Flame atomic absorption determination of trace cobalt in steel samples using a flow‐injection on‐line separation system

Abstract

A flow-injection on-line system was developed for the trace determination of cobalt by flame atomic absorption spectrometry (FAAS) with separation and preconcentration on a minicolumn packed with a poly(aminophosphonic acid) chelating resin (PAPhA). This resin allows the selective separation of cobalt at pH 2 because Co(II) and Fe(III) are the only metal ions retained quantitatively at this pH level, and Co(II) presents a greater selectivity coefficient than Fe(III); therefore, Co(II) is preferentially complexed over Fe(III) on the active groups of the chelating resin. Elution was performed by using a small volume of 0.2 M nitric acid. At a consumption of 7 mL sample volume, the procedure resulted in an enhancement factor of 83 and yielded a detection limit of 0.15 μg/L (3σ) at a sampling frequency of 32 h−1. The precision (coefficient of variation, n = 11) was in the range 0.5–1.0% at the 1–15 μg/L level. The procedure was applied to the determination of cobalt in steel samples with high tolerance to interferences, and results obtained for a standard reference material were in good agreement with the certified value. © 1998 John Wiley & Sons, Inc. Lab Robotics and Automation 10: 299–305, 1998