SINGLE-PHASE LIQUID-LIQUID-EXTRACTION IN MONOSEGMENTED CONTINUOUS-FLOW SYSTEMS

Monosegmented continuous-flow analysis (MCFA) was evaluated for the re alization of automatic single-phase liquid-liquid extraction. The sing le-phase mixture is generated by confluence of three solutions (isobut yl methyl ketone-thenoyltrifluoroacetone (IBMK-TTA), aqueous sample so lution and ethanol). The resulting homogeneous solution is passed thro ugh a sample loop of an MCFA manifold and introduced into a reaction c oil. Rapid and almost complete reaction between the analyte and comple xing agent is obtained in the single phase. Subsequently, the single-p hase monosegment containing the analyte complexed by TTA is broken int o two phases (organic and aqueous) by adding saturated NaNO3 solution. The organic portion containing the extracted analyte finally occupies the superior part of the monosegment and is passed through an on-line spectrophotometric detector. The system does not make use of a segmen ter or separation device such as is usually employed in continuous-flo w extraction methods. The sensitivity of the MCFA single-phase approac h is closer to that of the conventional manual extraction method while samples can be processed at 60-80 h(-1).