Design and evaluation of a sandwich phase separator for on-line liquid/liquid extraction

Sandwich phase separators with various groove dimensions were constructed and as part of a post-column extraction detector for liquid chromatography and for a flow-injection system. The construction materials are stainless steel and PTFE; no membranes are used. The groove volumes vary between 8 and 43 μl; the dimensions of the groove are not critical. Several aqueous (acetonitrile/water and methanol/water mixtures) and organic (1,2-dichloroethane and n-heptane) phases were successfully separated by gravity as well as by wetting. Measurement of statistical second moments showed the total disperson of the extraction system to be 2.5–4 s at the optimum separation efficiency (organic flow through detector/total organic flow) of 0.3–0.4.