Spectral analysis is a type of analytical chemistry method based on the electromagnetic radiation emitted by a substance or the interaction of electromagnetic radiation with matter. These electromagnetic radiations include all electromagnetic spectrum ranges from g-rays to radio waves, and are not limited to optical spectral regions. The way electromagnetic radiation interacts with matter is emission, absorption, reflection, refraction, scattering, interference, diffraction, polarization, and so on.
Spectral analysis can be divided into two major categories: spectroscopic and non-spectral methods.
Spectroscopy is a method of analyzing the wavelength and intensity of emitted, absorbed, or scattered radiation produced by a transition between energy levels that are quantized within a substance, when the substance interacts with radiant energy. According to the interaction of electromagnetic radiation and matter, three types of spectra can be generated, which are emitted, absorbed and scattered.
First, emission spectroscopy
The substance obtains energy by an excitation process such as electro-excitation, thermo-excitation or photo-excitation, and becomes an excited-state atom or molecule M*, which generates an emission spectrum when transitioning from an excited state to a low-energy state or a ground state. A method for qualitative and quantitative analysis by measuring the wavelength and intensity of the emission spectrum of a substance is called emission spectroscopy.
Type of emission spectrum:
Line spectrum
When the radiating substance is a single gaseous atom, a line spectrum of the ultraviolet and visible light regions is generated. The X-ray line spectrum can be generated by the transition of the inner layer electrons.
2. Band spectrum
The band spectrum is formed by superimposing a number of quantized vibrational energy levels on the ground state electron energy levels of the molecules.
3. Continuous spectrum
Heating a solid to a hot glow emits a continuous spectrum called thermal radiation. Black body radiation is generated by the excitation of numerous atoms and fractions in the aggregates by thermal energy.
The heated solids emit a continuous spectrum that is an important source of light for the infrared, visible, and long-wave side ultraviolet region analysis instruments.
According to the spectral region where the emission spectrum is located and the excitation method, the emission spectroscopy is divided into:
G ray spectroscopy
The nucleus of a natural or artificial radioactive substance, after emitting a and b particles in the process of decay, tends to excite its own nucleus, which then returns to the ground state by emitting g-rays. By measuring the energy (or wavelength) of this characteristic g-ray, qualitative analysis can be performed to measure the intensity of the g-ray, which can be quantitatively analyzed.
2. X-ray fluorescence analysis
The atom is excited by high-energy radiation, and its inner electron level transitions, that is, emits characteristic X-rays, called X-ray fluorescence. It is the most common method to excite X-ray fluorescence with an X-ray generated by an X-ray tube. The energy (or wavelength) of the X-rays can be measured qualitatively, and the intensity can be measured quantitatively.
3. Atomic Emission Spectroscopy
Flame, arc, plasma torch, etc. are used as excitation sources to make the outer electrons of gaseous atoms or ions excited to emit characteristic optical spectra. The method of analyzing by this spectrum is called atomic emission spectrometry. The wavelength range is from 190 to 900 nm and can be used for both qualitative and quantitative analysis.
4. Atomic Fluorescence Analysis
After the gaseous free atom absorbs the characteristic wavelength of the radiation, the outer electron of the atom transitions from the ground state or the low energy state to the higher energy state, and after about 10-8 s, it transitions to the ground state or the low energy state, and emits the same wavelength as the original excitation wavelength ( Resonance fluorescence) or different radiation (non-resonant fluorescence), called atomic fluorescence.
The emitted wavelength is in the ultraviolet and visible regions. Quantitative analysis can be performed by measuring the intensity of the fluorescence at a certain angle (usually 90°) from the excitation source.
5. Molecular fluorescence analysis
After some substances are irradiated by ultraviolet light, the substance molecules absorb the radiation and become excited molecules, and then return to the ground state to emit fluorescence longer than the incident wavelength. A method of measuring the intensity of fluorescence for analysis is called fluorescence analysis. The wavelength is in the optical spectral region.
6. Molecular Phosphorescence Analysis
After the material absorbs light energy, an electron in the ground state molecule is excited to transition to the first excited singlet orbital, the lowest energy level of the first excited singlet state, and the intersystem crossover transition to the first excited triplet state (intersystem It is leaping) and is relaxed by vibration to the lowest vibrational level. Therefore, when the excited state transitions back to the ground state, phosphorescence is emitted.
