The new design of the horizontal flow-through centrifure permits continuous elution through a pair of coiled separation columns without the use of rotating seals. Mathematical analysis of the planetary motion discloses a characteristic pattern of the acceleration field acting on each column, one capable of efficient mixing of the two phases in a narrow-bore column and the other providing a stable retention of teh stationary phase in a large-bore column. Consequently, the present scheme enables both micro-scale and preparative-scale separations with a high partition efficiency.