A sensitive spectrophotometric method for determination of carbon tetrachloride with the aid of ultrasonic decolorization of methyl orange

A sensitive method for carbon tetrachloride (CCl₄) determination has been developed with the aid of ultrasonic oxidation decolorization of methyl orange (MO). It is found that the ultrasonic oxidation decolorization rate of MO can be significantly promoted by adding a little amount of CCl₄. The increased ultrasonic decolorization rate of MO is strongly dependent on the concentration of CCl₄ added, and a linear correlation is observed between the amount of CCl₄ and the decolorization rate of MO in the ultrasonic oxidation process. Thus, the CCl₄ determination is transformed to a simple and direct determination of the decoloration extent of MO solution at a given concentration. As an indirect spectrophotometric determination of CCl₄, the new method is sensitive and easy of operation with a maximum wavelength of 508 nm, molar absorptivity of 3.83 × 10⁴ L mol⁻¹ cm⁻¹, and a Sandell sensitivity of 7.96 × 10⁻³ μg cm⁻². Under optimized conditions, Beer's law is obeyed in the range of 0.4-20 mg L⁻¹ of CCl₄ (DL = 0.19 mg L⁻¹, r = 0.9996). The concentrations of CCl₄ in several practical samples have been determined satisfactorily by using this method.     

Spectrophotometric determination of micro amounts of tetrathionate via its oxidation with permanganate

The reaction conditions of tetrathionate with permanganate were investigated by varying reaction time, temperature and amounts of sulphuric acid and permanganate. Under the optimal conditions for the reaction of tetrathionate with permanganate, both penta- and hexathionate were also oxidised; each one mol of polythionates (S _x O ₆ ^2– x=4, 5 and 6) reacts with (x–1.5) mol of permanganate. The proposed method is based on the reaction of tetrathionate with a given excess amount of permanganate in a sulphuric acid medium and on the spectrophotometric measurement of the iodine as triiodide formed by the oxidation of iodide with the excess of permanganate. This method could be successfully applied to the determinations of tetrathionate (4 × 10^–7 to 2 × 10^–5 M), pentathionate (3 × 10^–7 to 1.43 × 10^–5 M) and hexathionate (2 × 10^–7 to 1.11 × 10^–5 M), and gave a higher sensitivity than any previous methods without solvent extraction.     

Spectrophotometric analysis of iodide oxidation by chlorine in highly mineralized solutions

A spectrophotometric method for determining the concentrations of various iodine compounds (I⁻: initial compound, I₃⁻: under-oxidized iodine form, I₂ and I₂Cl⁻: target iodine forms and ICl₂⁻: over-oxidized iodine form) in their joint presence has been developed in order to study iodine processing from underground brines in Turkmenistan which are characterized by considerably higher mineralization and lower iodide content compared than those in Japan and USA. It was found that solutions with constant iodine concentrations and variable chloride concentrations had an isosbestic point at 474 nm with a molar absorbtivity of I₂ plus I₂Cl⁻ of 610.2 l mol⁻¹ cm⁻¹, while the absorbance of other iodine forms at this wavelength was negligible. This allowed us to use an absorbance at 474 nm for calculating the iodine concentration in solutions of variable chloride concentration. For calculating concentrations of other iodine compounds, absorbances at other wavelengths were used: 225 nm (I⁻ and ICl₂⁻), 248 nm (I₂Cl⁻) and 350 nm (I₃⁻). Beer’s law was valid for all iodine compounds in solutions with constant salt concentrations at all wavelengths. The authors have also developed a detailed algorithm for calculating the concentrations of the various iodine forms in their joint presence. The method was applied to solutions with various chloride concentrations and additions of microcomponents of natural solutions (bromide and iron ions, naphthenic acid and hydrogen sulfide). The overall precision for calculating the concentrations of various iodine compounds was <5% for solutions with an oxidant excess of <2-fold, and with chloride concentrations of <5 mol l⁻¹.     

