Sequential injection chromatographic determination of ambroxol hydrochloride and doxycycline in pharmaceutical preparations

The validation parameters have shown good results: linearity of determination for both compounds including internal standard (ethylparaben) >0.999; repeatability of determination (R.S.D.) in the range 0.5-5.4% at three different concentration levels, detection limits in the range 0.5-2.0 μg ml−1, and recovery from the pharmaceutical preparation in the range 99.3-99.9%. The chromatographic resolution between peak compounds was >5.0 and analysis time was <9 min under the optimal conditions. The method was found to be applicable for routine analysis of the active compounds ambroxol hydrochloride and doxycycline in various pharmaceutical preparations.