On-line separation and preconcentration of hexavalent chromium on a novel mesoporous silica adsorbent with determination by solution-cathode glow discharge-atomic emission spectrometry

Abstract

A flow injection (FI)-technique based on an on-line solid phase extraction (SPE) separation system coupled with solution-cathode glow discharge-atomic emission spectrometry (SCGD-AES) detection was developed for the determination of hexavalent chromium in aqueous samples. In this system, Cr(VI) was separated and preconcentrated on a novel lysine-modified mesoporous silica (Fmoc-SBA-15) at pH 5, and detected after elution. An enrichment factor of 91 was achieved under optimized experimental conditions, at a FI flow rate of 1.5 mL min⁻¹ and 0.1 mol L⁻¹ NH₃·H₂O for Cr(VI) elution. A FI-SCGD-AES detection limit of 0.75 μg L⁻¹ could be achieved, with a linear range of 10–10 000 μg L⁻¹. The precision of nine replicate Cr(VI) measurements was 4.2% at 100 μg L⁻¹. The accuracy was validated using a certified reference material of riverine water (GBW08607).