Carbon Nanotubes-Loaded Silica Gel for Preconcentration of Trace Silver with Detection by Flame Atomic Absorption Spectrometry

Carbon nanotubes (CNTs) were loaded onto the surface of silica gel (SG) beads, and the CNTs/SG composite was used as a novel adsorbent for the preconcentration of trace silver in a flow system by adsorbing nascent Ag2O in solution. This treatment of the material significantly improved the mechanical strength and capability of preconcentration of CNTs. With NaOH as precipitating reagent, the nascent Ag2O in the solution was readily retained on the surface of the CNTs/SG composite and recovered afterward by elution with nitric acid (10%, V/V). The eluate was finally introduced into a flame atomic absorption spectrometer for quantification. By loading 5.4 mL of sample solution, a liner range of 1–120 μg L−1, an enrichment factor of 34.5, a detection limit of 0.35 μg L−1 and a precision of 0.5% RSD at 40 μg L−1 level (n = 7) were obtained, along with a sampling frequency of 47 h−1. The enrichment factor, the detection limit and the precision of this procedure are obviously superior to those achieved by using wither pure CNTs or pure silica gel as adsorbents. The procedure was applied for the determination of silver in water samples, and satisfactory spiking recoveries were obtained in the range of 96%–108%.