Is the recovery rate of blood drug related to taking standard samples? why

I'm watching this today, too. By the way, tell me what I think. First of all, the verification content of in vivo drug analysis method in Chapter 5 of Pharmacological Analysis, Seventh Edition is p 194.

My understanding has nothing to do with the sampling amount, because the recovery rate is used to evaluate the ability of sample treatment methods to extract drugs from biological media. As far as methods are concerned, there are differences between methods, but there should be no differences within methods. This is one of them. Secondly, from the method point of view, the determination of R is carried out in parallel by the quality control group and the standard sample group plus biological medium. In order to evaluate the influence of biological media or extraction methods, aqueous solutions without biological media are usually used for comparison. For drugs, the loss mainly exists in the combination with plasma protein, the loss caused by reaction, extraction and dissolution with substances in plasma, and the loss caused by evaporation and dissolution can be corrected by adding an internal standard, so the concentration of the internal standard should not be like this.

Next, it is actually influential in actual operation. The main influence is the problem of accuracy. Because the drug concentration in blood is relatively low and there are many impurities, its detection needs high sensitivity. However, the lower the concentration, the lower its accuracy will be due to system error, so its limit requirement is that the RSD of medium and high concentration is not more than 15% and that of low concentration is not more than 20%.

If the RSD is up to standard, if the recovery rate is low, it means that there is something wrong with the extraction method, and it is suggested to improve the method. If the RSD is high, it is likely that the operation or instrument accuracy is not enough.

I learned it here, too, and it may not be completely right. Welcome to correct me.