Utility of solid phase extraction for UV-visible spectrophotometric determination of gallium in environmental and biological samples

Abstract

A sensitive, selective and rapid method for the determination of gallium based on the sensitive reaction of Ga(III) with 1-(2-benzothiazolylazo)-2-hydroxy-3-naphthoic acid (BTAHN) and the solid phase extraction of the BTAHN–Ga(III) complex on a column of Amberlite XAD-4 resin was developed. In the presence of 2.0 mol L⁻¹ of nitric acid solution and cetylpyridinium chloride (CPC) medium, BTAHN reacts with gallium(III) to form a deep red complex with a molar ratio of 2 : 1 {BTAHN to Ga(III)}. The complex was enriched by solid phase extraction with an Amberlite XAD-4 resin. An enrichment factor of 500 was obtained by elution of the complex from the column with a minimal amount of dimethylformamide (DMF). The molar absorptivity of the complex in DMF medium was 5.57 × 10⁷ L mol⁻¹ cm⁻¹ at 599 nm. Beer's law was obeyed in the range of 0.01–0.70 μg mL⁻¹. The relative standard deviation for eleven replicate samples at the 0.50 μg mL⁻¹ level was 0.95%. The attained detection and quantification limits amounted to 3.1 and 10.2 ng mL⁻¹, respectively. This method was applied to the determination of gallium in environmental water and biological samples with good results.