Key Roles of Internal Standards in Clinical Mass Spectrometry Metabolite Analysis

Internal standards in mass spectrometry metabolite analysis are measured alongside target analytes to help assess analytical accuracy and reliability. They are generally added to samples and remain with the target molecules throughout sample preparation and analysis. An internal standard has chemical properties similar to those of the target analyte and is added at a known concentration, providing a reference for comparing variability between samples.

Internal standards help account for potential sources of error, such as variation in sample preparation, changes in instrument response and inconsistent analytical conditions. Their signals can be used to correct for these effects and improve the accuracy and reliability of results.

Selecting a suitable internal standard is important. It should have chemical and physical properties similar to those of the target analyte so that both are affected similarly during sample preparation and analysis. It should also be stable, resistant to environmental influences and free from interfering peaks in the mass spectrometric analysis.

Common internal standards include drugs or their metabolites and isotopically labelled compounds. For example, stable-isotope-labelled compounds at known concentrations are often used in drug metabolism research. Their chemical properties closely match those of the target molecules, while mass spectrometry can distinguish and quantify their signals. The internal-standard signal can therefore serve as a correction reference for determining the amount of the target analyte.

The selection and use of internal standards in clinical mass spectrometry require verification and validation, typically including sensitivity, linear range, accuracy and reproducibility. Appropriate quality-control procedures are also needed to ensure stability and reliability.