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On-line preconcentration of niobium(V) and tantalum(V) as 4-(2-pyridylazo) resorcinol–citrate ternary complexes in geological samples by ion interaction high-performance liquid chromatography

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Vachirapatama, N and Doble, P and Haddad, PR (2000) On-line preconcentration of niobium(V) and tantalum(V) as 4-(2-pyridylazo) resorcinol–citrate ternary complexes in geological samples by ion interaction high-performance liquid chromatography. Journal of Chromatography A, 885 (1-2). pp. 369-375. ISSN 0021-9673

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Abstract

4-(2-Pyridylazo) resorcinol (PAR) and citrate were used as pre-column complexing agents for the determination of Nb(V) and Ta(V) as ternary complexes in geological samples. Aliquots of 2 ml of the standard and sample solutions containing the Nb(V) and Ta(V) complexes were loaded onto a concentrator column (C18, 0.4 cm×4.6 mm) with a carrier mobile phase comprising 20% (v/v) methanol and containing 5 mM acetic acid, 5 mM citric acid and 10 mM tetrabutylammonium bromide (TBABr), pH 6.5 at 2 ml/min for 2 min, with the effluent being directed to waste. An automatic switching valve was then switched to flush both complexes from the concentrator column onto a C18 analytical column using a mobile phase comprising 32% (v/v) methanol and containing 5 mM acetic acid, 5 mM citric acid and 3 mM TBABr, pH 6.5 for 2.5 min. The switching valve was then switched back to the original position, and cleaned with methanol for 7 min to eliminate unwanted species still adsorbed to the concentrator column. This procedure prevented later eluting compounds from reaching the analytical column, which reduced the overall run time. The detection limits of Nb(V) and Ta(V) (determined at a signal-to-noise ratio of 3, detection wavelength of 540 nm and a 2-ml sample volume) were 0.012 and 0.039 ppb for Nb(V) and Ta(V), respectively. Recoveries of Nb(V) and Ta(V) were 99.4 and 96.2%, respectively. The HPLC results obtained from the reference granite and basalt samples agreed well with inductively coupled plasma MS and certified values, but the HPLC method yielded slightly low values of the Nb/Ta ratio.

Item Type: Article
Keywords: Niobium; Tantalum; Inorganic cations; Metal complexes; Geological samples; Sample preparation; Complexation
Journal or Publication Title: Journal of Chromatography A
Page Range: pp. 369-375
ISSN: 0021-9673
Identification Number - DOI: 10.1016/S0021-9673(99)01159-0
Additional Information: The definitive version is available at http://www.sciencedirect.com
Date Deposited: 31 Oct 2008 05:39
Last Modified: 18 Nov 2014 03:52
URI: http://eprints.utas.edu.au/id/eprint/7921
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