Organic media enhanced spectrofluorimetric determination of L-ascorbic acid

A novel spectrofluorimetric method for the determination of L-ascorbic acid is proposed. It is based on the inhibition of L-ascorbic acid on the formation of 2,3-diaminophenazine, which is an oxidation product ofo-phenylenediamine catalyzed by laccase. The fluorescence (at λ_cx/λ_cm=464 nm /530 nnm) was enhanced strongly in the presence of organic media. The mechanism ofo-phenylenediamine oxidation reaction catalyzed by laccase in the presence of L-ascorbic acid is discussed. L-ascorbic acid is determined in the ethanol, 1,4-dioxane and acetone over the linear range of 4.0×10⁻⁷≈1.2×10⁻⁴ mol/L, 4.0×10⁻⁷≈8.0×10⁻⁵ mol/L and 4.0×10⁻⁷≈1.0×10⁻⁴ mol/L with a detection limit of 1.20×10⁻⁵ mol/L, 1.19×10⁻⁵ mol/L and 1.24×10⁻⁸ mol/L, respectively. The method has been successfully applied to the simple and rapid determination of L-ascorbic acid in pharmaceuticals and milk powder. Supported by National Natural Science Foundation of China and the Special Funds of State Education Committe for Doctorate Research Huang Zuyun: born in Aug. 1963. Ph.D     

Determination of isocarbophos by cathodically sweeping oscilliopolarography

Determination of isocarbophos by cathodically sweeping oscilliopolarography is described. In a 1.0×10⁻⁵ mol/L sodium dodecylbenzene sulfonate (SDS)+0.1 mol/L HAC-NaAC (pH=4.0) buffer medium, isocarbophos and its alkaline hydrolysate exhibited sensitive second derivative wave at −0.50 V and −0.48 V respectively. The peak current was linearly proportional to the concentration of isocarbophos in the range of 5.40×10⁻⁶−1.05×10⁻⁴ mol/L by detecting isocarbophos directly. The detection limit was 3.60×10⁻⁶ mol/L with the relative standard derivation (RSD) of 7.3%. By employing an alkaline hydrolysis, the peak current was linearly proportional to the concentration of isocarbophos in the range from 7.70×10⁻⁷ mol/L to 1.24×10⁻⁴ mol/L, and the detection limit was 5.80×10⁻⁷ mol/L with RSD of 3.1%. The hydrolysis procedure and the electrode reaction were studied by voltammetry. Foundation item: Supported by the Foundation of Chinese-France Cooperation Program on Advanced Research Biography: ZHANG Wu-ming (1929-), female, Professor.     

Voltammetric Response of Epinephrine at Carbon Nanotube Modified Glassy Carbon Electrode and Activated Glassy Carbon Electrode

0Introduction Epinephrine(EP)isanimportantcate cholamineneurotransmitterinthemammaliancentralnervoussystem,whichissecretedbythesu prarenalglandalongwithnorepinephrine.Itisgen erallyusedtotreathypertension,bronchialasthma,organicheartdisease,andincardiacsurgeryand myocardialinfarction[1].VariousmethodshavebeendevelopedforEPstudy,suchascapillaryelectro phoresis(CE)[2],highperformanceliquidchroma tography(HPLC)andflowinjectionanalysis(FIA)[3].Numerousobservationsontheelectro chemicalbehavio…     

Determination of omethoate by cathodically sweeping oscillopolarography

Determination of omethoate by cathodically sweeping oscillopolarography is described. The product of the alkaline hydrolysis exhibited a sensitive second derivative wave at −0.50 V (vs. SCE) in a 1.0 ×10⁻⁵mol/L sodium dodecylbenzene sulfonate (SDBS)+0.1 mol/L HAc-NaAc (pH 4.0) buffer. The peak current was linearly proportional to the concentration of omethoate in the range from 6.4×10⁻⁷ to 5.1×10⁻⁵ mol/L. The detection limit is 2.0×10⁻⁷ mol/L with the relative standard derivation (RSD) of 3.5%. The hydrolysis procedure and the electrode reaction were studied by voltammetry. Supported by the Foundation of Chinese-Franch Cooperation Programme on the Advanced Research Wang Yu: born in 1964. Lecturer. Cangzhou Teacher’s College, Cangzhou, Hebei, 061001     

