Kenta Hagiwara

Speciation of inorganic arsenic in drinking water by wavelength-dispersive X-ray fluorescence spectrometry after in situ preconcentration with miniature solid-phase extraction disks.

A rapid and simple method using wavelength-dispersive X-ray fluorescence (WDXRF) spectrometry after in situ solid-phase extraction (SPE) was developed for the speciation and evaluation of the concentration of inorganic arsenic (As) in drinking water. The method involves the simultaneous collection of As(III) and As(V) using 13 mm ϕ SPE miniature disks. The removal of Pb(2+) from the sample water was first conducted to avoid the overlapping PbLα and AsKα spectra on the XRF spectrum. To this end, a 50 mL aqueous sample (pH 5-9) was passed through an iminodiacetate chelating disk. The filtrate was adjusted to pH 2-3 with HCl, and then ammonium pyrrolidine dithiocarbamate solution was added. The solution was passed through a hydrophilic polytetrafluoroethylene filter placed on a Zr and Ca loaded cation-exchange disk at a flow rate of 12.5 mL min(-1) to separate As(III)-pyrrolidine dithiocarbamate complex and As(V). Each SPE disk was affixed to an acrylic plate using adhesive cellophane tape, and then examined by WDXRF spectrometry. The detection limits of As(III) and As(V) were 0.8 and 0.6 μg L(-1), respectively. The proposed method was successfully applied to screening for As speciation and concentration evaluation in spring water and well water.

On-site quantitation of arsenic in drinking water by disk solid-phase extraction/mobile X-ray fluorescence spectrometry

A rapid and simple method was developed for As determination in drinking water by solid-phase extraction (SPE)/mobile X-ray fluorescence (XRF) spectrometry. A 50 mL aqueous sample was adjusted to pH 3 with dilute hydrochloric acid, and then passed through a Ti and Zr-loaded carbon disk (TiZr-CD) to pre-concentrate the As. The SPE disk was adhered to an acrylic plate with cellophane tape, and then examined by mobile XRF spectrometry. The TiZr-CD adsorbed inorganic As (as As(III) and As(V)) and organic As (as methyl, phenyl and aromatic arsenic compounds) from water. The As calibration curve had good linearity over the range of 0.5-5 μg, and the limit of detection was 0.10 μg (2.0 μgL(-1) in As concentration). The concentrations of As in well water samples were determined using the proposed method were similar to results obtained from atomic absorption spectrometry. The proposed method did not require a power supply or a toxic solution and/or gas in any analytical step, therefore it is suitable for the on-site determination of As in drinking water.