Abstract: A novel absorption spectrometric method for the rapid and accurate determination of the colorants tartrazine and sunset yellow in beverages was established. In Tris-HCl medium with a certain acidity, ethyl violet could react with tartrazine (pH 5.69) and sunset yellow (pH 8.68) to form an ion association complex. At 506 and 646 nm, tartrazine and sunset yellow exhibited characteristic absorption, respectively, allowing their quantitative analysis. Their apparent molar absorption coefficients were 1.37 × 105 and 7.68 × 104 L/(mol·cm), respectively. There was a linear relationship between the concentration of tartrazine in the range of 0.04–9.6 mg/L and the absolute value of absorbance, and the detection limit and the quantitation limit were 0.024 mg/L and 1.29 mg/kg, respectively. There was a linear relationship between the concentration of sunset yellow in the range of 0.04–6.3 mg/L and the absorbance, the detection limit and the quantitation limit were 0.031 mg/L and 1.68 mg/kg, respectively. The spiked recoveries of tartrazine and sunset yellow in real samples were 97.0%–104% and 97.3%–103%, respectively, with relative standard deviations (n = 5) of 1.5%–2.6% and 1.2%–2.6%, respectively. The method was simple and rapid, and it could be used for the determination of tartrazine and sunset yellow in beverages with satisfactory results.

Key words: ethyl violet; tartrazine; sunset yellow; absorption spectrometry; acidity control