Ionic liquid-based ultrasound-assisted emulsification microextraction for the determination of ranitidine in water samples and pharmaceutical preparations

Abstract

A new extraction method is proposed for the isolation of the histamine H₂ receptor antagonist ranitidine (RNT) from aqueous samples. For this purpose, a low solvent consumption method using ultrasound-assisted emulsification microextraction (USAEME) was proposed. Ionic liquids (IL), such as 1-butyl-3-methylimidazolium hexafluorophosphate [C₄mim][PF₆] and 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide [C₄mim][Tf₂N], were used for the isolation of ranitidine. The microextraction parameters of the studied antihistaminic drug, namely, volume of extractant, pH of the sample and shaking time were optimized. The influence of foreign substances on the isolation process was tested. The separation of RNT using the IL-USAEME method enables the effective extraction and preconcentration of this analyte. The ionic liquid extracts after ultrasound-assisted emulsification microextraction were determined by spectrophotometry (UV) and high performance liquid chromatography (HPLC-UV) methods. The precision of procedures developed for the determination of the studied H₂ receptor antagonist ranged from 0.8% to 4.2%. These methods, USAEME-UV and USAEME-HPLC-UV, enable the detection of ranitidine in real samples at levels of 3 × 10⁻⁶ mol L⁻¹ and 1 × 10⁻⁷ mol L⁻¹, respectively. The developed procedures were applied for the determination of ranitidine in river water and pharmaceutical preparations.