Simultaneous determination of bromide and nitrate in contaminated waters by ion chromatography using amperometry and absorbance detectors

This study describes a new ion chromatography method using a low-capacity anion exchange column with amperometric and absorbance detection for rapid and simultaneous determination of Br⁻ and NO₃⁻ in contaminated waters where one of these ions is present in excess compared to other. The use of two detectors overcomes the problem of baseline separation for Br⁻ and NO₃⁻ for accurate quantification, which was commonly encountered when using a low-capacity anion exchange column and suppressed conductivity detection mode. The method achieved accurate quantification of these two ions without requirement of baseline separation. The accuracy of 2.8% for NO₃⁻ was determined using a quality control sample obtained from UN GEMS/Water PE Study No. 6. The detection limits for Br⁻ and NO₃⁻ were 20 and 6 μg l⁻¹ (25 μl sample), respectively. Linearity of these two ions was over three orders of magnitude with a correlation coefficient >0.998. The influence of potential interfering ions was also studied followed by the determination of Br⁻ and NO₃⁻ in seawater, unsaturated zone water, soil extract and groundwater.