Study of the voltammetric behavior of heme and its direct analysis application

The electroanalytical method of ferriheme was studied by linear sweep voltammetry in medium of 0.05 mol/L Tris+0.05 mol/L NH₃−NH₄Cl buffer at hang mercury drop electrodes (HMDE). Heme exhibits two pair reversible redox peaks and one irreversible peak. The cathodic peak potentials are−;0.236 V, −0.422 V and −1.408 V respectively. The first and the third peaks can be used for directly quantitative determination of heme concentrations. The peak currents are good linear relationship with heme concentration in ranges of 3×10⁻⁶–6×10⁻⁵ mol/L and 3×10⁻⁷–1.5×10⁻⁵ mol/L respectively. Supported by the National Natural Science Foundation of China Lju Huihong: born in 1965, Lecturer. Visiting scholar from Xiangyang Teacher’s College, Hubei, 441053     

Electrocatalytic oxidation of H<Subscript>2</Subscript>O<Subscript>2</Subscript> at a carbon paste electrode modified with a nickel (II)-5, 11, 17, 23-tetra-tert-butyl-25, 27-bis(Diethylcarbamoylmethoxy) calix[4] arene complex and its application

Electrochemical behavior of a carbon paste electrode (CPE) modified with nickel(II)-5, 11, 17, 23-tetra-tert-butyl-25, 27-bis(diethylcarbamoylmethoxy) calix[4]arene (Ni (II)-L) complex and its electrocatalytic activity towards the oxidation of hydrogen peroxide were investigated by cyclic voltammetric technique in a 5.0×10⁻² mol/L NaClO₄+1.0×10⁻³ mol/L NaOH solution. It was found that Ni(II)-L acts as an effective catalyst for the oxidation of hydrogen peroxide. The modified electrode exhibited a linear response over a hydrogen peroxide concentrations in the range of 2.0×10⁻⁵−1.0×10⁻⁴ mol/L with a detection limit as low as 1.0×10⁻⁶ mol/L. The relative standard deviation was 3.5% for 5 successive determinations of H₂O₂ at 1.0×10⁻⁵ mol/L. The modified electrode was used successfully in rainwater analysis. Foundation item: Supported by the Natural Science Foundation of Hubei Province (98J040). Biography: Li Chun ya(1972-), Ph. D. candidate, research direction: electroanalysis and electrosynthesis.     

HPLC determination of ascorbic acid using luminol-Cu (II) chemiluminescence-application to the analysis of Juice beverage

The chemiluminescence (CL) of luminol-Cu (II) was applied to HPLC determination of ascorbic acid, which was separated by a C₁₈ reverse-phase column with a mobile phase of 0.25 mol/L HAc. The eluted ascorbic acid was mixed with 0.3 mmol/L luminol and 0.05 mol/L CuSO₄. The light emission from the reaction of Cu(II) oxidized ascorbic acid and luminol was detected by a modified luminometer. The detection limit was 3.6×10⁻⁶ mol/L for ascorbic acid at aS/N ratio of 3, and the linear calibration range was 2×10⁻⁴–2×10⁻³ mol/L. The relative standard deviation for 5 replicate injections of 1×10⁻³ mol/L ascorbic acid was calculated as 4.3%. The method was successfully applied to determination of ascorbic acid in juice beverage. Foundation item: National Natural Science Foundation of China (29605001) Biography: Wu Feng-wu(1963-), male, research direction: analytical chemistry.     

