Catalytic Spectrophotometry for Vanadium Determination Based on Oxidation of Arsenazo Ⅲ by Bichromate

A catalytic spectrophotometry for the determination of trace amount of vanadium was developed based on its catalytic effect on the oxidation of arsenazo by potassium bichromate in weak acidic medium. The optimized conditions for determinations are: cK2Cr2O7=3.010-5 molL-1, carsenazo =3.010-5 molL-1, pH=4.0, t=90. The calibration graph is linear for 0.020.2 gml-1, and the detection limit is 0.02 gml-1 V. The apparent active energy of this catalytic reaction is 21.72 kJmol-1. Most foreign ions do not interfere with the determination of vadadium, except for Fe() and Co(), and their interferences could be eliminated by ion exchange. The present method has been used to make the determination of vanadium in human hair, tea, potato and wastewater, and the results were satisfactory.

Spectrophotometric Determination of Water-Soluble Hexavalent Chromium and Determination of Total Hexavalent Chromium Content of Portland Cement in the Presence of Iron (III) and Titanium (IV) Using Derivative Ratio Spectrophotometry

A rapid, reliable and accurate method for the determination of hexavalent chromium in Portland cement is developed. The proposed method includes direct spectrophotometric determination of Cr (VI) in Portland cement with 1, 2, 5, 8 Tetrahydroxyanthraquinone, (Quinalizarin, QINZ) at pH 1.5. The European Directive (2003/53/EC) limits the use of cements so that it contains no more than 2 mg.Kg-1 of water-soluble Cr (VI). The absorbance at 565 nm due to Cr (VI)-QINZ complex is recommended for the determination of water-soluble Cr (VI) in Portland cement. The quantification of Cr (VI) released from cement when mixed with water is performed according to TRGS 613 (Technical Rules of Hazardous Substances). The validity of the method is thoroughly examined and the proposed method gives satisfactory results. A derivative spectrophotometric method has been developed for the determination of total Cr (VI) in Portland cement in the presence of Fe (III) and Ti (IV). The hexavalent chromium complex formed at pH 1.5 allows precise and accurate determination of chromium (VI) over the concentration range 0.05 to 3.0 mg.L-1of chromium (VI). The validity of the method was examined by analyzing several Standard Reference Material (SRM) Portland cement samples. The MDL (at 95% confidence level) was found to be 25 ng/mL for chromium (VI) in National Institute of Standards and Technology (NIST) cement samples using the proposed method.

Kinetic Investigation of Ce,Y-CPAmA Systems and Simultaneous Determination of Sc,Y,Ce via Complementary Tristimulus Spectrophotometry

In the past ten years the eomplementary tristimulus speetrophotometryll],eTs,has seen its diverse appli-eations{2一61 though most researehes remain in relatively simpe systems,and less work has been involvinkinetie reaetions. An attemPt has been made on the investigation of some comPlieated systems eontainingrare earths and meta一acetylchloroPhosPhonaz

SIMULTANEOUS DETERMINATION OF NEODYMIUM AND PRASEODYMIUM BY ZERO-ORDER AND FOURTH-ORDER DFRIVATIVE SPECTROPHOTOMETRY

With derivative spectrophotometric method,the complexes of lanthanides with 2-(5-bromo-2-pyridylazo)-5-diethylaminophen- ol(5-Br-PADAP)in the presence of octylphenol poly(ethyleneg- lycol)ether(TX-100)were studied.It is found that the maximum absorption of fourth-order derivative spectra of the neodymium complex by 4f electron transitions is at 579(+)nm and 582(-)nm with molar derivative absorptivities of 5.2×10~3 1.mol^(-1).cm^(-1). The maximum absorption of the zero-order derivative spectra of the complexes for neodymium and praseodymium is at 580hm,the molar absorptivities are 1.47×10~5 l.mol^(-1).cm^(-1)for Nd and 1.26 ×10~5 l.mol^(-1).cm^(-1)for Pr.The component ratio of the complex is Nd:5-Br-PADAP=1:4.Beer's law is obeyed in the range of 0-3.75μg of Nd and Pr in 25ml of solution.The method has been used for the simultaneous determination of Nd and Pr in four synthetic samples and the results obtained are satisfactory.

