Determination of methylarginines in human plasma by HPLC with pre-column derivatization using naphthalenedicarboxaldehyde as fluorogenic agent

A method has been developed for the determination of the main methylated L-Arginines, N G-monomethyl-L-arginine (L-NMMA), N G,N G-dimethyl-L-arginine (symmetric dimethylarginine, L-SDMA), and N G,N ′G-dimethyl-L-arginine (asymmetric dimethylarginine, L-ADMA) in biological samples. The assay involves precolumn derivatization of methylarginines with naphthalenedicarboxaldehyde and cyanide followed by HPLC with fluorescence detection. The separation of derivatized methylated arginines on a reversed-phase column was achieved in less than 25 min. The SPE procedure developed, based on a cation-exchange resin, permits quantitative determination of analytes at concentrations as low as 0.54, 3.42, and 0.75 μg L–1, respectively, i. e. lower than their plasma levels. Recoveries in plasma were over 81% and the inter- and intra-day relative standard deviation values as measures of repeatability were less than 4.5%. This novel and rapid method can be employed in a routine clinical setting.