Patent ID: 8315820

Claim:
A potentiometric titration method for conducting titration based on an amount of a titrant added and an indicator potential, said method comprising: calculating a continuous line prepared by plotting a value (Y) of the indicator potential on an ordinate axis and plotting a value (X) of a volume of the titrant on an abscissa axis, as a titration curve, the values (X) and (Y) being determined according to the titration procedure; calculating a continuous line prepared by plotting an absolute value of a rate of change in potential (dY/dX) on an ordinate axis and plotting the value (X) of a volume of the titrant on an abscissa axis, as a differential curve; calculating a value on the titration curve which corresponds to a peak (P 1 ) on the differential curve, as a tentative terminal point (P); computing, on a computer, a straight line (D) connecting two measured values on the titration curve which are present adjacent to the tentative terminal point (P); computing, on a computer, a linear first estimation line (B 1 ) by a least squares method based on measured values (d 1 ), (d 2 ) and (d 3 ) on the titration curve which are present in the range of from [(tentative terminal point (P))−(number of decision points (n))] to [(tentative terminal point (P))−(number of decision points (n))+2], and computing a linear second estimation line (B 2 ) by a least squares method based on measured values (d 4 ), (d 5 ) and (d 6 ) on the titration curve which are present in the range of from [(tentative terminal point (P))+(number of decision points (n))−2] to [(tentative terminal point (P))+(number of decision points (n))] wherein the number of decision points (n) represents the number of the measured values on portions of the titration curve previously set and used for determination of a terminal point of the titration, with the proviso that the number of the measured values are not less than 3 in each of the portions of the titration curve which extend in positive and negative directions, respectively, along the abscissa axis, on the basis of the tentative terminal point (P) as a reference point; computing, on a computer, an intermediate line (C) between the first estimation line (B 1 ) and the second estimation line (B 2 ); and computing, on a computer, an intersection point (A) of the intermediate line (C) and the straight line (D) to read out a value of the intersection point on the abscissa axis as a terminal point (a) of the titration.