Solvent extraction–sequential injection without segmentation and phase separation based on the wetting film formed on a Teflon tube wall

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Abstract
A novel solvent extraction–flow/sequential injection system was developed. The system is based on the film-forming characteristics of an organic phase on a Teflon tube wall. The coating solvent, aqueous sample solution and eluting solution, which were separated by air segments, were sequentially aspirated into a Teflon extraction coil. A stationary organic wetting film was formed on the wall of the extraction coil. The extractable substances in the following aqueous solution were extracted into the wetting film and remained on the tubing wall. The extracted analytes were then washed out by microlitre amounts of eluting solution and the absorbance of the eluting solution was measured in a flow-through sandwich cell. The extractable and unextractable components can be efficiently separated and simultaneously determined. The need for a segmenter and a phase separator has been eliminated and the consumption of organic solvents has been reduced to microlitres. The system can be operated at sample frequencies of 30 and 10 h–1 with enrichment factors of 30 and 150, respectively.