Flow-injection microcolumn on-line preconcentration for the determination of chromium (VI)

A rapid and sensitive on-line preconcentration method for spectrophotometric determination of chromium (VI) in nature water is described. Preconcentration and determination are based on (i) the quantitative and fast adsorption of chromium (VI) on the high surface area nanometer-size TiO₂ (anatase) powders, which prepared by a sol-gel method from hydrolysis of TiCl₄ and (ii) the quantitative and reproducible elution of Cr (VI) by 2.0 mol·L⁻¹ HCl. A mini-column system for preconcentration is developed, Cr(VI) on the mini-column is eluted and merged with a stream water and DPCB (1,5-diphenylcarbazide) as the chromogenic reagent. The proposed system permits throughputs of 6 sample h⁻¹ (0.001 μg·mL⁻¹ Cr(VI)) or 20 sample h⁻¹ (0.1 μg·mL⁻¹ Cr(VI)). The preconcentration factor is 55. The detection limit is 0.8 ng · mL⁻¹ Cr(VI). The reproducibility is satisfactory with a relative standard deviation of less than 3.35% (0.01 μg·mL⁻¹ Cr(VI),n=5). Supported by the National Natural Science Foundation of China Ma Wanhong: born in 1961, Ph. D. Graduate student, Associate professor     

Determination of ciprofloxacin hydrochloride in pharmaceutical preparation and biological fluid by Rayleigh light scattering technique

A highly sensitive and simple Rayleigh light scattering (RLS) method for determination of ciprofloxacin hydrochloride has been developed. Ciprofloxacin hydrochloride (CPFH) reacted with tetraphenylboron sodium(TPB) to form an ion-association complex in pH 5.31 aqueous solution, which resulted in a significant enhancement of the RLS intensity, which was linear with the concentration of CPFH in the range of 12.7–419 ng·mL⁻¹. The limit of detection for CPFH was 6.99 ng·mL⁻¹. The method is simple, highly sensitive and selective within a wide linear range. Appliying this method to determination of ciprofloxacin hydrochloride in pharmaceutical preparations and biological fluids obtained satisfactory results. Foundation item: Supported by the National Natural Science Foundation of China(20675059) and Research Foundation of Leshan Teachers’ College, China (Z0625)     

Spectrophotometric determination of aluminium with 2,3,7-trihydroxy-9-[4-(2,4-dihydroxy)phenylazo] phenylfluorone

The conditions of color reaction of Aluminium(III) with a new organic reagent 2,3,7-trihydroxy-9-[2,4-dihydroxy)phenylazo] phenylfluorone (ARPF) in the presence of cetyltrimethyammonium bromide (CTMAB) were studied. It was found that Aluminium(III) reacts with ARPF and CTMAB in pH 6.5 HAc-NaAc buffer solution to form a 1∶2 red complex with maximum absorption at 562 nm. The molar absorptivity is 1.10×10⁵ L·mol⁻¹·cm⁻¹. Beer’s law is obeyed in the range of 0–5.5 μg Al(III) per 25 mL. The method has been applied to determination of Aluminium in the limestone with satisfactory results. To whom Correspondence should be addressed Foundation item: Supported by Special Funds of State Education Committee for Doctorate Research Biography: Huang Ying-ping (1963-), male, Ph.D Candidate.     

Application of Nanometer-Size Titanium Dioxide in Extreme-Trace V（Ⅴ） Analysis

0Introduction Vanadiumplaysanimportantroleinmodernindustry,es peciallyinsteelandchemicalindustry.Forinstance,itscompoundsarewidelyappliedintheproceduresofvitrioland petroleumchemicalmanufactureascatalyzers[14].Vanadium hasseveralvalences,butgenerallyitslowvalencesturnintohighoneseasilyinenvironment[5].BecauseV(Ⅴ)isthemost stableandpoisonousone,weoftenlayemphasisonitinenvi ronmentalpollutioncontrol.Vanadiumexistsinenvironmentalwaterwithextremelylowconcentration.Inseawateritscontentislessthan…     

Sensitive Determination of DNA by RLS Enhancement of Metal Ions

0　IntroductionThequantitativeanalysisofnucleicacids,especiallythemi cro determinationofnucleicacids,isbecomingmoreandmoreimportantinmanybiologicalstudies.Recently ,apromisingspectraltechnique ,whichwasbasedonthemeasurementofen hancedresonancelightscattering (RLS) [1 ,2 ] ,hasgivenrisetostronginterestbyanalystsandbiochemistsfornucleicacidsandproteinassay[3 9] .Uptonow ,manykindscompoundshavebeenfoundRLSenhancementwhilebindingtoDNA ,andallthesecompoundsarecharacterizedofpositivechargewhicha…     

Investigation of Ru （ phen ）3^2＋-Hydrazine-Ce（Ⅳ） Chemiluminescence System and Its Analytical Application