DIRECT DETERMINATION OF NEODYMIUM AND ERBIUM IN RARE EARTH MIXTURE BY DERIVATIVE SPECTROPHOTOMETRY

The absorption spectra of 4f electron transitions of the complexes of neodymium and erbium with 8-hydroxyquinoline-5-sulphonic acid in the presence of diethylamine and ethanol have been measured by normal and third-derivative spectrophotometry. Their molar absorptivities are 70.7 l.mol^(-1).cm^(-1) for Nd and 62.5 l.mol^(-1).cm^(-1) for Er. They are 7.6 times and 14.9 times greater than those of corresponding chlorides, respectively. Use of the third-derivative spectra both eliminates the interference of Ce(Ⅳ) and increases the sensitivity for Nd and Er. Beer,s Law was obeyed from 0-10 ug/ml of Nd and Er. The method has been applied to the determination of neodymium and erbium in rare earth mixtures.

STUDY ON THE DETERMINATION OF TRACE BISMUTH(III) BY THIN-LAYER RESIN PHASE SPECTROPHOTOMETRY

In this paper, a new thin-layer ion-exchange resin phase analytical method is introduced. It is based on that, the bismuthous cation can associate with iodic anions, so as to formed an anion complex [BiI4-] in a strong acidic environments. This anion complex can also exchanges with a weaker anions on the surface active site of anion exchange resin, so that a [R+] [BiI4-] solid phase binary associational system is produced. Owing to the solid system is a great many dispersive particulates, it can be pressed to a thin-layer by press tools of the so called 搕hin-layer resin phase?or 搑esin phase? and using this solid association system spectrophotometry for the determination of trace metals. So it can increase the analytical sensitivity. This association system exhibits maximum absorbance at 460nm, and obeys Beer抯 law over the concentration range 0.01ug/ml^1.20ug/ml of bismuthous(III). It has a molar absorptivity of 7.1×105 [L/mol穋m]. It indicated the resin phase spectrophotometry is a sensitive analytical method for trace bismuthous. It is 18 times higher than routine aqueous spectrophotometry. The relative standard deviations is 1.82% (n=6) for the measurements of 0.5ug/ml Bi(III). The detection limit of Bismuthous(III) is 1.4×10-8mol/L. The method has applied to the analysis Bi(III) in environmental water samples.

Kinetic spectrophotometric determination of vanadium in steels based on the catalytic oxidation of thionine by potassium bromate

A sensitive and selective kinetic spectrophotometric method for the determination of V（V） was developed based on the catalytic oxidation of thionine by KBIO3 in 0.6 mol·L^-1 HaPO4 medium. The linear calibration range and detection limit at 25℃ were 0-0.5 μg·mL^-1 and 0.01 μg·mL^-1, respectively. In the presence of NaF and urea, most of the common ions did not interfere with the determination of V（V）. The proposed method was applied for the determination of vanadium in steels and satisfactory results were obtained.

Simultaneous kinetic spectrophotometric determination of cephalexin and trimethoprim in pharmaceutical preparation and human urine with the aid of chemometrics

A procedure for the simultaneous kinetic spectrophotometric determination of cephalexin and trimethoprim was described. It was based on the different reaction rate of oxidation of these compounds with yellow ammonium cerous （Ⅳ） sulfate in acidic medium and colorless cerous （Ⅲ） sulfate was produced. The overlapped kinetic data was quantitatively resolved by the use of chemometric methods, partial least squares （PLS）, principal component regression （PCR） and radial basis function-artificial neural network （RBF-ANN）. The proposed method was also applied to the simultaneous determination of cephalexin and trimethoprim in pharmaceutical preparation and human urine with satisfied results, which compared well with those obtained by HPLC.

Spectrophotometric Determination of Trace Amounts of Vanadium(Ⅴ) by Means of Its Catalytic Effect on Oxidation of Azomethine-H by Bromate

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.

