Flow injection spectrophotometric determination of anionic polyelectrolytes using the cationic dyes

The reaction of the cationic dye, crystal violet (CV) with the anionic polyelectrolytes such as potassium poly (vinyl sulfate) (PVSK) results in a decrease of the absorbance of CV at the maximum absorption wavelength (590 nm). This change of the absorption spectra of the CV was applied to the determination of anionic polyelectrolytes using flow injection analysis (FIA) method. Anionic polyelectrolytes such as PVSK and carageenan could be determined in the concentration range from 5 × 10^-7 to 2 × 10^-5-mol/l by the proposed method. The detection limit was ca. 1 × 10^-7M for PVSK. The sampling rate was ca. 25 samples h^-1. The coexistence of foreign ions (Na⁺, Cl^-, Br^-, K⁺, SO^2-,₄, NO^-₃) at 200 times excess to an anionic polyelectrolyte did not interfere with the determination of the anionic polyelectrolyte.