0 IntroductionThbiep ycroidmipnlee)xru ctahteinoinu mof(Ⅱ r)u t(he Rniuu(mbip,y m)3ai2n +ly) atrnids- t(r2is -,(21’ -,10-phenanthroline)ruthenium(Ⅱ) (Ru(phen)32 +) ,is a kindof sensitive analytical reagent for electrogenerated chemilumi-nescence(ECL) and chemiluminescence(CL) ,on which a par-ticular review has been presented[1]. The earliest publicationon the synthesis of Ru(bipy)32 +appeared in 1936[2], andduringthefollowing30 years ,theinvestigations relatedtothissubstance were only in…     

Studies on the inclusion complex reaction and fluorescent analytical application of β-cyclodextrin with hymecromone

The inclusion complex reaction condition and the mechanism of β-cyclodextrin with hymecromone have been studied by fluorescent spectrum. The fluorescent intensity and the stability of the system can be qreatly increased in qiven condition, and the formation constant of the inclusion complex reaction has been determined too. The system can be applied to the determination of trace amounts of hymecromone, the maximum fluorescent intensity is obtained with excitation and emission wavelength at 362 nm and 452 nm, respectively. The linear range for hymecromone is 8.0×10⁻⁹ mol·L⁻¹ to 1.0×10⁻⁵ mol·L⁻¹. The detection limit is 1.8×10⁻⁹ mol·L⁻¹. A simple, rapid and highly sensitive fluorimetric method is proposed for the determination of hymecromone. The results obtained are in agreement with those given by an official method. Foundation item: Supported by the National Natural Science Foundation of China (G1999046703) Biography: Luo Zhao-fu(1947-), female, Associate professor.     

Fluorescence Determination of Artemisinin Using Hemoglobin as Catalyst and Pyronine B as Substrate

0 IntroductionMaalnadria siusb atr ompajicosr .he aAltrthe pmrisoibnlienmi (n qtihneghtraoopsiucs,QHS,Fig.1) is a sesquiterpene endoperoxide isola-ted fromArtemisia annuaL., an ancient Chineseherbal medicine usedfor treatment of fever and ma-laria.Studies of the structure and activity relation-ship have shownthat endoperoxide groupis essentialfor anti malarial activity of QHS and absence of thismoiety lead to completely loss in activity of thedrug. Many techniques have been developed to de…     

Direct determination of trace silicon in lanthanum oxide by using a selective volatility and slurry sampling-FETV-ICP-AES

A new method for determination of trace sillicon in high purity lanthanum oxide by using electrothermal vaporization (ETV)-ICP-AES with polytetrafluoroethylene (PTFE) slurry as a fluorinating reagent has been proposed. Under the optimized experimental conditions, the fluorination reactions of analyte (Si) and matrix(La) with PTFE in the graphite furnace took place at high temperature, and the fractional volatilily between Si and La was observed. Based on this principle the matrix interference could be eliminated. The detection limit of Si was 4.0μg·L⁻¹, and the RSD was 3.4%(C=0.2mg·L⁻¹,n=10). The procedure proposed has been applied successfully to determine trace Si in La₂O₃ without any chemical pre-treatment. Supported by the National Natural Science Foundation of China Qin Yongchao: born in Dec. 1953, ph. D., Assciate Professor     

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.     

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.     

On the Pólya conjecture and the weak Weyl-Berry conjecture

The Pólya conjecture and its connection with the weak Weyl-Berry conjecture are studied Specifically let Ω⊆R ⁿ (n≥1) be a non-empty bounded open set with boundary ∂Ω. LetN ₀(λ, −Δ,Ω) be the Dirichlet counting function and φ(λ) the associated Weyl term. If the interior Minkowski dimension of ∂Ω is δ∈[n−1,n], then under certain realisable conditions we prove that for λ sufficiently large the Pólya conjecture φ(λ) −N ₀(λ,−Δ,Ω)≥0 is true. Under related conditions we also prove thatϕ(λ)−N ₀(λ,−Δ, Ω)≈λ^5/2, as λ→+∞. That is, the Weak Weyl-Berry conjecture is true. Similar results are obtained for the Neumann counting function. Partially supported by the National Natural Science Foundation of China and the Royal Society of London Chen Hua: born in March 8, 1956, Professor     

Investigation of performances and mechanism of fluoride removal by Fe (III)-loaded ligand exchange cotton cellulose adsorbent

Novel adsorbent, Fe(III)-loaded ligand exchange cotton cellulose adsorbent [Fe(III)LECCA], was used to investigate the adsorption performances and mechanism of fluoride removal from aqueous solutions. The adsorbent was found to adsorb fluoride rapidly and effectively. The fluoride removal was influenced by pH. Adsorption model followed first-order reaction at different temperature, theapparent adsorption activated energyE, was 6.37 kJ·mol⁻¹, and adsorption enthalpy ΔH was 5.35 kJ·mol⁻¹. The adsorption capacity of fluoride on adsorbent was 3.2 mmol·g⁻¹ (dry weight). The maximal integer coordination ratio of fluoride with Fe(III) LECCA was 3∶1. The ligand exchange mechanism of adsorption was elucidated through chemical methods and IR spectral analysis. Foundation item: Supported by the National Natural Science Foundation of China (29977010) and Shanghai Priority Academic Discipline Biography: ZHAO Ya-ping (1974-), female, Ph.D., research direction: water and wastewater treatment.     

