We have developed a method to detect non-fluorescent analytes on standard microfluidic chip platforms equipped with fluorescence detection. We leverage isotachophoresis (ITP) to electrophoretically segregate both analytes and fluorescent species termed mobility markers into distinct zones. The fluorescent marker zones bound analyte zones, so that gaps in the fluorescent signal indicate the presence and concentration of analytes. We here demonstrate separation and indirect detection of amino acids, serine and phenylalanine and organic acids, acetic acid and phenylpropionic acid (∼10 μM) using this technique. We also present an indirect detection of the environmental toxin phenol [1][2] (∼10 μM) using two mobility markers. We show preliminary numerical simulation results that provide useful guidelines in design and optimization of our indirect detection assay.

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