Determination of Protamine and Insulin Using Short-End Injection Capillary Electrophoresis

A fast and inexpensive method for simultaneous determination of total protamine and insulin has been developed using capillary electrophoresis in the short-end injection setup with a bare-fused silica capillary. Optimized background electrolyte consists of 45 mM aqueous solution of phosphoric acid, pH 1.85. Separation is finished within 1 min; total analysis time including preconditioning is 4 min. The method exhibits excellent linearity within the concentration range 2.5–500 μg mL⁻¹ for both analytes. Limits of detection are 1.0 and 0.7 μg mL⁻¹ for protamine and insulin, respectively. Accuracy of the method has been successfully tested on a real sample of Neutral Protamine Hagedorn Insulin (NPH insulin) injection. The background electrolyte employed is inexpensive and experiments have shown that it does not need to be exchanged for at least 20 subsequent analyses.