Simultaneous Spectrophotometric Determination of Three Components Including Deoxyschizandrin by Partial Least Squares Regression

The computer auxiliary partial least squares is introduced to simultaneously determine the contents of Deoxyschizandin, Schisandrin, r-Schisandrin in the extracted solution of wuweizi. Regression analysis of the experimental results shows that the average recovery of each component is all in the range from 98.9% to 110.3% , which means the partial least squares regression spectrophotometry can circumvent the overlappirtg of absorption spectrums of mlulti-components, so that sctisfactory results can be obtained without any scrapple pre-separation.

ISOSBESTIC DUAL WAVELENGTH SPEOTROPHOTOMETRIC SIMULTANEOUS DETERMINATION OF ZINC AND OADMIUM USING meso-TETRAKIS[4-(TRIMETHYLAMMONIUM) PHENYL] PORPHINE

Iin this paper an isosbestic dual--wavelength spectrophotometric method for the simultaneous determination of zinc and cadmium using meso--tetrakis [4-(trimethylammonium) phenyl] porphine has been developed. The interference from excess of reagent was masked by adding lead ions solution.The molar absorptivities (Ae) for zinc and cadmium were 6. 54 × 105 and 4. 27 × 105 L. mol-1. cm-1,respectively. The method could be used to determine zinc and cadmium in synthetic mixtures, and the satisfied results were obtained.

Simple and sensitive method for the determination of trace amounts of thorium using a benzoquinone derivative

A novel simple, sensitive, rapid, direct, and spectrophotometry-based procedure was investigated to determine Th(IV) at trace amounts. The new method is based on Th(IV) chelation with 3,6-dichloro-2,5-dihydroxy-l,4-benzoquinone(DDBQ). The reagent reacts with Th(IV) in 0.1 M HCl to form an orange 1:2 complex. The stability constant value is 6.62×10~4 for the Th(IV)complex. The Th(IV)-DDBQ obtained shows one peak with a maximum at about 346 nm. The chelate forms immediately and the absorbance remains stable for over24 h. Beer's law was obeyed in the concentration range0–10 μg mL^(-1). The molar absorptivity and Sandell's sensitivity were 4.4×10~4 L mol^(-1)cm^(-1) and 0.0053 μg cm^(-2), respectively. Different analytical parameters were tested in detail. Interfering ion(cations and anions) effects were tested. Methods for Th(IV) determination by second and third-derivative spectrophotometry were also introduced at about 344 and 341 nm, respectively. These two derivative orders offer the feature of sensitivity without the necessity for solvent extraction,heating, or pre-concentration steps. Finally, the methods were successfully utilized for Th(IV) determination in monazite, environmental water, and wastewater samples.

Procedure for Sensitive Kinetic Determination of Silver Based on Catalytic Effect on Ligand Substitution Reaction

A kinetic procedure for determination of trace silver was established based on the catalytic effect of Ag(Ⅰ) on the ligand substitution reaction between hexacyanoferrate (Ⅱ) and urea in acidic medium under the optimized conditions of [hexacyanoferrate]=8.0×10 -4 mol·L -1 , [CO(NH 2) 2]=6.0×10 -4 mol·L -1 , [CH 3COOH]=0.12 mol·L -1 , 80℃, 720 nm. The calibration curve is linear for 10～100 ng·ml -1 , and the detection limit is 0.4 ng·ml -1 Ag. The active energy of catalytic reaction is 18.12 kJ·mol -1 . The selectivity of this procedure is much better than that of other kinetic methods. Equal amount of mercury does not interfere with the determination of silver, and its sensitivity was also improved.

Simultaneous Spectrophotometric Determination of Four Components including Acetaminophen by Taget Factor Analysis

UV Spectrophotometric Target Factor Analysis （TFA） was used for the simultaneous determination of four components （acetaminophen, guuaifenesin, caffeine, Chlorphenamine maleate） in cough syrup. The computer Frogram of TFA is based on VC＋＋ language. The difficulty of overlapping of absorption spectra of four compounds was overcome by this procedure. The experimental results show that the average recovery of each component is all in the range from 98.9% to 106.8% and each component obtains satisfactory results without any pre-separation.

