光谱法分析方法
光谱分析方法基于电磁辐射与物质的相互作用。撰写本文的目的是向您介绍常用光谱技术的基本概念
电磁频谱
电磁频谱为光谱学家提供了大量信息。电磁光谱的每个区域的特征是一系列频率或波长，并在化学家和物理学家手中找到了多个应用。电磁光谱的波长范围从原子间尺寸（高能伽玛射线）到几公里（无线电波）
Spectroscopic Techniques
光谱技术基于基本上基于三种类型的电磁辐射与物质相互作用。
- 排放
- Absorption
- Scattering
排放Spectroscopy
排放spectroscopic methods are based on the emission of characteristic wavelengths emitted by the elements constituting the sample when excited by thermal, electrical or radiation energy
- ICP - OES光谱法
A plasma sources at high temperature is used to excite the constituent elements which emit characteristic wavelength radiations which can be used for quantitative estimation of the sample
- Fluorescence Spectroscopy
On absorption of light the absorbing molecule gets excited and certain species which are photoluminiscent re-emit the absorbed light after a time delay Fluorescence refers to re-emission \((10^-^8 to 10^-^9sec)\) whereas delayed emission after minutes, hours or even days is referred to as phosphorescence.
Fluorescence intensity is directly proportional to fluorescent species present. Some substances which are not naturally fluorescent can be derivatized with fluorescent moieties to improve the detection limits.
Absorption Spectroscopy
吸收光谱的基础是测量样品中特定原子或分子对特定波长的吸收。可以在特定波长或在一定范围的波长上进行吸收测量，以同时测定。
- 紫外线 - 可见光谱法
The region 180 – 780nm constitutes the UV – visible region and can be used for atomic, molecular or ionic species determinations. Absorption in this region results from electronic transitions between the electron levels of the absorbing species.
- Infrared Spectroscopy
从大约2吸收发生在这个地区5,000 cm-1(near IR) to around 10 cmi-1(far IR) depending on the energy of vibration or rotation of the absorbing molecules. The prerequisite for absorption in this region is change in dipole moment of the absorbing molecule. The key area of application is functional group identification of molecules. FT – IR has completely replaced dispersive IR instruments due to the multitude ofFT IR提供的优势technique.
- Turbidimetry
浊度法用于确定均匀分散在液体培养基中的悬浮液。这种悬浮液的不透明度是根据发光的强度测量的。浊度法最多可以给出浓度的粗略估计
- X射线光谱
高能X射线辐射用于从原子的内壳中淘汰电子，这些电子被外壳的电子所取代。能量发射为光子，这是每个元素的特征
Light scattering spectroscopy
- Nephelometry
肾小管法基于液体介质中颗粒的均匀悬浮液对散射光的研究
- Raman Spectroscopy
液体样品中的RAMA转移是由于入射辐射引起的激发到更高振动状态的。拉曼效应涉及光的散射以及波长的变化。拉曼和红外光谱是免费的技术，但拉曼具有主要优势，即可以直接处理水性样品，因为水不会干扰拉曼测量
- X-ray Diffraction
X-ray diffraction is not a chemical identification tool but it serves to characterise the atomic and molecular structure of crystalline materials. By measuring the angles and intensities of diffracted x-rays it is possible to arrive at the densities of electrons within the crystal lattice from which the spatial distribution of atoms within the crystal lattice can be deduced.
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