Spectrofluorimetric determination of tetrabenazine after photochemical derivatization in basic medium

Photochemical derivatization is proposed for the spectrofluorimetric determination of tetrabenazine (TBZ). A central composite design was used to adjust experimental conditions (60 min of UV in a 0.45 mol L(-1) NaOH solution) enabling the improvement of the analyte signal-to-blank ratio of one order of magnitude, when compared to the TBZ original fluorescence. Limit of quantification was 4.7×10(-8) mol L(-1) but the detection power can be improved at least 10 times using solid phase extraction that also allows the separation of the analyte from matrix components, enabling the analysis of biologic fluids. Linear range covered at least three orders of magnitude. The combined uncertainty of the determination (at a 5×10(-6) mol L(-1)) was 16%. Recoveries of TBZ in the analyses of a pharmaceutical formulation were in agreement with the ones obtained using a HPLC method. Recovery in saliva (5×10(-7) mol L(-1) of TBZ) was 90±3% (n=3). The procedure minimizes the use of toxic chemical derivatization reagents and the generation of hazardous waste.