New reagent for indirect spectrophotometric red-ox determination of osmium (Ⅵ)

A highly sensitive indirect spectrophotometric red-ox method for the determination of osmium is reported. The method is based on the oxidation of iodide by osmium （Ⅵ） and the spectrophotometric detection of the liberated iodine in the form of complex anion and ion associate with 2-（4-diethylaminostyryl）-1,3,3-trimethyl-6-nitro-3H-indolium chloride reagent. The appropriate reaction conditions have been established. The molar absorptivity is （ 1.6-5.6） × 10^4 L mol^-1 cm^-1. Beer＇s law holds for the concentration range of 0.5-11.4 μg mL^-1 of Os（Ⅵ）.

A novel kinetic procedure for the determination of iron in environmental samples

A novel kinetic procedure for the determination of trace iron(Ⅲ) was proposed based on the aerial oxidation of Gallocyanine by oxygen dissolved in water at pH 7 0. The calibration graph is linear for 0 05—0.6 μg/ml, and the detection limit is 0 01μg/ml (Fe). The present procedure is selective for iron(Ⅲ) and very easy to control compared with kinetic procedures for iron. It had been used to the determination of trace iron in environmental samples, and the results were satisfactory.

Determination of Trace Copper with a Novel Kinetic Procedure/O_2 gallocyanine Indicator Reaction

A novel kinetic procedure for determination of trace copper was proposed based on the catalytic effect of Cu 2+ on the aerial oxidation of gallocyanine (GC), by which GC was oxidized and a colourless product was produced. The reaction was monitored spectrophotometrically in hexamethylene tetramine hydrochloric acid buffer solution. The calibration graph is linear for 0.05～0.5 μg/ml, and the detection limit is 0 02 μg/ml (Cu 2+ ). The selectivity for copper is satisfied as the interferences of Fe 3+ and Al 3+ could be easily and effectively eliminated by the addition of NH 4HF 2. The method was applied to the determination of copper in soil, tap water and simulated water samples, and the results were satisfactory.

Study on Cobalt(Ⅱ)Ionprobe for Cysteine Determination

A spectrophotometric method for the determination of cysteine was developed basing on the reaction of cysteine with cobalt (Ⅱ) in NH 4Cl NH 4OH. The molar absorptivity is 7.98×10 3 L·mol -1 ·cm -1 at 284 nm. Beer′s law is obeyed for cysteine in the range of 0～2.0×10 -4 mol·L -1 . The method was applied to the assay of cysteine in urine.

Determination of Light Rare Earths by a Spectrophoto-metry Based on the Linear Combination of Multiwavelength Data

The present paper proposes a new method of spectrophotometry based on linear combination of multiwavelength data by means of selecting a set of properly weighted coefficients and combination methods. It is clear that the weighted combination absorbance attained is only in direct proportion to the concentration of the analysed component and independent of coexisting interferents.The accuracy of the analytical results is improved greatly for the analysis of light rare earths with the coexistence of heavy rare earths.The analyti- cal error from the reagent blank and co-coloration of light and heavy rare earths have also been overcome. The greatly improved linearity and additivity of absorbance are obtained.

Determination and Analysis of Flavonoid Contents in Different Batches of Dried Radix Rehmannia and Prepared Radix Rehmanniae

[Objectives] This study was conducted to understand Radix Rehmannia quality and provide reference for selection in application. [Methods] The contents of flavonoids in five batches of commercially available samples were determined by ultraviolet spectrophotometry, and the precision and reproducibility of the determination method were analyzed. [Results] The contents of flavonoids in different batches of Radix Rehmannia samples were not completely the same, but the differences were not large overall. The experiment results have good reliability. As a medicinal plant, the climate and soil conditions of the producing areas would have an impact on the quality of Radix Rehmannia. [Conclusions] The contents of flavonoids determined in Radix Rehmannia were relatively stable, the quality was basically the same, and the overall quality was good.