用H NMR光谱学量化威士忌同源的量化
Marc Stockwell1, Ian Goodall2, Dušan Uhrín1
1EaStCHEM School of Chemistry Joseph Black Building University of Edinburgh Edinburgh UK.
Analytical science advances
|May 8, 2024
概括
核磁共振 (NMR) 光谱为分析威士忌同源提供了一种快速的方法,为制造和质量控制提供了洞察力. 该技术在小样本中量化关键化合物,改进了传统的染色学方法.
科学领域:
- 分析化学 分析化学
- 频谱学是一种光谱学.
- 食品科学 食品科学 食品科学
背景情况:
- 威士忌分析对于了解生产,确保质量和检测假货至关重要.
- 传统的染色学方法耗时,需要大量的样本,并且可能无法同时识别所有化合物.
研究的目的:
- 开发一种更快,更有效的方法,使用核磁共振 (NMR) 谱学分析威士忌同源.
- 在威士忌的NMR分析中克服灵敏度和光谱复杂性的挑战.
主要方法:
- 使用高场 (600 MHz) H NMR光谱与冷探测器提高灵敏度.
- 使用Chenomx软件对重叠的光谱信号进行定量分析.
- 在小样本体积 (500μL威士忌+100μL缓冲体) 中分析了21种目标威士忌同源.
主要成果:
- 成功量化了21种目标威士忌同源中的13种,与名义度的平均相对差异为6.4%.
- 对于各种同源物,确定检测极限 (LOD) 和量化极限 (LOQ).
- 鉴定了某些化合物的局限性 (例如,异氨基酸,n-butanol) 由于低度和光谱重叠.
结论:
- 1H NMR光谱学为分析主要威士忌类同源提供了可行的,快速的染色体替代方案.
- 该方法对大多数量化化合物具有很好的准确性,为质量控制和真实性评估提供了潜力.
- 为了准确量化低度化合物和复杂碳水化合物混合物,可能需要进一步优化.
相关概念视频
01:10¹H NMR of Labile Protons: Temporal Resolution
1.1K
Protons bonded to heteroatoms such as nitrogen and oxygen exhibit a range of chemical shift values. This is due to the varying degree of hydrogen bonding between the proton and the heteroatom in other molecules. The extent of hydrogen bonding affects the electron density around the proton, thereby giving different chemical shift values for the protons in the proton NMR spectrum.
The –OH proton in alcohols typically appears in the range of δ 2 to 5 ppm but can vary depending on the specific...
The –OH proton in alcohols typically appears in the range of δ 2 to 5 ppm but can vary depending on the specific...
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01:15¹H NMR of Conformationally Flexible Molecules: Variable-Temperature NMR
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The axial and equatorial protons in cyclohexane can be distinguished by performing a variable-temperature NMR experiment. In this process, except for one proton, the remaining eleven protons are replaced by deuterium. The deuterium substitution avoids the possible peak splitting caused by the spin-spin coupling between the adjacent protons. The remaining proton flips between the axial and equatorial positions.
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01:13¹H NMR: Complex Splitting
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A proton M that is coupled to a proton X results in doublet signals for M. However, NMR-active nuclei can be simultaneously coupled to more than one nonequivalent nucleus. When M is coupled to a second proton A, such as in styrene oxide, each peak in the doublet is split into another doublet.
Splitting diagrams or splitting tree diagrams are routinely used to depict such complex couplings. While drawing splitting diagrams, the splitting with the larger coupling constant is usually applied...
Splitting diagrams or splitting tree diagrams are routinely used to depict such complex couplings. While drawing splitting diagrams, the splitting with the larger coupling constant is usually applied...
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00:52¹H NMR of Conformationally Flexible Molecules: Temporal Resolution
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At room temperature, the chair conformer of cyclohexane undergoes rapid ring flipping between two equivalent chair conformers at a rate of approximately 105 times per second. These two chair conformers are in equilibrium. The rapid ring flipping results in the interconversion of the axial proton to an equatorial proton and an equatorial to the axial proton. Such interconversions are too rapid and cannot be detected on the NMR timescale. Hence, the NMR spectrometer cannot distinguish between the...
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01:192D NMR: Heteronuclear Single-Quantum Correlation Spectroscopy (HSQC)
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Heteronuclear single-quantum correlation spectroscopy (HSQC) is a 2D NMR technique that reveals one-bond correlations between hydrogen and a heteronucleus. The HSQC experiment is similar to the heteronuclear correlation experiment (HETCOR) but is more sensitive. In the HSQC spectrum, the proton chemical shift is plotted on the horizontal F2 axis, while the 13C chemical shift is plotted on the vertical F1 axis. The corresponding proton and 13C spectra are also shown. The HSQC contour plot does...
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00:58¹H NMR Signal Integration: Overview
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The intensity of a signal, which can be represented by the area under the peak, depends on the number of protons contributing to that signal. The area under each peak is shown as a vertical line called an integral, with the integral value listed under it, as seen in the proton NMR spectrum of benzyl acetate. Each integral value is divided by the smallest integral value to obtain the ratio of the number of protons producing each signal. The ratio reveals the relative number of protons and not...
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