Arsenic exists in the form of various chemical species differing in their physicochemical behaviour, toxicity, bioavailability and biotransformation. The determination of arsenic species is an important issue for environmental, clinical and food chemistry. However, differentiation of these species is a quite complex analytical task. Numerous speciation procedures have been studied that include electrochemical, chromatographic, spectrometric and hyphenated techniques. This review presents the relevant research in the field of arsenic speciation analysis with novel applications and significant advances. Stability of arsenic species and each of the analytical steps (sample collection, storage, preservation, extraction) of the arsenic speciation methods is particularly evaluated. Analytical validation and performance of these methods are also reviewed.

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The point of zero charge (pH pzc ) of three samples of commercial aluminum oxide in aqueous KNO 3 (10 -3 -10 -1 mol/dm 3 ) solution was investigated using batch equilibration, mass titration and acid-base titration methods. Structural and chemical characteristics of the alumina samples were determined by X-ray diffraction (XRD) and energy-dispersive X-ray fluorescence spectroscopy (EDXRFS). The obtained pH pzc values (5 to 8.5) dependent on the alumina/solution ratio increase with increasing ratio to a constant value. The concentration of dissolved aluminum ions as a function of solution pH (pH = 3.5 -11) exhibit a parabolic trend, with the minimum solubility at pH pzc .

Determination of total halogens in coal was investigated with oxygen bomb combustion followed by ion chromatography. Experimental parameters were optimized by fractional factorial design Downloaded by [University of Otago] at 10:25 05 July 20152 and response surface methodology. Fractional factorial design was employed in screening experiments to evaluate the influence of the oxygen pressure, catalyst, absorption solution, reduction reagent, bomb cooling time, and a combustion aid on the combustion of coal in an oxygen bomb. Response surface methodology was conducted to further refine the results obtained by fractional factorial design and to define parameters for the procedure. The accuracy and precision of combustion with ion chromatography were evaluated by the use of two certified reference materials and by fortified in-house coal standards. The limits of detection and quantification for total halogens were 0.84 and 2.80 milligrams per kilogram, respectively, for 500 milligrams samples. Ion chromatography provided relative standard deviations less than 4 percent, recoveries exceeding 95 percent, and was convenient. This method is recommended for routine determination of total halogens in coal because of its reliability.