8-quinolinol-5-sulfonic acid as a non-selective post-column reagent for fluorimetric detection of trace metals in ion chromatography

A method is presented for the determination of a variety of trace metals, many of which do not form fluorescent species with 8-quinolinol-5-sulfonic acid (8-HQS). The analytes are separated from each other and other eluting species, in most cases, by using aqueous lactic acid eluents in conjunction with a low-capacity, strong cation-exchange, stationary phase. After separation the analyte ions react with Mg-EDTA to displace free magnesium ions which in turn react with 8-HQS to produce the fluorescent species [λ(em) = 390 nm, λ(em) = 510 nm]. Calibration graphs were linear for at least two orders of magnitude for all analytes with detection limits ranging from 3.3 × 10-7 to 1.4 × 10-6 M.