Electrochemical determination of trace amounts of lead (II) and cadmium (II) at a calix[6]arene modified carbon paste electrode

An electrochemical method for the simultaneous determination of lead(II) and Cadmium(II) with a calix[6]arene modified carbon paste electrode (CPE) has been developed. Pb²⁺ and Cd²⁺ were accumulated at the surface of the modified electrode via formation of chemical complexes with calix[6]arene, and reduced at 1.40 V. During the following anodic potential sweep, reduced lead and cadmium were oxidized, and two well-defined striping peaks appeared at about −0.60 V and −0.84 V. Compared with a bare carbon paste electrode, the calix[6]arene modified CPE greatly improves the sensitivity of determining lead and cadmium. The stripping peak currents change linearly with the concentration of Pb²⁺ 3.0×10⁻⁸–8.0×10⁻⁶ mol·L⁻¹ and with that of Cd²⁺ 6.0×10⁻⁸–1.0×10⁻⁵ mol ·L⁻¹. The detection limits of Pb²⁺ and Cd²⁺ are found to be 8.0×10⁻⁹ mol·L⁻¹ and 2.0×10⁻⁸ mol·L⁻¹, respectively. The modified carbon paste electrode was applied to determine trace levels of lead and cadmium in water samples. Comparing with that of atomic absorption spectrometry, the results suggests that the calix[6]arene modified CPE has great potential for the practical sample analysis. Foundation item: Supported by the National Natural Science Foundation of China (60171023) Biography: JI Xiao-bo (1980-), male, Master, research direction: electroanalytical chemistry.     

Synthesis of meso-tetra-(2-chloro-4-sulfophenyl) prophyrin and spectrophotometric determination of trace amounts of cadmium

Synthesis of a new high sensitive water soluble chromogenic reagent meso-tetra-(2-chloro-4-sulfophenyl) prophyrin and the conditions for the reaction of this reagent with cadmium (I) were studied. The apparent molar absorption coefficient at 434 nm is 5.20×10⁵ L·mol⁻¹·cm⁻¹. The method has been applied to the determination of 5.0×10⁻⁹ (content by weight) Cadmium (I) in honey. Supported by the National Natural Science Foundatyion of China Xiao Ling: born in Oct. 1962, Ph.D gradute student     

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…     

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     

Carbonaceous particles in Muztagh Ata ice core,West Kunlun Mountains,China

Carbonaceous particles concentrations of OC and EC are determined using a two-step gas chroma- tography system in Muztagh Ata ice core covering the time period of 1955--2000. Over the period represented by the core, OC and EC concentrations appear to have changed significantly, varied in the range of 17.7--216.7 and 6.5--124.6, and averaged 61.8, 32.9 ng·g^-1, respectively. The average concentration of EC in Muztagh Ata ice core is much lower than that in an Alpine ice core record （100--300 ng·g^-1） during the same period, but it is a factor of 14 in Greenland ice core （2.3 ng·g^-1）, this may induce a strong impact on the snow albedo in the last 46 years in our study area. Observations indicate two periods with obviously high deposition concentrations （1955--1965 and 1974--1989） and two periods with low concentrations （1966--1973 and 1990--1995）, as well as a recent increasing trend. By comparing EC and SO4^2- concentration variations and deciphering OC/EC ratios recorded in the same ice core, we can judge roughly that the carbonaceous particles deposited in Muztagh Ata ice core were attributed to fossil fuel combustion sources.     

Synthesis and Characterization of Polyamide-Containing 2, 6- （Substituded） pyridine Derivatives

0 IntroductionPayrriodminaetiics hoenteer oofc ythcleics m .os tC oambupnoduanndts a cnodn tbaeisntin kgno twhnepyridine ring are widely distributedin nature,principally asenzymes and alkaloids . Pyridine enzymes have been foundintissues of all plants and ani mals examined thus far ,andare derivedfromeither nicotinic acid or Vitamin B6[1].Pyr-idine derivatives are also the building block of many phar-maceuticals with a wide range of functionalities that includeantitubercular compounds ,antivi…     

A Novel Degradation Pathway of Zn（dmid） （ phen）2 in Pyridine

The light-oxidation degradation processes of Zn(dmid)(phen)2(dmid = 4, 5-dimercapto-1,3-dithiole-2 one, phen = 1,10-phenanthroaline) in pyridine solvent has been monitored, h has been found under the light, dmid^2- of Zn(dmid)(phen)2 in pyridine solution could generate NCS^- and NCS^-replaces dmid^2- to form Zn(NCS)2 (phen)2 simultaneously. The crystal structure of Zn(NCS)2 (phen)2 has been determined. In the crystal of Zn(NCS)2 (phen)2. two NCS^- ligands are arranged in syn-configuration, and there is strong π-π interaction between the two adjacent parallel phen.