走向稳定同位素数据的兼容性:对相关概念的审查,参考材料的最新进展和当前的挑战
1Independent Researcher, Austria.
Isotopes in environmental and health studies
|June 12, 2024
概括
通过实验室和年份对稳定同位素数据进行比较,需要共同的尺度和可靠的参考材料 (RMs). 对数据兼容性至关重要的计量学概念在稳定同位素研究中未得到充分利用,影响了数据质量和可比性.
科学领域:
- 环境科学 环境科学
- 分析化学 分析化学
- 计量学 计量学 计量学
背景情况:
- 稳定同位素数据的可比性对于各种研究领域至关重要,包括水文学,气候科学和食品分析.
- 数据兼容性依赖于使用可靠的参考材料 (RMs) 与分配的值和不确定性的常规化.
- 数据兼容性和不确定性的计量概念已在分析化学中建立,但尚未完全应用于稳定同位素研究.
研究的目的:
- 对稳定同位素尺度,RMS和校准等级体系的计量学概念进行审查.
- 评估这些概念的应用,以确保稳定同位素研究中的数据兼容性.
- 突出影响数据质量的RM的历史问题和局限性.
主要方法:
- 对计量学原理的审查及其对稳定同位素参考材料的应用.
- 分析历史数据和 RM 问题,包括 δ13C 的 VPDB 尺度.
- 对RMS的价值和不确定性赋值的检查.
主要成果:
- 目前在稳定同位素研究中测量学的应用不足,影响了数据的兼容性.
- 关于RM的历史问题,例如LSVEC的δ13C漂移和不确定性的低估,对当前的做法有教训.
- 在 δ13C VPDB 尺度中的尺度不连续性可以显著降低数据兼容性.
结论:
- 采用计量学概念对于改善稳定同位素数据的可比性和质量至关重要.
- 了解RM的局限性和适当的值/不确定性赋值对于研究人员来说至关重要.
- 解决规模不连续性和历史的RM问题将提高多实验室稳定同位素研究的可靠性.
相关概念视频
01:17Chemical Shift: Internal References and Solvent Effects
630
In an NMR sample, precise measurement of the absolute absorption frequencies of nuclei is difficult. A standard internal reference compound is added, and the frequency difference between the reference signal and sample signals is measured.
The internal reference compound generally used in NMR spectroscopy is tetramethylsilane (TMS). TMS is preferred because it is chemically inert, soluble in NMR solvents, and easily removable. Also, the highly shielded methyl protons in TMS yield an intense...
The internal reference compound generally used in NMR spectroscopy is tetramethylsilane (TMS). TMS is preferred because it is chemically inert, soluble in NMR solvents, and easily removable. Also, the highly shielded methyl protons in TMS yield an intense...
630
01:13Mass Spectrometry: Isotope Effect
2.0K
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 difference between the molecular mass. Furthermore, the intensity of these signals is dependent on the...
2.0K
01:12Isotopes
56.8K
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,...
An element's atomic mass, or weight,...
56.8K
03:18Nuclear Stability
18.7K
Protons and neutrons, collectively called nucleons, are packed together tightly in a nucleus. With a radius of about 10−15 meters, a nucleus is quite small compared to the radius of the entire atom, which is about 10−10 meters. Nuclei are extremely dense compared to bulk matter, averaging 1.8 × 1014 grams per cubic centimeter. If the earth’s density were equal to the average nuclear density, the earth’s radius would be only about 200 meters.
To hold positively charged protons together...
To hold positively charged protons together...
18.7K
01:28Isotopes and Radioisotopes
8.6K
In the early 1900s, English chemist Frederick Soddy realized that an element could have atoms with different masses that were chemically indistinguishable. These different types are called isotopes — atoms of the same element that differ in mass. Isotopes differ in mass because they have different numbers of neutrons but are chemically identical because they have the same number of protons. Soddy was awarded the Nobel Prize in Chemistry in 1921 for this discovery.
An isotope containing...
An isotope containing...
8.6K
02:48Radioactive Decay and Radiometric Dating
33.8K
Radioactivity is a spontaneous disintegration of an unstable nuclide and is a random process, as all the nuclei in the sample do not decay simultaneously. The number of disintegrations per unit time is called the activity (A), which is directly proportional to the number of nuclei in the sample. The decay constant (λ) is an average probability of decay per nucleus in unit time.
33.8K