Determination of scandium in river water by ICP-OES with flow-injection on-line preconcentration using knotted reactor and ultrasonic nebulization

Abstract

An on-line scandium preconcentration and determination system implemented with inductively coupled plasma optical emission spectrometry (ICP-OES) associated with flow injection (FI) with an ultrasonic nebulization system (USN) was studied. The scandium was retained as the scandium-2-(5-bromo-2-pyridylazo)-5-diethylaminophenol, Sc-(5-Br-PADAP), complex, at pH 9.5. The 5-Br-PADAP solution concentration was 1 × 10⁻⁴ mol l⁻¹ and it was dissolved in a 17% (v/v) ethanol–water solution. The scandium complex was removed from the knotted reactor (KR) with 30% (v/v) nitric acid. A total enhancement factor of 1120 was obtained with respect to ICP-OES using pneumatic nebulization –Meinhard, Pneumatic Nebulizer– (25 for USN and 45 for KR) with a preconcentration time of 300 s. The value of the detection limit for the preconcentration of 30 ml of sample solution was 0.45 ng l⁻¹. The precision for 10 replicate determinations at 10 ng l⁻¹ Sc level was 3.5% relative standard deviation (RSD), calculated from the peak heights obtained. The calibration graph using the preconcentration system for scandium was linear with a correlation coefficient of 0.9996 at levels near the detection limits up to at least 50 µg l⁻¹. The method was successfully applied to the determination of scandium in river water samples.