please tell me the formula of purity of product calculation against reference standard by HPLC
% Purity of product can be calculated as follows, in case of HPLC method.
Sample response (peak area ratio of sample) ÷ Standard response(peak area ratio of std.) × (Weight std. in mg ÷ Weight of sample in mg) × (Std. Dilutions ÷ Sample dilutions) × (% Assay of Reference Std. on as is basis).