Extraction based on the flow-injection principle: Part 2. Determination of codeine as the picrate ion-pair in acetylsalicylic acid tablets

Abstract

Codeine in aqueous samples is extracted as its picrate ion pair into chloroform in a continuous flow system. The sample is introduced into an aqueous picrate stream buffered at pH 6.5 ; its dispersion gives controlled mixing before the aqueous stream is segmented by a chloroform stream. A specially constructed fitting is included to produce segments, typically 5–10 mm long, which pass into a Teflon coil (2 m long; inner diameter, 0-8 mm). At the outlet of the coil. the phases are separated and a fraction of the chloroform phase is passed through a spectrophotometric flow cell. The sample volume is in the range 25–40 μl, the sampling rate about 60 h , and the relative standard deviation of the order of 1%.