Application of quality by design elements for the development and optimization of an analytical method for protamine sulfate.

The purpose of this study was to develop a robust reverse phase-HPLC method for the separation of hydrolyzed protamine sulfate peptides using a quality by design approach. A Plackett-Burman experimental design was utilized to screen the effects of mobile phase pH, flow rate, column temperature, injection volume and methanol concentration on peak resolution and USP tailing. Multivariate regression and Pareto ranking analyses showed that mobile phase pH, column temperature and injection volume were statistically significant (p<0.05) factors affecting the resolution and tailing of the peaks. A Box-Behnken experimental design with response surface methodology was then utilized to evaluate the main, interaction, and quadratic effects of these three factors on the selected responses. A desirability function applied to the optimized conditions predicted peak resolutions between 1.99 and 3.61 and tailing factor between 1.02 and 1.45 for the four peptide peaks of protamine sulfate with the following chromatographic conditions; an isocratic mobile phase consisting of 100mM monosodium phosphate buffer pH 2.25, 1.8% acetonitrile and 0.3% methanol. The injection volume was 20 μl, with a column temperature of 24 °C and a flow rate of 1.0 ml/min and a total run time of less than 25 min. The optimized chromatographic method was validated according to ICH Q2R1 guidelines and applied to separate and compare the peaks of protamine sulfate from five different sources. Analyses of the peptide peaks of the five protamine sulfate samples showed no significant differences in their compositions. The results clearly showed that quality by design concept could be effectively applied to optimize an HPLC chromatographic method for protein analysis with the least number of experimental runs possible.