[Preconcentration of Trace Cu(II) in Water Samples with Nano-Sized ZnO and Determination by GFAAS].

The content of copper in natural water is very low, and direct determination is difficult. Therefore, it is very meaningful for the combination of efficient separation-enrichment technology and highly sensitive detection. Based on the high adsorption capacity of Cu(II) onto nano-sized ZnO, a novel method by using nano-sized ZnO as adsorbent and graphite furnace atomic absorption spectrometry as determination means was in this work. The adsorption behaviors of Cu(II) on nano-sized ZnO was studied. Effects of acidity, adsorption equilibrium time, adsorbent dosage and coexisting ions on adsorption rates were investigated. The results showed that the adsorption efficiency was above 95% in a pH range from 3.0 to 7.0. Compared with other adsorbents for trace element enrichment such as activated carbon, nano-sized TiO2 powder, the most prominent advantage is nano-sized ZnO precipitate with the concentrated element can directly dissolved in HCl solution without any filtration and desorption process can directly analyzed by graphite furnace atomic absorption spectrometry or inductively coupled plasma atomic emission spectrometry. Compared with colloid nano materials, nano-sized ZnO is the true solution after dissolving have small matrix effect and viscosity more suitable for graphite furnace atomic absorption spectrometry or inductively coupled plasma atomic emission spectrometry detection. The proposed method possesses low detection limit (0.13 µg · L(-1)) and good precision (RSD=2.2%). The recoveries for the analysis of environmental samples were in a rang of 91.6%~92.6% and the analysis results of certified materials were compellent by using the proposed method.

[Preconcentration of ultra-trace germanium in water samples with nano-sized TiO2 colloid and determination by HGAFS with colloid sampling].

A novel method for preconcentration of ultra-trace germanium and determination by hydride generation atomic fluorescence spectrometry (HGAFS) was presented in this work. When the pH values of solution were 6.0-8.0, the adsorption efficiency of nano-sized TiO2 colloid for germanium was 97.0%-99.0% in a short time. Nano-sized TiO2 colloid was used to concentrate the ultra-trace germanium in water sample due to its high absorption capacity. After centrifugation, the supernatant fluid was removed. The sediment which contained the concentrated Ge(IV) was inverted to colloid by adding HCl of certain concentration. Ge(IV) in colloid was directly determined by HGAFS. The proposed method possesses low detection limit (3sigma) (0.060 microg x L(-1)) and good precision (the relative standard deviation (RSD) is 2.0%, n=6). The method is was also quite simple and time saving (without any filtration and desorption process). Satisfactory results were obtained when applying this method to the determination of ultra-trace germanium in water samples.

[Preconcentration of trace Pd (II) on crosslinked chitosan and determination by graphite furnace atomic absorption spectrometry].

A novel crosslinked chitosan(CCTS) not dissolved in acidic or alkaline solutions was synthesized by the crosslinking reaction of chitosan (CTS) with crosslinking agent (3-chloro-1,2-epoxypropane). The adsorption capability of Pd(II ) by CCTS was studied at different pH value. The results showed that the adsorption efficiency was above 98% after preconcentration for 20 minutes when pH values were 1-4. The effects of preconcentration time, dosage of CCTS, adsorption capacity of CCTS, sample volume, coexistent elements, and elution of Pd(II) were investigated. The mechanism of adsorption of CCTS for Pd(II) was discussed. A novel method for the preconcentration and separation of trace Pd(II) with crosslinked chitosan (CCTS) and its determination in water by graphite furnace atomic absorption spectrometry has been developed. The detection limit (3sigma, n=8) was 0.143 microg x L(-1), the relative standard deviation(RSD) was less than 5.47%, and this preconcentration method was used to detect Pd(II) in lake water and sea water with recoveries of 92%-96%. It also can be used to recycle Pd(II).

Speciation of antimony by preconcentration of Sb(III) and Sb(V) in water samples onto nanometer-size titanium dioxide and selective determination by flow injection-hydride generation-atomic absorption spectrometry.

A novel method for prevention of the oxidation of Sb(III) during sample pretreatment, preconcentration of Sb(III) and Sb(V) with nanometer size titanium dioxide (rutile) and speciation analysis of antimony, has been developed. Antimony(III) could be selectively determined by flow injection-hydride generation-atomic absorption spectrometry, coexisting with Sb(V). Trace Sb(III) and Sb(V) were all adsorbed onto 50 m g TiO2 from 500 ml solution at pH 3.0 within 15 min, then eluted by 10 ml of 5 mol/l HCl solution. One eluent was directly used for the analysis of Sb(III); to the other eluent was added 0.5 g KI and 0.2 g thiourea to reduce Sb(V) to Sb(III), then the mixture was used for the determination of total antimony. The antimony(V) content is the mathematical difference of the two concentrations. Detection limits (based on 3sigma of the blank determinations, n=11) of 0.05 ng/ml for Sb(III) and 0.06 ng/ml for Sb(V), were obtained.

[Adsorption of p-nitrophenol by nanosized titanium dioxide surface modified with 3,5-dinitrosalicylic acid].

Nanometer size titanium dioxide modified with 3,5-dinitrosalicylic acid (3,5-DA) was prepared using chemical adsorption method. The influences of surface modification on the adsorption of p-nitrophenol (PNP) and the dispersion in solvent such as water, benzene and ethanol were studied. The 3,5-dinitrosalicylic acid is bonded to the surface hydroxyl from TiO2 nanoparticles, results in the formation of a stable, six-ring complex which color is buff. The 3, 5-DA-modified TiO2 nanoparticles have good dispersive capacity in water, benzene and ethanol. Under the optimum conditions such as pH value 3, adsorption time 10 min, the adsorption ratio of PNP by TiO2 is improved from 43% to 99.9% through surface modification. A new method could be used to remove directly 3 approximately 10mg/L PNP, and the residual concentrations is below the integrated wastewater discharge standard (GB 8978-1996).