A multivariate calibration method based on principal component regression analysis is applied to the resolution of mixtures by kinetic methodology. Gallium(III) and Al(III) were determined in mixtures on the basis of their different rate of reaction with 4-(2-pyridylazo)resorcinol in a slightly basic medium by using a stopped-flow injection procedure. Mixtures containing 1-5 mg/l. Ga(III) and 20-100 mg/l. Al(III) were successfully resolved with errors less than 10%. © 1993.