A researcher reproducing an HPLC method in which simultaneously 9 compounds are determined in Blood samples. But he wants to anlayze only 4 compounds for his study using the same method. Does this effects the validation of method or he need to follow the same process of 9 compounds or use another method for his 4 compounds?
Not likely! The 4 other compounds may be totally different than the compounds you have validated (see ICH Q2) and thus have a different solubility... You are more likely to develop and validate a gradient HPLC procedure and validate all 9.
It's not really clear from your question: are the 4 compounds from among the 9 already validated? If yes, then sure, you can use your method; but if they are substantially different chemically, you definitely need to develop a new method.
Yes of course, the valid analytical method for a group of analytes is valid for any of them.
Yes, it can as long as the 4 compounds are within the same concentration ranges used in the original method.
Dear Sir @Bruce Neagle ,
Yes the 4 compounds belong to the same type enlisted in those 9 compounds.
Thank you all for clearing my problem. @Julius Pavlov @Nidal Batrawi @William Letter @Mahboubeh Saeidi
@Asmat Ullah : Since the method for detecting the nine substances is valid, and all parameter of calibration model, LOD, LOQ, Precision, Interference study, stability study and dilution integrity are proved to be valid, there will be no problem to use the same method (AS VALID ONE) for the four substances as long as the 4 compounds have the same characters of the 9 compounds.
If the 4 compounds belong to the group of 9 compounds that are validated, then you can use the same validated method.
Yes. If the method was properly validated for the nine analytes, it is surely validated for analysis of the 4, and can be used without any problem. However, if there is any change in the analysis parameter, such as linearity range, change of sample matrix, detection system different from the validated method or any other change in the sample preparation, a revalidation must be performed and for this purpose there are official guides that establish the protocols of revalidation of analytical methods.
Remember, each molecule (9) is unique and will have a different response to the detector even if they are structurally or chemically similar.
Dear Bruce Neagle, if I have an official validated method for 9 analytes, I can readily reproduce the methodology for analyzing compound 1, 2, 3, 4, 5, 6, 7 without any problem. The method is validated for analysis of all 9 analytes. If I am going to reproduce the method I must consider under what conditions the validation and preproduction was done, this includes detection system (UV, DAD, MS ...), chromatographic column (HPLC, GC ...). Use of analytical standards as described in the validated method.
yes, definitely you can use that method which is validated for 9 compounds, but condition is your targeted 4 compounds should present in previous 9 compounds.
If not then you have to validate that method again or develop another method.
Valmir,
Full validation includes a linearity curve for each of your 9 compounds (the slope of this curve is your response factor). It also demonstrates that the method is appropriate for your sample in your hands. Is there are comparability report between the official method and your adjustments? In addition the USP and others allow adjustments without full validation.
Dear Bruce Neagle, Asmat Ullah
When we propose to use a validated method or official compendium, we must consider all the criteria of the previously validated method. This includes: linearity range, limits of detection and quantification and possible observations in the parameters of robustness. Of course, if the method was validated in the philosophy of quality by design, then the conversation is another and one can work with flexibility and eventually move beyond the limits of a traditional validation.
If the material to be analyzed does not have the same characteristics as the validated material, then a new method validation or revalidation of the method should be considered, evaluating only a few parameters.
In case of revalidation one must follow validation guides.
For validation according to the philosophy of quality by design, there is also official literature in this approach.
OK. But don't be surprised if the reviewer/regulator asks similar questions. Be sure to cover all your bases and don't give the regulator bullets (information) to shoot you with!
I will amend my answer! While I expect similar linearity due to injection volume (mass on the column), wavelength, m/z ratio.... I do not expect peaks to be of the same size for the same mass. A smaller particle size, particle shape will give sharper peaks with a lower LOQ. In fact the retention time may change radically in your sample matrix. You MUST be successful in the 'defense' of this method or you subject ALL lots tested with this method to a recall.
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