The current HPLC autosampler only allows a maximum injection volume of 50 uL, while the validated bioanalytical method states 80 uL injection volume. This shall be applied to an on-going clinical study of rat serum.
Hello, really you need somehow prove that all requirements reached. You not need to perform full validation, really decreasing the sample volume can decrease the analyte signal intensity if it not a problem for you and if your sensitivity limit, LOD, LOQ is reached and meets established requirements that is ok. Not mandatory but the calibration curve with new injection volume is better to perform recalibration again.
According to the European Pharmacopoeia chapter 2.2.46 "Injection volume: may be decreased, provided detection and repeatability are satisfactory; no increase permitted"
The answer depends on which regulatory guidelines you need to satisfy. Please review the appropriate guidelines to learn what changes require re-validation. Many of the guidelines allow reductions in the HPLC injection volume (same conc. which achieves acceptable sensitivity.), but in all cases a new multi-level calibration table must be created and documented too.
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