The Research And Application Of Potentiometric Titration Coupled With Multivariate Calibration

In chapter 1, a new potentiometric titration method for the simultaneous determination of mixed organic acids was described. In this method, the titrant is a mixture of sodium hydroxide and potassium chloride, both pH indicating electrode and chloridion indicating electrode are inserted in the titration solution. In a process of titration, both the added volume of titrant and the solution acidity at each titration point can be obtained simultaneously from two electrodes, and then the concentration of each component in the mixture can be obtained from the titration curves by multivariate calibration method. The method is free of volumetric measurements, and is independent of titration end point. The method is simple, convenient and precise. This method has been applied to the simultaneous determination of benzoic acid and salicylic acid in mixture samples with the relative standard deviation of 0.19 %～0.54 % and the recovery of 98.0 %～101.8 %.In chapter 2, a potentiometric complexometric titration method coupled with multivariate calibration was studied and a novel method for the simultaneous determination of mixed metal ions has been developed. The titrant is a mixture of EDTA and sodium fluoride, both mercury film electrode and fluorinion indicating electrode are inserted in the titration solution. In a process of titration, both the added volume of titrant and the concentration of mercury ion at each titration point can be obtained simultaneously from the potentials of two electrodes, and then the concentration of each component in the solution can be obtained from the titration curves by multivariate calibration. The method is free of volumetric measurements and independent of titration end point. The method has been applied for the simultaneous determination of copper, lead and zinc in some samples with the relative standard deviation of 0.18%～0.45% and the recovery of 99.5%～101.6%. In chapter 3, we studied a potentiometric precipitation titration method coupled with multivariate calibration and developed a novel method for the simultaneous determination of mixed halide ions. The titrant is a mixture of silver nitrate and sodium fluoride, both fluorinion indicating electrode and silver ion indicating electrode are inserted in the titration solution. In a process of titration, both the added volume of titrant and the concentration of silver ion at each titration point can be obtained simultaneously from the potentials of two indicator electrodes, and then the concentration of each component in the mixture can be obtained from the titration curves by multivariate calibration. The method is free of volumetric measurements, and is independent of titration end point. The method has been applied to the simultaneous determination of chloride, bromide, iodide in mixture samples with the relative standard deviation of 0.18%～0.45% and the recovery of 99.5%～101.6%.In chapter 4, a new potentiometric titration method coupled with multivariate calibration using a flow injection technique for the simultaneous determination of mixed organic acids has been developed. In this method, the titrant is a mixture of sodium hydroxide and potassium chloride, both pH indicating electrode and chloridion indicating electrode are inserted in the flow cell. In a process of titration, both the pH value and the volume ratio of the flowed acid and alkali solution at each titration point can be obtained simultaneously from the two electrodes, and then the concentration of each component in the mixture can be obtained from the titration curves by multivariate calibration method. The method is free of volumetric and time measurements, and reduces the consumption of reagent and sample. The method is also very quick in analysis rapidity. The method has been applied to the simultaneous determination of benzoic acid and sorbic acid in mixture samples with the relative standard deviation of 0.19%～0.37% and the recovery of 97.3%～102.6%.