Verification with a second method

As an example, Urakova et al. compared the analysis of chlorogenic acid in green coffee bean extracts by thin layer chromatography on silica (i.e. normal-phase liquid chromatography) and by reversed-phase HPLC The validation data (LOD, LOQ, repeatability, and various precision parameters), the recoveries and the quantitative results were totally comparable. It can be assumed that both methods find the true value. Either method can be used, depending on the preference or instrumentation of a laboratory. 

This kind of verification is virtually mandatory for completely new procedures and for samples with difficult matrix. It is obvious that the verification is performed previously to the validation (Section 20.3) of the method which will be chosen finally. 

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