Studies on the equilibria in Ag(I) - 1,4,8,11-tetraazacyclotetradecane and Ag(I) - 1,4,8,11-tetramethyl-1,4,8,11-tetraazacyclotetradecane systems in water

Summary Protonation constants of 1,4,8,11-tetraazacyclotetradecane (T ACT) and 1,4,8,11-tetramethyl-1,4,8,11-tetraazacyclotetradecane (TMT ACT) (=0.1) were determined bypH-metry. The values are logK ₁=10.922, logK ₂=10.511, logK ₃=2.646, logK ₄=1.620 forT ACT, and logK ₁=9.387, logK ₂=9.050, logK ₃=2.491, logK ₄=1.380 forTMTACT. Absorption maxima of the complexes AgTA CT(NO₃)₂ and AgTMTACT(NO₃)₂ were found to be ₁=280 nm, ₂=350 nm, and ₁=290 nm, ₂=400 nm, respectively. The disproportionation constants of Ag(I) ions in the presence of the amines were determined by potentiometry: forTA CT logK _d =12.778, and forTMT ACT logK _d =11.778. The mechanisms of the electrode processes taking place in solutions of the complexes under investigation were examined by means of chronovoltamperometric and coulometric measurements. The formal potential,E _f ⁰ , of the system: AgTMT ACT ²⁺+e AgTMT ACT ⁺ is +0.450 V vs. NHE.

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Untersuchungen zu den Gleichgewichten Ag(I) -1,4,8,11-Tetraazacyclotetradekan und Ag(I) -1,4,8,11-Tetramethyl-1,4,8,11-tetraazacyclotetradekan in Wasser

Zusammenfassung Die Protonierungskonstanten von 1,4,8,11-Tetraazacyclotetradekan (TACT) und 1,4,8,11-Tetramethyl-1,4,8,11-tetraazacyclotetradekan (TMT ACT) wurdenpH-metrisch bei =0.1 bestimmt. Folgende Werte wurden ermittelt: logK ₁=10.922, logK ₂=10.511, logK ₃=2.646, logK ₄=1.620 fürTACT und logK ₁=9.387, logK ₂=9.050, logK ₃=2.491, logK ₄=1.380 fürTMT ACT. Die Absorptionsmaxima der Komplexe AgTACT(NO₃)₂ und AgTMTACT(NO₃)₂ waren ₁=280 nm, ₂=350 nm, bzw. ₁=290 nm, ₂=400 nm. Die Disproportionierungskonstanten der Ag(I)-Ionen in Gegenwart der Amine wurden potentiometrisch bestimmt: logK _d =12.778 fürTACT und logK _d =11.778 fürTMTACT. Der Mechanismus des Elektrodenprozesses in den Komplexlösungen wurde mittels Chronovoltamperometrie und Coulometrie überprüft. Das formale PotentialE _f ⁰ des Systems AgTMT ACT ²⁺+eAgTMT ACT ⁺ ist +0.450 V gegenüber NHE.

     

Solid-phase extraction and spectrophotometric determination of trace amounts of copper in water samples

A simple method for rapid and selective extraction, preconcentration and determination of copper as it's neocuproine complex by using octadecylsilica membrane disks and spectrophotometry is presented. Extraction efficiency and the influence of flow rates of sample solution and eluent, pH, amount of neocuproine and hydroxylamine hydrochloride, type and least amount of eluent for elution of copper complex from disks, break through volume and limit of detection were evaluated. Also the effects of various cationic interferences on percent recovery of copper were studied. Extraction efficiencies >99% were obtained by elution of the disks with minimal amount of solvent. The limit of detection of the proposed method is 0.12 ppb. The method was applied to the recovery and determination of copper in different water samples.     

Electron paramagnetic resonance study of partially oriented clay platelets intercalated with copper(II) 1,4,8,11-tetraazacyclotetradecane

Electron paramagnetic resonance (EPR) spectra of powder and oriented films of montmorillonite, hectorite, and saponite intercalated with [Cu(cyclam)](2+) (cyclam = 1,4,8,11-tetraazacyclotetradecane) exhibit three components: an orientation-dependent component without hyperfine features, an orientation-dependent component with hyperfine features, and an orientation-independent component without hyperfine feature. EPR spectra of [Cu(cyclam)](2+)-saponite, which exhibit only two components and the best resolved hyperfine features, were simulated. The spectra indicate that a large portion of the saponite platelets are inclined to the glass surface, although they tend to align with their basal planes parallel to the glass surface. The orientation-dependent spectra could be simulated by introducing a Gaussian distribution with a standard deviation of 20 degrees for the inclination angle. The standard deviation may be used as a disorder parameter for the microcrystals assembled on glass plates. Spectral simulation also shows that the CuN(4) plane of [Cu(cyclam)](2+) is parallel to the clay layers. EPR spectra of some other partially oriented systems are also discussed.     

