Total Internal Reflected Resonance Light Scattering Determination of Chlortetracycline in Body Fluid with the Complex Cation of Chlortetracycline−Europium−Trioctyl Phosphine Oxide at the Water/Tetrachloromethane Interface

A highly selective method of chlortetracycline (CTC) is proposed on the basis of the measurements of total internal reflected resonance light scattering (TIR-RLS) at water/tetrachloromethane (H2O/CCl4) interfaces. In the pH range of 7.54−8.14, the interaction of the binary complex of Eu(III)/CTC in the presence of trioctyl phosphine oxide (TOPO) occurs at the H2O/CCl4 interface, resulting in greatly enhanced TIR-RLS signals with the maximum peak located at 340 nm. The enhanced TIR-RLS intensity is in proportion to the CTC concentration in the range 0.98∼20.0 × 10-7 mol/L. The limit of detection is 9.8 × 10-9 mol/L. Synthetic samples and body fluid samples including human urine, human serum, and fresh milk were determined with the recovery of 95.4−106.4% and RSD of 2.9−3.9%