The homogeneity and stability of reference materials for the determination of Cd in white and brown rice grains were evaluated using atomic absorption spectrometry (AAS) after HNO 3 H 2 SO 4 digestion. months. The rice grain reference materials were stable for 5 months for white rice grain and for 6 months for brown rice grain. Elemental mapping images of the Cd of a longitudinal section of a white rice grain and a brown rice grain, using a micro-X-ray fluorescence instrument, suggested that the added Cd is present in the outer layers of the rice grain reference materials. The rice grain reference materials with a Cd concentration of approximately 0.31 mg kg –1 , prepared in this study, can be used for validating the AAS determination of Cd in white and brown rice grains.

We developed a reference material (RM) for the determination of hexavalent chromium (Cr(VI)) in tap water. The tap water RM was prepared by adding a Cr(VI) standard solution to the raw material without acidification, i.e. , under the original pH conditions of 7.6, because the decrease in the concentration of Cr(VI) was observed when the tap water had been adjusted to pH 1 with HNO_3. The prepared tap-water RM (2 L) was packed in 10 fluororesin (PFA) bottles with an inside plug (200 mL each). Each PFA bottle (Cr(VI)-containing tap water) was sealed in a reclosable poly bag and then stored at 5°C in a refrigerator. The tap water RM had a Cr(VI) concentration of 51 μg L^−1. The concentration of Cr(VI) was determined by diphenylcarbazide absorptiometry using a 100-mm quartz cell. The detection limit of Cr(VI) in the sample solution corresponding to three-times the standard deviation ( n = 5) of blank values was 0.51 μg L^−1. The homogeneity of Cr(VI) in the tap water RM was evaluated by an analysis of the variance after the Cochran test. There was no significant difference between the within-bottle and between-bottle variances of the analytical results, indicating that the tap water RM was sufficiently homogeneous. The stability of Cr(VI) in the tap water RM was investigated by monitoring the Cr(VI) concentration over a period of 6 months. The slope of the regression line of the Cr(VI) concentration versus the storage time did not significantly differ from zero, indicating that the tap water RM was stable for 6 months. The concentrations (50–51 μg L^−1) of Cr(VI) in the tap water RM were in good agreement with the total chromium concentrations (50–51 μg L^−1) obtained by atomic absorption spectrometry.

A preparation method of arsenic‐containing white rice grains as calibration standards was developed for the X‐ray fluorescence (XRF) analysis of arsenic in rice grains. Calibration standards were prepared by adding 10 g of white rice grains (from Japan) to 100 ml methanol‐containing dimethylarsinic acid corresponding to 2–100 µg arsenic. The mixture was heated, dried at 150 °C, cooled to room temperature, and then stored in a silica gel desiccator. A total of 5.0 g of each calibration standard was packed into a polyethylene cup (32 mm internal diameter and 23 mm height) covered with a 6‐µm‐thick polypropylene film and then analyzed by wavelength‐dispersive XRF spectrometry. The calibration curve for arsenic obtained from the white rice grains containing arsenic showed good linearity over a concentration range of 0.21–5.00 mg kg−1 arsenic. The limit of detection of arsenic was 0.080 mg kg−1. To check the reliability of the XRF method, the concentrations of arsenic in six samples of grain cereals and two samples of flour were compared with those obtained by atomic absorption spectrometry after acid decomposition. The values obtained by both analytical methods showed good agreement. Copyright © 2016 John Wiley & Sons, Ltd.

