Analytical Sciences

7-Amino-4-azaheptyl Grafted onto a Silica Gel as a Sorbent for the On-line Preconcentration and Determination of Iron(III) in Water Samples

Sandra V. M. de MORAES,* Mateus M. TISOTT,* Caroline D. MILCHAREK,* Jorge L. BRASIL,* Tania M. H. COSTA,* Márcia R. GALLAS ,** Edilson V. BENVENUTTI,* and Eder C. LIMA*

*Colégio Militar de Porto Alegre, Av. José Bonifácio, 363, 90040-130, Porto Alegre, RS, Brazil
**Universidade Federal do Rio Grande do Sul-Instituto de Física, Porto Alegre, RS, Brazil

A new sorbent was synthesized by anchoring 7-amino-4-azaheptyltrimetoxisilane, freshly prepared, to silica gel, producing 7-amino-4-azaheptyl anchored silica gel (AAHSG). This material was characterized by infrared spectroscopy (IR), elemental analysis (CHN), and nitrogen adsorption-desorption isotherms. Isotherms of the adsorption of Fe³⁺, Fe²⁺ and Cu²⁺ on AAHSG were recorded, which indicated that Fe³⁺ presents a higher affinity by the sorbent. Therefore, AAHSG was successfully employed as a sorbent in a simple flow system for the preconcentration of Fe³⁺ in natural water samples, such as, river water, lagoonwater, springwater, stream water, well water and two water reference materials (NIST-SRM 1640, NIST-SRM 1643d). The obtained preconcentration factor was 82.2, and the detection limit achieved was 5.9 ng ml^-1. The recovery of spiked water samples ranged from 95.0 - 103.1%.

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