Membrane disordering induced by chloroform and carbon tetrachloride

We studied effects of chloroform and carbon tetrachloride on bilayer membranes of dimyristoyl-phosphatidylcholine (DMPC) and egg yolk phosphatidylcholine (Egg-PC) by birefringence, dynamic light scattering and fluorescence methods. It is shown that interference light due to the membrane birefringence considerably decreases by addition of the organohalogen compounds for both lipid membranes, indicating a significant decrease in membrane order. In addition, results of dynamic light scattering and turbidity measurements show a rupture of multilamellar DMPC vesicles induced by addition of chloroform at concentrations above 0.2 v/v%. No rupture of the vesicles is observed within the limit of solubility of carbon tetrachloride in water, but excessive addition of carbon tetrachloride (above 0.2 v/v%) induces the vesicle rupture. Chain orientational order was estimated from the interference light intensity at low concentrations of the organohalogen compounds without the occurrence of the vesicle rupture. The estimation shows a monotonic decrease in the chain order with increasing the concentration. The decreases in DMPC chain order by chloroform and by carbon tetrachloride are about 17% at 0.2 v/v% and 23% at 0.05 v/v%, respectively. The reduction in the chain order is correlated with an increase in the membrane fluidity observed by excimer fluorescence of pyrene incorporated to the membrane. Behavior of membrane disordering of Egg-PC is approximately similar with that of DMPC. This implies the strong interaction between the organohalogen compounds and the lipid chains, whether or not the bilayer has the vacancy resulted from unsaturated double bonds and different chains in length. The results of this work suggest that damages of biological membranes by chloroform and tetrachloride are not only induced by a direct attack on proteins but also by a significant membrane disorder.     

苦参碱在多壁碳纳米管修饰玻碳电极上的电催化氧化及其电分析方法

研究了苦参碱(Matrine, MT) 在多壁碳纳米管修饰玻碳电极(MWCNT/GCE)上的电化学行为. 与GCE相比, MT在MWCNT/GCE上峰电位负移120 mV, 峰电流增大约2.5倍, 表明MWCNT/GCE对MT的电化学氧化具有良好的催化作用. 同时测定并计算了MT在MWCNT/GCE上的电极过程动力学参数: 电子转移系数α、电极反应速率常数ks、扩散系数D. 运用差分脉冲伏安法对苦参碱样品含量进行测定, 相对标准偏差为0.12%～2.9%, 加标回收率为98.4%～99.0%. 该方法可用于MT的电化学定量测定.     

Chlorination of various substrates in subcritical carbon tetrachloride

Various aliphatic hydrocarbons and the side chains of aromatic hydrocarbons were chlorinated in subcritical carbon tetrachloride. Chlorination of aromatic compounds including 1,4-disubstituted benzenes was investigated. Ketones and sulfones were stable under the employed conditions. Sulfoxides were converted into sulfides in a low to modest yields. The coupling adducts between olefins and carbon tetrachloride were obtained from the reactions of olefins.     

Spectrophotometric determination of aluminum and copper ions using spadns

Aluminum and copper ions are selectively estimated spectrophotometrically. These ions form colored complexes with spadns which have a maximum absorbance at 580 nm. The complexes formed with both cations are stable and pH dependant; aluminum is favorably complexed at pH 5, while copper is complexed at pH 7.The percentage recoveries were found to be 99.69 ± 0.75 and 99.32 ± 0.6 with a minimum detection limit of 0.08 and 0.23 g ml^–1 for aluminum and copper ions respectively. There is insignificant interference from the 10-fold concentrations of other metal ions under the proposed reaction conditions.     

Simultaneous Determination of Micro Bromide and Iodide by Kinetic Spectrophotometric Method

ABSTRACT

ABSTRACTA new kinetic spectrophotometric method for the simultaneous determination of concentrations of micro bromide and iodide has been proposed. It is based on their catalytic effects on the reaction of m-cresol purple oxidized by potassium periodate in hydrochloride acid medium. The reaction rate was monitored by measuring the decrease in absorbance at 528nm and the increase in absorbance at 455nm. The total difference in absorbance of the sum of bromide and iodide is identical with determination of bromide was carried out after Cr(VI) oxidized I? to I₂, and I₂ was removed by extraction with CCI₄, and the amount of iodide was measured by subtracting the absorbance change of bromide from the total absorbance change in the presence of bromine and iodide. The optimum conditions influencing the reaction rate were studied. The linear range of determination is 0～4.0μg/ml for Br? and 0～3.0 μg/ml for I?. The detection limits are 0.032μg/ml for Br? and 0.059 μ/ml for I?. The method was successfully applied to the determination of micro amounts of bromide and iodide in food and life samples.     

