Matrix effect and application of field-amplified sample injection in the analysis of four tetracyclines in waters by capillary electrophoresis

The system abilities of two chromatographic techniques, capillary electrophoresis (CE) and high performance liquid chromatography (HPLC), were compared for the analysis of four tetracyclines (tetracycline, chlorotetracycline, oxytetracycline and doxycycline). The pH, concentration of background electrolyte (BGE) were optimized for the analysis of the standard mixture sample, meanwhile, the effects of separation voltage and water matrix (pH value and hardness) effects were investigated. In hydrodynamic injection (HDI) mode, a good quantitative linearity and baseline separation within 9.0 min were obtained for the four tetracyclines at the optimal conditions; the analytical time was about half of that of HPLC. The limits of detection (LODs) were in the range of O. 28-0. 62 mg/L, and the relative standard deviations (RSDs) ( n=6) of migration time and peak area were 0. 42% -0. 56% and 2. 24% -2. 95%, respectively. The obtained recoveries spiked in tap water and fishpond water were at the ranges of 96. 3%107. 2% and 87. 1% - 105. 2%, respectively. In addition, the stacking method, field-amplified sample injection (FASI), was employed to improve the sensitivity, and the LOD was down to the range of 17.8-35.5 mu g/L. With FASI stacking, the RSDs (n= 6) of migration time and peak area were 0. 85%-0. 95% and 1. 69%-3. 43%, respectively. Due to the advantages of simple sample pretreatment and fast speed, CE is promising in the analysis of the antibiotics in environmental water.