Simultaneous stopped-flow determination of morphine and naloxone by time-resolved chemiluminescence

The first application of the flow analysis coupled with chemiluminescence detection and based on stopped-flow chemistry to the simultaneous determination of two components, using a two equation system, is described. The proposed method to determine simultaneously morphine and naloxone is based on the chemiluminescence oxidation of these compounds by their reaction with potassium permanganate in an acidic medium. The main feature of the system used is that the recording of the whole chemiluminescence intensity-versus-time profiles can be obtained, using the stopped-flow technique in a continuous-flow system. Then, the chemiluminescent signals obtained at two times of these profiles can be used to determine the concentration of both opiate narcotics. The effect of common emission enhancers on the chemiluminescence emission of these compounds in different acidic media, using the above-mentioned technique, was studied, in order to achieve the best conditions in which, the CL profiles of both compounds should be additive. The parameters selected were sulphuric acid 1.0 mol L⁻¹, permanganate 0.2 mmol L⁻¹ and formaldehyde 0.8 mol L⁻¹. Taken in account the different profiles of the transient CL signal obtained with each compounds, using the selected chemical conditions, two measurement times (1.4 and 4.8 s) of these responses curves were considered with the purpose to establish a simple 2 × 2 matrix calculation. Using the chemiluminiscent signals obtained at these times, a linear calibration graph was obtained for each one of the compounds between 0.01 and 1.00 mg L⁻¹ for morphine and 0.10–1.50 mg L⁻¹ for naloxone. The present chemiluminescence procedure was applied to the determination of both compounds in mixtures and was found to be satisfactory.