Browsing by Author "Lai, B"
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- ItemThe application of synchrotron radiation induced X-ray emission in the measurement of zinc and lead in Wistar rat ameloblasts(Elsevier, 2007-10) Arora, M; Kennedy, BJ; Ryan, CG; Boadle, RA; Walker, DM; Harland, CL; Lai, B; Cai, ZH; Vogt, S; Zoellner, H; Chan, SWYThe development of analytical techniques for the measurement of trace elements in cellular compartments of developing teeth remains an important methodological issue in dental research. Recent advances in third generation synchrotron facilities have provided high brilliance X-ray sources that can be effectively used to study trace element distributions in small spatial regions with low detection limits. The present study describes for the first time the application of synchrotron radiation induced X-ray emission (SRIXE) in measuring the distribution of zinc and lead in the ameloblasts of developing Wistar rat teeth. Wistar rats were fed a standard rat diet, containing the normal dietary requirements of zinc, ad libitum and exposed to 100ppm of lead in drinking water. Resin embedded sections of first mandibular molars were analysed using a 13.3keV incident monochromatic X-ray beam focussed to a 0.2μm spot. Characteristic X-rays arising from the entire thickness of the sample were measured using an energy dispersive detector for quantitative analysis of elemental concentrations. The results showed that intranuclear concentrations of zinc were greater than levels in the cytoplasm. Furthermore, nuclear and cytoplasmic concentrations of zinc in the maturation stage (742±27 and 424±25ppm, respectively) were significantly higher than the zinc levels observed in the nucleus and cytoplasm of presecretory stage ameloblasts (132±10 and 109±10ppm, respectively) (p<0.05). A clear lead signal above the background was not detected in the ameloblasts and lead concentrations could only be reliably measured in the developing enamel. Overall, SRIXE was an effective method of studying the spatial distribution of zinc in the cells of developing teeth and offered a unique combination of sub-micron spatial resolution and parts-per-million detection limits (0.8–1 and 0.6–1ppm for zinc and lead, respectively). © 2007, Elsevier Ltd.
- ItemCan synchrotron micro-x-ray fluorescence spectroscopy be used to map the distribution of cadmium in soil particles?(CSIRO Publishing, 2007-10-30) Milham, PJ; Payne, TE; Lai, B; Trautman, RL; Cai, ZH; Holford, P; Haigh, AM; Conroy, JPPlants take up cadmium (Cd) from the soil, and the concentration of Cd in some plant products is a health concern. Plant uptake of Cd is poorly predicted by its concentration in soils; consequently, there is interest in the binding and distribution of Cd in soil. Synchrotron micro-X-ray fluorescence spectroscopy (micro-XRFS) is the most sensitive method of observing this distribution. We used beam-line 2-ID-D of the Advanced Photon Source (APS), Argonne, to test whether this technique could map the Cd distribution in 5 soils from Greater Sydney that contained 0.3-6.4 mg Cd/kg. A subsample of one soil was spiked to contain similar to 100 mg Cd/kg. Cadmium was readily mapped in the Cd-enriched subsample, whereas in the unamended soils, only one Cd-rich particle was found; that is, sensitivity generally limited Cd mapping. We also examined a sample of Nauru phosphorite, which was a primary source of much of the Cd in farm soils on the peri-urban fringe of Greater Sydney. The phosphorite contained similar to 100 mg Cd/kg and the Cd was relatively uniformly distributed, supporting the findings of an earlier study on an apatite from Africa. The micro-XRFS at beam-line 2-ID-D of the APS can be reconfigured to increase the sensitivity at least 10-fold, which may allow the distribution of Cd and its elemental associations to be mapped in particles of most agricultural soils and facilitate other spectroscopic investigations. © 2007, CSIRO Publishing