In Matrix Derivatization Combined with LC-MS/MS Results in Ultrasensitive Quantification of Plasma Free Metanephrines and Catecholamines

Authors:
Open Access
Publisher website
Google Scholar
Abstract
Plasma free metanephrines and catecholamines are essential markers in the biochemical diagnosis and follow-up of neuroendocrine tumors and inborn errors of metabolism. However, their low circulating concentrations (in the nanomolar range) and poor fragmentation characteristics hinder facile simultaneous quantification by liquid chromatography and tandem mass spectrometry (LC-MS/MS). Here, we present a sensitive and simple matrix derivatization procedure using propionic anhydride that enables simultaneous quantification of unconjugated L-DOPA, catecholamines, and metanephrines in plasma by LC-MS/MS. Dilution of propionic anhydride 1:4 (v/v) in acetonitrile in combination with 50 µL plasma resulted in the highest mass spectrometric response. In plasma, derivatization resulted in stable derivatives and increased sensitivity by a factor of 4–30 compared with a previous LC-MS/MS method for measuring plasma metanephrines in our laboratory. Furthermore, propionylation increased specificity, especially for 3-methoxytyramine, by preventing interference from antihypertensive medication (β-blockers). The method was validated according to international guidelines and correlated with a hydrophilic interaction LC-MS/MS method for measuring plasma metanephrines (R2 > 0.99) and a high-performance liquid chromatography with electrochemical detection method for measuring plasma catecholamines (R2 > 0.85). Reference intervals for L-DOPA, catecholamines, and metanephrines in n = 115 healthy individuals were established. Our work shows that analytes in the sub-nanomolar range in plasma can be derivatized in situ without any preceding sample extraction. The developed method shows improved sensitivity and selectivity over existing methods, and enables simultaneous quantification of several classes of amines.
Funding Information
  • VHL Alliance

This publication has 36 references indexed in Scilit: