What are external standard method, internal standard method, and normalization method? What are their areas of application, as well as their advantages and disadvantages?

The external standard method, also known as the standard curve method, is divided into peak height quantification and peak area quantification. It involves preparing standard samples of known concentrations, introducing exactly the right weight and volume of these standard samples for analysis, measuring the peak area or peak height of each component to determine the correction factors for each component. A standard working curve is then created by plotting peak height or peak area against concentration. Under identical conditions as those used for the standard samples, the same amount of the substance under examination is injected; the peak area or peak height of the sample is measured, and the content of the respective components is determined using the standard curve established earlier. This law requires that the conditions used for analysis must be identical to those used for marking, imposing high demands on sample injection. Otherwise, the repeatability is poor. Internal standard method: This method can be used when it is necessary to determine only certain components in a sample, and these components all produce signals under the specified conditions and their peak values can be measured. In this method, a set of pure substances is used as internal standards and added to the sample to be analyzed; chromatographic analysis is then performed to determine the peak areas of several components in the sample. Mass correction factors are applied to calculate the percentage mass content of the sample. The internal standard method offers high accuracy, has no of the limitations associated with the normalization method, and is therefore widely used. The disadvantage of this method is that it requires accurately weighed internal standards and samples for each analysis, which makes the procedure rather cumbersome, and it also demands high standards for separation. Normalized quantification provides accurate results; the injection volume has no impact on the quantification outcomes, and changes in the instrument or conditions have little effect on the results. It is particularly suitable for samples with small injection volumes whose volume is difficult to measure accurately. This method requires that all components of the substance be known and capable of producing peaks; by using the relative correction factors for each component, the content of each component can be determined.

I’ve learned it, thanks! ! ! :lol:lol:lol

I’ve learned it! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! !