ELSEVIER Journal of Chromatography A, 767 (1997) 303-310 JOURNAL OF CHROMATOGRAPHYA Determination of barium and strontium by capillary zone electrophoresis using an electrolyte containing sulfonazo III Miroslav Macka, Brett Paull, Per Andersson, Paul R. Haddad* Department of Chemistry., University of Tasmania, GPO Box 252C, Hobart, Tasmania 7001, Australia Received 30 July 1996; revised 29 October 1996; accepted 25 November 1996 Abstract Capillary zone electrophoresis has been applied to the separation and detection of barium(lI) and strontium(II) in the presence of excess levels of calcium and magnesium using an electrolyte containing sulfonazo III. The analytes were separated and detected as their anionic chelates, using direct spectrophotometric detection at 654 nm. Calibration curves for areas were linear in the range of 1.25 to 80 txM with correlation coefficients r=0.9996 for both barium(II) and strontium(II). Precision (as %R.S.D.) was 0.8% and 0.4% for migration times and 1.2% and 2.9% for peak areas for barium(II) and strontium(II), respectively. Recovery was determined by the standard addition method and found to be 108% for barium(II) and 104% for strontium(II). Limits of detection (based on a signal-to-noise ratio of 2 and a noise level of 2.8 10 5 AU) of 0.35 ~M (0.048 mg dm -3) for barium(II) and 0.47 ~M (0.041 mg dm 3) for strontium(II) were possible in up to 2+ 100 000-fold excess levels of Ca 2+ and Mg . The method was applied to the determination of barium(II) and strontium(II) in a mineral water sample. Keywords: Electrolytes; Barium; Strontium; Sulfonazo III 1. Introduction There is increasing interest in the determination of trace levels of barium(II) and strontium(II) in certain environmental and biological samples. Due to a number of cardiovascular problems associated with the ingestion of soluble barium(II) salts, new safe limits are being established for the level of barium(II) allowed in potable water supplies, includ- ing a proposed EC limit of 0.7 mg dm -3 placed upon the level of barium(II) allowed in bottled mineral waters [1]. Ion chromatography (IC) has been applied to the determination of all the alkaline earth metals in a *Corresponding author. wide variety of samples [2]. However, due to the retention order of the alkaline earth metals obtained when using IC, the determination of trace levels of barium(II) and strontium(II) becomes difficult when the samples contain higher levels of both calcium(II) and magnesium(II). These are eluted prior to barium(II) and strontium(II) and can cause total or partial masking of the analyte peaks. Dilution of the sample does not solve this problem when only trace levels of the analytes are present. One solution to this problem was reported by Jones et al. [3] who used a novel chelating exchange resin which allowed the elution of barium(II) and strontium(II) prior to calcium(II) and magnesium(II). This method was applied to the analysis of barium(II) and stron- tium(II) in mineral waters and gave detection limits 0021-9673/97/$17.00 Copyright © 1997 Elsevier Science B.V. All rights reserved PII S0021-9673(96)01066-7