前言：

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

　　Recently, we reported an LC-MS/MS method for measuring Pmets using ion-pairing solid phase extraction (IP-SPE) and porous graphitic carbon (PGC) column chromatography1, 2. Although the method is fast and analytically sensitive, it can be further improved by automating the offline sample preparation with online sample preparation technology, which is more time- and cost-effective.

仪器：

Thermo Scientific TSQ Quantum mass spectrometer

结论：

　　A fast, automated and analytically sensitive LC-MS/MS method was developed to quantify plasma metanephrines for clinical research purposes4. By using TurboFlow technology, the sample preparation procedure was significantly simplified compared to a previously reported offline IP-SPE method. The presence of PFHA during the online sample preparation was critical to the success of this method. A PGC column was used for chromatographic separation of metanephrines. The total online extraction and analytical LC runtime was 12 minutes. This method was linear from 6.3 to 455.4 pg/mL for metanephrine and 12.6 to 954.5 pg/mL for normetanephrine, with an accuracy of 80.6% to 93.5% and 80.9% to 101.7%, respectively. The lower limit of quantitation was 6.3 pg/mL for metanephrine and 12.6 pg/mL for normetanephrine. Inter-assay and intra-assay precision for metanephrine and normetane-phrine at low and high concentration level ranged from 2.0% to 10.5%.

　　Overall, the analytical performance achieved with this automated online TurboFlow method is consistent with the previously reported offline SPE method2. More importantly, the online method significantly saved sample preparation time by more than 50% and eliminated the expense of SPE cartridges with an offline approach.