Copper determination in natural water samples by using FAAS after preconcentration onto amberlite XAD-2 loaded with calmagite

Abstract

A procedure for separation and preconcentration of trace amounts of copper in natural water samples, has been proposed. It is based on the adsorption of copper(II) ions onto a column of Amberlite XAD-2 resin loaded with calmagite reagent. This way amounts of copper within the range from 0.0125 to 25.0 μg, in a sample volume of 25 to 250 ml, and pH from 3.7 to 10.0 was concentrated as calmagite complex in a column of 0.50 g of Amberlite XAD-2 resin. Copper (II) ion was desorpted by using 5.0 ml of 2 mol l −1 hydrochloric acid. Detection and determination limits of the proposed procedure for 250 ml sample volume were 0.15 and 0.50 μg l −1, respectively. Selectivity test showed that (in the indicated concentration), calcium(II) (500 mg l −1), magnesium(II) (500 mg l −1), strontium(II) (50 mg l −1), iron(III) (10 mg l −1), nickel(II) (10 mg l −1), cobalt(II) (10 mg l −1), cadmium(II) (10 mg l −1) and lead(II) (10 mg l −1) did not interfere in copper determination by this procedure. Precision of the method, evaluated as the relative standard deviation by analyzing a series of seven replicates, was 2.42% for a copper mass of 1.0 μg in a sample volume of 100 ml. The accuracy of the proposed procedure was evaluated by means of copper determination in reference biological samples. The achieved results were in good agreement with certified values. The extractor system had a sorption capacity of 1.59 μmol of copper per gram of resin loaded with calmagite. The proposed procedure was applied for copper determination by FAAS in natural water samples. Samples were collected from different places of Salvador city, Bahia, Brazil. The achieved recovery, measured by the standard addition technique, showed that the proposed procedure had good accuracy. A good enrichment factor (50×) and simplicity are the main advantages in this analytical procedure.