A highly sensitive method of kinetic differentiation (KD) mode high-performance liquid chromatography (HPLC) with fluorimetric detection was established using 8-quinolinol to measure aluminum adhering to the gastric mucosa. After sucralfate was hydrolyzed by 1 mol/l hydrochloric acid, an 8-quinolinolate-aluminum complex was produced by reacting aluminum with an 8-quinolinol solution. Then contaminants in the gastric mucosa and sucralfate were removed by liquid-liquid extraction with chloroform. Next, the 8-quinolinolate-aluminum complex was separated on a reversed-phase column that was specifically designed to detect aluminum (50 x 4.6-mm I.D.). Separation was done at a flow-rate of 0.8 ml/min, using BES buffer containing sodium dodecyl sulfate (pH 7.0) as the mobile phase. Fluorescence was detected at 370 nm (excitation) and 504 nm (emission). The sensitivity of this method was more than 1000 times greater than that of absorptiometry using 8-quinolinol. The detection and quantitation limits were 1.68 and 5.11 ng/ml, respectively. When tested with aluminum solutions of 10, 30, and 90 ng/ml, the intra-assay and inter-assay coefficients of variation were below 7.1%, with an error of less than 8.3%. Aluminum adhering to the gastric mucosa was determined by HPLC and absorptiometry after administration of sucralfate to rats. The HPLC method showed that aluminum levels were higher at sites of ulceration than in the normal mucosa at all times after sucralfate administration. When the values above zero obtained for absorptiometry were assessed, there was a significant correlation (r=0.993, P<0.0001) between the aluminum concentrations measured by the two methods. This new HPLC method could be applied to the determination of aluminum in small samples, such as human gastric mucosal biopsy specimens.