Abstract: A portion (200 µL) of anionic polyelectrolyte solution was injected into a water stream (0.5 ml/min), which passed through a Dowex 50W-X4 cation-exchange column (19.5 cm x 2 mm i.d.), merged with a stream (0.5 ml/min) of NH3 buffer solution of pH 10 and passed through a mixing coil (1 m x 0.5 mm i.d.). A stream (0.5 ml/min) of 0.5 mM Cat-floc polymer (Wako Pure Chem. Co.) merged with a stream (0.5 ml/min) of 20 mM NaNO3 containing 0.6 mM sodium dodecylbenzenesulfonate, passed through a mixing coil (3 m x 0.5 mm i.d.), merged with the polyelectrolyte-containing stream and passed through a similar 1 m mixing coil prior to detection by a dodecylbenzenesulfonate-selective PVC-membrane electrode (cf. Anal. Sci., 1987, 3, 121). The calibration graph was linear from 0.1-1 mM potassium poly(vinyl sulfonate), the detection limit was 25 µM and the RSD (n = 5) was ~1.3%. The sampling rate was 10/h. Linear calibration graphs were also obtained for 0.1-1 mM sodium alginate and 0.1-1 mM carrageenan.