[Detector] Chromatography, mass spectrometry, spectroscopy, spectrum PK! Which of the four great names is the most invincible? -Huaqiang Electronic Network

In the field of detection, there are four famous spectrums, namely, chromatography, mass spectrometry, spectroscopy, and spectroscopy. The four famous genealogy have their own advantages and disadvantages. In order to maximize the maximum advantage of each analytical instrument, two or three can be used. The instrument is used in conjunction with the analysis of the sample.

The combined technology can overcome the defects of the instrument when it is used alone, which is the trend of future development of analytical instruments.

1. Chromatographic analysis

2. Mass spectrometry

Mass spectrometry is the method of collecting and recording ions of different masses in order of mass-to-charge ratio (m/z), obtaining mass spectrum, qualitative and quantitative analysis and structural analysis by mass spectrometry.

Mass spectrometry is a physical analysis method. It is mainly used for the determination of relative atomic mass and the identification and structural analysis of certain complex compounds.

· With the success of instruments such as GC and HPLC and mass spectrometers, and the rapid development of computers, mass spectrometry has become the most effective tool for analyzing and identifying complex mixtures.

There are many types of mass spectrometers, and the working principle and application range are also very different. From the application point of view, mass spectrometers can be divided into the following categories:

Organic mass spectrometer:

Due to different application characteristics, it is divided into:

1 Gas Chromatography-Mass Spectrometry (GC-MS)

In this kind of instrument, due to the different working principle of the mass spectrometer, there are gas chromatography-quadrupole mass spectrometer, gas chromatography mass spectrometry book-time-of-flight mass spectrometer, gas chromatography-ion trap mass spectrometer and so on.

2 Liquid Chromatography-Mass Spectrometry (LC-MS)

Similarly, there are liquid chromatography-quadrupole mass spectrometers, liquid chromatography-ion trap mass spectrometers, liquid chromatography-time-of-flight mass spectrometers, and various liquid chromatography-mass spectrometry-mass spectrometers.

3 Other organic mass spectrometers, mainly include:

Matrix-assisted laser desorption time-of-flight mass spectrometer (MALDI-TOFMS), Fourier transform mass spectrometer (FT-MS)

Inorganic mass spectrometers, including:

1 Spark source dual focus mass spectrometer.

2 Inductively Coupled Plasma Mass Spectrometer (ICP-MS).

3 Secondary ion mass spectrometry (SIMS) but the above classification is not very rigorous. Because some instruments come with different accessories, they have different functions. For example, a gas chromatography-double-focus mass spectrometer, if switched to a fast atom bombardment ionization source, is no longer a gas chromatography-mass spectrometer, but a fast atom bombardment mass spectrometer (FAB MS). In addition, some mass spectrometers can be connected to either a gas chromatograph or a liquid chromatograph, and therefore are not well classified. Among the above types of mass spectrometers, the most widely used ones are organic mass spectrometers.

In addition to the above classification, the mass spectrometer can be divided into a dual focus mass spectrometer, a quadrupole mass spectrometer, a time-of-flight mass spectrometer, an ion trap mass spectrometer, a Fourier transform mass spectrometer, etc., depending on the mass analyzer used in the mass spectrometer.

Outstanding features (compared to nuclear, infrared, and ultraviolet):

Mass spectrometry is the only way to determine molecular mass

High sensitivity, low sample usage (usually only microgram samples, detection limit up to 10-14g)

Wide range of applications (many types of mass spectrometers, wide range of applications, can be used for isotope analysis, chemical analysis, inorganic composition analysis, organic structure analysis)

Objects analyzed: gas, liquid, solid

3. Spectral analysis

Since each atom has its own characteristic line, it is possible to identify the substance based on the spectrum and determine its chemical composition. This method is spectral analysis.

Advantages and disadvantages of spectroscopy

(1) Analytical speed The atomic emission spectrum is used for analysis before steelmaking furnace, and the analysis results of more than 20 elements can be given in 1~2 minutes.

(2) Simple operation Some samples can be directly analyzed by spectrum without any chemical treatment. Using computer technology, sometimes the analysis, data processing and printing of the analysis results can be automatically performed by simply pressing the keyboard. In the aspect of poison alarm and air pollution detection, molecular spectroscopy telemetry is used, and no sample is collected, and within a few seconds, an alarm can be issued or the degree of pollution can be detected.

(3) Spectral qualitative analysis can be performed without using pure samples by using known spectra. This is a very prominent advantage of spectral analysis.

(4) Simultaneous determination of multiple elements or compounds eliminates complex separation operations.

(5) Selectively, the elements and compounds with similar chemical properties can be determined. For example, the determination of lanthanum, cerium, zirconium, hafnium and mixed rare earth oxides, their lines can be separated without interference, and become a powerful tool for the analysis of these compounds.

(6) High sensitivity The trace analysis can be performed by spectroscopy. At present, the relative sensitivity can reach one ten-thousandth to one-billionth, and the absolute sensitivity can reach 10-8g~10-9g.

(7) Less sample damage can be used in antiquities and criminal reconnaissance.

With the adoption of new technologies (such as the application of plasma sources), the linear range of quantitative analysis is widened, allowing high and low levels of different elements to be measured simultaneously. Micro-area analysis is also possible.

limitation:

Spectral quantitative analysis is based on a relatively comparative basis. A standard sample must be used as a reference, and the composition and structural state of the standard sample should be consistent with the sample being analyzed, which is often difficult.

4. Spectral analysis

The four famous genealogy:

UV: four absorption bands, generation, wavelength range, absorbance

Infrared: characteristic peak, influence factor of absorption peak, correlation and difference of different compound maps

Nuclear magnetic: N+1 rate, factors affecting chemical shift, chemical shift of various compounds

Mass spectrometry: characteristic ions, rearrangement, mass spectrometry characteristics of each compound (eg, presence or absence of molecular ion peaks, etc.)

Characteristics of spectral analysis:

The specific functions of the four spectral analyses are as follows:

Summary: The four famous genealogies have their own advantages and disadvantages, but when they are united, they are invincible, and the tacit understanding of each other can play the biggest role.

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