Simultaneous detection and quantitation of sodium, potassium calcium and magnesium in ocular lenses by high- performance capillary electrophoresis with indirect photometric detection

Abstract

A high-performance capillary electrophoresis (HPCE) method which can be used to quantitatively determine Na +, K +, Ca 2+ and Mg 2+ simultaneously in ocular lenses has been developed. The proteins in the lens aqueous homogenates were precipitated by 10% trichloroacetic acid. The precipitated proteins were removed after a brief centrifugation, and the supernatant containing the cations was washed with ether and directly used for HPCE analysis. A 50 μm × 75 cm fused-silica capillary was used for separation and the detection wavelength was set at 214 nm. A 20-m M imidazole at pH 6.0 containing 0.1% hydroxypropyl methyl cellulose was used as background electrolyte. Sample solution was injected at 15 kV for 10 s, and the electrophoresis was carried out at 15 kV. All the cations can be separated and quantified from the peak areas within 9 min. The values obtained by this method were comparable with commonly used flame atomic absorption and flame atomic emission spectroscopy. It is demonstrated that this HPCE method can be used to quantify all the cation levels simultaneously within a short time even in a small single rat or mice lens.