A simple and rapid analytical method based on solid-phase extraction and liquid chromatography-tandem mass spectrometry for the simultaneous determination of free catecholamines and metanephrines in urine and its application to routine clinical analysis

Objectives: Urinary catecholamines and metanephrines are biochemical indicators of pheochromocytoma. We developed and validated a rapid and precise analytical method based on solid-phase extraction (SPE) and liquid chromatography separation coupled to tandem mass spectrometry (LC-MS/MS) for measuring urinary free catecholamines and metanephrines in a clinical setting. Methods: Following SPE purification of catecholamines and metanephrines from urine specimens, chromatographic separation and quantitative detection were performed using LC-MS/MS. The developed method for simultaneous measurement of urinary free catecholamines and metanephrines was validated with clinical urine specimens and was compared with other clinical and biochemical results, including urinary total metanephrines, vanillylmandelic acid (VMA), and plasma free metanephrines. Results: The performance of our newly developed method for measuring urinary free epinephrine (EPI), norepinephrine (NE), dopamine (DA), metanephrine (MN), and normetanephrine (NMN), was acceptable. The recoveries and matrix effects of analytes were 61-107% and 84.5-130.7%. The linear ranges of each analyte were 3.8-2163 μg/L, 7.4-2,359 μg/L, 5.4-2,825 μg/L, 3.5-2,466 μg/L, and 3.7-2,569 μg/L, and the coefficients of variation (CV) were less than 10% with respect to imprecision. Carryover and sample stability were also validated. Validation using clinical urine specimens by comparison with various biochemical results showed that urinary free metanephrines had comparable sensitivity (100%) and superior specificity (97.1%) to urinary total and plasma free metanephrines. Conclusions: The facile and reliable simultaneous measurement method for urinary free catecholamines and metanephrines using LC-MS/MS developed in this study is helpful in obtaining information about multiple metabolites and is applicable to routine clinical settings for the screening of pheochromocytoma.