A solid sampling/graphite furnace atomic absorption spectrometry was developed for the determination of Dy in rock with a lithium tetraborate glass-bead technique. A 1 : 1 glass bead was prepared from a rock sample and lithium tetraborate flux for the cross-validation of the glass bead/X-ray fluorescence analysis, and then crushed into fine powder under 250 of particle size. The resulting powder was mixed with graphite powder at a ratio of 1 : 3 in an alumina mortar. A 1.0-2.0 mg portion of the mixture was weighed on a platform, inserted into a graphite tube, and atomized according to an optimized heating program. Dy was determined by using a calibration curve drawn with the glass bead powder of volcanic rock reference materials. The lifetime of the graphite tube and the platform were prolonged, and the integrated absorbance of Dy improved remarkably with the addition of graphite powder to glass bead powder. The coexistence of a large amount of lithium tetraborate caused a sensitizing effect to direct the atomization of Dy in rock. The calibration curve of Dy showed good linearity (r = 0.998) up to 1.4 ng, and the lower limit of detection was 0.07 ng, which corresponds to 0.28 ppm using 0.25 mg rock sample. Analytical values of Dy in plutonic rock reference materials showed good agreement with the reference values. The relative standard deviations (n = 5) of the proposed method were 6.6 % for 9.4 ppm of Dy and 8.9 % for 1.2 ppm of Dy in plutonic rock reference materials. The proposed method was useful for the cross-validation of glass bead/X-ray fluorescence analysis of Dy in granitic rock samples.

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 13mm ϕ SPE miniature disks. The removal of Pb2+ from the sample water was first conducted to avoid the overlapping PbLα and AsKα spectra on the XRF spectrum. To this end, a 50mL 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 12.5mLmin−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 0.6μg L−1, respectively. The proposed method was successfully applied to screening for As speciation and concentration evaluation in spring water and well water.

Standard bottom ash for elemental analysis of trace elements was developed and evaluated. Standard ash of municipal solid waste was prepared by sieving, pulverizing and homogenizing ash sample (bottom ash; Kyushu, Japan). The concentrations of Cr, Ni, Cu, Zn, Sr, Zr, Cd, Sn, Sb and Pb in the ash standard were given with alkali fusion/atomic absorption spectrometry (AAS) or inductively coupled plasma atomic emission spectrometry (ICP-AES) analysis. The homogeneity of the ash powder was estimated by analysis of variance after Cochran test. The concentrations of 12 hazardous elements (Cl, Cr, Ni, Cu, Zn, Br, Sr, Zr, Cd, Sn, Sb, Pb) determined by X-ray fluorescence (XRF) analysis were used for analysis of variance, after validation of the quantitative results of these elements with reference materials (coal fly ash: NIST 1633b, fly ash: BCR-176R). For the determination of Cl and Br, X-ray tube power was used under 1.0 kW (50 kV-20 mA) to prevent the volatilization with X-ray irradiation. There is no significant difference between the within-bottle variance and the between-bottle variance, indicating that the ash powder was sufficiently homogenous. The concentrations determined using XRF analysis were approximately the same as those resulting from AAS or ICP-AES analysis.

A new method for the separate determination of Chromium(III) (Cr(III)), Chromium(VI) (Cr(VI)), and Cr(III) acetylacetonate (Cr(acac)3) in water was developed using a cation-exchange extraction disk (CED) and an anion-exchange extraction disk (AED) combined with metal furnace atomic absorption spectrometry (MFAAS). A 100-mL water sample was adjusted to pH5.6 and passed through the CED placed on the AED. Cr(acac)3 and Cr(III) were adsorbed on the CED, and Cr(VI) was adsorbed on the AED. The adsorbed Cr(acac)3 was eluted with 50mL of carbon tetrachloride, followed by the elution of Cr(III) with 50mL of 3molL−1 nitric acid. Cr(VI) was eluted with 50mL of 3molL−1 nitric acid. The chemical species of Cr eluted from the CED with carbon tetrachloride was identified as Cr(acac)3 using infrared spectroscopy. The eluate of Cr(acac)3 was diluted to 100mL with carbon tetrachloride, and those of Cr(III) and Cr(VI) were diluted to 100mL with deionized water. All of the solutions were subsequently analyzed by MFAAS. The calibration curve for the Cr(acac)3 aqueous solutions exhibited good linearity in the range of 0.1 to 1ng. The detection limit of Cr, which corresponded to three times the standard deviation (n=10) of the blank values, was 20pg. The recovery test for Cr(III), Cr(VI), and Cr(acac)3 exhibited desirable results (96.0%–107%) when 5μg of each species (50μgL−1) was added to 100mL water samples (i.e., tap water, rainwater, and bottled drinking water). In a humic acid solution, Cr(acac)3 was quantitatively recovered (103%), but Cr(III) and Cr(VI) exhibited poor recoveries (i.e., 84.8% and 78.4%, respectively).

