Simultaneous Identification and Determination by LC-MS of Quaternary Ammonium Compounds with Other Active Ingredients in Drugs

The feasibility of using ultrahigh-performance liquid chromatography (UHPLC) in combination with high-resolution time-of-flight mass spectrometry (TOFMS) for simultaneous identification and determination of quaternary ammonium compounds and other active ingredients (gramicidin C, tyrothricin, benzocaine, oxybuprocaine, fenoterol) in various dosage forms was assessed. Analytes were identified using retention times, exact ion masses, and coincidence of isotope distribution patterns (mSigma). The detection limit and limit of quantitation were 0.01 - 0.05 and 0.05 - 0.1 ng/mL (ng/g), respectively, for all studied compounds. The ranges of determined concentrations were 0.01(0.05) - 100 ng/mL (ng/g). The method was verified using actual drugs. The relative standard deviation of the analytical results was <= 0.1.