Micellar enhanced spectrofluorometric determination of labetalol through complexation with aluminium(III): application to dosage forms and biological fluids.

Two simple, sensitive, and specific spectrofluorometric procedures have been developed for the determination of labetalol (LBT) in pharmaceuticals and biological fluids. LBT was found to react with Al3+, both in acetate buffer of pH 4.5 (Procedure I) and borate buffer of pH 8.0 (Procedure II), to produce highly fluorescent stable complexes. The fluorescence intensity could be enhanced by the addition of sodium dodecyl sulfate, resulting in 3.5- and 2.7-fold increases in the fluorescence intensity for Procedures I and II, respectively. In both procedures, the fluorescence intensity was measured at 408 nm after excitation at 320 nm. The different experimental parameters affecting the development and stability of the fluorescent products were carefully studied and optimized. The fluorescence intensity-concentration plots were rectilinear over the range of 0.02-0.1 and 0.01-0.05 microg/mL with a detection limit of 0.003 and 0.001 microg/mL for Procedures I and II, respectively. The proposed method was successfully applied to commercial tablets containing LBT. The results were in good agreement with those obtained using a reference spectrofluorometric method. Furthermore, the method was applied for the determination of LBT in spiked human plasma, and the recovery (n = 4) was 93.30 +/- 2.62%. A proposal of the reaction pathway was postulated for Procedures I and II, respectively.