Electrochemical determination of iodide on a vanadium oxide-polypropylene carbonate coated glassy carbon electrode

A vanadium oxide-modified glassy carbon electrode was simply and conveniently fabricated by casting vanadium tri(isoproxide) oxide (VO(OC₃H₇)₃) and poly(propylene carbonate) (PPC) onto the glassy carbon electrode surface. The electrochemical properties of iodide at the VO(OC₃H₇)₃-PPC film-modified glassy carbon electrode were investigated by cyclic voltammetry, and an anodic peak was observed at approximately +0.71 V (vs. SCE). Based on this, a sensitive and convenient electrochemical method was proposed for the determination of iodide. Flow injection amperometry (FIA) exhibited a good linear relationship with the concentration of iodide in the range of 5 × 10⁻⁷ mol L⁻¹ and 1 × 10⁻³ mol L⁻¹, and the detection limit was 1 × 10⁻⁷ mol L⁻¹. Quantitative recovery of iodide in synthetic samples has been obtained and the interferences from different cations and anions have been studied. The method has been successfully applied to the determination of iodide in dry edible seaweed. The concentrations of iodide measured by this method are in good agreement with those obtained by spectrophotometric method.     

Phylogenetic characterization of a mixed microbial community capable of degrading carbon tetrachloride

Two bacterial communities (NO92 and GBS) capable of degrading carbon tetrachloride (CT) were enriched from in-house CT-contaminated water. These communities are able to degrade CT in the presence of toluene. To characterize the community structure and diversity, one enrichment (NO92) was subjected to 16S ribosomal RNA (rRNA) gene-based molecular analysis. The 16S rRNA genes were amplified from the bulk genomic community DNA and cloned into plasmid vectors. Unique 16S rRNA gene clones, i.e., phylotypes, were detected by four tetrameric restriction enzymes. Together, 123 16S rRNA gene clones were obtained; thirty-one showed different restriction fragment length polymorphism (RFLP) patterns. About 73% of the clones belong to two dominant RFLP patterns. Phylogenetic analysis based on the partial 16S rRNA gene sequences of 10 major phylotypes showed that all the phylotypes that were sequenced were affiliated with the high G+C Gram-positive bacteria. Whereas seven of the phylotypes (∼80% of the clones) were closely related to Rhodococcus, the other three (∼5% of the clones) were related to Curtobacterium. These results suggest that this CT-degrading community is diverse but is predominated by closely related bacterial groups.     

Spectrophotometric determination of cloud point of Brij 35 nonionic surfactant

The cloud point of nonionic surfactant polyoxyethylene (23) lauryl ether (Brij-35) was determined in the presence of various inorganic electrolytes. The measurements of cloud point (CP) were carried out with UV-vis spectrophotometer instead of visual observation. CP of Brij-35 could not be measured directly because its CP is more than 100 °C. Therefore, CP values of Brij-35 were lowered by the addition of electrolytes. In this study, NaF, NaCl, NaBr, KNO₃, K₂CO₃, K₃PO₄, Li₂SO₄, Na₂SO₄, K₂SO₄, (NH₄)₂SO₄, CuSO₄, ZnSO₄, CoSO₄ were used as electrolytes. Linear lines which were drawn with CP values were extrapolated to zero electrolyte concentration. The real CP value of Brij-35 which is merely listed as >100 °C in the literature was found as 118.5 ± 0.5 °C for all samples. Furthermore, the effects of the nature of the cation and the anion and the valencies of the cations on CP were reported and the rate of decrease in CP with concentration is discussed.     

Spectrophotometric determination of microamounts of yttrium with 1-amino-4-hydroxyanthraquinone

Summary 1-amino-4-hydroxyanthraquinone (AMHA) is proposed as a spectrophotometric reagent for the determination of yttrium. The solution equilibria ofAMHA complexes with Y(III) have been studied spectrophotometrically in 50% (v/v) ethanol at 25°C and an ionic strength ofI=0.1 mol·dm^–3 (NaClO₄). The complexation reactions were investigated and characterized using graphical logarithmic analysis of the absorbance graphs. The composition, molar absorptivities, and stability constants of the chelates ofAMHA with Y(III) have been determined spectrophotometrically. A simple, rapid, selective, and sensitive method for the spectrophotometric determination of microamounts of Y(III) is developed based on the formation of the violet YLH⁺ complex with _max=580nm atpH 6.2(=0.98×10⁴l·mol^–1·cm^–1). Interferences and their elimination have been studied. Many foreign ions are tolerated in considerable amounts; 45–60 fold amounts of rare earths do not interfere with the determination of yttrium. In the determination of yttrium in synthetic polymetallic samples the relative error and relative standard deviation of the method were found to be better than 1 and 0.5%, respectively.

