Immunologic trapping in supported liquid membrane extraction

To obtain a high degree of selectivity in sample preparation, supported liq uid membrane (SLM) extraction was combined with immunologic recognition, Th e SLM employs a hydrophobic polymer for supporting the immobilization of an organic solvent, thus forming a nonporous membrane. Said membrane separate s the aqueous sample on one side (donor) from a receiving aqueous phase on the other (acceptor), The extraction involves the partitioning of neutral c ompounds between the sample solution, continuously pumped alongside the mem brane, and the membrane. From the membrane, reextraction takes place into a second aqueous phase containing antibodies specific for the target compoun d(s), Hence, there is a formation of an antibody-antigen complex at the hea rt of the sample preparation (ImmunoSLM). When the immunocomplex: forms, th e antigen can no longer redissolve in the organic membrane, thus being trap ped in the acceptor. Consequently, the concentration gradient of free antig en over the membrane is ideally unaffected, this being the driving force fo r the process. With a surplus of antibody, the concentration of analyte in the receiving phase will easily exceed the initial sample concentration. In this work, the so formed immunocomplex was quantified on-line, using a flu orescein flow immunoassay in a sequential injection analysis (SIA) setup, T he outlined ImmunoSLM-SIA scheme was successfully applied for the extractio n of 4-nitrophenol from spiked water solutions as well as from a spiked was tewater sample, indicating that the immunoextraction can be suitable when d ealing with difficult matrixes.