Brief introduction and principle of 18 common labo

2022-06-22
  • Detail

Introduction and principle of 18 commonly used laboratory instruments

introduction and principle of 18 commonly used laboratory instruments

october17,2018

ultraviolet absorption spectroscopy, fluorescence spectroscopy, infrared absorption spectroscopy... These are the commonly used instrument analysis methods in the laboratory. Today, I will briefly sort out the abbreviations, analysis principles, representation methods of spectrogram and information provided for you

1. UV absorption spectrum

abbreviation: UV

analysis principle: absorb ultraviolet energy and cause the transition of electronic energy levels in molecules

spectral representation: the change of relative absorbed light energy with the wavelength of absorbed light

information provided: the position, intensity and shape of the absorption peak are too high at the experimental temperature, providing information on different electronic structures in the molecule

2. Fluorescence spectrometry

abbreviation: FS

analysis principle: after being excited by electromagnetic radiation, it returns from the lowest singlet excited state to the singlet ground state and emits fluorescence

spectral representation: the variation of the emitted fluorescence energy with the light wavelength

information provided: fluorescence efficiency and lifetime, providing information on different electronic structures in molecules

3. Infrared absorption spectrometry

abbreviation: IR

analysis principle: absorption of infrared light energy causes the vibration and rotation energy level transition of molecules with dipole moment change

spectral representation: the relative transmitted light energy changes with the transmitted light frequency

information provided: the position, intensity and shape of the peak, and the characteristic vibration frequency of the functional group or chemical bond

4. Raman spectroscopy

abbreviation: ram

analysis principle: after absorbing light energy, it will cause molecular vibration with polarization change and generate Raman scattering

spectral representation: the change of scattered light energy with Raman shift

information provided: the position, intensity and shape of the peak, and the characteristic vibration frequency of the functional group or chemical bond

5. Nuclear magnetic resonance spectroscopy

abbreviation: NMR

analysis principle: in the external magnetic field, the atomic nucleus with nuclear magnetic moment absorbs RF energy and produces the transition of nuclear spin energy level

spectrogram: change of absorbed light energy with chemical shift

information provided: chemical shift, intensity, crack fraction and coupling constant of the peak, providing information on the number of nuclei, chemical environment and geometric configuration

6. Electron paramagnetic resonance spectroscopy

abbreviation: ESR

analysis principle: in the external magnetic field, unpaired electrons in the molecule absorb RF energy, resulting in electron spin level transition

spectral representation: absorbed light energy or differential energy changes with magnetic field strength

information provided: spectral line position, intensity, number of splits and hyperfine splitting constant, providing unpaired electron density, molecular bond characteristics and geometric configuration information

7. Mass spectrometry

abbreviation: MS

analysis principle: molecules are bombarded by electrons in vacuum to form ions, which are separated according to different m/e by electromagnetic field

representation of spectrogram: the change of relative kurtosis of ions with m/e is represented in the form of bar graph

information provided: the mass number and relative kurtosis of molecular ions and fragment ions, and information on the inflexibility of molecular state-owned enterprise system and mechanism, element composition and structure

8. Gas chromatography

abbreviation: GC

analysis principle: the components in the sample are separated between the mobile phase and the stationary phase due to different partition coefficients

spectrogram: change of effluent concentration after column with retention value

information provided: the retention value of the peak is related to the thermodynamic parameters of the components, which is the qualitative basis; The peak area is related to the component content

9. Reverse gas chromatography

abbreviation: IGC

analysis principle: the change of the retention value of the probe molecule depends on the interaction between it and the polymer sample as the stationary phase; The purpose is to break the established concept of "this kind of material should be used for this kind of use". The expression method of spectrogram is as follows: the logarithm value of probe molecular specific retention volume changes with the reciprocal of column temperature

information provided: the relationship between the retention value of probe molecules and temperature provides thermodynamic parameters of polymers

10. Pyrolysis gas chromatography

abbreviation: PGC

analysis principle: under certain conditions, polymer materials can be split instantaneously to obtain fragments with certain characteristics

spectrogram: change of effluent concentration after column with retention value

information provided: fingerprint or characteristic fragment peak of the spectrum, characterizing the chemical structure and geometric configuration of the polymer

11. Gel chromatography

abbreviation: GPC

analysis principle: when the sample passes through the gel column, it is separated according to the hydrodynamic volume of the molecules, and the macromolecules flow out first

spectrogram: change of effluent concentration after column with retention value

information provided: average molecular weight of polymer and its distribution

12. Thermogravimetry

abbreviation: TG

analysis principle: in the temperature control environment, the sample weight changes with temperature or time

representation method of spectrogram: variation curve of sample weight fraction with temperature or time

information provided: the steep drop of the curve is the weight loss zone of the sample, and the platform zone is the thermal stability zone of the sample

13. Thermal difference analysis

abbreviation: DTA

analysis principle: the sample and the reference material are in the same temperature control environment. Due to their different thermal conductivity, there is a temperature difference. Record the change of temperature with the ambient temperature or time

representation method of spectrum: variation curve of temperature difference with ambient temperature or time

information provided: provide information on polymer thermal transition temperature and various thermal effects

14. Differential scanning calorimetry

abbreviation: DSC

analysis principle: the sample and the reference substance are in the same temperature control environment. Record the change of energy required with the ambient temperature or time when the temperature difference is zero

spectrum representation: curve of heat or its change rate with ambient temperature or time

information provided: information on polymer thermal transition temperature and various thermal effects

15 Static thermal mechanical analysis

abbreviation: TMA

analysis principle: the deformation of the sample under constant force changes with temperature or time

spectrogram: curve of sample deformation value changing with temperature or time

information provided: thermal transition temperature and mechanical state

16. Dynamic thermal mechanical analysis

abbreviation: DMA

analysis principle: the deformation of the sample under the action of periodic external force changes with temperature

representation of spectrum: modulus or tan δ Temperature dependent curve

information provided: thermal transition temperature modulus and Tan δ 。

17. Transmission electron microscopy

abbreviation: TEM

analysis principle: scattering, absorption, interference and diffraction occur when the high-energy electron beam penetrates the sample, so that the contrast is formed in the phase plane and the image is displayed

spectral representation: mass thickness contrast image, bright field diffraction contrast image, dark field diffraction contrast image, lattice fringe image and molecular image

information provided: crystal morphology, molecular weight distribution, micropore size distribution, multiphase structure, lattice and defects, etc

18. Scanning electron microscopy

abbreviation: SEM

analysis principle: use electronic technology to detect secondary electrons, backscattered electrons, absorbed electrons, X-rays, etc. generated when the high-energy electron beam interacts with the sample, and enlarge the imaging

spectral representation: backscattering image, secondary electron image, absorption current image, line and area distribution of elements, etc

information provided: fracture morphology, surface microstructure, microstructure inside the film, micro area element analysis and quantitative element analysis, etc

怀孕产后腹胀是怎么回事
薇婷
薇婷脱毛蜡纸
京万红软膏

Copyright © 2011 JIN SHI