A micellar electrokinetic chromatographic method is described for the determination and quantitation of allantoin, an end-product of purine metabolism in mammals that is applicable to biofluids of different mammal species and man. The method was optimised following a study on the effect of pH and sample preparation procedure. Final conditions were 30 mM sodium tetraborate, pH 9.5, 75 mM sodium dodecyl sulphate, 20 kV and 20 degrees C. Allantoin was well resolved from endogenous compounds and could be determined in horse, dog, mouse and rabbit urine. No allantoin could be found in man. No complicated sample treatment was necessary, thus the developed method was rapid (<5 min), sensitive (5 mu M) and simple. Results from this work will permit the determination of allantoin in man as a measure of free radical generation reactions as well as its presence in the plasma and other biofluids with modification of the sample preparation procedures. (C) 1998 Elsevier Science B.V. All rights reserved.