Since the relation given below exists among the ratio (k),the time for which the mobile phase is passed through the column (t0: time measured from the time of injection of a compound with k = 0 to the time of elution at the peak maximum),and the retention time (tR: time measured from the time of injection of a compound to be determined to the time of elution at the peak maximum), the retention time for a compound on a column has a characteristic value under fixed chromatographic conditions.