Multi-Wavelength Determination of Cobalt by Tungsten Coil Atomic Emission Spectrometry

Abstract

A simple tungsten coil atomic emission device is used for the determination of Co in a polluted water sample. Multiple cobalt emission lines in the 340.5 to 352.7 nm range are detected simultaneously. Limits of detection at five different wavelengths ranged between 20 and 70 ng Co in a 25 μL sample volume. Summing the signals for the five different Co emission lines improves the detection limit to 10 ng. The combination of the five lines also results in improved precision (2.2% relative standard deviation for a 4 mg/L Co solution) and accuracy (102% for a polluted water reference material).

Keywords:

• Atomic emission
• Cobalt
• Multiple lines
• Tungsten coil atomizer

This article was submitted as part of a Special Memorial Issue honoring Prof. George G. Guilbault.

This material is based upon work supported by the National Science Foundation and the Department of Homeland Security through the joint Academic Research Initiatives program: NSF CBET 0736214 and DHS 2008-DN-077-ARI020-03. J.A. Nóbrega is thankful to Fundação de Amparo à Pesquisa do Estado de São Paulo for traveling funds (Process 07/57564-2).

Notes

^a The temperature (T) in Kelvin of the dry coil surface may be estimated from the current (I) in amps: T ≈ 309 I + 325 (Salido 1999).

^b Atomic emission signals were collected during this step.

^a The five emission lines used for quantitation are designated A–E.

^b Relative intensities calculated as I_345.4/I_λ where 345.4 nm is the most intense line in the region (Sansonetti 2003).

^a Based on 3 standard deviations for the blank signal and a 25 µL sample volume.

^b Precision reported as % relative standard deviation for a 4 mg/L Co solution (n = 10).

^c VHG water pollution standard 1, WPS1–100. Found values are the mean ± 1 standard deviation (n = 5).