COLUMN PRECONCENTRATION OF ALUMINUM AND COPPER(II) IN ALLOYS, BIOLOGICAL SAMPLES, AND ENVIRONMENTAL-SAMPLES WITH ALIZARIN-RED-S AND CETYLTRIMETHYLAMMONIUM-PERCHLORATE ADSORBENT SUPPORTED ON NAPHTHALENE USING SPECTROMETRY

A column method has been established for the preconcentration of alumi num and copper(II) with Alizarin Red S and a cetyltrimethylammonium-pe rchlorate ion pair supported on naphthalene, using a simple glass-tipp ed tube. Aluminum and copper(II) react with Alizarin Red S to form wat er-soluble colored chelate anions. These chelate anions form water-ins oluble ternary complexes with the adsorbent on the inactive surface of naphthalene packed into a column. They are quantitatively retained in the pH ranges of 4.7-5.2 for aluminum and 5.0-10.0 for copper. The so lid mass is dissolved out from the column with 5 ml of dimethylformami de (DMF) for aluminum and 5 ml of ethanol for copper and the absorbanc e was measured with a spectrometer at 525 nm for aluminum and at 529 n m for copper. The calibration curves were linear over the concentratio n ranges of 0.25-5.0 mu g of aluminum in 5 mi of DMF solution and 0.50 -12.0 mu g of copper in 5 mi of ethanol solution. The molar absorptivi ties and Sandell's sensitivities were respectively calculated to be 2. 8 x 10(4) liter . mol(-1) cm(-2) and 9.62 x 10(-4) mu g . cm(-2) for a luminum and 2.5 x 10(4) liter . mol(-1) cm(-1) and 2.5 x 10(-3) mu g . cm(-2) for copper. Seven replicate determinations of sample solutions containing 2.5 mu g of aluminum and 6.0 mu g of copper gave mean abso rbances of 0.520 and 0.480 with relative standard deviations of 1.67 a nd 0.33%, respectively. Interference due to various foreign ions has b een studied and the method has been applied to the determination of al uminum in standard alloys, tea leaves, vehicle particulates, copper in coal fly ash, and commercial salt samples. (C) 1995 Academic Press, I nc.