Online incorporation of cloud point extraction to flow injection analysis

The on-line incorporation of cloud point extraction (CPE) to flow injection analysis (FIA) is demonstrated for the first time, The technical difficult ies of inducing the cloud point phenomenon, separating the surfactant-rich phase from the aqueous phase, and detecting trace amounts of analyte(s) in the presence of the highly scattering surfactant medium in an on-line FIA s ystem were resolved by the following: (1) mixing the sample solution contai ning the analyte(s) and CPE surfactant with an appropriate salting-out agen t, (2) using a collection column to entrap the analyte-containing surfactan t aggregates, and ( 3) employing the peroxyoxalate chemiluminescence reacti on for the sensitive and selective determination of the analyte(s) in the p resence of surfactant micelles, The figures of merit for the determination of coproporphyrin in pretreated urine samples were as follows: precision, 1 .1-2.2% (RSD); limit of detection, 2.0 mug/L; and the calibration curve was linear from 46 to 2319 (mu /L(r = 0.9996).