Speciation of Dissolved Iron(III) and Iron(II) in Water by On-Line Coupling of Flow Injection Separation and Preconcentration with Inductively Coupled Plasma Mass Spectrometry

Abstract

A method has been developed for the speciation of trace dissolved Fe(II) and Fe(II) in water by on-line coupling of flow injection separation and preconcentration with inductively coupled plasma mass spectrometry (ICPMS). Selective determination of Fe(III) in the presence of Fe(II) was made possible by on-line formation and sorption of the Fe(III)-pyrrolidinecarbodithioate (PDC) complex in a PTFE knotted reactor over a sample acidity range of 0.07-0.4 mol L(-1) HCl, elution with 1 mol L(-1) HNO3, and detection by ICPMS. Over a sample acidity range of 0.001-0.004 mol L(-1) HCl, the sum of Fe(III) and Fe(II), i.e., Fe(III + II), could be determined without the need for preoxidation of Fe(II) to Fe(III). The concentration of Fe(II) was obtained as the difference between those of Fe(III + II) and Fe(III). With a sample flow rate of 5 mL min(-1) and a 30-s preconcentration time, an enhancement factor of 12, a retention efficiency of 80%, and a detection limit (3s) of 0.08 microg L(-1) were obtained at a sampling frequency of 21 samples h(-1). The relative standard deviation (n = 11) was 2.9% at the 10 microg L(-1) Fe(III) level. Recoveries of spiked Fe(III) and Fe(II) in local tap water, river water, and groundwater samples ranged from 95% to 103%. The concentrations of Fe(III) and Fe(II) in synthetic aqueous mixtures obtained by the proposed method were in good agreement with the spiked values. The result for total iron concentration in the river water reference material SLRS-3 was in good agreement with the certified value. The method was successfully applied to the determination of trace dissolved Fe(III) and Fe(II) in local tap water, river water, and groundwater samples.

Simultaneous Separation and Quantification of Iron and Transition Species Using LC-ICP-MS

“…Measurements of both dissolved Fe(II) and Fe(III) concentration are important in assessing iron's contribution in mediating numerous biogeochemical processes that involves many elements [6]. Most analytical approaches require a separate analysis of dissolved Fe(II) and total dissolved Fe, and the calculation of Fe(III) by the difference [4].…”

“…Ferrozine reacts with Fe(II) to form a stable magenta complex species, with a maximum absorbance at 562 nm, which is measured spectrophotometrically. When Fe(III) is also present in the aqueous samples, either as a true dissolved complex or in colloids, a separate reduction step with hydroxylamine (NH 4 OH·HCl) is performed to measure the total iron, with the difference ascribed to Fe(III) [5,6]. The approach lacks sufficient sensitivity for determining iron concentrations in natural waters at µg/L levels, and therefore a pre-concentration is usually required.…”

“…Alternative approaches to the ferrozine method have been proposed [6,8,9]. Yan [6] reported a method of on-line coupling of flow injection separation and preconcentration with ICP-MS, with a sample volume of 2.5 mL and detection limit of 0.08 µg/L.…”

Speciation and preconcentration of iron by cloud point extraction combined with fibre optic linear array detection spectrophotometry

“…For the determination of iron species in various samples, the following techniques have been used: complexation with specific chelating reagent followed by spectrophotometric measurement (Giokas et al, 2002;Bagheri et al, 2000;Kara and Alkan, 2001), capillary electrophoresis (Ashdown and Marriott, 2000), inductively coupled plasma mass spectrometry (Yan et al, 2000), adsorptive cathodic stripping voltammetry (Croot and Johansson, 2000), atomic adsorption spectrometry (Giokas et al, 2002;Bagheri et al, 2000), differential pulse polarography (Pournaghi-Azar and Fatemi, 2000), chemiluminescence (de Jong et al, 1998;Elrod et al, 1991) and inductively coupled plasma-optical emission spectrometry (Xia et al, 2003). The analytical techniques for determination of Fe(II) and Fe(III) were reviewed by Pehkonen (Pehkonen, 1995) and Achterberg et al (Achterberg et al, 2001).…”

Multi-Element Analysis of Saline Matrices by Inductively Coupled Plasma Mass Spectrometry Following On-line Preconcentration Using a Knotted Reactor

“…More recently, researchers have begun to explore the potential of KRs for preconcentration and matrix removal in multielemental techniques such as ICPOES [8][9][10] or ICPMS. [11][12][13][14] Metal complexations by 8-hydroxyquinoline, 15 sodium dithiocarbamates, 16 ammonium diethyldithiophosphate, 17 and ammonium 1-pyrrolidinedithiocarbamate (APDC) [18][19][20][21] have been most frequently applied in these KR sorption/preconcentration methods. KR precipitation/coprecipitation methods are based on the formation of sparely soluble precipitates, either by direct on-line precipitation/coprecipitation of the analytes from the sample matrix, or by coprecipitation on an added carrier.…”