Potentiometric determination of some food additives and their binding to a polycationic species using polyion sensors

Polycation-sensitive membrane electrodes based on dinonylnaphthalene sulfonate (DNNS) were examined for the determination of some polyanions, namely xanthan (Xanth), alginate (Alg), carboxymethyl cellulose (CMC), and carrageenan (Carr). The potentiometric titrations of polyanionic analytes yielded sharp end points and correlative stoichiometries. After the determinations were successfully performed in saline, these polyanions were also determined in some food products consumed in Bolu (Turkey). In addition, the titration data were used to estimate the interactions between titrant and polyanionic analytes. The equilibrium constants, Keq , and the number of titrant binding sites (n) per mole of analyte polyanion were calculated using Scatchard plots. The accuracy of the assayed method was confirmed by recovery experiments in spiked samples. Dynamic ranges for the determination of polyanionic analytes were 2–20 μg/mL for CMC, 1–8 μg/mL for Xanth, 0.5–4 μg/mL for Alg, and 2–20 μg/mL for Carr. LOD values were 2 μg for CMC and Carr, 1 μg for Xanth, and 0.5 μg for Alg.