相关实验视频
Updated: Jun 29, 2026

11:43
Hyperpolarized 13C Metabolic Magnetic Resonance Spectroscopy and Imaging
Published on: December 30, 2016
概括
蜂蜜中碳-13与碳-12同位素的比率表现出极小的变化,这使得它成为检测高果糖玉米糖伪造的可靠指标. 这一发现支持来自C3植物的蜂蜜的真实性.
科学领域:
- 农业科学 农业科学
- 分析化学 分析化学
- 食品科学 食品科学 食品科学
背景情况:
- 用高果糖玉米糖 (HFCS) 改蜂蜜对消费者和食品行业来说是一个重大问题.
- 碳-13/碳-12 (13C/12C) 同位素比是检测蜂蜜中HFCS的潜在生物标志物.
- 了解这种比例在真蜂蜜中的自然变异性对于开发可靠的检测方法至关重要.
研究的目的:
- 为了评估碳-13/碳-12 (13C/12C) 同位素比例在各种蜂蜜样本中的自然变异性.
- 建立蜂蜜中13C/12C比的基线,以方便检测HFCS造.
主要方法:
- 分析了来自美国34个州的84个蜂蜜样本中的13C/12C同位素比率 (报告为delta13C).
- 样本代表了来自17个植物家族的37种花型.
- 统计分析以确定delta13C值的平均值,变化系数和范围.
主要成果:
- 所有蜂蜜样本的平均delta13C值为每毫升25.2.
- 变化系数为3.7%,代表了任何蜂蜜成分或物理性质观察到的最低变化.
- 观察到的delta13C值的范围和大小强烈地表明,这些蜂蜜的花源是C3植物.
结论:
- 真正蜂蜜中13C/12C同位素比率的低可变性为检测HFCS造提供了强大的分析基础.
- 这些发现证实,大多数分析的蜂蜜来源于C3植物,进一步支持这种同位素分析的可靠性.
- 这项研究有助于确保蜂蜜的真实性,并保护消费者免受欺诈性产品的侵害.
更多相关视频
相关概念视频
Isotopes
Elements have a set number of protons that determines their atomic number (Z). For example, all atoms with eight protons are oxygen; however, the number of neutrons can vary for atoms of the same element. The sum of the number of protons and the number of neutrons is the mass number (A). Atoms with the same atomic number but different mass numbers are called isotopes. Elements can have multiple isotopes, for example, carbon-12, carbon-13, and carbon-14.An element's atomic mass, or weight, is a...
Carbon-13 (¹³C) NMR: Overview
Carbon-13 is a naturally occurring NMR-active isotope of carbon with a low natural abundance of 1.1%. In contrast, carbon-12 is the most abundant isotope of carbon with zero nuclear spin. Therefore, it is NMR inactive. The gyromagnetic ratio of carbon-13 is smaller than that of protons. As a result, carbon-13 resonance is about 6000 times weaker than proton resonance. For a given magnetic field strength, the resonance frequency of carbon-13 is about one-fourth of the resonance frequency for...
¹³C NMR: Distortionless Enhancement by Polarization Transfer (DEPT)
When proton-coupled carbon-13 spectra are simplified by a broadband proton decoupling technique, structural information about the coupled protons is lost. Distortionless enhancement by polarization transfer (DEPT) is a technique that provides information on the number of hydrogens attached to each carbon in a molecule. While the DEPT experiment utilizes complex pulse sequences, the pulse delay and flip angle are specifically manipulated. The resulting signals have different phases depending on...
High-Resolution Mass Spectrometry (HRMS)
The resolution of a mass spectrometer depends on the efficiency of separating ions with different ion masses. The mass of an atom is approximated to the sum of the masses of protons and neutrons inside, considering the masses of protons and neutrons as equal. However, the masses of the proton (1.6726 × 10−24 g) and neutron (1.6749 × 10−24 g) are not truly equal. There is a minor error in the expression of atomic masses relative to the simplest atom of hydrogen. For example, the mass of helium...
¹³C NMR: ¹H–¹³C Decoupling
The probability of having two carbon-13 atoms next to each other is negligible because of the low natural abundance of carbon-13. Consequently, peak splitting due to carbon-carbon spin-spin coupling is not observed in spectra. However, protons up to three sigma bonds away split the carbon signal according to the n+1 rule, resulting in complicated spectra.
A broadband decoupling technique is used to simplify these complex, sometimes overlapping, signals. Broadband decoupling relies on a...
A broadband decoupling technique is used to simplify these complex, sometimes overlapping, signals. Broadband decoupling relies on a...
Mass Spectrometry: Isotope Effect
Most elements exist in nature as a mixture of isotopes. The isotopes differ in weight due to their respective number of neutrons. The molecular weight of a molecule is different depending on the specific isotope of its elements involved. As a result, the mass spectrum of the molecule exhibits peaks from the same fragment at multiple positions. The positions of these mass signals depend on the mass differences between isotopes. Furthermore, the intensity of these signals is dependent on the...

