Amperometric determination of morphine on cobalt hexacyanoferrate modified electrode in rat brain microdialysates

The analysis of morphine in biological fluids is of vital interest in monitoring opiate abuse and in drug abuse research. In this paper, a cobalt hexacyanoferrate (CoHCF) chemically modified electrode (CME) was prepared. The electrochemical behavior of morphine at this modified electrode has been studied by cyclic voltammetry (CV). The results indicated that the modified electrode exhibited efficiently electrocatalytic oxidation for morphine with relatively high sensitivity and stability. The CoHCF CME was employed as the detector of high-performance liquid chromatography (HPLC). The peak current was linearly related to the morphine concentration in the range of 1.0 x 10^-6 M to 5.0 x 10^-4 M at + 0.60 V (vs. Ag/AgCl) with a detection limit of 5.0 x 10^-7 M (S/N of 3). Typical intra-day reproducibility (n = 5) of 2.0% and inter-day reproducibility (n = 5) of 3.8% were obtained at the 2.0 x 10^-5 M level. This method was for the first time applied to study the pharmacokinetics of morphine in rat brain after an intravenous administration of morphine (25 mg kg^-1).