Differential- Pulse Polarographic Determination of Doxycycline in Serum and Urine

The polarographic behavior of doxycyline has been studied in phosphate buffer at different pH (2-9). The compound shows four reduction peaks at pH 2-4 , three reduction peaks are observed at pH 5&6 and only two reduction peaks at pH 7-9.
The best well-defined two peaks observed at pH 7.0, appearing at-1.09 V and -1.26 V versus Ag/AgCl, sat.KCl are used in this study for microdetermination of doxycycline. The lowest experimental determination limit is 1.85 x 10-7 M . The method is successfully applied to the determination of doxycycline in vivo (serum and urine).