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"I have noticed that in recently published FDA warning letters, the use of 'test injections' comes up as an adverse observation quite regularly. Does this mean that I shouldn't use test injections prior to HPLC analysis? I usually perform one or more injections before system suitability to make sure that the chromatography is as expected, since sometimes the first injection is not the same as those injected afterwards."
"Most chromatographers would agree that it is quite legitimate to perform an injection to check if the system is ready to use and that for some methods the test injection may be different to subsequent injections. Thus 'test injections' are a common feature in many analytical laboratories.
Unfortunately, the practice was seemingly willfully misinterpreted in some laboratories to provide an opportunity to falsify data and this has resulted in intense scrutiny of the use of 'test injections' during regulatory inspections.
My main piece of advice is that it should not be necessary to use the sample solution (i.e. the test solution prepared from the material that you will generate a reportable result for) for a test injection and it is wise to avoid this. In my opinion, a test solution which was prepared for use as a standard would be appropriate as a test injection but even this approach has come under suspicion due to observed manipulation of the data from sequences of standard injections.
Therefore, an explicit procedure which details exactly how test injections will be used and also how the results will be recorded is advisable. Storing test injection raw data (e.g. chromatograms) separately to the data for the analysis (i.e. in a different file electronically) is often seen as suspicious. Obviously, knowledge of the contents of this SOP is essential for all analysts using HPLC. This information could be included in a generic HPLC SOP which details other important information, e.g., use of blank injections, system suitability, injection sequence setup, integration policy, etc.
Since the use of a test injection is usually method specific it would also be advantageous if relevant information was included in the particular analytical method."
Guidance on this topic is available from the FDA in their draft guidance on data integrity, click here.
The topic of 'test injections' is an important data integrity issue and is thoroughly examined in the MTS course, Laboratory Data Integrity. Visit the MTS website for more information.