Improved real-world UHPLC-MS/MS iohexol analysis; thawed samples, improved calibration curve, and additional matrices

Area of Science:

• Analytical Chemistry
• Clinical Chemistry
• Pharmacokinetics

Background:

• Plasma clearance of iohexol is a key method for assessing glomerular filtration rate (GFR).
• Existing UHPLC-MS/MS methods require improved validation for real-world sample handling, including thawing and analysis in diverse matrices.
• Enhanced stability and matrix validation are crucial for reliable iohexol determination.

Purpose of the Study:

• To improve an existing UHPLC-MS/MS method for iohexol determination in plasma.
• To conduct enhanced stability testing under various storage conditions.
• To optimize calibration curves and perform partial validation in additional biological matrices.

Main Methods:

• Stability testing of iohexol in plasma up to 9 weeks at temperatures ranging from room temperature to 37°C with intermittent 55°C exposure.
• Comparison of eight-point versus two-point calibration curves for iohexol quantification.
• Partial validation of the method in serum, heparin plasma, urine, EDTA whole blood, and heparin whole blood.

Main Results:

• The improved method demonstrated compliance with US FDA and European Medicines Agency bioanalytical guidelines.
• Human EDTA plasma samples showed stability for up to 9 weeks under tested conditions.
• The method is partially validated for multiple biological matrices, including serum and whole blood.

Conclusions:

• The optimized UHPLC-MS/MS method provides enhanced stability for iohexol in human plasma.
• A two-point calibration curve is sufficient for accurate iohexol analysis.
• The method's partial validation across various matrices supports its broader application in GFR assessment.