Determination of Sulfate in Aminoglycoside Antibiotics by Capillary Electrophoresis with Indirect UV Detection

Abstract

Sulfate in aminoglycoside antibiotics was determined by capillary electrophoresis (CE) with indirect UV detection. Best results were achieved with background electrolytes prepared by titration of 15 mM chromic acid with 40 mM tris(hydroxymethyl)methylamine to pH 8.1; 0.2 mM cetyltrimethylammonium bromide (CTAB) was added, and finally, an applied voltage of −20 kV in a bare fused‐silica capillary. Indirect UV detection was performed at a wavelength of 276 nm. The application of a small amount of inlet pressure during the separation assisted in the attainment of a stable baseline. The optimized method was validated regarding selectivity, linearity, accuracy, precision, ruggedness, repeatability, and detection limits. The linear range for sulfate was 0.06–0.17 mg/mL. The limit of quantitation (LOQ) was 6 µg/mL. The relative standard deviation (RSD) for peak area ratio (PAR, the area of sulfate peak, divided by the area of the internal standard peak) was 0.6%. The results agreed with those obtained by the method of the current British Pharmacopoeia (BP). This method can also be applied in the determination of sulfate in some other sulfate salts of antibiotics.