Stable isotopically labeled internal standards in quantitative bioanalysis using liquid chromatography/mass...

Area of Science:

• Analytical Chemistry
• Mass Spectrometry
• Bioanalysis

Background:

• Quantitative bioanalytical assays commonly employ internal standards to enhance accuracy and precision.
• Stable isotopically labeled (SIL) internal standards are widely believed to offer superior performance in liquid chromatography/mass spectrometry (LC/MS) assays.

Purpose of the Study:

• To evaluate the performance of stable isotopically labeled (SIL) internal standards versus structural analogues in quantitative bioanalytical LC/MS assays.
• To discuss the advantages and disadvantages of different internal standard types.

Main Methods:

• Comparative analysis of assay performance using SIL internal standards and structural analogues.
• Evaluation of potential issues such as retention time differences, recovery variations, and ion suppression.

Main Results:

• While SIL internal standards are generally preferred, deuterium-labeled compounds can exhibit different retention times and recoveries compared to the analyte.
• SIL internal standards with identical chemical properties may mask underlying assay problems like instability or ion suppression.
• Structural analogues present a viable alternative when SIL standards are unavailable or costly, but require careful consideration during method validation.

Conclusions:

• The choice of internal standard in LC/MS bioanalysis requires careful consideration of potential issues.
• Deuterium-labeled compounds may not always behave identically to the analyte, and structural analogues can be effective if validated properly.