Study on the Solid Phase Extraction and Spectrophotometric Determination of Cobalt with 2-(2-Quinolylazo)-5-Diethylaminoaniline

A sensitive, selective and rapid method for the determination of cobalt based on the rapid reaction of cobalt(II) with QADEAA and the solid phase extraction of the Co(II)-QADEAA chelate with C18 membrane disks was developed. In the presence of pH = 5.5 buer solution and cetyl trimethylammonium bromide (CTMAB) medium, QADEAA reacts with cobalt to form a violet complex with a molar ratio of 1:2 (cobalt to QADEAA). This chelate was enriched by the solid phase extraction with C18 membrane disks. An enrichment factor of 50 was obtained by elution of the chelate from the disks with a minimal amount of isopentyl alcohol. In isopentyl alcohol medium, the molar absorptivity of the chelate is 1.43 105L mol−1 cm−1at 625 nm. Beer's law is obeyed in the range of 0.01  0.6 g mL−1 in the measured solution. The relative standard deviation for 11 replicate samples of 0.01 g mL−1 level is 1.18%. The detection limit reaches 0.02 g L−1 in the original samples. This method was applied to the determination of cobalt in environmental samples with good results.

Key Words: 2-(2-quinolylazo)-5-diethylaminoaniline, cobalt, spectrophotometry, solid phase extraction.

Introduction Cobalt is an important element,

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