前言：

　　Plasma free metanephrine (MN) and normetanephrine (NMN), collectively known as Pmets, are important molecules for clinical research. Liquid chromatography-tandem mass spectrometry (LC-MS/MS) has become widely used to measure Pmets because of its high analytical sensitivity and specificity.

　　Because Pmets are very polar, special solid phase extraction (SPE) and chromatographic methods have been developed for their analysis. Ion-paring (IP)-SPE, which has been used to purify a wide range of polar compounds, is well suited for the purification of Pmets.

仪器：

Thermo Scientific TSQ Quantum mass spectrometer

结论：

　　A sensitive LC-MS/MS method was developed to quantify plasma free metanephrines in clinical research laboratories. This method has an LLOQ of 7.2 and 18.0 pg/mL for metanephrine and normetanephrine, respectively. Method precision ranged from 2.0% to 10.9%. Ion-pairing SPE was used for sample preparation, and a Hypercarb column was used for chromatographic separation of metanephrines.