Suspended droplet solvent microextraction-flame atomic absorption spectrometry (SDSME-FAAS) determination of trace amounts of copper in river and sea water samples

A simple and sensitive suspended droplet solvent microextraction (SDSME) method is proposed for the preconcentration and determination of copper by flame atomic absorption spectrometry (FAAS). The analytical procedure is based upon the formation of a complex between Cu(II) and 1-phenyl-1,2-propandione-2-oxime-thiosemicarbazone (PPDOT) as a complexing agent. After extraction of the complex by 1-octanol, copper concentration in the solvent drop was determined by FAAS. The effect of different parameters such as pH, PPDOT concentration, kind of buffer, kind and volume of organic solvent, volume of aqueous phase, extraction time, stirring rate of sample solution, temperature, and ionic strength were investigated. The effect of foreign ions on the determination was also studied. Under the optimized chemical and instrumental conditions, a linear calibration curve was achieved in the range of 0.0050–0.26 mg/L, with the limit of detection of 3 μg/L and the enrichment factor of 52.6. This method can be applied successfully to the determination of copper in water samples.     

Determination of trace amounts of phosphate in river water by flow-injection analysis

A flow-injection analysis system for the determination of trace amounts of phosphate in river water has been developed. The phosphate is reacted with molybdate and Malachite Green in acidic medium to form a green species, the absorbance of which is measured at 650 nm. Phosphorus (as inorganic phosphate) can be determined at the level of several ng ml in water. Analyses can be done at a rate of up to 40 per hour.     

Determination of trace amounts of carbaryl in water by solid-phase laser-induced fluorescence

A quick and very sensitive method is proposed for the determination of the insecticide carbaryl, following transformation in 1-naphthol, using solid-phase fluorescence excited by a pulsed nitrogen laser and detected with a charge-coupled device. Carbaryl is hydrolized in an alkaline medium resulting in 1-naphthol. This hydrolysis product is fixed on QAE Sephadex A-25 gel at pH 11.20. The fluorescence of the gel, packed in a 1 mm silica cell, was measured directly using a solid-surface attachment. The detection limit obtained was 1.8 ng. A recovery study was carried out on several types of water samples to check the efficiency of the method. The results obtained are compared with data published in a previous paper where the LS-50 spectrofluorimeter was used. The detection and quantification limits are improved here by an order of magnitude.     

Simultaneous determination of trace amounts of zinc, lead and copper in rum by anodic stripping voltammetry

The determination of traces of Zn, Pb and Cu in rum samples by anodic stripping voltammetry without previous treatment or addition of a supporting electrolyte, using a hanging mercury drop electrode, is described. The choice of an appropriate stripping voltammetric method and deposition potential minimizes the influence of the organic content and ensures good reproductibility of the measurements. The reliability of the method was tested by comparing the results with those given by absorption spectrometry, the differences being about 10%. The method allows heavy metal ions to be determined in the mug l(-1) concentration range.     

Trivalent Copper Complexes with 1,4,8,11-Tetramethyl-1,4,8,11-tetraazacyclotetradecane in Aqueous Solutions. A Pulse Radiolysis and Electrochemical Study

The mechanisms and kinetics of the formation and decomposition of the complexesCu^IIIL_aq and [LCu^IIIN₃]²⁺ are reportedand discussed.     

Essential serum trace metals: II. Determination of copper and zinc

Several complexing ligands for copper and zinc were tested for their feasibility as analytical reagents. Of these, tetraethylthiuram disulfide and its analog, bis (1-piperi-dylthiocarbonyl) disulfide were selected for copper with some advantages determined to accrue to each. Two others, 1-(2-pyridylazo)-2-naphthol and 1-[(5-chloro-2-pyridyl) azo]-2-naphthol were selected for zinc with the preference given to the former for stability of color formed and accessibility of the reagent although the chloro analog is inherently the more sensitive of the two reagents. For those who do not have atomic absorption spectrophotometry at their disposal, the molecular absorption approach still appears to be an excellent one with good selectivity for the two metals described.     

Steric effects in the complexation kinetics of copper(II) with rac-5,5,7,12,12,14-hexamethyl 1,4,8,11-tetraazacyclotetradecane in basic aqueous media

Copper(II) reacts with rac-5,5,7,12,12,14-hexamethyl-l,4,8,11-tetraazacyclotetradecane (tet-b) in strongly basic aqueous media to give [Cu(tet-b) (OH) (blue)]⁺ which contains trigonal bipyramidally co-ordinated Cu²⁺ with the tet-b ligand in its most stable, folded form. The kinetics of formation of this blue complex have been studied at 25.0° ± 0.1°C using the stopped-flow technique. Second-bond formation is proposed as the rate-determining step for tet-b reaction with Cu(OH)^-₃ and Cu(OH)^2-₄. Possible mechanisms for the reaction and the steric effects resulting from the methyl groups on the alkyl backbone of the macrocyclic ligand are considered.     

阻抑动力学光度法测定水样中的痕量铋

基于弱酸介质中, 在十二烷基磺酸钠(SDS)存在下, 痕量Bi3 对H2O2氧化结晶紫(CV)的褪色反应有明显的阻抑作用, 建立了测定痕量Bi3 的阻抑动力学光度法, 研究了该反应的最佳实验条件和动力学参数. 结果表明, 该方法检出限为2.77×10-8 g/L, 线性范围为0～0.008 μg/mL. 可用于环境水样中铋的测定.     