Myoglobin as Mimetic Enzyme and Its Analytical Application in Determination of H2O2

0 IntroductionSltougdiiceasl csoynstceermnsin gharveeac btieveen o txhyeg ei nm psopretcaienst ( oRbjOecSt) iinn bbiioo--medicine and analytical chemistry in recent years[1-4]. Manyi mportant life phenomena and diseases are relatedtotheinter-mediates of ROS[5-7].ROS have beeni mplicated as ani mpor-tant causative factor in cell damage,including apoptosis andnecrosis . Their proposed actions comprise lipid peroxidation,DNAdamage,the mitochondrial respiratory chain destructionand protein mo…     

Spectrofluorimetric method for the determination of triamcinolone acetonide

0　IntroductionTriamcinoloneAcetonide,9 fluoro 11β,2 1 dihydroxy 16α,17[(1 methylethylidene)bis (oxy) ] pregn 1,4 diene 3,2 0 dione,Mris 4 34.4 8(abr.TA ) .Itbelongstoaclassofadrenalcortexhormonedrug ,whosefunctionsareaffectionofsugarmetabolism ,anti inflammationandresistancehypersusceptibilityetc.TAcanbesuitabletorheumatoidarthritisanddermatosissuchashypersusceptibilityandneuropathicdermatitis .ThefunctionsofTAisstrongerandlongerthantriamcinolone[1 ,2 ] .ThecommonmethodsofdetectingTAm…     

Chemiluminescence determination of thiourea using tris (1,10-phenanthroline)-ruthenium (II) KMnO4 system

The light emission produced by thiourea in oxidation process by permanganate in acidic solution in the presence of Ru(phen) ₂ ^{3 +} is used to determine 1.0×10⁻⁵ −1.0×10⁻⁵ mol/L thiourea. The limit of detection is 9.8×10⁻⁹ mol/L and the relative standard deviation is 1.1% for a 1.0×10⁻⁵ mol/L thiourea solution (n=10). The method was applied satisfactorily to the determination of thiourea. Foundation item, Support by Ministry of Education, Wuhan University and Alumni Association of it Biography: Wu Feng-wu(1963-), Male, Ph. D, research direction: analytical chemistry.     

Chemiluminescence determination of tetracycline and oxytetracycline in pharmaceutical preparations using Ru (bipy)3 2+-cerium (IV) system

A new chemiluminescence (CL) method for the determination of tetracycline and oxytetracycline is developed, based on the CL reaction of tetracycline and oxytetracycline with Ru (bipy)₃ ²⁺ and Ce (IV). In sulfuric acid medium, the CL emission is generated upon continuous oxidtion of Ru(bipy)₃ ²⁺ by cerium (IV). The emission intensity is greatly enhanced when tetracycline and oxytetracycline are introduced into the reaction system after acid degradation. Under the optimum conditions, the calibration curves are linear over the range of 8.0×10⁻⁸∼4.0×10⁻⁶ mol/L for tetracycline and of 2.0×10⁻⁷∼4.0×10⁻⁵ mol/L for oxytetracycline, with the detection limits are 4.2×10⁻⁸ mol/L for tetracycline and 1.5×10⁻⁷ mol/L for oxytetracycline, respectively. The proposed method was used for the determination of tetracycline and oxytetracycline in pharmaceutical formulations with good results. Foundation item: Supported by the National Natural Science Foundation of China and the Natural Science Foundation of Hubei Province. Biography: HAH He-you (1962), male, Associate profeddor, Ph.D graduate candidate. Present address, Department of Chemistry, Huainan Teacher's College, Huainan.     

Determination of some carbonyl carboxylic acids using chemiluminescent reaction of Ru(bipy)3 2+−Ce(IV)

A coupled chemiluminescence method for the determination of some carboxylic acids was developed, based on their enhancement the chemiluminescence light emission of the reaction of tirs (2,2′-bipyridine) ruthenium(II) and Ce(IV) in sulfuric acid medium. The conditions for their determination were optimized. The following detection limits were obtained: oxalic acid, 2.67×10⁻⁸ mol/L; propandioic acid, 1.20×10⁻⁶ mol/L; pyruvic acid, 1.35×10⁻⁸ mol/L; citric acid, 5.10×10⁻⁸ mol/L; barbituric acid, 2.48×10⁻⁷ mol/L. The proposed method was successfully applied to determination of oxalic acid. The coupled chemiluminescent reaction mechanism and rate equation are proposed. Foundation item: Supported by the National Natural Science Foundation of China and the Natural Science Foundation of Hubei Province Biography: HAN He-you (1962-), male, Associate professor, phD, graduate candidate     

