Preconcentration of Trace Metals in Water Using a Newly Designed Thermoresponsive Chelating Polymer for the Sensitive Determination by Graphite Furnace Atomic Absorption Spectrometry

A thermoresponsive polymer containing highly dense iminodiacetic acid segments was newly designed for the efficient preconcentration of trace metals in water. The polymer was synthesized by the water-soluble carbodiimide-mediated condensation of poly(N-isopropylacrylamide-co-acrylic acid) with polyallylamine and the subsequent conversion of amino groups to iminodiacetic acid. Metal ions in water were collected by adding the thermoresponsive polymer, sodium nitrate, dodecyltrimethylammonium chroride, and buffer components and then heating the resulting solution to form polymer deposits. The use of 0.02% (w/v) thermoresponsive polymer allowed the nearly complete (>99.8%) collection of seven metals (Be, Co, Ni, Cu, Cd, In, and Pb) in the pH range of 6.8-8.3. The polymer deposits were readily collected as a condensed coagulate and dissolved with a small amount of water for the analysis by graphite furnace atomic absorption spectrometry. Because of highly efficient (100-fold) concentration, these metals at pg cm(-3)-ng cm(-3) levels were successfully determined. The precision and accuracy were evaluated by analyzing certified reference water samples.