Determination of cobalt by ICP-AES in drinking water samples using a knotted reactor with flow injection on-line

FARIAS, GUSTAVO F.; MOYANO, SUSANA; GÁSQUEZ, JOSÉ A.; WUILLOUD, RODOLFO G.; MARTINEZ, LUIS D.

The Journal of the Argentine Chemical Society

ASOCIACION QUIMICA ARGENTINA

Año: 2002 vol. 9 p. 77 - 86

An on-line cobalt preconcentration and determination system using a knotted reactor (KR) implemented with inductively coupled plasma atomic emission spectrometry (ICP-AES) associated to flow injection (FI) with ultrasonic nebulization (USN) was studied. The cobalt was retained as the complex cobalt-2-(5-bromo-2-pyridylazo)-5-diethylaminophenol (Co-(-Br-PADAP)), at pH 8.2. The cobalt complex was removed from the KR with 30% v/v nitric acid. A total enhancement factor of 140 was obtained with respect to ICP-AES using pneumatic nebulization (14.8 for USN and 9.5 for KR). The value of detection limit for the preconceniration of 10 ml of aqueous solution was 0.03 ng.ml -1. The precision for 10 replicate determinations at the 5 ?g.l-1 Co level was 2.3% relative standard deviation (RSD), calculated with the peak heights obtained. The calibration graph using the preconcentration system for cobalt was linear with a correlation coefficient of 0.9993 at levels near the detection limits up to at least 100 ng ml -1. The method was successfully applied to the determination of cobalt in drinking water samples.