Determination Of Amino Acid By Multivariate Calibration Titration

The study of Life-science is very important in 21st century, and Amino acid analysis is one of the most important technologies in the life-science research. The main methods for amino acid analysis are reviewed. These methods include ion exchange chromatography(IEC),high performance liquid chromatography(HPLC),gas chromatography(GC) and capillary electrophoresis(CE). But it is rare to use multivariate calibration titration to study the amino acid. Multivariate calibration titration belongs to potentiometric titration. This method is based on the proportion between the concentration of the unknown sample and the volume of the titration. The determination of pure and mixed amino acids is studied by automatic potentiometric titrator, with NaOH as the titrant, whose concentratioin is settled, Hydrogen ion selective electrode as the directing electrode, Ag-AgCl electrode as the inside-reference-electrode, 1.0mol/L NaNO₃ as ionic strength adjustment buffer, and when it's necessary,0.02mol/L HCl is used to adjust the acidity of the solution. The job includes:(1) The concentration of Glu, Ser, His, Ala, Lys is determined and the results can be accepted.The errors are basically under 3%.(2) The concentration of the mixed amino acids is determined,such as Glu and Ser,His and Glu,Ser and His,Glu and Ala,His and Lys, the results are satisfying. The errors of the determination are all under 5%. Two potential ranges are selected in the determination of Ser and His,so the cumulative errors increase,the errors of this group are a little big correspondingly.(3) The existent form of amino acids is investigated and the sequence of the reactions between different amino acids,then do further research on the regularity of their ionization equilibrium constants and the pH of the different kinds of amino acids.(4)According to their titration curves, the reaction in the mixed amino acids is studied.On this basis, a summary is made on how to select the working potential of multivariate calibration titration.(5) The factors which may cause errors are discussed.(6) The virtue and the limitation of the determination of amino acid by multivariate calibration titrimetry is summarized.