Determination of dimethylated arginines in human plasma by high-performance liquid chromatography

Using high-performance liquid chromatography (HPLC) with multigradient elution, N(G),N(G)-dimethyl-L-arginine (asymmetric-DMA, ADMA) and N(G),N'(G)-dimethyl-L-arginine (symmetric-DMA, SDMA) can be separated from human plasma samples. The dimethylarginine compounds in plasma, after extraction with a cation-exchange column, are converted to fluorescent derivatives with o-phthaldialdehyde (OPA) in an alkaline medium and the derivatives are separated simultaneously within 50 min on a reversed-phase column (Ultracarb 3 ODS(20)). The recoveries of ADMA and SDMA are over 80% and the method permits quantitative determination of dimethylated arginines at concentrations as low as 0.1 micromol/l in human plasma.