Principles for the development of new methods for pesticide residue detection (2)

5.
Qualitative identification The so-called qualitative identification is to determine the attribution of chromatographic peaks
.

For a simple sample, it can be qualitatively determined by reference material control, that is, under the same chromatographic conditions, the standard sample and the actual sample are injected separately, and the retention value can be used to determine which peak on the chromatogram is the component to be analyzed

In daily analysis, sometimes the chromatographic column at the end of the injection port is contaminated due to the large amount of analysis sample or the complicated sample matrix, which affects our analysis
.

At this point, we need to cut off a section of the chromatographic column to remove the pollution effect

6.
Quantitative analysis This step is to determine what quantitative method is used to determine the content of the component to be tested
.

Commonly used chromatographic quantitative methods are nothing more than the peak area (or peak height) percentage method, normalization method, external standard method, internal standard method and standard addition method (also called superposition method)

(1) Peak area (or peak height) percentage method
.

This method is the simplest, but the least accurate

(2) Normalization method
.

In contrast, the normalization method is more complicated.

(3) External standard method
.

This method is used more frequently.

(4) Internal standard method
.

Relatively speaking, the internal standard method has the highest quantification accuracy because it uses the response value of the relative internal standard substance to quantify

(5) Standard addition method
.

This method is to quantitatively add the standard product of the analyte to the unknown sample, and then perform a quantitative calculation based on the increase in the peak area (or peak height)

Figure 2-3 shows the general steps of testing method development
.

Figure 2-3 General steps of testing method development

Related Links: Principles for the Development of New Methods for Pesticide Residue Testing (1)