GC-MS quantification of urinary symmetric dimethylarginine (SDMA), a whole-body symmetric l-arginine methylation index

Abstract

Circulating and excretory N^G,N^´G-dimethyl-l-arginine (symmetric dimethylarginine, SDMA) and N^G,N^G-dimethyl-l-arginine (asymmetric dimethylarginine, ADMA) are cardiovascular risk factors. Despite close chemical structures, the gas chromatography-mass spectrometry (GC-MS) measurement of SDMA is remarkably more difficult than that of ADMA for as yet unknown reasons. Here, we describe an improved GC-MS method for the quantitative determination of SDMA in human urine using commercially available N^G,N^´G-di-[²H₃]methyl-l-arginine (d₆-SDMA) as internal standard. The method is based on a single derivatization step with pentafluoropropionic anhydride (PFPA) in ethyl acetate (30 min, 65 °C) to N,N,N,O-tetrakis-pentafluoropropionyl derivatives, electron-capture negative-ion chemical ionization and selected-ion monitoring of the mass-to-charge (m/z) ions of m/z 456 for SDMA and m/z 462 for d₆-SDMA.

Keywords: ADMA; Deuterium; Guanidine methylation; Pentafluoropropionic anhydride; SDMA.