Reasons for calibration standard curve slope variation in LC-MS assays and how to address it

摘要

A consistent calibration curve slope is a positive indication of assay performance in a validated bioanalytical method using LC-MS/MS. It is one of the quality indicators utilized by bioanalytical scientists during the data review process. However, it is not uncommon that a calibration curve slope varies significantly across different analytical runs during sample analysis. The causes for such variation and their potential impacts on the assay ruggedness have been discussed on multiple occasions [1,2]. Although there is no specific requirements for the acceptability of calibration curve slope in regulatory guidelines, a scientific understanding of what is behind the observed deviation is valuable during method development, validation and sample analysis. Large variance in curve slope often indicates potential issues associated with a method. We advocate always assessing and understanding root cause for such variance and this paper tries to illustrate possible causes for the calibration curve slope variation (including the linearity change) and assess their impacts on the analysis results.