MSACL 2024 Abstract

Structure: This one hour teaching session regarding Internal Standards will be delivered in three 20 minute vignettes. The first session will describe in detail the "What, Why and How" Internal standards should be used in isotope dilution LC-MS/MS assays. The second session "But what about when?" will describe situations where Internal Standards fail criterion for use and how to correct deficiencies for effective LC-MS/MS assays. The third session will describe the "Unique capabilities" afforded to analytical measurement when used as pre-analytic correction tools, internal calibrators, discrimination between recovery and ionization effects (duplicate IS's) and in method development (as surrogates for analytes).

Take Home Pearls: Key experimental considerations and "cause-effect" will be detailed to establish when internal standards are behaving in a manner consistent with the analyte.

Session 1 will include: What level should I add IS at? what does the IS actually do? Qualitative details and error observations, quantitative assessment of binding equivalency (Reverse admixing - and when it can be misleading), drift over time using dynamic extraction and automation tools (and how to both elucidate and correct errors).

Session 2 will highlight examples of internal standardization failures such as the impact of excessive labeling, Isotopic contribution (from and to analyte), and when to use an "analog" internal standard - correctly.

Session 3 will detail expanded uses of Internal standards such as differentiation between recovery error and ionization effects (to confidently determine release or repeat for patient results), in-plate dilution for results reporting outside the calibration range and how an internal standard can be used as a calibration system (and when not to!).