Determination of trace amounts of morphine in human plasma by anodic adsorptive stripping differential pulse voltammetry

New adsorptive anodic differential pulse stripping voltammetry method for the direct determination of morphine at trace levels in human plasma of addicts is proposed. The procedure involves an adsorptive accumulation of morphine on a HMDE, followed by oxidation of adsorbed morphine by voltammetry scan using differential pulse modulation. The optimum conditions for the analysis of morphine are pH 10.5, Eacc of −100 mV (vs. Ag/AgCl), and tacc of 120 s. The peak current is proportional to the concentration of morphine, and a linear calibration graph is obtained at 0.01–3.10 μg mL−1. A relative standard deviation of 1.06% (n = 5) was obtained, and the limit of detection was 3 ng mL−1. The capability of the method for the analysis of real samples was evaluated by the determination of morphine in spiked human plasma and addicts human plasma with satisfactory results.