Very fast and direct capillary zone electrophoresis method for the determination of creatinine and creatine in human urine

A capillary zone electrophoresis (CZE) method was investigated for the determination of creatinine and creatine in human urine by using a fused-silica capillary (75 (mu)m ID × 30 cm total length, 10 cm effective length). The separation was performed using an hydrodynamic injection time of 3 s (0.5 psi), a voltage of -15 kV and a 60 mM phosphoric buffer solution at pH 2.2 as electrolyte separation. Under these conditions, the analysis takes less than 2.7 min. A linear response over the 3.0– 120 mg L^-1 concentration range was investigated for compounds. A dilution of the sample (water:urine) was the only step necessary before the electrophoresis analysis. Detection limits of 0.7 and 1.3 mg L^-1 for creatinine and creatine (S/N=3) were obtained. The developed method is easy, rapid and sensitive and has been applied to determine creatinine and creatine in different human urine samples.