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Spektrophotometrische Bestimmung von Mikromengen Yttrium mit 1-Amino-4-hydroxyanthrachinon

Zusammenfassung 1-Amino-4-hydroxyanthrachinon (AMHA) wird als spektrophotometrisches Reagens zur Bestimmung von Yttrium vorgeschlagen. Die Gleichgewichte von Komplexen ausAMHA und Y(III) in Lösung wurden in 50% (v/v) Ethanol bei 25°C und einer lonenstärke vonI=0.1M (NaClO₄) untersucht. Die Komplexierungsreaktionen wurden durch graphische logarithmische Analyse der Extinktionskurven charakterisiert. Die Zusammensetzungen, die molaren Extinktionen und die Stabilitätskonstanten der Chelate vonAMHA mit Y(III) wurden spektrophotometrisch bestimmt. Eine einfache, schnelle, selektive und empfindliche Methode zur spektrophotometrischen Bestimmung von Mikromengen Y(III) wurde entwickelt. Sie basiert auf der Bildung des violetten YLH⁺-Komplexes mit _max=580 nm beipH 6.2 (=0.98×10⁴l·mol^–1·cm^–1). Störungen und ihre Beseitigung werden ebenfalls diskutiert. Viele Fremdionen werden in beträchtlichen Mengen toleriert; 45–60 facher Überschuß an Seltenen Erden stört die Bestimmung von Yttrium nicht. Der relative Fehler und die relative Standardabweichung der Methode bei der Bestimmung von Yttrium in synthetischen polymetallischen Proben waren besser als 1 bzw 0.5%.

     

Sequential injection spectrophotometric determination of trace amounts of iodide by its catalytic effect on the 4,4'-methylenebis(N,N-dimethylaniline)-chloramine-T reaction

A simple and sensitive sequential injection spectrophotometric procedure is proposed for the determination of trace amounts of iodide in pharmaceutical preparations. The method is based on the catalytic effect of iodide on the (tetra base) 4,4′-methylenebis(N,N-dimethylaniline)-chloramine-T reaction in acidic solution. The method involves a sequential aspiration of 255 μl sample/standard followed by 170 μl tetra base and then 128 μl chloramine-T solutions into a carrier stream to be stacked inside a holding coil and flow reversed through a reaction coil towards a detector. The resulting colored compound is measured at 600 nm using an UV/Vis-spectrophotometer. All the parameters that affect the reaction were evaluated and the calibration curve is linear over a range of 0.1–6.0 μg l⁻¹ of iodide concentration with detection limit of 0.05 μg l⁻¹. A sample throughput of 80 samples per hour and relative standard deviation of less than 2.0% was achieved. The method is successfully applied for the determination of iodide in three different samples (tablets).     

Spectrophotometric determination of tin in copper-based alloys using pyrocatechol violet

In the present paper, a new procedure using Pyrocatechol Violet (PCV) for the determination of tin in copper-based alloys is proposed. The use of HEDTA as masking agent allowed tin to be determined in the presence of large amounts of copper, without any separation procedure. The method is more selective than previous methods. Cetyltrimethylammonium bromide (CTAB) and Tween-20 are used to increase the stability of the system.

The method can be applied directly to an acidic solution of Sn(IV) in the range 2.0–60.0 μg with a final volume of 50 ml. The pH is adjusted to 2.0 ± 0.2 with glycine buffer and, after 30 min, the absorbance is measured at 660 nm. Al(III), Cd(II), Co(II), Mg(II), Ca(II), Mn(II), Ni(II) and Pb(II) do not interfere at the 500 mg level; 20 000 μg of Cu(II) and 400 μg of NaCl can be present. The interference at 100 μg of Fe(III) can be masked with ascorbic acid. Bi(III), Sb(V), Ti(IV), Mo(VI), EDTA, tartrate, citrate and iodide interfere. The proposed method was used for tin determination in several copper-based alloys and a comparison of the analytical results with certified values indicates that the procedure provides accurate and precise results.     

Generation of alkyl hypochlorites in oxidation of alcohols with carbon tetrachloride catalyzed by vanadium and manganese compounds

Primary alcohols and diols with various structures were subjected to transformations into esters, aldehydes, ketones, and lactones under the action of carbon tetrachloride in the presence of manganese compounds (MnCl₂, MnO₂, Mn(OAc)₂, Mn(acac)₃) and vanadium compounds (VCl₅, V₂O₅, VO(acac)₂) as catalysts. These transformation proceeded with the involvement of alkyl hypochlorites, which were generated in the course of oxidation of alcohols with carbon tetrachloride catalyzed by manganese or vanadium compounds. The optimum molar ratios between the catalyst and reagents were determined, and the reaction conditions for the highly selective synthesis of esters, aldehydes, ketones, and lactones from alcohols were found.     

