Determination of varenicline after photochemical fluorescence enhancement using spectrofluorimetry and high-performance liquid chromatography

Photochemical derivatization (at 253 nm) of varenicline in alkaline medium (in NaOH 0.64 mol L−1) was successfully achieved aiming to induce strong fluorescence for quantitative purposes. The intense fluorescence from the produced photo-derivative covered a linear range of three orders of magnitude (10−8-10−6 mol L−1 range) allowing the spectrofluorimetric determination of the analyte in pharmaceutical formulations. For urine, the UV exposed sample was analyzed by high-performance liquid chromatography using borate buffer (0.01 mol L−1, pH 10.0). Separations were made using a C18 column with borate buffer (0.01 mol L−1, pH 10)/methanol (30:70% v/v) in isocratic elution. Detection limit was 2.5 × 10−7 mol L−1 for determination using HPLC. Measurement uncertainty was estimated and both methods were applied for the determination of varenicline in a pharmaceutical preparation and urine samples with acceptable recoveries using no expensive and toxic derivatization dyes.