In vitro monitoring picogram roxithromycin in human urine using flow injection chemiluminescence procedure

A sensitive chemiluminescence method, based on the enhancive effect of roxithromycin on the chemiluminescence reaction between luminol and hydrogen peroxide in a flow injection system, was proposed for the determination of roxithromycin. The increment of chemiluminescence intensity was linear with roxithromycin concentration in the range 1.0-1000 pg ml(-1) with the detection limit of 0.3 pg ml(-1) (3sigma). At a flow rate of 2.0 ml min(-1), a complete analytical process could be performed within 0.5 min, including sampling and washing, with a relative standard deviation of less than 5%. The proposed procedure was applied successfully in the monitoring of roxithromycin in human urine without any pre-treatment procedures and it was found that roxithromycin in urine reached its maximum after orally administrated for two hours, presenting an excretive ratio of 4.6% in 12 h. With urinary excretion rate method, the total elimination rate constant k and half-life time t(1/2) of roxithomycin was calculated, which was 0.1831, 3.785 h.