Optosensor for Cinchona Alkaloids With C18 Silica Gel as a Substrate

Abstract

A flow-through optosensor for cinchona alkaloids with C ₁₈ silica gel as a substrate is proposed. The sensor is developed in conjunction with a flow-injection analysis system and is based on the retention of the cinchona alkaloids on a C ₁₈ column and the enhancement of their fluorescence. The analytical performance characteristics of the proposed sensor for the detection and quantification of these alkaloids were as follows: the detection limits for quinine, cinchonine, quinidine and cinchonidine were 2.3, 31.6, 2.3 and 31.6 ng ml ^{- 1} , respectively, with relative standard deviations of 0.9% for quinine and quinidine (20 ng ml ^{- 1} , n = 7) and 1.1% for cinchonine and cinchonidine (4.0 µg ml ^{- 1} , n = 7), respectively. Most of the common species did not interfere. The recommended method has been successfully tested for determination of quinine in pharmaceutical preparations and soft drinks.