Determination of epinephrine using poly (neurtral red) modified carbon fibre microelectrodes by anodic stripping voltammetry

Poly(neutral red) film modified carbon fibre microelectrodes offer substantial improvement in voltammetric sensitivity and selectivity towards epinephrine (EP). The poly (neutral red) film was electropolymerized by cycling the potential between −0.8 V and +0.8 V. The anodic stripping voltammetric response for EP was found to be dependent on accumulation time and potential. By using a poly(neutral red) film modified carbon fibre microelectrode with a 1 min preconcentration at −1.2 V in biological phosphate buffer solution (pH=7.4). a good linear relationship between the anodic stripping peak currents and EP concentrations was obtained in the range of 2.0×10⁻⁷⊂2.0×10⁻⁵ mol/L. The detection limit was up to 9.0 ×10⁻⁸ mol/L. Moreover, 400 times higher concentrations of vitamin C did not interfere with the measurement of EP. This method was used for determining EP concentrations in epinephrine hydrochloride injection solution with satisfactory results. Supported by the National Natural Science Foundation of China Tang Xiaorong: born in 1974, Master     

Effect of Dy3+on osteogenic and adipogenic differentiation of mouse primary bone marrow stromal cells and adipocytic trans-differentiation of mouse primary osteoblasts

A series of experimental methods including 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) test, alkaline phosphatase (ALP) activity measurement, mineralized function, Oil Red O stain and measurement were employed to assess the effect of Dy³⁺ on the osteogenic and adipogenic differentiation of mouse primary bone marrow stromal cells (BMSCs) and the adipogenic trans-differentiation of mouse primary osteoblasts (OBs). The results showed that Dy³⁺ had no effect on BMSC proliferation at concentrations of 1×10⁻⁸ and 1×10⁻⁵ mol/L, but inhibited BMSC proliferation at other concentrations. Dy³⁺ had no effect on OB proliferation at concentrations of 1×10⁻¹⁰ and 1×10⁻⁹ mol/L, but inhibited OB proliferation at other concentrations. Dy³⁺ had no effect on the osteogenic differentiation of BMSCs at concentrations of 1×10⁻⁹ and 1×10⁻⁷ mol/L, and promoted osteogenic differentiation of BMSCs at other concentrations at the 7th day. The osteogenic differentiation of BMSCs was inhibited by Dy³⁺ at concentration of 1×10⁻⁵ mol/L at the 14th day, but promoted osteogenic differentiation of BMSCs at concentrations of 1×10⁻⁹, 1×10⁻⁸, 1×10⁻⁷ and 1×10⁻⁶ mol/L with the maximal effect at concentration of 10⁻⁶ mol/L. Dy³⁺ promoted mineralized function of BMSCs at any concentration. Dy³⁺ had no effect on adipogenic differentiation of BMSCs at concentration of 1×10⁻⁷ mol/L, but inhibited adipogenic differentiation of BMSCs at other concentrations. Dy³⁺ inhibited adipocytic trans-differentiation of OBs at any concentration, suggesting that Dy³⁺ had protective effect on bone and the protective effect on bone may be mediated by modulating differentiation of BMSCs away from the adipocyte and inhibiting adipocytic trans-differentiation of OBs which may promote differentiation and mineralization of OBs. These results may be valuable for better understanding the mechanism of the effect of Dy³⁺ on pathogenesis of osteoporosis. Supported by the Foundation for Key Program of Ministry of Education of China (Grant No. 208018)     

聚L-谷氨酸/石墨烯修饰电极对碘的测定

使用循环伏安法制备了聚L-谷氨酸/石墨烯修饰电极,应用扫描电镜和阻抗对修饰电极进行了表征,建立了示差脉冲伏安法测定碘的新方法。研究结果表明,在最佳实验条件下,使用示差脉冲伏安法(DPV)法测定碘,碘浓度在1.00×10-3～5.00×10-7 mol/L浓度范围内与峰电流呈现良好的线性关系,检出限为1.00×10-7 mol/L。该方法用于测定样品中的碘,结果令人满意。     

