Vanadio En Cromatografia

Determination of Vanadium(IV) and Vanadium(V) in Benfield Samples by IEC with Conductivity Detection
2010, 72, 141–144

T. S. M. Tengku Azmi1,2,&, A. R. Mohd. Yusoff1, K. J. Abdul Karim1
1 2

Department of Chemistry, Faculty of Science, Universiti Teknologi Malaysia, 81310 UTM Skudai, Johor, Malaysia Centre of Excellence for Catalysis Science and Technology, Faculty of Science, UniversitiPutra Malaysia, 43400 UPM Serdang, Selangor, Malaysia; E-Mail: t_marliza@putra.upm.edu.my

Received: 21 October 2009 / Revised: 22 April 2010 / Accepted: 22 April 2010 Online publication: 29 May 2010

Abstract
In this study, the determination of vanadium valence state, V(IV) and V(V) has been achieved using ion-exchange chromatography with conductivity detector. In this method, V(IV) wasdetermined as V(IV)-EDTA complex and V(V) as vanadate ion. Determination of V(IV) was successfully done using 3 mM carbonate/bicarbonate/EDTA at pH 8.6 as the eluent. The additive, EDTA in the mobile phase did not seem to interfere with the V(IV) analysis. The detection of V(V) was achieved with 5 mM disodium hydrogen phosphate buffer at pH 10.4. A linear calibration graph over VO3- and V(IV) withconcentration ranges 5–15 mg L-1 gave the detection limit at 0.09 and 0.1 mg L-1, respectively. Both V(IV) and V(V) were successfully determined in Benfield sample, with concentrations of V(IV) and V(V) at 4 and 11,000 mg L-1, respectively.

Keywords
Ion-exchange chromatography Conductivity detection Benfield sample Vanadium

Introduction
The Benfield process is a well known process for H2S and CO2removal. However, during the process, corrosion is likely to occur wherever acid gases are boiling out of the rich amine solution. Because of this reason, vanadium is used Full Short Communication DOI: 10.1365/s10337-010-1630-x 0009-5893/10/07

as a corrosion inhibitor and usually added to the solution as vanadium pentoxide, V2O5 and dissolved to form vanadate ions, V5+. To be effective it mustbe maintained in the V4+/V5+ equilibrium state as this corresponds to the free corrosion potential of steel in the solution. This corrosion behavior is re-

lated to the concentration ratio of V5+ and V4+, so that by monitoring V5+ concentration can manage the corrosion protection. However, the concentrations of V5+ and V4+ are not often measured in plant due to the difficulty in measurement [1]. Awide variety of separation techniques such as ion chromatography with different separation modes coupled with various detection schemes has increasingly attracted attention for the determination of vanadium species. Since the introduction of this technique, conductivity detection has been an attractive mode of detection. It provides universal, reproducible, high-sensitivity detection of allcharged species and makes the analysis easier and more reliable. In previous studies, the total content of vanadium was determined by liquid chromatography [2–4], spectrophotometry [5–9], flow injection analysis [10, 11], atomic absorption spectrometry [12, 13], atomic emission spectrometry [14], colorimetric [15] and electrochemical methods [16]. De Beer and Coetzee [2] studied vanadium speciation byion chromatography conjunction with ultraviolet (UV) detector using a carbonatebuffered (1,2-cyclohexylenedinitrilo)tetraacetic acid (CDTA) for the simultaneous

Chromatographia 2010, 72, July (No. 1/2) Ó 2010 Vieweg+Teubner Verlag | Springer Fachmedien Wiesbaden GmbH

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determination of V(IV) and V(V). They found that interfering metals such as Cr(VI) eluted at the solvent front, close tothe V(IV) peak. Moreover, the absorbance of the V(IV)-CDTA complex at 766 nm is slightly weak, hence showing the lack of sensitivity of this complex [2]. Komarova et al. [3] applied suppress ion chromatography using sodium carbonate as eluent and conductivity as a detector to speciate ethylenediaminetetraacetic acid (EDTA) complexes of V(IV) and V(V), and the EDTA monoperoxo complexes of V(V)....