Quantitative analysis of quinidine analogs using ion-pairing HPLC

Area of Science:

• Pharmacology
• Analytical Chemistry
• Organic Chemistry

Background:

• Quinidine is an antiarrhythmic drug often contaminated with dihydroquinidine, which also possesses antiarrhythmic properties.
• The presence of dihydroquinidine complicates the quality control, potency determination, and pharmacokinetic analysis of quinidine products.
• Developing methods to separate and quantify these related compounds is crucial for accurate pharmaceutical assessment.

Purpose of the Study:

• To explore the complete hydrogenation of quinidine to dihydroquinidine derivatives.
• To establish a method for eliminating analytical interferences in quinidine quality control.
• To enable precise determination of pharmacological potency and pharmacokinetic parameters without impurity interference.

Main Methods:

• Investigated the complete hydrogenation of quinidine and subsequent conversion to dihydroquinidine derivatives.
• Attempted separation of quinidine analogs (dihydrocupreidine and its benzoyloxy ester) using standard chromatography techniques.
• Developed and optimized an ion-pairing chromatography method utilizing n-octanesulfonate in a methanol:water mobile phase.
• Employed 9-hydroxy-4-methoxy acridine as an internal standard for quantitation.

Main Results:

• Standard chromatographic methods failed to resolve the quinidine and dihydroquinidine analogs.
• Ion-pairing chromatography proved effective in separating dihydroquinidine analogs from related compounds.
• The developed method achieved efficient separation and quantitation of dihydroquinidine analogs in spiked plasma samples, with 92-95% efficiency.

Conclusions:

• Ion-pairing chromatography is a viable and efficient technique for separating and quantifying dihydroquinidine analogs.
• This method can overcome the analytical challenges posed by dihydroquinidine impurities in quinidine products.
• Accurate quantification of dihydroquinidine enables reliable quality control, potency assessment, and pharmacokinetic studies of quinidine.