Introduction to Qualitative and Quantitative Methods of Meteorological Chromatographs

1. Qualitative analysis

A more convenient method is to use the retention value to qualify. Theoretical analysis and a large number of experimental results show that under a certain stationary phase and certain operating conditions, any substance has a definite retention time, so by measuring the appearance time of each chromatographic peak, it can be determined which chromatographic peak represents. kind of substance.

If the sample components are complex and the distance between adjacent elution peaks is very close, there will be some errors in the measurement of retention values, but the retention values ​​can help preliminarily determine which compounds may be, and then select the pure compounds of these compounds. Take one sample and add it to the sample, and observe whether the unidentified peak on the chromatogram increases. If it increases, this peak is the substance. If it is suspected that they have the same retention value under this condition and this overlapping peak appears, you can use a column with a different fixative and test at different temperatures to check.

2. Quantitative analysis

There are several chromatographic quantitative methods, such as external standard method, normalization method, internal standard method, conversion method, and volume chromatography. Relatively simple is the external standard method and normalization method.

(1) The external standard method is also called the standard line method. The principle is to prepare a standard sample of known concentration (known sample) for chromatographic test, measure the peak height or peak product of each component, find out the component content per unit peak height or peak area, or calculate the peak height ( Or peak area,) and concentration of the standard line, and then under the same operating conditions as the standard sample test, inject the same amount (usually volume) of the analyzed sample, then the concentration of the analyzed sample can be calculated from the standard line.

(2) Normalization method. When the injection volume is not easy to be measured accurately, and all components in the sample can flow out, and the chromatographic column has corresponding chromatographic peaks, this method can be used to calculate the content of each component, and the calculation formula is as follows:

If the correction factors of each component are the same, the product percentage of each component is its weight percentage.