Determination of agmatine in biological samples by capillary electrophoresis with chemiluminescence detection

A fast and simple method based on capillary electrophoresis (CE) with chemiluminescence (CL) detection has been developed for the determination of agmatine, a recently identified neurotransmitter/modulator. The CE run time was approximately 2 min for each sample injected. CL detection employed a lab-built reaction flow cell and a photon counter. The CL reagents used were luminol and NaBrO. The optimized conditions for the CL detection were 5 × 10−4 M luminol added to the CE running buffer and 5.0 × 10−4 M NaBrO in 100 mM NaCO3–NaOH buffer solution at pH 12.5 introduced post column. Detection limit for agmatine was 4.3 × 10−6 M (S/N = 3). The precision (R.S.D.) on peak height (at 1 × 10−5 M agmatine) and migration time were 3.7 and 2.5%, respectively. The present CE-CL method was evaluated with the determination of agmatine in tissue samples taken from rat brain, and rat and monkey stomachs. Samples were directly injected into the CE-CL system after the removal of proteins. A higher level of agmatine was detected in the stomach samples. Agmatine concentrations in the tissue samples taken from rat and monkey stomachs were similar at ∼1950 ng/g wet tissue.