High-performance liquid chromatographic determination of tiapride and its phase I metabolite in blood plasma using tandem UV photodiode-array and fluorescence detection

New bioanalytical SPE–HPLC–PDA–FL method for the determination of the neuroleptic drug tiapride and its N-desethyl metabolite was developed, validated and applied to xenobiochemical and pharmacokinetic studies in humans and animals. The sample preparation process involved solid-phase extraction of diluted plasma spiked with sulpiride (an internal standard) using SPE cartridges DSC-PH Supelco, USA. Chromatographic separation of the extracts was performed on a Discovery HS F5 250 mm × 4 mm (Supelco) column containing pentafluorophenylpropylsilyl silica gel. Mobile phase (acetonitrile–0.01 M phosphate buffer pH = 3, flow rate 1 ml min−1) in the gradient mode was employed in the HPLC analysis. Tandem UV photodiode-array → fluorescence detection was used for the determination of the analytes. Low concentrations of tiapride and N-desethyl tiapride were determined using a more selective fluorescence detector (λ(exc.)/λ(emiss.) = 232 nm/334 nm), high concentrations (500–6000 pmol ml−1) using a UV PDA detector at 212 nm with a linear response. Each HPLC run lasted 15 min. Lower limits of quantification (LLOQ) for tiapride (N-desethyl tiapride) were found to be 8.24 pmol ml−1 (10.11 pmol ml−1). The recoveries of tiapride ranged from 89.3 to 94.3%, 81.7 to 86.8% for internal standard sulpiride and 90.9 to 91.8% for N-desethyl tiapride.