As drugs can be considered to be complex mixtures (composed of many different substances and/or including simultaneously high and very low quantities of compounds), NMR is a good tool for studying such formulations. The capability of nuclear magnetic resonance (NMR) spectroscopy to provide valuable information regarding mixture analysis has created broad applicability in chemistry, biochemistry, biology and medicine. Stéphane Balayssac, a Véronique Gilard, a Marc-André Delsuc b and Myriam Malet-Martino aĪUniversité de Toulouse, UPS, Laboratoire de Synthèse et Physico-Chimie de Molécules d’Intérêt Biologique (SPCMIB), Groupe de RMN Biomédicale, 118 route de Narbonne, 31062 Toulouse cedex 9, France bInstitut de Génétique et de Biologie Moléculaire et Cellulaire (IGBMC), 1 rue Laurent Fries, BP 10142, 67404 Illkirch, France Introduction ![]()
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