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 (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.