Urinary metanephrine and normetanephrine determined without extraction by using liquid chromatography and coulometric...

Area of Science:

• Clinical Chemistry
• Analytical Chemistry
• Biochemistry

Background:

• Metanephrine (MN) and normetanephrine (NMN) are key biomarkers for diagnosing neuroendocrine tumors.
• Accurate and efficient measurement of MN and NMN in urine is crucial for clinical diagnosis.
• Existing methods often involve complex extraction procedures, limiting throughput and increasing potential for error.

Purpose of the Study:

• To develop and validate a direct measurement procedure for MN and NMN in hydrolyzed urine.
• To enhance selectivity and simplify sample preparation compared to existing methods.
• To provide objective peak purity information for reliable quantification.

Main Methods:

• High-performance liquid chromatography (HPLC) with coulometric array detection.
• Isocratic reversed-phase ion-pair chromatography for separation.
• Eight serial coulometric sensors with incrementally increasing anodic potentials for stepwise oxidation and interference screening.

Main Results:

• The method demonstrated high selectivity and objective peak purity assessment.
• Reproducibility was excellent, with between-run coefficients of variation (CV) of 5.45-9.22% and within-run CV of 1.60-4.52%.
• Excellent correlation with a dual ion-exchange extraction method (r = 0.963 for MN, r = 0.9768 for NMN) was observed, with low limits of detection (2.6 µg/L for MN, 2.8 µg/L for NMN).

Conclusions:

• The described HPLC procedure offers a simplified and highly selective method for direct MN and NMN measurement in hydrolyzed urine.
• This approach significantly simplifies sample preparation while maintaining high analytical performance.
• The method provides reliable quantification and objective peak purity assessment, suitable for clinical diagnostic applications.