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Thirty μL of a 5 mM solution of sodium 2,2,3,3-tetradeutero-3-(trimethylsilyl)propanoate (TSP) was added as an internal quantification reference before NMR analysis (concentration of 0.181 mM in the NMR tube). After centrifugation, 800 μL of the supernatant was introduced in an NMR tube. The mixture was then sonicated for 5 min and finally magnetically stirred for 20 min. Second, around 10, 20, 30, and 40 mg exact weights of the DS 2 capsule content were vortexed for approximately 15 s with 1.0 mL of CD 3OD.
#Viewing dosy spectra mestrenova series
First, from a stock solution of authentic sildenafil citrate (sample 1), a series of 3 diluted samples (dilution by a factor of 1.33, 2, and 4) were prepared. The respective addition of 1.5, 1.5, 2.5, and 3.0 mL of CD 3OD was required to obtain 600 μL of supernatant.Ĭomparative 1H NMR quantification studies with high-field (HF) and low-field (LF) spectrometers were performed on solutions of standard sildenafil and of DS 2 that was adulterated with this compound. However, for the four DS, 1 and 12 (both nonadulterated) and 11 and 7 (both adulterated), adding 1 mL of CD 3OD to the powder did not allow recovery of a sufficient volume. The mixture was vortexed for 15 s and, after sedimentation, ≈600 μL of the supernatant were transferred into an Aldrich ColorSpec disposable 5 mm × 8 in. To the powdered tablet or the whole content of the capsule (weight range of 188–802 mg see Table S-1 in the Supporting Information), 1 mL of deuterated methanol (CD 3OD) containing 0.03% of tetramethylsilane (TMS) as chemical shift reference was added. The sample preparation was kept as simple as possible. They were previously analyzed in our laboratory and were chosen because they contain a variety of adulterants. All these products claimed as “100% natural” were bought on Internet Web sites. Ten adulterated and one nonadulterated sexual enhancement DS as well as four adulterated and one nonadulterated slimming DS were analyzed (Table S-1 in the Supporting Information). This method should be of low cost, rapid, sensitive, specific, and accurate and would require minimum sample preparation. (19) Currently, there is a need for an ideal screening method to characterize adulterated DS. The spectral fingerprint recorded by 1H NMR makes the technique a unique and powerful tool for identification of molecules in general and in the adulteration field in particular. (16-18) While its sensitivity is excellent, its specificity for detecting unknown adulteration can be problematic. (15) To analyze these products, the gold-standard method is HPLC hyphenated to MS. Among the 237 DS recalled by the FDA from 2004 through 2012 because they contained hidden ingredients that could be harmful, sexual enhancement products were the most numerous (40%), followed by body-building (31%) and weight loss products (27%). The QC of DS is therefore of paramount importance to ensure their safety and to protect consumers. This represents an alarming emerging risk to public health. (14) A significant number of unscrupulous manufacturers add pharmaceutical compounds to DS to improve their effects. Considering the cost and space efficiency of these spectrometers, we anticipate their introduction in QC laboratories as well as in governmental agencies, especially in the field of fraud detection.ĭietary supplements (DS) are products between medicines and conventional foods whose consumption is rising steeply. We also showed that the quantification by the internal standard method can be done on the low-field NMR spectrometer and leads to results similar to those obtained with high-field NMR. We demonstrated that the adulterant(s) can readily be detected in ≈20 min of recording after a very simple and rapid sample preparation. In this paper, we evaluated the potential of a benchtop cryogen-free 60 MHz spectrometer for uncovering adulteration of “100% natural” sexual enhancement and weight loss dietary supplements. The recent release of benchtop cryogen-free low-field NMR spectrometers represents a technological break in the NMR field. However, due to cost constraints, NMR is rarely used in routine quality control (QC) analysis.
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Nuclear magnetic resonance (NMR) spectroscopy is a unique tool for detection, structural characterization, and quantification of compounds in complex mixtures.