Addition standard recovery rate introduction

Everyone knows that an analytical method needs to be used as a spike recovery rate. What is the purpose of the spike recovery rate? The purpose of the spike recovery rate is mainly to verify the accuracy and reliability of the selected method, so how to do it is very important.

How to do the spike recovery experiment, some people have proposed the following two options:

1. The standard addition recovery rate is to add a standard solution to the treated sample solution, and then the measured value is used to see the recovery effect of the element to be tested in the sample solution.

2. Standardized recycling means that in the pretreatment process, the standard substance is added to the solid sample, and then the solution is digested together, and finally becomes a solution, and then the content is determined to determine the recovery effect of the sample.

For the definition of spike recovery, the definition of spike recovery is also given:

The spiked recovery rate is determined by adding a certain amount of standard substance to a sample of a sample while measuring the sample. The measurement result is deducted from the measured value of the sample to obtain a recovery rate of the added standard substance. Its calculation formula is:

Recovery rate P = (spiked sample measured value - sample measured value) / spiked amount × 100 %

The size of the spiked amount has a greater impact on the recovery rate of the spike:

(1) Adding too much or too little standard substance does not guarantee that the concentration of the analyte contained in the spiked sample and the sample is within the same precision range;

(2) When the content of the sample to be tested is high, the standard substance added is too high, so that the measured value after the standard addition is close to the upper limit of the method, so that the error of the sample to be tested in the standard sample is larger, and the standard is added. The concentration of the concentration is preferably between 0.4 and 0.6 (C). If the analytical method is spectrophotometry, the absorbance of the standard is too high, which will cause the error of the instrument itself. For the spectrophotometer, the absorbance A is below 0.7, and the reading is more accurate.

(3) When the content of the analyte in the sample is low, too little standard substance is added, and the recovery value is poor; if too much standard substance is added, the background of the test substance in the spiked sample and the sample is changed;

(4) When the standard substance is an organic solvent, if the amount of the standard is too large, it will make it difficult for the solvent and the standard substance to dissolve in the water, which may affect the spike recovery rate due to the solubility problem.

I personally think that the two solutions have their own uses. The first one can be used to test whether the sample has an influence on the analysis result after the sample is processed into a solution; the second can be used to check whether there is a problem in the whole analysis process; In combination with the first and second types, it can be judged whether or not the loss of the analysis component or the contamination of the analysis component is caused when the sample is processed.

As for the size of the spiked amount when doing the spike recovery, I basically agree with the above statement, that is, the amount of addition should be appropriate, too high or too low will not get the expected effect. Because there is a phenomenon of self-priming of the line in the atomic emission spectrum, the amount of addition is too high, which will cause an error, thereby affecting the judgment; if the amount added is too low, it is close to the detection limit, or is significantly smaller than the content of the analysis component. There will also be a big error. Therefore, in the case of spiked recovery, the standard addition amount is significantly higher than the detection limit, and the second is to be as consistent as possible with the analysis component, but at the same time, the spectral line self-priming cannot be considered.

Finally, there is another point that is very important, and it is also a problem that many people tend to overlook. The method of standardizing and recycling must solve the background problem and overlapping interference of the spectral line, if not, even if the background and spectral line interference signals As a result of the analysis measured as part of the analysis signal, a satisfactory recovery value can be obtained after the spiked recovery experiment.

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