Abstract: A novel non-chromatographic approach for direct speciation of mercury, based on the selective retention inorganic mercury and methylmercury on the inner wall of a knotted reactor by using ammonium diethyl dithiophosphate and dithizone as complexing agents respectively, was developed for flow injection on-line sorption pre-concentration coupled with chemical vapor generation non-dispersive atomic fluorescence spectrometry. With the sample pH kept at 2.0, the pre-concentration of inorganic mercury on the inner walls of the knotted reactor was carried out based on the exclusive retention of Hg-DDP complex in the presence of methylmercury via on-line merging the sample solution with ammonium diethyl dithiophosphate solution, and selective pre-concentration methylmercury was achieved with dithizone instead of ammonium diethyl dithiophosphate. A 15% (v/v) HCl was introduced to elute the retained mercury species and merge with KBH4 solution for atomic fluorescence spectrometry detection. Under the optimal experimental conditions, the sample throughputs of inorganic mercury and methylmercury were 30 and 20 h- 1 with the enhancement factors of 13 and 24. The detection limits were found to be 3.6 ng L-1 for Hg2+ and 2.0 ng L-1 for CH3Hg+. The precisions (RSD) for the 11 replicate measurements of each 0.2 µg L-1 of Hg2+ and CH3Hg+ were 2.2% and 2.8%, respectively. The developed method was validated by the analysis of certified reference materials (simulated natural water, rice flour and pork) and by recovery measurements on spiked samples, and was applied to the determination of inorganic mercury and methylmercury in biological and environmental water samples.

Abstract: It is recognized that aluminum (Al) is a potential environmental hazard. Acidic deposition has been linked to increased Al concentrations in natural waters. Elevated levels of Al might have serious consequences for biological communities. Of particular interest is the speciation of Al in aquatic environments, because Al toxicity depends on its forms and concentrations. In this paper, advances in analytical methodologies for Al speciation in environmental and biological samples during the past five years are reviewed. Concerns about the specific problems of Al speciation and highlights of some important methods are elucidated in sections devoted to hybrid techniques (HPLC or FPLC coupled with ET-AAS, ICP-AES. or ICP-MS), flow injection analysis (FIA), nuclear magnetic resonance (Al-27 NMR), electrochemical analysis, and computer simulation. More than 130 references are cited.

Abstract: An electrochemical procedure is proposed for the speciation of aluminum (At) by derivative adsorption chronopotentiometry on a hanging mercury drop electrode (HMDE) using pyrocatechol violet (PCV) as a complexing agent. Labile monomeric Al fraction (mainly inorganic Al) was determined at PH 4.9 (accumulation time 60 s, accumulation potential -0.45 V, PCV concentration 1.5 x 10^-6 mol L-1 and stripping current 5 muA), while total monomeric At fraction was determined at pH 8.2 (accumulation time 60 s, accumulation potential -0.50 V, PCV concentration 2.5 x 10^-6 mol L-1 and stripping current 5 muA). This sensitive and simple fractionation method was successfully applied to the speciation of Al in natural water samples. Five fractions were determined and measured: i) labile monomeric At (Ali); ii) total monomeric At (Ala) iii) acid reactive Al (Alr); iv) nonlabile monomeric At (Alo); v) acid soluble At (Als). The results were satisfactorily in agreement with those of the 8-hydroxyquinoline extraction/ion exchange method.

Abstract: In the present work, a new method was established by applying solid-phase extraction (SPE) to pre-concentrate and separate polymeric aluminum (Al) and using ICP-AES to determine the polymeric Al, the total monomeric Al, and the total Al in soil extracts, respectively. A modified resin was prepared with impregnated 8-hydroxyquinoline-5-sulfoxinate (HQS) on the anion-exchange resin. It has good recognition ability for Al fractions, compared to the commonly used cation ion-exchange resin, which has a better ability to adsorb cations and a weak ability to recognize detailed Al species. The optimum conditions for Al fractionation sorption, elution and separation and the interference of foreign ions were studied with the prepared resin by continuous column and batch procedures. Monomeric Al was bound to Pyrocathecol Violet (PCV) at pH 6.2, whereas the polymeric Al species did not react with PCV for at least 15 min. Because a stable complex of Al-PCV was not absorbed on the HQS modified resin, the polymeric Al could be pre-concentrated on-line by the HQS-modified resin. The adsorbed polymeric Al was eluted with 3 mL of 3 mol L-1 of HCl, and then detected by ICP-AES. The method has been applied to directly determine polymeric Al in soil extracts with high selectivity as well as a high pre-concentration factor. It gives a limit of detection of 0.6 ng mL-1 with a relative standard deviation of less than 5.7% (n = 5, 0.24 µg mL-1 Al).