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Chapter 7 Flow-injection on-line liquid—liquid separation and preconcentration atomic spectrometry

DOI: 10.1016/s0926-4345(99)80011-x


Publisher Summary This chapter discusses the coupling of liquid–liquid separations to the principal atomic spectrometric techniques. There are two variants of liquid–liquid continuous separations: (1) dialysis and (2) liquid–liquid extraction. The main difference between them lies in the miscibility of the two liquids involved that in turn dictates the way they are brought into contact for mass transfer in practice. In dialysis processes, the two phases are miscible, so an isolation barrier is mandatory. The membrane acts as an active or passive filter that allows analytes, reaction products or interferences to be continuously separated from the liquid sample matrix. The dialyzer is thus a continuous device in which the two phases involved enter and leave. Continuous liquid–liquid extraction involves mass transfer between two immiscible phases—namely, the aqueous and the organic phase. Both phases are brought into contact to form a stream of regular, alternate segments that are subsequently separated. The dynamic extraction interface comprises both the zone of contact between the segments and the film area of the phase that wets tubing walls. A continuous liquid–liquid extractor consists of three essential elements that work in a sequential fashion —namely, a segmenter, an extraction coil, and a phase separator.

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