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

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 232 m(2) g(-1), 0.0303 cm(3) g(-1), and 1.7 nm, respectively. To accomplish the on-line sorbent preconcentration, 20.0 mL of a pH 9.0 Cd(II) solution at a flow rate of 10.0 mL min(-1) were preconcentrated onto 320 mg of the SiO2/MnOx material packed into a mini-column and then eluted with 1.0 mol L-1 HNO3 toward the FMS detector. The following analytical features were obtained: linear responses to Cd(II) ions in the range of 1.0-50.0 mu g L-1 (r = 0.9968), detection limit of 0.20 mu g L-1, preconcentration factor of 39.4, concentration efficiency of 19.7 min(-1), consumptive index of 0.51 mL, and analytical frequency of 20 h(-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). (C) 2012 Elsevier B.V. All rights reserved.