The difference between infrared absorption spectroscopy and ultraviolet visible absorption spectrosc

First, the principle of the two is different:

1. Ultraviolet spectrophotometer.

The principle of matter: the absorption spectrum of matter is essentially that the molecules and atoms in the substance absorb some specific wavelengths of light energy in the incident light, and the molecular vibrational energy level transition occurs accordingly.

and the result of electron level transitions. Since various substances have different molecules, atoms, and different molecular spatial structures, their absorption of light energy will not be the same.

As a result, each substance has its own unique, fixed absorption spectrum curve, which can be based on the absorbance at certain characteristic wavelengths on the absorption spectrum.

The high and low of the substance is determined or determined, which is the basis of spectrophotometric qualitative and quantitative analysis. Spectrophotometry is an effective means to study the composition, structure and interaction between substances according to the absorption spectrum of substances.

2. The principle of infrared spectrophotometer: the light emitted by the light source is divided into two beams of equal and symmetrical energy, one beam is the sample light passing through the sample, and the other beam is the reference light as the reference. After these two beams of light enter the photometer through the sample chamber, they are modulated by the fan mirror at a certain frequency to form an alternating signal, and the sum of the two beams of light is one beam;

It alternately enters the monochromator through the incident slit, and the beam is projected parallel to the grating through an off-axis parabolic lens, and the dispersion is dispersed.

And after passing through the exit slit, it is filtered.

The advanced subspectra are filtered out and then focused on the receiving surface of the detector through an ellipsoidal mirror. The detector converts the above-mentioned alternating signal into the corresponding electrical signal, and after the voltage amplification is carried out by the amplifier, it is transferred to the A D conversion unit, and the computer processes it to obtain a high wavenumber.

Infrared absorption spectra to low wavenumbers.

Second, the overview of the two is different:

1. Overview of ultraviolet spectrophotometer: absorption according to some characteristics on the absorption spectrum, especially the maximum absorption wavelength max and molar absorption coefficient.

It is a common physical parameter for the characterization of substances. This has a wide range of applications in pharmaceutical analysis. In the pharmacopoeia at home and abroad, the maximum absorption wavelength and absorption coefficient of ultraviolet absorption spectrum of many drugs have been loaded into it, which provides a good means for drug analysis.

2. Overview of infrared spectrophotometer: The light emitted by the light source is divided into two beams of equal energy symmetry, one beam is the sample light passing through the sample, and the other beam is the reference light as the reference. These two beams of light pass through the sample chamber and enter the photometer, where they are modulated by a fan-shaped mirror at a certain frequency to form an alternating signal.

Third, the application of the two is different:

1. Application of ultraviolet spectrophotometer: the analysis sample and the standard sample are prepared in the same solvent at the same concentration, and the UV-Vis absorption spectrum is determined separately under the same conditions.

If the two are the same substance, the spectra of the two should be identical. If standards are not available, they can also be compared with readily available standard spectra. This method requires the accuracy and precision of the instrument.

high, and the measurement conditions should be the same.

2. Application of infrared spectrophotometer: it can be widely used in petroleum, chemical industry, medicine, environmental protection, teaching, material science, public security, national defense and other fields.

Ultraviolet absorption spectroscopy and visible absorption spectra are both electron spectra, which are produced due to the transition of valence electrons.

Infrared absorption spectroscopy belongs to molecular vibration and rotation spectroscopy, which mainly studies the structure of complex macromolecules through the vibration and rotation characteristics of molecules.

Infrared absorption spectroscopy distinguishes between different organic groups by the energy generated by the vibration and stretching of polar bonds.

The ultraviolet absorption spectrum you are talking about is generally done by ultraviolet-visible light, mainly by the size of the energy level between the bonding pi bond and the anti-bond pi bond in the organic matter.

Summary. Ultraviolet spectrum is a spectrum produced by certain valence electrons in a molecule absorbing electromagnetic waves of a certain wavelength and jumping from a low energy level to a high energy level, also known as electron spectrum. The wavelength range of the UV spectrometer currently in use is 200 to 800 nm.

Ultraviolet spectrum is a spectrum produced by certain valence electrons in a molecule absorbing electromagnetic waves of a certain wavelength and jumping from a low energy level to a high energy level, also known as electron spectrum. The wavelength range of the extra-photographic spectrometer used before the defeat was 200 to 800 nm in the middle of the band.

Fluorescence spectroscopy. High-intensity lasers are capable of lifting a significant number of molecules in absorbing species to the excited quantum state. As a result, the sensitivity of fluorescence spectroscopy is greatly improved.

Fluorescence spectroscopy with laser as light source is suitable for the detection of ultra-low concentration samples, for example, the single-pulse detection limit of sodium fluorescein by a tunable dye laser pumped with a nitrogen molecular laser has reached 10-10 mol liters, which is an increase of one magnitude higher than the z-high sensitivity obtained by staring at the canopy with ordinary light sources.

Infrared absorption spectroscopy and ultraviolet-visible spectroscopy have the same point: they are both absorption spectra.

Differences: 1) The wavelength of absorption is different. In infrared absorption spectroscopy, the sample absorbs electromagnetic radiation in the infrared band; In UV-Vis spectroscopy, the sample absorbs electromagnetic radiation in the UV-Vis band.