Trace determination of zirconium using anodic adsorptive voltammetry at a carbon paste electrode modified with multi-walled carbon nanotubes

A carbon paste electrode modified with multi-walled carbon nanotubes （MWCNT） was prepared and the determination of ultra trace amount of zirconium based on the anodic adsorptive voltammetry of the zirconium-calcium-alizarin red S mix-polynuclear complex is described in this paper for the first time. The results showed that the sensitivity and the selectivity of the method are excellent. The second derivative linear scan voltammograms of the complex were recorded by polarographic analyzer from 200 to 1200 mV （vs. SCE） and it was found that the complex can be adsorbed on the surface of the electrode, yielding a peak at about 840 mV, corresponding to the oxidation of ARS in the complex. The peak current increases linearly with Zr （IV） concentration in the range of 6.0×10^-12--6.0×10^-11 mol. L^-1 （accumulation time 120 s）, 6.0×10^-11--2.0×10^-9 mol. L-1 （accumulation time 90 s） and 2.0×10^-9--1.0×10^-7 mol. L^-1 （accumulation time 60 s） and the detection limit （S/N = 3） is 2.0×10^-12 mol. L^-1 （accumulation time 180 s）. The procedure has been successfully applied to the determination of zirconium in the ore samples.     

Study on state of terbium ion in liposome by one-order derivative fluorescence quenching method

The state of Tb³⁺ is investigated in liposome. When the concentration of PC is below CMC (critical micell concentration), most of Tb³⁺ is associated with PC, the binding constant is about 3.35×10³ L/mol. When the concentration of PC is beyond CMC, most of Tb³⁺ is dimerized, the dimerization constant is about 3.92×10⁴L/mol. In PC−CH−H₂O system, the binding constant of Tb³⁺−CH complex 2.93×10⁴L/mol is obtained. Biography:Mu Xiao-jing (1974-), female, MS.     

Determination of ammonium ion in lake water by voltammetry

0　IntroductionDetectionofammoniumionisveryimportantinmanyfields,suchashealthcare,agriculture ,cultivationandenviron mentalpollutioncontrol.Severalanalyticalmethodshavebeende velopedforammoniumdeterminationincludingionchromatography ,spectrophotometry,fluorimetryandchemiluminescence .MostofthemarebasedonspectrophotometryusingtheBerthelot reactionbetweenammonium ,phenol,andhypochloriteleadingtothefor mationofanindophenoldye[1 ] .Thereactiontimeisaboutanhour,andsomedissolvedorganicnitrogencompo…     

铂微粒修饰固体石蜡碳糊电极对过氧化氢的电催化特征及分析应用

研究铂微粒修饰的固体石蜡碳糊电极(Pt-SCPE)对H2O2的电催化行为。在pH值4.6的柠檬酸盐-0.03 mol/L硝酸钾溶液中,用该电极H2O2在+0.18V(vs．SCE)可产生灵敏的还原电流,线性范围为1.0×10-1 mol/L～3.0×10-7 mol/L,检出限为7.5×10-8 mol/L。Pt-SCPE与液体石蜡碳糊电极比较,在峰电位、线性响应范围、检出限方面有更好的结果。用该电极测定样品中的过氧化氢,获得满意结果。     

Third-order optical nonlinearities for lanthanum (III) complexes with 1, 10-phenanthroline components

The nonlinear refractive indexesn ₂ for the ethanol solutions of 1, 10-phenanthroline (2.0 × 10⁻³ mol · L⁻¹), [bis(l, 10-phenanthroline) lanthanum (III)] nitrate (1.0 × 10⁻³ mol · L⁻¹), and [nitrato-fluoracil-bis (1, 10_{-phenanthroline}) lanthanum (III) ] nitrate (1.0 × 10⁻³ mol · L⁻¹) are first measured, the third-order nonlinear optical susceptibilities χ(³) and 〈γ〉 are calculated, and the mechanisms of the third-order optical nonlinearities enhanced by lanthanum (III) are discussed preliminarily.