Effect of pH on stability and solid phase extraction of urinary free metadrenaline measurement by liquid chromatography tandem mass spectrometry.

This article focuses on evaluating the stability and analytical implications of measuring urine free metadrenalines—biomarkers used in detecting phaeochromocytomas and paragangliomas (PPGL)—with and without acidification of samples. The study found that free metadrenalines remain stable in urine for up to 28 days at room temperature, regardless of acid preservation, although unacidified samples showed variable increases in concentrations over time at low levels. Additionally, acidification significantly reduces analyte recovery during solid-phase extraction (SPE) using weak cation exchange (WCX) methods, whereas polarity-based SPE retains analytes effectively at both acidified and unacidified pH. These findings suggest that urine free metadrenalines can be reliably measured without acidification, potentially simplifying sample collection and improving extraction efficiency in clinical testing for PPGL.