Rapid optimized separation of bromide in serum samples with capillary zone electrophoresis by using glycerol as additive to the background electrolyte.

Lithium salts are still one of the most popular therapeutic approaches to the treatment of bipolar disorders, notwithstanding the introduction of more modern, less toxic drugs. Because of a narrow therapeutic range, lithium serum concentrations must be strictly monitored during the treatment to avoid life-threatening neurotoxicity. For this purpose, methods based on flame photometry or ion-selective electrodes are usually applied. The aim of the present work was to develop and validate a simple method for the determination of lithium in serum based on capillary zone electrophoresis with indirect detection. A validation of the method was carried out, including a comparison with an automated routine method based on ion-selective electrodes.

After decades of neglect, bromide has recently been re-introduced in therapy as an effective anti-epileptic drug. The present paper describes the methodological optimization and validation of a method based on capillary zone electrophoresis for the rapid determination of bromide in serum using a high-viscosity buffer and a short capillary (10 cm). The optimized running buffer was composed of 90 mM sodium tetraborate, 10mM sodium chloride, pH 9.24 and 25% glycerol. The separation was carried out at 25 kV at a temperature of 20 degrees C. Detection was by direct UV absorption at 200 nm wavelength. The limit of detection (signal-to-noise ratio=5) in serum was 0.017 mM. The precision of the method was verified in blank serum samples spiked with bromide, obtaining intra-day and day-to-day tests, relative standard deviation values <or=0.2% in terms of migration times and values <2% in terms of peaks areas, respectively.