The cause of matrix effect

1.

According to the different effects of the matrix on the response value of the detection signal, the matrix effect can be divided into matrix enhancement effect and weakening effect

Figure 2-12, the majority of pesticides have different degrees matrix enhancing effect, methamidophos , acephate , mevinphos , omethoate , phosphamidon , pirimiphos-methyl Pesticide strong enhancement effect, and Chlorothalonil is degraded in the matrix

2.

Figure 2-12 Matrix enhancement effect of some pesticides (1mg/L) in acetonitrile solvent and matrix solvent

1.

9.

3.

(1) Relative response value method is simpler

Matrix effect (%)=B/A×100%

In the formula: A——response value of pesticide in pure solvent;

B——The response value of the same pesticide added in the sample matrix

(2) The standard curve method is more complicated

4.

At present, many standard methods for pesticide residue detection use matrix-matched standards for calibration, so that the matrix environment in the standards is the same as that in the samples.

Since the matrix effect has a great relationship with the type of matrix, strictly speaking, each type of sample must match the corresponding matrix standard, which is not realistic for daily testing

One is to select a general matrix for preparation after evaluation for each type of matrix

Another option is the application of analyte protectants

Figure 2-13 Analysis of the compensation effect of the protective agent on the matrix effect of pesticide residues

5.

In the method confirmation process of conventional liquid chromatography-mass spectrometry, blank samples of the same source are generally used to prepare a series of standard samples and quality control samples, and the result is often that the precision and accuracy of the method are good
.
However, in the actual application of the method, because the samples to be measured have different sources, the matrix components of the samples are somewhat different from those of standard samples and quality control samples
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Due to the difference in matrix components, the determination results of samples from different sources containing the same concentration of the target compound are very different, which has a direct and serious impact on the precision and accuracy of the determination results
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Therefore, the matrix effect should be studied in the method establishment stage, otherwise the existence of matrix effect will sometimes lead to wrong judgments and conclusions
.