β-Correction Spectrophotometry to Improve the Determination of Trace Amounts of Cobalt with 1-(2-Pyridylazo)-2-Naphthol

Abstract

Cobalt has been determined in ammoniacal solution with 1-(2-pyridylazo )-2-naphthol (PAN) by β-correction. spectrophotometry.   The reaction is sensitive and very selective in the presence of   thiourea to mask other ions. β-correction spectrophotometry is a   new analytical method and it can eliminate completely the effect   of excess PAN in its Co(II) coloured solution to give out the real   absorbance of the produced Co-PAN complex. All of the sensitivity,   precision and accuracy are increased. With the help of the updated   principle the complex-ratio of the formed chelate and its true molar   absorptivity and its instability constant have been still determined.   Results for cobalt showed that the detection limit was 0.014 mg/L   and Beer's law was obeyed over the concentration range 0–1.20   mg/L Co at 620 nm. It has been applied to the determination of   trace amounts of cobalt in environmental water with satisfactory results.