Quality by Design (QbD) is well established in pharmaceutical industry for manufacturing processes which includes analytical methods development. The knowledge obtained during development can establish the design space and determine suitable process controls. The application of the multivariate approach over the traditional one-factor-at-a-time (OFAT) study will be able to evaluate both each individual factor effects and factor to factor interactions. The use of QbD tool is very effective in development of analytical methods and in optimization of assay conditions.