A new selective and sensitive kinetic method for determination of trace amounts of vanadium(Ⅴ) (0.5～40ng/ml) based on its catalytic effect on the oxidation of azomethine H by bromate at pH 4.2 and 25 ℃ was reported...A new selective and sensitive kinetic method for determination of trace amounts of vanadium(Ⅴ) (0.5～40ng/ml) based on its catalytic effect on the oxidation of azomethine H by bromate at pH 4.2 and 25 ℃ was reported and its reaction mechanism was studied.The reaction was monitored spectrophotometrically by measuring the increase in absorbance of oxidation product of azomethine H at 436 nm after a fixed time ( 5 min ).The detection limit of the method is down to 2.0×10 -10 g/ml and the relative standard deviation (RSD) for 30 ng/ml of V(Ⅴ) is 0.26 % ( n =6). The effect of foreign ions on V(Ⅴ) determination was also discussed,and the method is mostly free from interferences of other ions.The proposed method was successfully applied to the determination of trace amounts of vanadium in water samples.展开更多
A new method is proposed for the preconcentration of vanadium(Ⅴ) with crosslinked chitosan (CCTS) and determination by graphite furnace atomic absorption spectrometry (GFAAS). The adsorption rate of vanadium(Ⅴ) by C...A new method is proposed for the preconcentration of vanadium(Ⅴ) with crosslinked chitosan (CCTS) and determination by graphite furnace atomic absorption spectrometry (GFAAS). The adsorption rate of vanadium(Ⅴ) by CCTS was 97% at pH 4.0, and vanadium(Ⅴ) was eluted from crosslinked chitosan with 2 mL 2.0 mol·L -1 chlorhydric acid and determined by GFAAS. The detection limit (3σ,n=7) for vanadium(Ⅴ) was 4.8×1 0 -12g and the relative standard deviation (R.S.D) at concentration level of 2.6 μg·L -1 is less than 3.6%. The method shows a good selectivity and high sensitivity, and it was applied to determination of vanadium(Ⅴ) in oyster and water samples. The analytic recoveries are (97±5)%.展开更多
Divanadium(Ⅴ) complex [VO(aptch)(μ-OCH3)]2(1) and two monovanadium(Ⅴ) complexes [VO(apfah))(OEt)](2a and 2b,H2aptch = 2-hydroxyacetophenone thiophene-2-car-boxylic hydrazone,H2apfah = 2-hydroxyacetophenone 2-furoic...Divanadium(Ⅴ) complex [VO(aptch)(μ-OCH3)]2(1) and two monovanadium(Ⅴ) complexes [VO(apfah))(OEt)](2a and 2b,H2aptch = 2-hydroxyacetophenone thiophene-2-car-boxylic hydrazone,H2apfah = 2-hydroxyacetophenone 2-furoic acid hydrazone) have been synthesized and characterized.Single-crystal X-ray diffraction studies reveal that 1 is a cen-trosymmetric dimer bridged by two methoxido O-atoms.Complex 1 crystallizes in the monoclinic crystal system,space groups P21/c with a = 7.4825(4),b = 17.0928(11),c = 11.6961(7) ,β = 98.172(4)o,Z = 2,F(000) = 728,μ = 0.829 mm-1,the final R = 0.0457 and wR = 0.1137 for 2654 observed reflections with I > 2(I).The vanadium(V) is coordinated to the tridentate ligand,ethanol molecule to form a distorted square-pyramidal geometry,complexes 2a and 2b.Although 2a and 2b have the same asymmetric unit,they belong to different space groups.Complex 2a crystallizes in the monoclinic crystal system,space groups P21/n with a = 10.2293(2),b = 15.6660(3),c = 10.6298(2) ,β = 116.259(1)o,Z = 4,μ = 0.676 mm-1;complex 2b crystallizes in the triclinic crystal system,space groups P with a = 8.2808(4),b = 9.4704(5),c = 10.0819(5) ,α = 86.133(3),= 81.956(3),γ = 80.248(3)o,Z = 2 and μ = 0.670 mm-1.The hydrogen bonds are found to exist in 2b only.The crystal structure is stabilized by intermolecular hydrogen bonds of C-H···O.展开更多
文摘A new selective and sensitive kinetic method for determination of trace amounts of vanadium(Ⅴ) (0.5～40ng/ml) based on its catalytic effect on the oxidation of azomethine H by bromate at pH 4.2 and 25 ℃ was reported and its reaction mechanism was studied.The reaction was monitored spectrophotometrically by measuring the increase in absorbance of oxidation product of azomethine H at 436 nm after a fixed time ( 5 min ).The detection limit of the method is down to 2.0×10 -10 g/ml and the relative standard deviation (RSD) for 30 ng/ml of V(Ⅴ) is 0.26 % ( n =6). The effect of foreign ions on V(Ⅴ) determination was also discussed,and the method is mostly free from interferences of other ions.The proposed method was successfully applied to the determination of trace amounts of vanadium in water samples.
文摘A new method is proposed for the preconcentration of vanadium(Ⅴ) with crosslinked chitosan (CCTS) and determination by graphite furnace atomic absorption spectrometry (GFAAS). The adsorption rate of vanadium(Ⅴ) by CCTS was 97% at pH 4.0, and vanadium(Ⅴ) was eluted from crosslinked chitosan with 2 mL 2.0 mol·L -1 chlorhydric acid and determined by GFAAS. The detection limit (3σ,n=7) for vanadium(Ⅴ) was 4.8×1 0 -12g and the relative standard deviation (R.S.D) at concentration level of 2.6 μg·L -1 is less than 3.6%. The method shows a good selectivity and high sensitivity, and it was applied to determination of vanadium(Ⅴ) in oyster and water samples. The analytic recoveries are (97±5)%.
基金supported by the Scientific Research Common Program of Beijing Municipal Commission of Education,PRC (KM200910028011)
文摘Divanadium(Ⅴ) complex [VO(aptch)(μ-OCH3)]2(1) and two monovanadium(Ⅴ) complexes [VO(apfah))(OEt)](2a and 2b,H2aptch = 2-hydroxyacetophenone thiophene-2-car-boxylic hydrazone,H2apfah = 2-hydroxyacetophenone 2-furoic acid hydrazone) have been synthesized and characterized.Single-crystal X-ray diffraction studies reveal that 1 is a cen-trosymmetric dimer bridged by two methoxido O-atoms.Complex 1 crystallizes in the monoclinic crystal system,space groups P21/c with a = 7.4825(4),b = 17.0928(11),c = 11.6961(7) ,β = 98.172(4)o,Z = 2,F(000) = 728,μ = 0.829 mm-1,the final R = 0.0457 and wR = 0.1137 for 2654 observed reflections with I > 2(I).The vanadium(V) is coordinated to the tridentate ligand,ethanol molecule to form a distorted square-pyramidal geometry,complexes 2a and 2b.Although 2a and 2b have the same asymmetric unit,they belong to different space groups.Complex 2a crystallizes in the monoclinic crystal system,space groups P21/n with a = 10.2293(2),b = 15.6660(3),c = 10.6298(2) ,β = 116.259(1)o,Z = 4,μ = 0.676 mm-1;complex 2b crystallizes in the triclinic crystal system,space groups P with a = 8.2808(4),b = 9.4704(5),c = 10.0819(5) ,α = 86.133(3),= 81.956(3),γ = 80.248(3)o,Z = 2 and μ = 0.670 mm-1.The hydrogen bonds are found to exist in 2b only.The crystal structure is stabilized by intermolecular hydrogen bonds of C-H···O.