The method of analyzing according to the intensity of phosphorescence becomes a phosphorescence method. It is mainly used for the determination of organic compounds in environmental analysis and pharmaceutical research.
7. Chemiluminescence analysis
The chemical reaction provides sufficient energy to cause the electrons of one of the reacting molecules to be excited to form an excited state molecule. When the excited state molecules jump back to the ground state, a certain wavelength of light is emitted. Its luminescence intensity changes with time, and a strong luminescence (peak) can be obtained.
Under appropriate conditions, the peak is linear with the analyte concentration and can be used for quantitative analysis. Due to the different types of chemiluminescent reactions, the emission spectrum ranges from 400 to 1400 nm.
Second, absorption spectroscopy
An absorption spectrum is produced when the energy required for the electromagnetic radiation absorbed by a substance to transition between two energy levels of the atomic nucleus, atom or molecule of the substance satisfies the relationship ΔE = hv.
Absorption spectroscopy can be divided into:
1. MÅssbauer (Mossbauer) spectroscopy
From the same isotope as the element to be measured, as the emission source of the g-ray, the absorber (sample) nucleus produces a spectrum formed by the recoilless g-ray resonance absorption. The spectral wavelength is in the g-ray region.
From the MÅssbauer spectrum, information such as the oxidation state and chemical bond of the atom, the electron cloud distribution around the nucleus or the asymmetry of the adjacent environmental charge distribution, and the effective magnetic field at the nucleus can be obtained.
2. UV-visible spectrophotometry
The absorption spectrum formed by the electron-level transition of the outer layer of the molecule in the ultraviolet and visible regions by the molecules or groups in the solution can be used for qualitative and quantitative determination.
3. Atomic absorption spectroscopy
A method for quantitatively measuring the absorption of a resonance line by a gaseous atom of an element to be tested. Its absorption mechanism is the transition of the outer electron energy level of the atom, and the wavelength is in the ultraviolet, visible and near-infrared regions.
4. Infrared spectroscopy
The composition and structure of the substance are determined by the vibration-rotation absorption spectrum of the molecule in the infrared region.
5. Paramagnetic resonance spectroscopy
Under the action of strong magnetic field, the spin magnetic moment of electrons interacts with the external magnetic field to split into magnetic energy levels with different magnetic quantum numbers Ms. The transition between magnetic energy levels absorbs or emits electromagnetic radiation in the microwave region. Different coupling constants of different compounds in this absorption spectrum can be used for qualitative analysis. According to the coupling constant, it can be used to help determine the structure.
6. Nuclear magnetic resonance spectroscopy
Under the action of strong magnetic field, the nuclear spin magnetic moment interacts with the external magnetic field to split into nuclear magnetic energy levels with different energies, and the transition between nuclear magnetic energy levels absorbs or emits electromagnetic waves in the radio frequency region.
The absorption spectrum can be used to identify the structure of organic compounds, as well as chemical effects such as dynamic effects of molecules, formation of hydrogen bonds, and tautomeric reactions.
Third, Raman scattering
Monochromatic light with a frequency of n0 illuminates the transparent material, and the molecules of the material scatter. If this kind of scattering is the exchange of energy between photons and matter molecules, that is, not only the direction of movement of photons changes, but also the energy of them changes, it is called Raman scattering.
The frequency of this scattered light (νm) is different from the frequency of the incident light and is called the Raman shift. The magnitude of the Raman shift is related to the vibrational and rotational energy levels of the molecule. The method of studying the structure of matter using Raman shift is called Raman spectroscopy.
China manufacturers ,suppliers of Apis Raw,Naphazoline Powder Benefits,Naphazoline Hcl Powder,Neomycine Pharmaceutical API,
Now we have 3 GMP standard workshop, Meanwhile, the factory is equipped with the researching and quality inspection centre, with strong technology research and development strength. We also have 3 salesdepartments over 30 people and sell our products all over the world.
For customer`s needs, OEM service is also acceptable. If you have a good idea in new product production but lack of laboratory device and human resource, we are glad to solve this problem for you. Sincerely hope to strengthen exchanges and cooperation with friends from both home and abroad.
China manufacturers ,suppliers of Apis Raw,Naphazoline Powder Benefits,Naphazoline Hcl Powder,Neomycine Pharmaceutical API
Xi'an Henrikang Biotech Co.,Ltd , https://www.xianhenrikangbio.com