2) There is a difference in the principle of the instrument. At present, the infrared spectroscopy method applies the Fourier transform infrared spectrum, the infrared light is irradiated by the Michelson interferometer after interference, and the interferogram of the sample is collected and then the spectrum of the sample is obtained through the Fourier transform.

The ultraviolet-visible absorption spectrum uses two optical paths to detect the transmitted light intensity of the sample and the reference respectively, and then makes the difference to obtain the sample spectrum.

3) The meaning of spectral reflection is different. Infrared absorption spectroscopy can give the vibration-rotation structure information of the sample molecule, which can be used to identify the molecular structure.

UV-Vis spectroscopy gives information about the electronic state transitions of molecules, which are used to determine the excitation properties of molecules.

Ultraviolet-visible absorption spectroscopy is a method that uses the molecules of some substances to absorb radiation in the 10 800nm spectral region to carry out buried flushing determination, which is generated by the transition between the electron energy level of valence electrons and electrons in molecular orbitals, and is widely used for the qualitative and quantitative determination of organic and inorganic substances.

Ultraviolet-visible absorption spectroscopy of molecules is a commonly used spectroscopic analysis method based on the absorption spectra generated by electron transitions within molecules. The absorption of a molecule in the UV-Vis region is closely related to its electronic structure. Most of the research objects of ultraviolet spectroscopy are molecules with conjugated double bond structures.

The detailed division of the UV-Vis and near-infrared spectral regions is shown in the figure. The UV-Vis region is generally represented by a wavelength (nm). Most of the research objects were collected in the near-ultraviolet region of 200-380 nm and the visible region of 380-780 nm.

The sensitivity of UV-Cotan solution for absorption assays depends on the molar absorbance coefficient of the molecule that produces the light absorption.

The method is simple and widely used. For example, in the routine laboratory tests in hospitals, 95% of the quantitative analysis is done by UV-Vis spectrophotometry. In chemical research, ultraviolet-visible absorption spectroscopy is inseparable from the determination of equilibrium constants and the calculation of host-guest binding constants.

Ultraviolet absorption spectroscopy.

and visible absorption spectra are both molecular spectra, which are due to valence electrons.

of the jump. The ultraviolet-visible spectrum is produced by the absorption of ultraviolet and visible light by molecules or ions of a substance.

and the degree of absorption can be analyzed, measured and inferred about the composition, content and structure of the substance.

In organic compound molecules, there are electrons that form single bonds, electrons that form double bonds, and lone pairs of n electrons that are not bonded. When a molecule absorbs a certain amount of radiant energy, these electrons will jump to a higher energy level, and the orbital occupied by the electrons is called the antibond orbital, and this electronic transition has a close relationship with the internal structure.

In the ultraviolet absorption spectrum, there are four types of transitions of electrons: n* and n*.

The energy required for each type of transition decreases in the following order: n * n *

Both infrared absorption spectroscopy and ultraviolet-visible absorption spectroscopy can be used for the qualitative and quantitative determination of substances. It's just that the spectrum required is different.

Ultraviolet: 180 380, visible 380 750, infrared, 750 2000 nm, in different bands.

Infrared absorption spectroscopy is referred to as infrared spectroscopy. In general, the wavelength position of the infrared absorption band and the intensity of the absorption number collection band reflect the characteristics of the molecular structure, which can be used to identify the structural composition of the unknown substance or determine its chemical group. The absorption intensity of the absorption band, on the other hand, is related to the molecular composition or the content of chemical groups, and can be used for quantitative analysis and purity identification. It is often used for structural analysis of chemical components of traditional Chinese medicine.

Infrared spectroscopy analysis has strong characteristics, gas, liquid, and solid samples can be measured, and has the characteristics of low dosage, fast analysis speed, and no destruction of samples. As a result, infrared spectroscopy is not only qualitative and quantitative, like many other analytical methods, but it is also one of the most useful methods for identifying compounds and determining molecular structure.

Ultraviolet-visible absorption spectroscopy is a method to study the composition and structure of substances based on the absorption of radiant energy by the molecules in solution in the ultraviolet and visible spectral regions. Also known as UV and Vis absorbance photometry, it includes colorimetric analysis and UV-Vis spectrophotometry. It is widely used for the qualitative and quantitative determination of organic and inorganic substances.

Ultraviolet-visible absorption spectrometry is a method with high sensitivity, good accuracy, excellent selectivity, easy operation and good analysis speed.

Summary. Infrared absorption spectroscopy is an analytical method that uses the selective absorption characteristics of infrared light by substances to complete the qualitative and structural acquisition of measured substances. The similarity with ultraviolet absorption spectroscopy is that both are absorption spectroscopy; The difference is that it causes different changes to the irradiated object; The scope of the objects of analysis is different; The main purpose of its analysis is different.

Infrared absorption spectroscopy is an analytical method that uses the selective absorption characteristics of infrared light by substances to complete the qualitative and structural acquisition of measured substances. It is the same as ultraviolet absorption spectroscopy, and the lure bright point is two, both of which are absorption spectroscopy; The difference is that the cavity is irradiated to the early sales of different changes; The scope of the objects of analysis is different; The main purpose of its analysis is different.

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