An analytical method for short-lived nuclides in rainwater using gamma-ray spectrometry combined with solid-phase extraction on an ion-exchange extraction disk has been developed. Rapid pretreatment is important in determining radioactive nuclides in rainwater, because short-lived nuclides disintegrate and decrease for sampling and measurements. The appropriate measurement time for each radioactive nuclide in rainwater was considered. The disk-shaped ion-exchange resin and chelating resin enable a simple concentration of trace metals in environmental water. A rainwater sample was passed through Empore (TM) ion-exchange disks of Cation-SR and Anion-SR, pretreated with methanol for 10 minutes. The radioactivity of short-lived nuclides in rainwater samples was determined by using a HP-Ge spectrometer. Several environmental radionuclides (Be-7, I-131, Cs-134, Cs-137, (212)pb, (214)pb, Bi-212 and Bi-214) were identified on the gamma-ray spectra of rainwater samples. A spike test for three analytes (T1, Pb and Bi) showed good recoveries (94-100%) for rainwater. The present method is more rapid than the conventional method.

A preparation method of Cd-containing rice grain was developed for X-ray fluorescence (XRF) analysis. Cd-containing rice grain was prepared by putting the base rice grain (white rice; Akita, Japan) into methanol containing an appropriate amount of Cd and then heating and cooling. The resulting rice grain was packed into a polyethylene cup (32 mm internal diameter X 23 mm height) covered with a 6-mu m-thick polypropylene film for XRF analysis. In the XRF measurement of Cd K alpha, Cd-containing rice grain had a sufficient durability, stability, and repeatability. The calibration curve of Cd constructed with a suite of Cd-containing rice grains showed good linearity (r = 0.996) in the range of 0.50 - 9.8 mg kg(-1), whose concentrations of Cd were determined with atomic absorption spectrometry (AAS) using HNO3-H2SO4 decomposition after the XRF measurements. The lower limit of detection of Cd was 0.13 mg kg(-1). The target concentrations of Cd in rice grains were in good agreement with the values obtained by AAS after acid decomposition.

A simple method of graphite-furnace atomic-absorption spectrometry (GFAAS) after solid-phase extraction (SPE) was developed for the determination of diphenylarsinic acid (DPAA), phenylarsonic acid (PAA), and inorganic arsenic (iAs) in drinking water. This method involves the simultaneous collection of DPAA, PAA, and iAs using three stacked SPE disks, i.e ., an Empore SDB-XD disk (the upper layer), an activated carbon disk (the middle layer), and a Cation-SR disk loaded with Zr and Ca (ZrCa-CED; the lower layer). A 200-mL aqueous sample was adjusted to pH 3 with nitric acid and passed through the SPE disks at a flow rate of 15 mL min^–1, to concentrate DPAA on the SDB-XD disk, PAA on the activated carbon disk, and iAs on the ZrCa-CED. The As compounds were eluted from the disks with 10 mL of ethanol containing 0.5 mol L^–1 ammonia solution for DPAA, 20 mL of 1 mol L^–1 ammonia solution for PAA, and 20 mL of 6 mol L^–1 hydrochloric acid for iAs. The eluates of DPAA, PAA, and iAs were diluted to 20, 25, and 25 mL, respectively, with deionized water, and then analyzed by GFAAS. The detection limits of As (three-times the standard deviation ( n = 3) of the blank values) were 0.13 and 0.16 μg L^–1 at enrichment factors of 10 and 8, respectively, using a 200-mL water sample. Spike tests with 2 μg (10 μg L^–1) of DPAA, PAA, and iAs in 200 mL of tap water and bottled drinking water showed good recoveries (96.1 – 103.8%).

