Flow injection chemiluninescence for detecting picogram amounts of dobesilate in human urine

A sensitive method for the determination of dobesilate in pharmaceutical preparations and human urine is described by using controlled-reagent-release technology. The method entailed the use of luminol and periodate, which are immobilized on anion exchange resin and react in alkaline medium, giving chemiluminescence (CL) at 425 nm. Dobesilate was detected by measuring the decrease of CL intensity, and which was observed linear over the dobesilate concentration range of 10-600 pg ml(-1), and the limit of detection was 3.5 pg ml(-1) (3sigma) and a relative standard deviation of less than 3.0%. At a flow rate of 2.0 ml min(-1), the determination of dobesilate, including sampling and washing, could be performed in 0.5 min, giving a throughput of about 120 times per hour. The proposed method has an extremely low limit of detection down to 3.5 pg ml(-1), thus it can be applied directly in the assay of human urine without any pre-treatment. It was also found that the dobesilate concentration reached its maximum after orally administrated for 3.5h, and the excretion ratio in 24h was 58.8% in the body of volunteers.