FI-SPE-ETAAS determination of Cr(VI) by selective separation and preconcentration on a lab-made hybrid mesoporous solid microcolumn

MANUELA KIM, JORGE STRIPEIKIS, MABEL TUDINO.

Salvador, Bahía, Brasil

Simposio; 10th Rio Symposium on Atomic Spectrometry; 2008

We present the on-line determination of ultratrace levels of Cr(VI) in natural waters by means of a solid phase flow injection system coupled to an electrothermal atomizer (FI-SPE-ETAAS).  A lab-made  hybrid mesoporous material  was prepared with silica functionalized with 3-aminopropyltriethoxy sylane (APS) by sol-gel methodology  and one-pot synthesis and characterized by IR, DRX and SEM. Then, the solid was employed as filling of the microcolumn (bed volume: 7.9 µL) held in the flow through system for selective separation and preconcentration of Cr(VI). The maximum capacity of adsorption (4.35 mmol g-1) was observed for pH values between 2-3, whilst Cr (III) was found to remain in solution (adsorption capacity= 0.007 mmol g-1). Since the analyte was strongly retained by the filling in the anionic form, hydroxilamonium chloride 1.0.10-4 molL-1 in hydrochloric acid 1 mol L-1 was selected as eluent due to its redox characteristics. In this way, the sorbed Cr(VI) was easily released in the cationic form. The enrichment factor (EF) was found as a compromise between sensitivity and sample throughput and a value of 20 was obtained under optimized conditions: pH 2, sample loading 2 mL min-1, elution flow rate 1 ml min-1. Analytical performance will be presented in terms of limit of detection, linear range, RSD%, sample throughput, microcolumn lifetime, easiness of operation, etc. The applications to the determination of Cr(VI) in natural waters will be shown as well as the validation of the analytical results.