Validation of a high-performance liquid chromatographic method for the determination of doxycycline in turkey plasma

A high-performance liquid chromatographic method for the analysis of doxycycline in turkey plasma samples using demeclocycline hydrochloride as the internal standard was developed, optimized and validated. A one-step extraction procedure and an isocratic HPLC method with UV detection were used. No interferences with endogenous compounds or with the anticoagulant were observed. Linear calibration curves (r²>0.99) were obtained in water and plasma between 0 and 600 μg ml^-1. Good recoveries for doxycycline (>66%) and demeclocycline (>72%) were seen both in water and in plasma. The coefficient of variation was <9.86% for within-day reproducibility and <7.53% for the between-day reproducibility. The deviation between the mean value found and the true value was <14.5% (accuracy). The limit of detection was 0.1 μg ml^-1 in plasma samples. A good stability of doxycycline was observed in water and in plasma samples after storage for six months at -20°C (recovery >91%).