Variations in internal standard response: some thoughts and real-life cases

Area of Science:

• Analytical Chemistry
• Bioanalytical Science

Background:

• Internal standards are vital for the reliability of chromatographic bioanalytical methods.
• Adequate monitoring of the internal standard's response is a prerequisite for its effective use.

Purpose of the Study:

• To differentiate between isolated sample variations and complex deviations in internal standard response.
• To establish criteria for managing deviations and ensuring data integrity in bioanalytical assays.

Main Methods:

• Analysis of internal standard response variations within analytical runs.
• Development of objective criteria for sample re-analysis.
• Evaluation of scientific judgment for complex deviations like trends and systematic differences.

Main Results:

• Isolated variations can be managed with objective criteria leading to sample re-analysis.
• Trends or systematic differences require scientific judgment and may lead to analytical run rejection.
• Effective monitoring protocols are key to validating bioanalytical data.

Conclusions:

• Proper monitoring and management of internal standard response are essential for reliable bioanalytical results.
• A clear distinction between isolated variations and systematic deviations guides appropriate corrective actions.
• Ensuring the integrity of bioanalytical data relies on robust internal standard performance evaluation.