Simultaneous determination of theophylline and dyphylline by micellar electrokinetic chromatography and application in drug formulations

A simple micellar electrokinetic chromatography is described for well resolution of theophylline, dyphylline and caffeine. The separation was performed at 25 °C using a background electrolyte consisting of 10 mM borate buffer at pH 9 and 40 mM sodium dodecyl sulfate (SDS) as running buffer. Under this condition, good separation with high efficiency and short analyses time required is achieved. Several parameters affecting the separation of the drugs were studied, including the pH and concentrations of the borate buffer and sodium dodecyl sulfate. Using caffeine as an internal standard (I.S.), the linear range of the method for the determination of theophylline and dyphylline was over 0.03–1 μmol ml−1; the detection limit (signal-to-noise ratio 3; injection 0.3 psi, 3 s) was 0.01 and 0.02 μmol ml−1, respectively.