Chromatographic

 Structural analysis：

Structural analysis of unknown compounds, structural determination of synthetic compounds, biology, chemical industry, materials, scientific research, food and other fields. Chemical structure analysis mainly studies the atomic structure, molecular structure, crystal structure and the relationship between structure and properties, so as to determine the chemical structure and physicochemical properties of molecules by various means. This analysis plays an important role in the fields of biology, chemical industry, materials, scientific research, food and so on.

Detection of chemical reagents and quantitative methods

一、Understand the tested substance

1、Boiling point：It is important to set the temperature of the chromatograph；

2、Viscosity：The pretreatment of samples is very important；

3、Corrosivity：It is very important for the selection of chromatographic column；

4、 Impurity：The pretreatment of samples is very important；

5、Content：It is important for the choice of analysis method；

6、Which solvents are soluble：Provide a method for the detection of high boiling substances。

二、Instrument parameter setting

1、Temperature setting

1.1When the boiling point of the tested substance is not higher than 250 ℃ and the viscosity of the finished substance is small

The temperature of the vaporizer is slightly higher than the boiling point；

The temperature of the column chamber is slightly lower than the boiling point；

The detector temperature is slightly higher than the vaporization chamber temperature。

According to the peak effect of impurity peak, the temperature of column chamber can be changed appropriately or programmed heating can be used (how to modify it will be shared next time, which will not be repeated this time)

1.2When the boiling point of the tested substance is higher than 250 ℃ or the finished substance with high viscosity of the spectrometer

First dilute the substance to be tested with a soluble solvent, and the dilution ratio increases appropriately with the increase of boiling point, or the dilution ratio increases appropriately with the increase of viscosity.

The temperature of the vaporizer can be lower than the boiling point；

The temperature of column chamber is programmed；

The detector temperature is slightly higher than the vaporization chamber temperature；

If the boiling point is very high or the viscosity is high, the nitrogen of the carrier gas can be replaced with hydrogen.

2、Carrier gas flow rate

It shall be adjusted appropriately according to the peak effect and modified in the principle of good separation effect and short detection time.

3、Diversion and purging

Adjust appropriately according to the peak effect, and adjust according to the principle of good peak type (no forward extension, no trailing) and high effect value.

4、Selection of analytical methods

Normalization method: generally detect intermediate products or finished products

External standard method: generally used for constant detection

Internal standard method: generally used for microanalysis

Correction normalization: it is generally used for mixtures with large difference in response values

Index method: special for sulfur content detection

Addition method: generally used for qualitative analysis of substances

Gas chromatograph

    Gas chromatograph is widely used in various scientific research and production fields. The detection and analysis of meteorological chromatography through gas chromatograph is the most commonly used way. How to quantify it? Let's introduce four quantitative methods.

    Chromatographic analysis method is abbreviated as chromatography or chromatography. Gas chromatograph is an instrument that separates each component in the sample according to the difference of adsorption or distribution coefficient between gas-solid or gas-liquid phases with the movement of carrier gas. The separated components enter the detector in the order of retention time, automatically record the detection signal, and conduct qualitative and quantitative analysis according to the retention time and response value of components. The gas chromatograph is composed of gas source, gas path control system, sample injection system, chromatographic column, detector, electrical system, recording and processing system.

A method of separating mixtures by physical means through a gas chromatograph is called gas chromatography. Gas chromatography is to use gas (carrier gas) as the mobile phase in the column made of appropriate stationary phase to expand the sample (gas, liquid or solid) in the gas state. After separation in the chromatographic column, various components successively enter the detector and record the chromatogram with a recorder. After debugging the gas chromatograph, adjust the gas chromatograph column tube, gas chromatograph detector, temperature and carrier gas flow according to the specified conditions of each monomer. The temperature of the injection port should generally be 30-50 ℃ higher than the column temperature. If flame ionization detector spectrometer is used, its temperature shall be equal to or higher than the column temperature, but not lower than 100 ℃ to avoid water vapor condensation. The position of the peak of the component analyzed on the chromatography, in terms of retention time (from the time of injection of the sample solution to the peak of the component) and retention capacity (retention time) × Carrier gas flow). Under certain conditions, these can reflect the special value of the substance, and determine the composition of the sample accordingly. Quantitative methods can be divided into the following:

    The area standard method was used to obtain the standard tested components, according to the known quantity added or reduced in turn, respectively, to add the quantitative internal standard substance in each monomer, and to modulate the standard solution. Take a certain amount of the standard solution and inject it into the chromatographic column of the gas chromatograph. According to the chromatogram on the gas chromatograph, take the ratio of the peak area and peak height of the standard measured component to the peak area and peak height of the internal standard material as the ordinate, and take the ratio of the standard measured component to the mass of the internal standard material, or the standard measured component as the abscissa to make the standard curve.

    Then prepare the sample solution according to the method specified in the monomer. When preparing the sample solution, add the same amount of internal standard material as when preparing the standard solution in advance. Then, according to the chromatogram obtained under the same conditions when making the standard curve, calculate the ratio of the peak area or peak height of the tested component to the peak product or peak height of the internal standard material, and then calculate the content of the tested component according to the standard curve.