Analysis of insulins by high-performance liquid chromatography. III. Determination of insulins in various preparations.

A reversed-phase high-performance liquid chromatographic (HPLC) method for the determination of insulin in commercially available preparations has been developed. The HPLC method previously used for the separation of various insulins was subject to interference due to the preservatives in the preparations, so this HPLC method was modified. Insulin in preparations was determined without interference by the preservatives by means of HPLC method on a Lichrosorb RP-18 column using a mixture of acetonitrile and 5 mM tartrate buffer (pH 3.0) (27 : 73, v/v) containing 0.15 mM sodium sulfate as a mobile phase at 50°C. The values obtained by the modified HPLC method were 95.0-108.8% of the labeled potency as the sum of potencies of both insulin and desamido-insulin, and the coefficients of variation were 1.03-3.14% (n=3).