Selective and sensitive spectrophotometric determination of tetrafluoroborate in waste water after ion-pair extraction using bis[2-(5-chloro-2-pyridylazo)-5-diethylaminophenolato]cobalt(III) as a counter ion

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Abstract
A simple, selective and sensitive method has been proposed for the ion-pair extraction and spectrophotometric determination of tetrafluoroborate in waste water. Tetrafluoroborate is extracted as an ion pair with bis[2-(5-chloro-2-pyridylazo)-5-diethylaminophenolato]cobalt(III) into chlorobenzene. The absorbance of the organic phase is measured at 567 nm against a reagent blank. Beer's law is obeyed over the concentration range 0.05–1.0 mg l–1 of tetrafluoroborate and the detection limit (three times the standard deviation of the blank) was 0.009 mg l–1. Relative standard deviations were 0.6–2.0%. Nitrate seriously interferes with the determination but can be decomposed by shaking with zinc powder after adjusting the acidity with 0.05 mol l–1 sulfuric acid. The proposed method can be applied satisfactorily to the determination of tetrafluoroborate in industrial and laboratory waste waters containing high concentrations of fluoride, chloride, nitrate, sulfate, borate, silicate and many other metal ions.

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