Chemiluminescence analysis of enrofloxacin in surface water using the tris(1,10-phenantroline)-ruthenium(II)/peroxydisulphate system and extraction with molecularly imprinted polymers

This paper reports a sensitive, highly selective flow injection (FI) method for the chemiluminescence-based determination of enrofloxacin (ENRO), a fluoroquinolone (FQ) antibiotic, in natural water samples. The detection principle is the on-line monitored photoreaction of tris(1,10-phenantroline)ruthenium(II) [Ru(phen)32 +] with peroxydisulphate ion to give Ru(phen)33 +, which is then reduced by the antimicrobial producing the chemiluminescence (CL) signal. The low selectivity of the CL reaction required using solid-phase extraction with molecularly imprinted polymers (MISPE) in combination with the FI-CL system. Fluoroquinolone-selective MIP beads were obtained by acid etching of silica/MIP composites and packed into SPE cartridges to clean-up and preconcentrate samples prior injection into the FI-CL system. Various parameters influencing the CL signal intensity including pH, flow rate, and Ru(phen)32 + and peroxydisulphate concentrations, were optimized. The variables affecting the extraction efficiency of the polymers were also optimized in order to minimize non-specific interactions and enable the selective uptake of the antibiotics from real samples. CL measurements made over the pH range 3.8-4.2 allowed the selective determination of enrofloxacin, and measurements at pH 4.8-5.8 the quantitation of total FQs (enrofloxacin, ciprofloxacin, norfloxacin, sarafloxacin, lomefloxacin and danofloxacin). The limit of detection for enrofloxacin was 0.27 μg L− 1 when 10 mL water samples were preconcentrates. The proposed method was used to determine trace amounts of FQs in mineral and tap water, and also in water samples from the river Quibú (Cuba), all with good recoveries: 84-119% (RSD 2.1-9.3%, n = 3) for samples fortified with enrofloxacin at concentrations from 4 to 40 μg L− 1. The method was validated by HPLC with fluorescence detection.