Title: First Results on Fe Solid-Phase Extraction from Coastal Seawater Using Anatase TiO2 Nano-Particles
Citation: ANALYTICAL AND BIOANALYTICAL CHEMISTRY vol. 396 no. 6 p. 2349-2361
Publication Year: 2010
JRC N°: JRC44683
ISSN: 1618-2642
URI: http://publications.jrc.ec.europa.eu/repository/handle/JRC44683
DOI: 10.1007/s00216-009-3436-y
Type: Articles in periodicals and books
Abstract: This paper describes the application of high surface TiO2 nano-particles (anatase form) for the solid-phase extraction of iron from coastal seawater samples. We compared in batch and on-(mini)column approaches (0.1g and 0.05g TiO2 per sample, respectively), combined to inductively coupled plasma masss spectrometry at medium mass resolution. We investigated the adsorption characteristics of this titania phase both by infra red spectroscopy and by varying pH conditions, and the eluant and sample flow rates and concentrations. The Fe recovery rate increased quickly to ~ 80 % from pH 2 to pH 7, and progressed more slowly to ~ 95 % at pH 10. The level of residual salinity after extraction and sample elution was modest until pH 7 (< 0.002%) and increased quickly above (multiplication by 3 at pH 10). Between pH 2 and pH 7 the capacity of retention (g Fe/g TiO2) increased faster for ultra pure water (factor 6.9) than for seawater (factor 4.8) although, globally, this titania phase was slightly more efficient with seawater than with ultra pure water. Different reaction schemes are proposed between Fe (III) species and the two main categories of titania sites at pH 2 (adsorption of [FeLx](3-x)+ via possibly the mediation of chlorines) and at pH 7 (adsorption of [Fe(OH)2]+ and precipitation of [Fe(OH)3]0). Under optimized conditions our column was operated at pH 7 and the 0.05g TiO2 material was changed only after 20 samples (with 2 mn rinsing in between samples with 6 % HCl at 1.5 g mn-1). Typically, the inlet system was pre-cleaned by pumping 6% HCl for ~2 h, and the column was conditioned by aspirating ultra pure water (1.7 g mn-1) and 0.05% ammonia (0.6 g mn-1) for 1 mn. Then 3 grams seawater sample were loaded at the same flow rate while being mixed on-line with 0.05% ammonia at 0.6 g mn-1 to adjust pH conditions. The iron retained on the oxide powder was then eluted (1.5 g mn-1) with 6% HCl for 2 mn and the ammonia was directed to the waste. We evaluated that the overall procedural blank was 220 ± 46 (2s, n=16) ng Fe kg-1. The recovery rate estimated from the Canadian CRM CASS-2 was 69.5 ± 7.6 % (2s, n=4). Typically, the relative combined uncertainty (k = 2) estimated for the measurement of ~1 ng Fe g-1 (0.45 µm filtered and acidified to pH 1.5) of seawater was ~12%. We applied our method to a similar sample, from the coastal region of the North Sea. The agreement well within stated uncertainties of our result with the value obtained independently by isotope dilution mass spectrometry further validated our method.
JRC Institute:Institute for Reference Materials and Measurements

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