Cost effective dual-stage flow injection/sequential injection hybrid for continuous liquid-liquid extraction

Abstract

A simple and cost effective analytical system combining flow injection (FI) continuous liquid-liquid extraction and sequential injection colorimetric detection was exploited. The standard or sample was injected into a reagent stream to form a less polar ion-association compound in the aqueous phase before merging with organic solvent to produce tiny segments of aqueous and organic phases alternately. The extraction occurred at the interface of the two phases while they were flowing through an extraction coil to be collected in a test tube. Phase separation occurred in the test tube, then the organic phase was aspirated by a sequential injection (SI) system to monitor the absorbance signal with a simple LED-LDR colorimeter. The extraction and detection processes could be operated independently. That means that while the detection of the signal was in operation, a new sample could be immediately injected for the new cycle of extraction to minimize the use of chemicals and time consumption. The system has been successfully demonstrated for the determination of anionic surfactant in wastewater samples and diphenhydramine hydrochloride in pharmaceutical samples.