Study of silica-manganese oxide hybrid material as a new solid phase for on-line continuous flow enrichment of Cd(II) ions coupled to flame atomic absorption spectrometry
2013
Lima, Giovana de Fátima | Ferreira, Vitor Sottero | Godoy, Naiara Vieira | Medeiros, Rafael Franklin | Garrido, Francisco Manoel dos Santos | Ribeiro, Emerson Schwingel | Nakagaki, Shirley | Segatelli, Mariana Gava | Bezerra, Marcos Almeida | Tarley, César Ricardo Teixeira
The main purpose of the present work is to synthesize and characterize a new sorbent material, which contains manganese oxide particles finely dispersed in a silica matrix, and evaluate its ability to improve the detectability of flame atomic absorption spectrometry (FAAS) for on-line determination of trace Cd(II) in aqueous and biological samples. The surface area, pore volume and micropore size of the sorbent were found to be 232m²g⁻¹, 0.0303cm³g⁻¹ and 1.7nm, respectively. To accomplish the on-line sorbent preconcentration, 20.0mL of a pH 9.0 Cd(II) solution at a flow rate of 10.0mLmin⁻¹ were preconcentrated onto 320mg of the SiO₂/MnOₓ material packed into a mini-column and then eluted with 1.0molL⁻¹ HNO₃ toward the FAAS detector. The following analytical features were obtained: linear responses to Cd(II) ions in the range of 1.0–50.0μgL⁻¹ (r=0.9968), detection limit of 0.20μgL⁻¹, preconcentration factor of 39.4, concentration efficiency of 19.7min⁻¹, consumptive index of 0.51mL, and analytical frequency of 20h⁻¹. The dispersion of manganese oxide in the SiO₂ matrix promoted a 2.15-fold improvement on detectability of Cd(II) ions in comparison with an analytical curve built with SiO₂ as sorbent. The accuracy of the preconcentration method was verified through the analysis of natural water samples employing addition/recovery tests and GF AAS as reference technique, and analysis of certified reference materials — Lobster Hepatopancreas (TORT-2) and NIST SRM 1643e (“Trace elements in natural waters”).
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