Solid-phase luminescence determination of tetracycline in bottled water using chemically modified silica

Abstract

Possibility of using chemically modified silica (CMS) with covalently immobilized sulfonic and ethylenediaminetriacetate (ED3A) groups for the adsorption preconcentration and extraction of tetracycline (TC) from aqueous solutions is studied. The conditions of complex formation by europium(III) ions on the surface of these adsorbents are optimized. The effect of citrate and Eu³⁺ ions on the luminescence intensity of the Eu–TC complex is shown. The luminescence properties of SiO₂ED3AEu and SiO₂SO₃HEu systems with tetracyclines are studied depending on the acidity of the medium, time of phase contact, the ratio of the volume of the solution to the weighed portion of the adsorbent, and concentrations of the adsorbed substances. It is found that tetracycline is quantitatively extracted by CMS as a complex with europium(III) ions in pH range 6.5–8.0; adsorption capacity to tetracycline in the Henry region is as high as 0.07–0.09 mmol/g and partition coefficients are 10³–10⁴ mL/g. A procedure is developed for the solid-phase luminescence determination of tetracycline using SiO₂SO₃HEu and SiO₂ED3AEu systems with limits of detection of 0.8 and 2.0 nM, respectively; linearity range is 1 × 10^–9–1 × 10^–5 M. The procedure is tested in the analysis of model mixtures and samples of bottled water.