Effect of tetraphenylphosphonium chloride on d.c. and differential-pulse polarograms of synthetic food colouring matters

Abstract

Tetraphenylphosphonium chloride (TPPC) has a pronounced effect on the d.c. and differential-pulse (d.p.) polarograms of some synthetic food colouring matters. The d.c. half-wave potentials and d.p. peaks of two pyrazole azo colouring matters, tartrazine and Yellow 2G, and of the triphenylmethane colouring matter Brilliant Blue FCF, are shifted to more negative potentials on the addition of TPPC. The mean limiting diffusion currents and peak currents of these and certain other synthetic colouring matters are altered significantly on its addition, the changes being greater in d.p. polarography. For both d.c. and d.p. polarograms the changes occur at TPPC concentrations up to 100 µg ml–1; above this concentration half-wave and peak potentials and limiting diffusion and peak currents change very little in most instances. The implication of these effects on the use of polarography for the determination of synthetic food colouring matters is discussed.