Pre-Concentration and Solid Phase Extraction of Trace Amounts of Co(II)-BPHA On Octadecyl Bonded Silica Membrane Disk and its Application to the Determination of Trace Cobalt

DOI : http://dx.doi.org/10.13005/msri/040113

Download this article as: 

A sensitive, selective and rapid method has been developed for the determination μg l-1 level of cobalt based on the rapid reaction of cobalt(II) with N-benzoyl-N-phenylhydroxylamine (BPHA) and the solid phase extraction (SPE) of the colored chelate with Waters Porapak Sep-Park C18 disk. The BPHA can react with Co(II) in the presence of pH 3.9 acetic acid -sodium acetate buffer solution and cetyl trimethylammonium bromide (CTMAB) medium to form a violet chelate of a molar ratio 1:2 (cobalt to BPHA). This chelate can retained on Waters Porapak Sep-Park C18 disk quantitatively when they passed the disk as aqueous solution. After the enrichment finished, the retained chelate can be eluted from disk by 2.5 ml of ethanol (contain 5% acetic acid). In the measured solution, the molar absorptivity of the chelate is 1.58?105 l mol-1 cm-1at 636 nm, and Beer?s law is obeyed in the range of 0.01-0.42 μg ml-1. The relative standard deviation for 11 replicate sample of 0.01 μg ml-1 level is 2.28%. The detection limit is 0.01 μg l-1 (in original samples). This method can be applied to the determination of mg l-1 level of cobalt in drinking water with satisfactory results.

Cobalt; Solid phase extraction spectrophotometry; N-benzoyl-N-phenylhydroxylamine (BPHA)