Development of an acetylene black-dihexadecyl hydrogen phosphate composite-modified glassy-carbon electrode, and its application in the determination of lovastatin in dosage drug forms.

An electrochemical method has been established for the determination of lovastatin (LV). It is based on the enhanced oxidation of lovastatin at a novel acetylene black-dihexadecyl hydrogen phosphate composite-modified glassy-carbon electrode (AB-DHP/GCE) in the presence of Triton X-100. This electrode was prepared by dispersion of acetylene black particles in an aqueous suspension of DHP and the formation of a stable film of the resulting AB-DHP composite on the surface of a glassy carbon electrode (GCE). As a result of modification of the AB-DHP composite, the electrochemical response of lovastatin at GCE was apparently enhanced; this was apparent as amplification of the oxidation current and the negative shift of the oxidation potential. The oxidation current can be further increased in the presence of a trace amount of Triton X-100. The enhanced oxidation of lovastatin at AB-DHP/GCE was due to enlargement of the effective electrode area, catalysis of lovastatin oxidation by AB, and accumulation of lovastatin at the hydrophobic surface of the DHP layer, which would be enhanced by the coherence with Triton X-100. The effects of some working conditions on the oxidation current of lovastatin were tested and the calibration plot was examined. The result showed that the oxidation current was a linear function of lovastatin concentration in the range 2.5 x 10(-8) - 1.0 x 10(-6) mol L(-1) and a low detection limit of 4.0 x 10(-9) mol L(-1) was obtained under optimum conditions. This electrode system was applied to the determination of lovastatin in dosage drug forms and the results were in accordance with the ultraviolet-visible spectroscopy method.