Application Of Quartz Tube Coating With Nanometer Oxide On Its Inner Wall For The Atom Trap

Atom trap technology （AT） was adopted for the determination of the trace elements, especially for the hydride-forming elements, in the sample from clinic, medicine, and environment. The advantage of AT was online preconcentration, high sensitivity, simple structure, easy operation, and no pollution. But AT couldn’t eliminate effectively some interference from the coexisting elements. Arsenic cause serious interference on the determination of the Hg and Se by quartz tube atom trap-vapor generation atomic absorption spectrometry （QTAT-VGAAS）. Furthmore, the sensitivity and linear range of the conventional atom trap-atomic absorption spectrometry were so limited that it couldn’t be used for the determination of the samples which concentration were low and wide range.Because of their large specific surface area, high adsorption capacity, non-toxic, low cost, nanometer SiO₂ and TiO₂ have been used as solid-phase extractant for the preconcentration of trace metals. But the application of nanometer SiO₂ and TiO₂ on the atom trap of trace metals for atomic absorption spectrometry has not been reported until now.Most of the atoms of nanometer oxide were on the surface. The surface atoms were unsaturated could bind easily with the gaseous analyte atoms on ground state, the residence time of the analyte atoms in the light path could be increased and the interference from the stray light could be decreased. The concentration of the analyte atoms in atomizer improvement is attributed to the cumulative effects of the increased residence time. A new hyphenated technique was achieved, using atom trap with quartz tube and the adsorption of nanometer oxide to online enhance the sensitivity and to expand the linear range of calibration curves for atomic absorption spectrometry. These new techniques with high sensitivity, good selectivity, simple operation, and online preconcentration could be used for the determination of the sample from food, medicine and environment and were shown as follows.（1） A new atom trap technology was established for flame atomic absorption spectrometry （FAAS） and vapor generation atomic absorption spectrometry （VGAAS）, using quartz tube and nanometer SiO₂ adsorption at the same time. This technology has been used for the determination of zinc, copper, mercury, and selenium.The nanometer SiO₂ was coated on the inner wall of slotted quartz tube or T-shaped quartz tube. The residence time of the gaseous analyte atoms in the light path was increased by the atom trap with quartz tube and the adsorption of nanometer SiO₂ and then the sensitivity of FAAS, VGAAS was improved.After coating 41.7 mg SiO₂ on the slotted quartz tube, the linear range of calibration curves was expanded from 30.0²00.0 ng mL^-1 to 5.0⁴00.0 ng mL^-1 for Zn and from 100.0¹000.0 ng mL^-1 to 50.0²000.0 ng mL^-1 for Cu, the characteristic concentrations of Zn and Cu were 2.7 ng mL^-1/1% and 10.1 ng mL^-1/1%, respectively. The achieved technique was applied to determine the concentration of Zn and Cu in herbs and tomato leaves.After coating 42.5 mg SiO₂ on the T-shaped quartz tube, the linear range of calibration curves was expanded from 10.0⁸0.0 ng mL–1 to 5.0¹50.0 ng mL–1 for Hg and from 10.0⁷0.0 ng mL–1 to 4.5¹00.0 ng mL–1 for Se, the characteristic concentrations of Hg and Se were 1.0 ng mL–1/1% and 0.8 ng mL–1/1%, respectively. The achieved technique was applied to determine the concentration of Hg and Se in herbs and hair.（2） T-shaped Quartz tube and nanometer TiO₂ adsorption atom trap-vapor generation atomic absorption spectrometry was established to improve the detection performance of mercury and selenium. After coating 67.4 mg TiO₂ on the inner wall of T-shaped quartz tube, the linear range of calibration curves was expanded from 10.0⁸0.0 ng mL–1 to 5.0¹50.0 ng mL–1 for Hg and from 10.0⁷0.0 ng mL–1 to 5.0¹00.0 ng mL–1 for Se, the characteristic concentrations of Hg and Se were 1.06 ng mL–1/1% and 0.84 ng mL–1/1%, respectively. But it can’t improve the sensitivity of As. The nanometer TiO₂ had great adsorption capacity for As, so the ground state atoms of As can’t be released. The interference from the coexistence of As on the determination of Hg and Se, could be eliminated. This method was applied to determine the concentration of Hg and Se in herbs and hair.（3） Using above-mentioned new achieved technique, the influence of major nutrients （N, P） and different iron species additions on trace elements （Cu, Zn, Se） transfer from seawater to phytoplankton, then to marine copepod was studied. The nitrate addition could induce to an increase in the uptake （including adsorption and absorption） per cell of Cu and Zn （no obvious for Se） and the total uptake of Cu, Zn, and Se by marine microalgae, including Thalassiosira weissflogii, Skeletonema costatum, and Chlorella, and obvious alga-specific effects were observed. Such influence could transfer from marine microalgae with positive-correlation to marine copepod （Tigriopus japonicus）. The uptake and transfer of these three metals by marine plankton were also affected by the iron species （including EDTA-Fe and colloidal iron）. The biogeochemical cycle of these three metals in whole marine food chain were affected by both nitrate addition and the iron species.