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Capillary electrophoretic and micellar electrokinetic separations of asymmetric dimethyl‐L‐arginine and structurally related amino acids: Quantitation in human plasma
Author(s) -
Trapp Gabriele,
Sydow Karsten,
Dulay Maria T.,
Chou Tina,
Cooke John P.,
Zare Richard N.
Publication year - 2004
Publication title -
journal of separation science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.72
H-Index - 102
eISSN - 1615-9314
pISSN - 1615-9306
DOI - 10.1002/jssc.200401918
Subject(s) - micellar electrokinetic chromatography , chemistry , chromatography , capillary electrophoresis , arginine , detection limit , derivatization , electrokinetic phenomena , analyte , electrophoresis , resolution (logic) , amino acid , high performance liquid chromatography , biochemistry , artificial intelligence , computer science
We report the development of efficient electrophoretic methods for the separation and quantification of L‐arginine and six naturally occurring derivatives that are structurally and functionally related. Capillary electrophoresis (CE) employing a concentrated borate buffer at pH 9.4 achieves the separation of mixtures containing dimethyl‐L‐arginine, N G ‐monomethyl‐L‐arginine, L‐arginine, L‐homoarginine, L‐ornithine, and L‐citrulline as 4‐fluoro‐7‐nitrobenzofurazan derivatives. In addition, the separation of the isomeric dimethyl‐L‐arginine derivatives (symmetric and asymmetric) is attained with baseline resolution by micellar electrokinetic chromatography (MEKC) when a high concentration of deoxycholic acid is added as a surfactant to the same running buffer. The influence of buffer type, concentration, and pH on the separation was studied to optimize separation conditions. The limit of quantitation (LOQ) for asymmetric dimethyl‐L‐arginine in aqueous solution was determined to be 20 μM using UV absorption in a CE separation and 0.1 μM using laser induced fluorescence (LIF) detection in an MEKC separation. This newly developed method was successfully applied for the quantitation of asymmetric dimethyl‐L‐arginine and L‐arginine in human plasma samples at levels that might be used as a clinical diagnostic for cardiovascular disease (0.125 μM LOQ).