Determination of Silver with On-Line Preconcentration Using Dithiozone Chelate and Carbon Nanotubes for Preconcentration with Detection by Flame Atomic Absorption Spectrometry

Abstract

A novel flow injection system incorporating a micro-column packed with carbon nanotubes (CNTs) as an adsorbent has been applied to the on-line preconcentration of trace silver with detection by flame atomic absorption spectrometry. Silver is first chelated by dithizone (H₂Dz), then retained on the CNTs surface and afterward quantitatively eluted by methanol. Influencing parameters, including the concentration of reaction reagent, enrichment variables, and elution variables were investigated. The adsorption mechanisms of Ag-H₂Dz chelate retained onto the CNTs surface have also been studied. By loading 6.9 mL sample solution, a linear calibration graph is obtained within the range of 3–120 µg L⁻¹ with R of 0.9996, and a detection limit (3σ) of 0.8 µg L⁻¹ is achieved, along with a precision of 1.6% R.S.D. at the 30 µg L⁻¹ level (n = 7). The dynamic sorption capacity of CNTs for silver is 122 mg g⁻¹. The procedure is demonstrated by measurement of spike recovery in a series of water samples, giving rise to spike recoveries in the range of 96.8–99.7%.

Keywords:

• Carbon nanotubes
• Flame atomic absorption spectrometry
• Flow injection
• Separation and preconcentration
• Silver

Acknowledgments

This work is financially supported by the Natural Science Foundation of China (No.20807044), the Science and Technology Foundation of Education Department of Liaoning Province (No. L2011043), and the Science and Technology Foundation of Anshan City, China (No.08SF05).

Notes

Pb-DDTC: lead diethyldithiocarbamate; PTFE: polytetrafluoroethylene; MBTSG: 2-mercaptobenzothiazole-bonded silica gel; Salen/Al₂O₃: 2, 2-[3-aza-1,5-pentanediylebis(nitrilomethylidyne)]-bisphenol immobilized on surfactant coated alumina; AtuSG: amidinothioureido-silica gel; DDTC/Al₂O₃: diethyldithiocarbamate immobilized on surfactant-coated alumina; SG: silica gel; CNTs/SG: carbon nanotubes loaded silica gel; CNTs: carbon nanotubes.