A local anaesthetics diperodon by the action of hydrolazes in blood serum is decomposed. A method for its determination in blood serum in vitro has been worked out. It was found that during the first 2 hours it decomposes rather rapidly. During next 6 hours the rate of decomposition is decreased, and after 8 hours the blood serum contained yet about 33% of not decomposed diperodon. The separation of diperodon has been carried out in the chromatographic system which consists of 70% methanol in mobile phase in water with sodium acetate (6.8 g/l, pH = 7.4) and chemically bounded phase C18. The capacity ratio of diperodon has been 8.1, the limit of determination is 5 micrograms/ml, and the exctraction recovery is 70%.
