Kinetic determination of propyl gallate in edible and cosmetic oils with sensitized terbium(III) luminescence detection

Abstract

A very fast, selective kinetic method for the determination of propyl gallate is proposed. The analytical parameter used for this purpose is the initial rate of the luminescence reaction between propyl gallate and terbium(III) in the presence of sodium dodecyl sulfate, and is calculated from the slope of a kinetic plot of the luminescence signal as a function of time. The luminescence signal arises from an intramolecular energy transfer between excited propyl gallate and terbium(III), which is followed by the lanthanide emission. Kinetic data can be obtained within only 0.2 s, which entails using the stopped-flow mixing technique but facilitates automation. The calibration graph is linear over the range 0.08–3.0 µg ml–1 propyl gallate and the detection limit is 0.02 µg ml–1. The relative standard deviation is close to 2%. The proposed method was applied to the determination of propyl gallate in various edible and cosmetic oil samples with a mean recovery of 99.1%.