Anion exchanger as a reaction/separation medium—absorptiometric determination of trace amounts of boron in waters by on-line complexation with chromotropic acid presorbed on the anion-exchange column

Abstract

A novel method of on-line absorptiometric determination for trace amounts of boron was developed based on the complexation with chromotropic acid presorbed on an anion-exchange column. On-line reaction and separation were achieved by controlling pH conditions in solutions to accelerate the 1∶2 complex formation in the concentration process at pH 3 and to stabilize the complex in the separation process at pH 8. About 75% of the boron introduced into the stream was kinetically collected as the 1∶2 complex on the column under the experimental conditions. The 1∶2 complex was satisfactorily separated from excess reagent and matrix components by changing the concentration of NaClO₄ in the eluent and its peak height on the chromatogram monitored at 350 nm was used for calibration. The sensitivity could be enhanced by increasing the sample amount introduced and the detection limits (3σ) were 162 ng dm⁻³ and 45 ng dm⁻³ of boron, when 5.0 cm³ and 13.4 cm³ of the samples were used, respectively. The method has been successfully applied to the determination of boron in samples of river water, tap water and ion-exchanged water.