A preparation method for Cd-containing brown rice grains as calibration standards was developed for X-ray fluorescence (XRF) analysis of Cd in rice grains. Calibration standards were prepared by adding 10g of base rice grains (from Japan) to 100ml of methanol containing 5-100 mu g of Cd. The mixture was heated, cooled, and stored in a silica gel desiccator. Seven grams of each calibration standard was packed into a polyethylene cup (32-mm internal diameter and 23-mm height) covered with a 6-mu m-thick polypropylene film and then subjected to XRF analysis. The calibration curves of Cd in brown and white rice grains showed good linearity in 0.50-10mgkg(-1). The detection limits of Cd in brown and white rice grains were 0.14 and 0.12mgkg(-1), respectively. The slopes of the calibration curves for Cd in brown and white rice grains were slightly different owing to absorption effects. The absorption effects were corrected using the ratio of the intensity of Cd K to that of Rh K-Compton scattering. After correction, the calibration curves of Cd in brown and white rice grains showed identical slopes. The spike test for 5mgkg(-1) of Cd in white rice grains (from Thailand), using the corrected calibration curves, showed quantitative recoveries (92-97%). Copyright (c) 2013 John Wiley & Sons, Ltd.

A direct analysis method combining an iminodiacetate extraction disk (IED) with graphite furnace atomic absorption spectrometry was developed for the determination of Co, Ni, Cu, Cd, Sn, Pb, and Bi at sub-ppb levels in water.A 100 mL water sample was adjusted to pH 5.6 with nitric acid and a 1 mol•L -1 ammonium acetate solution, and then passed through an IED (diameter, 47 mm; effective filtering diameter, 35 mm) at a flow rate of 80 -100 mL•min -1 to preconcentrate seven analytes.The IED was dried at 100˚C for 20 min in an electric oven, and 110 -145 small disks, each 2 mm in diameter, were punched out from the IED.A small disk was introduced into the graphite furnace and atomized according to a heating program.For Cd, Sn, Pb, and Bi measurements, Pd was used as a chemical modifier to enhance the absorbances.Calibration was performed using aqueous standard solutions.The detection limits, corresponding to three times the standard deviation (n = 5) of the blank values, were 0.092 μg•L -1 for Co, 0.12 μg•L -1 for Ni, 0.40 μg•L -1 for Cu, 0.077 μg•L -1 for Cd, 0.92 μg•L -1 for Sn, 0.61 μg•L -1 for Pb, and 0.80 μg•L -1 for Bi with an enrichment factor of 140 using a 100-mL water sample.A spike test for the seven analytes in tap water, rainwater, river water, and mineral drinking water showed quantitative recoveries (93% -108%).

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%). Copyright © 2011 John Wiley & Sons, Ltd.

A simple method using solid-phase extraction combined with metal furnace atomic absorption spectrometry was developed for the determination of Cr(III) and Cr(VI) at sub-ppb levels in water. A 500-ml water sample was adjusted to pH 3 with nitric acid and then passed through an iminodiacetate extraction disk placed on a cation-exchange extraction disk at a flow rate of 20 - 40 ml min-1 for concentrating Cr(III). The filtrate was adjusted to pH 10 with aqueous ammonia and then passed through an anion-exchange extraction disk at a flow rate of 2 ml min-1 for concentrating Cr(VI). The Cr(III) and Cr(VI) collected were eluted with 40 ml of 3 moll-1 nitric acid for Cr(III) and 40 ml of 1 gl-1 diphenylcarbazide solution for Cr(VI). Each eluate was diluted to 50 ml with deionized water and injected into a U-type tungsten board on the metal furnace. The calibration curves of Cr(III) and Cr(VI) showed good linearity in the range of 0.1 - 0.5 ng. The detection limits corresponding to three times the standard deviation (n = 5) of blank values were 8.1 pg for both Cr(III) and Cr(VI). The analytical value of total Cr (Cr(III) + Cr(VI)) in certified reference material of river water (JSAC 0302-3) was in good agreement with the reference value. The recovery test for 0.50 μg (1.00 μgl-1) of Cr(III) and Cr(VI) added to 500 ml of the water samples showed sufficient values (98.1 - 106%), except for river water sampled downstream due to relatively higher CODMn value. The relative standard deviations (n = 5) were less than 5% for both Cr(III) and Cr(VI).