Bioanalytics – Chemical
2019 PharmSci 360
Traditionally, the integrity of sample concentration determinations by mass spectrometry has relied on rigorous assay validation and the use of stable isotope-labeled internal standards to correct for unexpected differences in extraction recovery or ionization recovery (suppression). However, the first is not directly monitored each study sample, and the second is assumed. In regulated LC-MS/MS biomarker bioanalysis, a new level of quality assurance for each study sample analyzed may be afforded by: i) confirming that the species detected is the molecular species one is measuring, ii) confirming selectivity of SRM detection, and iii) identifying whether ionization suppression has caused a change in the analyte response that might affect the reported results.
This presentation will highlight a 3–pronged approach that will ensure the quality of measured biomarker levels in every study sample using: fragment ion ratios and isotope ratios compared to validation or standard samples to confirm the identity of the species detected; SRM collision energy ratios to confirm selectivity of SRM detection, which is especially necessary for protein biomarkers; and SprayQA which will inform on the quality of the ESI response and flag potential problems. The latter is based on SprayDx cluster ion monitoring that allows the analyst to monitor the matrix effect for each sample in a run without adding any material to the system. The individual matrix effect can be used as a quality assurance metric for ionization suppression in individual study samples.