Determination of Cr(III) and Cr(VI) in water by wavelength-dispersive X-ray fluorescence spectrometry after preconcentration with an ion-exchange resin disk

Abstract

A rapid and simple method using an ion-exchange resin disk combined with wavelength-dispersive X-ray fluorescence (WDXRF) spectrometry was developed for the determination of Cr(III) and Cr(VI) in water. A 100-ml water sample was first adjusted to pH 3 with nitric acid and then passed through an anion-exchange resin disk placed on top of a cation-exchange resin disk at a flow rate of 1 ml min −1 to separate Cr(III) and Cr(VI). Anionic Cr(VI) was preconcentrated on the upper anion-exchange resin disk, whereas cationic Cr(III) was preconcentrated on the lower cation-exchange resin disk. Each ion-exchange resin disk was dried at 100 • C for 30 min in an electric oven and coated with a commercially available laminate film. The specimens were measured using a WDXRF spectrometer. The calibration curves of Cr(III) and Cr(VI) showed good linearity in the range 1-10 µg. The detection limits corresponding to three times the standard deviation (n = 5) of blank values were 0.17 µg for Cr(III) and 0.16 µg for Cr(VI). If a 1-l water sample is used, these limits would be 0.17 and 0.16 µg l −1 , respectively. A spike test for 50 µg l −1 Cr(III) and Cr(VI) in tap water and river water showed quantitative recoveries (94-114%), although this was not observed for mineral drinking water owing to the overlap of V Kβ with Cr Kα. The recovery after overlap correction was satisfactory (115%).

Determination of Diphenylarsinic Acid, Phenylarsonic Acid and Inorganic Arsenic in Drinking Water by Graphite-furnace Atomic-absorption Spectrometry after Simultaneous Separation and Preconcentration with Solid-phase Extraction Disks

“…A 0.1 mm thick laminate film (Meiko Shokai, Japan) was used to coat the SPE disk before XRF analysis, to prevent it from being damaged by X-rays. 18,19 A Demi-Ace Model DX-15 demineralizer (Kurita Water Industries, Japan) was used to prepare deionized water. An F-52 pH meter (Horiba, Japan) was used to monitor the pH of the sample solution.…”

“…In particular, membrane disk SPEs have been used to pretreat large-volume water samples because they allow relatively high flow rates, due to their large cross-sectional areas. 16 SPE disks keep their shape during the pretreatment process to assay, so they are useful for wet analyses 17 as well as direct analyses (e.g., X-ray fluorescence (XRF) spectrometry, [18][19][20] γ-ray spectrometry, 21,22 and laser-induced breakdown spectroscopy 23 ). An analytical method using an iminodiacetate extraction disk, followed by direct introduction into GFAAS instrument, has also been reported for determining heavy metals at sub-μg L -1 levels in water.…”

“…24 Therefore, SPE disks are adaptable, and can be used for quantitative analyses using various instruments. In addition, multiple SPE disk layers allow for the simultaneous collection of different analytes (e.g., Cr(III) and Cr(VI)) 17,18 from a water sample. In this paper, we describe a method for determining DPAA, PAA, and iAs (arsenite, As(III), and arsenate, As(V)) in drinking water using SPE, followed by GFAAS.…”

Determination of Heavy Metals at Sub-ppb Levels in Water by Graphite Furnace Atomic Absorption Spectrometry Using a Direct Introduction Technique after Preconcentration with an Iminodiacetate Extraction Disk

“…In this experiment, therefore, a 100-mL deionized water sample (pH 5.6) containing 1 mg each of Co, Ni, Cu, Cd, Sn, Pb, and Bi was passed through the conditioned IED at a flow rate of 1 mL·min -1 . The IED was then dried at 100˚C for 20 min in the electric oven, coated with a commercially available laminate film to prevent damage to the IED by X-ray irradiation [6,18], and measured using μ-EDXRF spectrometer. The mapping conditions were 100 points (1 mm diameter) in 18 × 18 mm 2 of the scanning area.…”

“…In particular, disk-type SPE has been widely used to preconcentrate a large-volume water sample (e.g., 100 -1000 mL) for inorganic [2][3][4][5][6] and organic [7][8][9][10][11] analyses because it offers higher flow rates than column-type SPE owing to its large cross-sectional area. Iminodiacetate Extraction Disks (IEDs) are useful for the preconcentration of trace metals in water because of their high selectivity for heavy metals.…”