oa South African Journal of Chemistry - The Synthesis of QADMAA and its Application to the Solid Phase Extraction and Spectrophotometric Determination of Cobalt

Volume 57, Issue 1
  • ISSN : 0379-4350



In this paper, the synthesis of a new chromogenic reagent, 2-(2-quinolylazo)-5-dimethylaminoaniline (QADMAA), is reported. A sensitive, selective and rapid method for the determination of cobalt based on the rapid reaction of cobalt(II) with QADMAA and the solid phase extraction of the Co(II)-QADMAAchelate withC&lt;sub&gt;18&lt;/sub&gt; membrane disks was developed. In the presence of a pH=5.5 buffer solution and a cetyl trimethylammonium bromide (CTMAB) medium, QADMAA reacts with cobalt to form a violet complex with a molar ratio of 1:2 (cobalt to QADMAA). This chelate was enriched by solid phase extraction with C&lt;sub&gt;18&lt;/sub&gt; membrane disks and an enrichment factor of 50 was obtained. The molar absorptivity of the chelate is 1.32x10&lt;sup&gt;5&lt;/sup&gt; L mol&lt;sup&gt;-1&lt;/sup&gt; cm&lt;sup&gt;-1&lt;/sup&gt; at 616 nm in the measured solution. Beer's law is obeyed in the range of 0.01~0.6 <span style='font-family:Graeca'>m<o:p></o:p></span>g mL<sup>-1</sup>. The relative standard deviation for eleven replicate sample at the 0.01 <span style='font-family:Graeca'>m<o:p></o:p></span>g mL&lt;sup&gt;-1&lt;/sup&gt; level is 1.35%. The detection limit reached 0.02 <span style='font-family:Graeca'>m<o:p></o:p></span>g L&lt;sup&gt;-1&lt;/sup&gt; in the original samples. This method was applied with good results to the determination of cobalt in environmental samples.

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