Simultaneous determination of 5-aminosalicylic acid, acetyl-5-aminosalicylic acid and 2,5-dihydroxybenzoic acid in endoscopic biopsy samples in humans by high-performance liquid chromatography with electrochemical detection

A high-performance liquid chromatographic method for the simultaneous determination of 5-aminosalicylic acid (5-ASA), acetyl-5-aminosalicylic acid (AC-5-ASA) and 2,5-dihydroxybenzoic acid (5-HSA) in human endoscopic intestinal biopsy with electrochemical detection has been developed and validated. A liquid-liquid extraction procedure was used to isolate these drugs from the biological material prior to analysis. The compounds were separated on an Erbasil S reversed-phase column using methanol-citric acid-sodium hydrogenphosphate-heptanesulfonic acid&disodium ethylenediaminetetraacetate (pH 3) as mobile phase. The method was linear from 1.0 to 300 ng ml-’ for 5-ASA, from 10 to 1000 ng ml-’ for AC-5ASA and from 0.1 to 10 ng m-’ for 5-HSA. The limit of detection for 5-ASA and for AC-5-ASA was 1 ng ml-’ and that for 5-HSA was 0.1 ng ml-‘. This procedure is suitable for pharmacological and clinical studies of 5-ASA.