Laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) was applied to characterize the diffusion behavior of doped Cr ions in ZnS crystals, in terms of Cr concentration, diffusion distribution, and diffusion coefficient. For quantification, calibration was performed with matrix-matched specimens prepared by diffusion techniques. The distributions of Cr at the crystal growth crosssections were determined by quantitative mapping to estimate the ion diffusion paths. Spatial variance of the Cr ions was obtained, revealing a sharp doping concentration gradient in the ZnS crystals. Based on the Cr distance-concentration data measured by LA-ICP-MS, the diffusion coefficients for Cr in the ZnS crystals were calculated using Fick's Second Law (simplified). The coefficient values increased with increasing temperature. This study provides not only a practical approach to the measurement of the distribution of a low-level dopant in crystals, but also a computational method for calculating diffusion coefficients from LA-ICP-MS data.

The determination of total selenium (Se) is described in nuts such as bacuri (Platonia insignis Mart.), baru (Dipteryx alata Vog.), bocaiuva (Acrocomia aculeata (Jacq.) Lodd), and cashew (Anacardium occidentale L.) (other than the well-known Brazilian nut) using hydride generation coupled to a flame atomic absorption spectrometer (HG-AAS). The best experimental conditions to generate the volatile hydride (H 2 Se) were established by multivariate statistical analysis. The conditions of the prereduction step to generate the Se hydride were optimized using the Pareto diagram and Doehlert design. Best results were achieved when 0.6 mol L -1 HCl, 1.0% (m/v) NaBH 4 in 0.5% (m/v) NaOH, and a 00-cm reaction coil were used. For Se determination by HG-AAS, analytical curves were built in the 0.50 -25.0 g L -1 range resulting in a linear coefficient correlation better than 0.9970. The accuracy of the sample preparation procedure and HG-AAS determination were evaluated by addition and recovery tests, and the recoveries were found in the 90.3-95.8% range with a relative standard deviation (%RSD) of < 4.7%. Using the proposed methodology, the limit of detection obtained was 0.1315 g L -1 with a %RSD up to 1.9%. The Se concentrations in the samples were in the 0.5150.017-0.6570.029 g g -1 Se range. The multivariate analysis applied to the experimental results showed to be a useful tool because it allows reducing the number of experiments (from 60 to 8) with satisfactory accuracy.

The present study evaluates the chemical fractionation of cadmium (Cd), a toxic heavy metal found in the coal samples of the Thar coalfield, Pakistan. An ultrasonic-assisted single-step extraction (USE) method was developed based on the reagents employed in the BCR three-step sequential extraction scheme (BCR-SES) for partitioning of Cd in coal samples. Validation of the methods was verified using certified reference material (CRM) BCR-701 Sediment and the standard addition method (recoveries > 97%). The Cd extracted through the different fractions from the CRM and the coal samples was determined by electrothermal atomic absorption spectrometry (ETAAS). The main advantage of USE is that it enhances the extraction efficiency of Cd and reduces the time from 51 hours to 2 hours using the same experimental conditions as applied for BCR-SES. The concentrations of Cd in terms of its mobility in the real samples were observed in decreasing order: acid soluble fraction < reducible fraction < oxidizable fraction. The extracted Cd obtained with BCR-SES and USE was about 6.32% lower in the coal samples obtained from the area of block-X in comparison to block-XI.

A spectroanalytical method for remediation of chromium species from contaminated water samples based on flow injection hyphenated to a flame atomic absorption spectrometer is proposed. Iminodiacetic acid (IDA) was used as the chelating agent, and the chromium-IDA complex was preconcentrated on the minicolumn filled with polytetrafluoroethylene (PTFE) beads. The chemical and flow variables were optimized. The effect of commonly occurring matrix ions on the recovery of the chromium species was also studied. For a preconcentration time of 120 s, preconcentration factors and detection limits achieved for Cr(III)/Cr(VI) were 68/59, 0.11/0.13 g L -1 , respectively. The relative standard deviation for 5 replicates of measurements for 100 g L -1 level was 1.2/1.4% for Cr(III)/Cr(VI), respectively. Real water samples collected from industrial sites and the Yamuna river were analyzed and spike recovery tests were performed. The method validation was done by analyzing the chromium concentration in NIST SRM 1640a Trace Elements in Natural Water.

A magnetic carboxyl-modified nanodiamond (MCND) was used for the magnetic solid phase extraction of Pb(II), Cd(II), and Co(II) prior to their quantification by flame atomic absorption spectrometry. The external magnetic field was used to separate the magnetic solid phase from the analyte solution in order to avoid sample loss during filtration and centrifugation. Various factors affecting the extraction efficiency of the adsorbent such as solution pH, adsorbent dose, sample volume, temperature, matrix effect, and desorption condition were optimized. The analytical parameters of the limit of detection (Pb: 0.99 g L -1 , Co: 1.73 g L -1 , Cd: 0.15 g L -1 ), preconcentration factor of 20 for the analytes, and percent relative standard deviation (Pb: 0.5%, Cd: 0.6%, Co: 0.6%) were calculated under optimized experimental condition. The kinetic data show that this adsorption process follows pseudo-second order kinetics. The thermodynamic data show that this adsorption process was feasible and exothermic in nature. The method was validated by applying the method to certified reference materials TMDA 64.2 and SPS-WW2 and natural water samples with satisfactory recovery results.

The rampant dumping of industrial effluents rich in chromium has increased pollution in the natural water bodies. The contrasting bio-toxicity of its two most stable forms, Cr(III) and Cr(VI), make it essential that they be separated and accurately determined by FI-FAAS when present together. A new chemically modified polymeric solid support, Dowex Optipore L493 functionalized with -picolinic acid, was used for the selective preconcentration of Cr(III), while Cr(VI) was determined by reduction to Cr(III). Singular analytical techniques suffer from low sensitivity and are unable to differentiate between the bio-essential Cr(III) and carcinogenic Cr(VI) states. Thus, the on-line preconcentration method aims to improve matrix elimination, enhance trace chromium detection limits, and provides faster sampling. The factors influencing Cr(III) preconcentration were optimized for maximum recovery. The chromium preconcentration efficiency in the presence of several matrix ions was studied. For a 100-second preconcentration time, a preconcentration factor of 78 and detection limit of 0.14 g L -1 were obtained. The RSD (n = 5) was 1.3%. The linearity of the determinations was up to 540 g L -1 . Spike recovery studies in real water samples were performed using standard NIST Cr(III) and Cr(VI) solutions, and a recovery of >95% was obtained. The proposed method was validated using NIST SRM 1640a Trace Elements in Natural Water.