Two simple and fast electrochemical methods for simultaneous determination of promethazine and codeine

Two new analytical procedures for fast and simultaneous determination of promethazine (PRO) and codeine (COD) have been developed. One method is based on batch injection analysis with multiple pulse amperometric detection (BIA–MPA) and the other is based on capillary electrophoresis with capacitively coupled contactless conductivity detection (CE–C4D). Both methods are simple, robust, precise (RSD < 1.6 %, n = 10), present high analytical frequency (∼80 injections h−1) and generate reduced volume of waste. The BIA–MPA procedure provides linear range from 5 to 25 mg L−1 and 8 to 40 mg L−1 (for PRO and COD, respectively) and limits of detection of 0.065 and 0.135 mg L−1 (for PRO and COD, respectively). The CE–C4D procedure provides linear range from 58 to 290 mg L−1 and 122–610 mg L−1 (for PRO and COD, respectively) and limits of detection of 20 and 28 mg L−1 (for PRO and COD, respectively). The results obtained with the CE–C4D and BIA–MPA methods were compared to those obtained by HPLC and similar results were obtained (95% confidence level).