theoretical analysis of peak asymmetry and sharpness of peptides by moment method

초록

The estimation of a peak shape helps not only the qualitative and quantitative analysis but an important conclusion about the operation of the chromatographic system. The peak shape may be characterized by the respective statistical moments, the peak skewness and excess. The asymmetry factor could be calculated by peak width at various peak heights and standard deviation of a chromatographic peak. The purpose of this work survey the effect of the third and fourth central moments from chromatographic elution curves of peptides, Angiotensin Ⅱ and Bradykinin on the peak shapes. The experimental variables were the sizes of different particles (5 and 15 ㎛), pore sizes (100 and 300 Å) and flow rate of mobile phase (0.5, 0.75, 1.0, 1.25, and 1.5 ㎖/min). In these experimental conditions, skewness, excess, and asymmetry factor were calculated. The chromatographic experiment was performed using Waters 600S solvent delivery system (Waters, Milford, MA, U.S.A.) with 2487 UV dual channel detector (Waters, Milford, MA, U.S.A.). Data acquisition system was Millenium32 (Waters) installed in an HP Vectra 500 PC. The flow rate of mobile phase was 1 ㎖/min and monitored at the fixed wavelength of 215 ㎚. The column (4.6x150 ㎜) was purchased from Alltech Co. As pore size in a packing is smaller, S tends to be larger. It means that the peak shape looks like a fronting. Also the same behavior was observed in particle size. At the optimum size of packings, symmetric profile will be feasible. In this work, the skewness was best in the condition of the smaller particle and larger pore, e.g.5㎛ particles with 300A pore size. The excess was a standard for sharpness of a peak. If it is larger, it is sharper. In the condition of small particle size and pore size, excess showed the largest value.