In this study, a simple and robust capillary electrophoresis method with capacitively coupled contactless conductivity detection (C4D) is developed for the determination of the tetracycline antibiotics (1) tetracycline, (2) chlortetracycline and (3) oxytetracycline. An uncoated, fused silica capillary (60.2 cm long, 75 µm i.d.) and a solution of 50 mM tris(hydroxymethyl) aminomethane, 50 mM l-histidine and 5 mM methyl-β-cyclodextrin, without pH adjustment (pH 8.76), was used as background electrolyte. Electrophoresis at + 25 kV showed a rapid analysis with sufficient resolution among the three antibiotics in the order of tetracycline, chlortetracycline and oxytetracycline. Successive inter-injection rinsing (20 psi) of the capillary ensured intra- and inter-day repeatability (0.9–2.2% RSD and 2.0–4.5% RSD, respectively, for relative peak areas). The method showed satisfactory performance in terms of selectivity, accuracy (99.3–101.4%) and linearity (R2 = 0.999). Finally, the method was applied to commercial samples of tetracycline, oxytetracycline and chlortetracycline. This method can be applied for rapid quality control in developing countries in particular, and across the globe in general.
- Capacitively coupled contactless conductivity detection
- Capillary electrophoresis
- Tetracycline antibiotics