Spectrophotometric and derivative spectrophotometric determination of copper (II) with dithizone in aqueous phase

A Spectrophotometric and derivative Spectrophotometric study of Cu-dithizonate complex in aqueous phase in the presence of Triton X-100, a neutral surfactant, is reported. The system obeys Beer's law between 1.0 × 10^–6–9.0 × 10^–6 mol/l of Cu²⁺; detection limit is 12 ng/ml. The molar absorption coefficient, specific absorptivity and Sandell's sensitivity of the complex are 3.06 × 10⁴ 1 mol^–1 cm^–1, 0.4825 ml g^–1 cm^–1 and 2.1 × 10^–3 g cm^–2, respectively. The conditional stability constant of the 1 2 complex, calculated considering simultaneously existing equilibria, has been found to be 1.73 × 10¹¹ I² mol² (I = 0.07, pH 1.4, temperature = 10 °C). Absorption studies in the derivative mode have been carried out to determine the absorption maximum of the complex and to overcome interference due to the presence of certain metal ions. The method has been validated by determination of copper in beers, wines, human hair, goat liver and fly ash samples.     

Surface and bulk behavior of (dialkylsulfoxides + carbon tetrachloride) mixtures

Surface tensions, surface tension deviations, densities, and excess molar volumes of binary mixtures of carbon tetrachloride (CCl₄) with dimethylsulfoxide (DMSO), diethylsulfoxide (DESO), dipropylsulfoxide (DPSO), and dibutylsulfoxide (DBSO) have been determined over the entire composition range at (298.15 and 313.15) K. The results were fitted by the Redlich–Kister polynomial equation and the corresponding binary coefficients have been derived.The obtained excess quantities show that both charge-transfer complex formation between CCl₄ and dialkylsulfoxides (DASO) molecules and on the other hand sulfoxides’ chain length are crucial factors conditioning the excess thermodynamic properties of (CCl₄ + DASO) binary mixtures.     

甲基红氧化褪色光度法测定食盐中碘

基于在盐酸介质中 ,碘酸根在溴化钾的催化作用下使甲基红氧化褪色的反应 ,建立了测定微量碘的新方法。方法的线性范围为 8μg/2 5mL～ 2 2 μg/2 5mL ,表观摩尔吸收系数为 6 .5× 1 0 4 L·mol- 1 ·cm- 1 ,已用于食盐中碘的测定。     

Catalysis of novel enzymatic iodide oxidation by fungal laccase

A fungal laccase (Myceliophthom thermophila) has been shown to function as an iodide oxidase. Unlike other halides which interact with the type 2 copper site and are inhibitors for the laccase, iodide interacts with the type 1 copper site and serves as a substrate capable of donating an electron to the laccase. Under anaerobic conditions, the interaction between the laccase and iodide results in the reduction of the laccase type 1 copper and the concomitant oxidation of iodide to form iodide. In aerated solutions, the laccase catalyzes the oxidation of iodide to iodine and the concomitant reduction of dioxygen to water. The reaction exhibits typical Michaelis kinetics with aK _m of 0.16 ± 0.02M and ak _cat of 2.7 ± 0.2 turnovers per min at the optimal pH (3.4). The catalysis can be enhanced by 2,2′-azino-bis-(3-ethylbenz-thiazoline-6-sulfonic acid), which shuttles electrons rapidly between iodide and the laccase. Bilirubin oxidase also demonstrates significant iodide oxidase activity, suggesting that the property could be a common feature for copper-containing oxidases. Possible industrial and medicinal applications for a laccase-based iodine production system are discussed.     

Spectrophotometric determination and kinetic studies of condensation of aromatic aldehydes with 1,3-dimethylbarbituric acid

The condensation reaction of 1,3-dimethylbarbituric acid with aromatic aldehydes in ethanol has been investigated spectrophotometrically at 25–35°C. The reaction follows overall second-order kinetics, first-order each in reactant. From the dependence of the rate constants on temperature, activation parameters have been calculated. The rate of condensation increases with the presence of electron donating groups on the aromatic ring of the aldehyde. The rate-determining step involves dehydration of the aldol intermediate. The reaction was found to be catalyzed by HCl solutions. Based on this reaction, determination of 10 aromatic aldehydes in a concentration range of 0.13–70.25 μg/ml is proposed. The method was applied for determination of barbituric and 1,3-dimethylbarbituric acids also.