Determination of zinc,cadmium, lead and copper in sea water by means of computerized potentiometric stripping analysis

Water samples from the Arctic Sea were analyzed by the potentiometric stripping technique. Lead(II) and cadmium(II) were determined after pre-electrolysis for 32 min at—1.1 V vs. Ag/AgCl, the detection limits being 0.06 and 0.04 nM, respectively. Zinc(II) was determined after the addition of gallium(III) by pre-electrolysis for 16 min at —1.4 V vs. Ag/AgCl, the detection limit being 0.25 nM. Problems in the determination of copper(II) at the very low concentrations found in oceanic waters are outlined. The average zinc(II), cadmium(II) and lead(II) concentrations in eight different samples were 2.5, 0.16 and 0.10 nM as determined by potentiometric stripping analysis and 1.9, 0.16 and 0.09 nM as determined by solvent extraction/atomic absorption spectrometry. The advantages of this computerized technique for the analysis of sea water are discussed.     

Determination of zinc and copper with morpholine

Summary In morpholine has been found an organic base which is useful as an analytical reagent, and may serve for the purpose of quantitative determination of zinc and copper. In both cases, the analytical procedure is of a very simple nature, and yields good results. Morpholine may be useful for the separation of amphoteric ions of electropositive character from those of electronegative character.

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Zusammenfassung Die organische Base Morpholin hat sich als analytisch brauchbares Reagens herausgestellt, das für die quantitative Bestimmung von Zink und Kupfer benützt werden kann. Bei beiden Bestimmungsarten ist die analytische Methode sehr einfach und liefert gute Ergebnisse. Morpholin dürfte sich für die Trennung amphoterer Ionen elektropositiven Charakters von solchen elektronegativen Charakters als nützlich erweisen.

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Résumé On pouvait montrer, que la base organique morpholine est un réactif, qui peut servir à la détermination du zinc et du cuivre. L'application de la méthode pour la détermination des deux ions, nommés ci-dessus, est très simple et donne de bons résultats. Il semble, que la morpholine pourra être utilisable pour la séparation des ions d'un caractère électropositif des ions d'un caractère électronégatif.

     

Determination of trace amounts of formaldehyde in acetone

A method to quantify sub-ppm levels of formaldehyde in acetone has been developed and it is reported here. In this method, the different reactivities and stabilities of sulfite with formaldehyde and acetone are used to separate the two carbonyl compounds. Sulfite reacts with formaldehyde to form hydroxymethanesulfonate (HMS), the non-volatile and stable nature of which allows its separation from bulk acetone solvent. The resulting HMS is then converted back to formaldehyde under basic conditions, and formaldehyde is derivatized with 2,4-dinitrophenylhydrazine (DNPH) and quantified in its DNP hydrazone form using high-performance liquid chromatography-UV detection. The method detection limit at the 99% confidence level was 0.051 mg L⁻¹. A batch of samples can be processed within 4 h. The method has been applied to quantify the amount of formaldehyde in an analytical-grade acetone and in a commercial nail polish remover and the level of formaldehyde was found to be 0.175 and 0.184 mg L⁻¹, respectively.     

Updated investigation of the reaction between copper and naphthol blue black b and determination of trace amounts of copper in water

The biological dye, naphthol blue black B (NBBB) was found to produce a sensitive reaction with copper(II) at pH over 7. This reaction was very interesting. The complexation of Cu(II) with NBBB happened at pH between 6 and 11 but the redox catalytic reaction happened at pH over 11, where copper(II) served as a catalyst. In this study, ordinary spectrophotometry was limited for use because of the serious interference of excess reactant. A new method, Β-correction principle, was applied because it can eliminate the above interference. This method can give the simple determination of properties of Cu-NBBB complex solution at pH 9.5, which involved the complex ratio, real molar absorptivity, and stability constant (K). Results showed that the formed Cu-NBBB complex occurred as Cu(NBBB) at pH 9.5, its real rather than apparent absorptivity was equal to 7.62 x 10³ L mol^-1 cm^-1 at 630 nm, and its stability constant was 1.32 x 10⁶. The redox catalytic reaction between Cu(II) and NBBB at pH 13 was used to determine trace amounts of copper in water. This reaction was very sensitive and highly selective. Most of the metals did not interfere with the direct determination of copper. The detection limit of copper was 0.002 mg/L, and the recovery was between 90 and 104% with the relative standard deviation of less than 11%. This article was submitted by the author in English.     

Determination of trace amounts of sulphur in selenium

Determination of trace amounts of sulphur as Methylene Blue after reduction of sulphate to sulphide by hydriodic and hypophosphorous acids in acetic acid solution is applied to the determination of trace amounts of sulphur in selenium after removal of the selenium by evaporation with hydrobromic acid. Samples of 100 mg or less of selenium are chosen if the sulphur content is greater than 5-10 ppm; the time required for the separation is about 1.5 hr; 100 ppm of sulphur has been determined with a coeffident of variation of 5.2%. If the sulphur content is less than 5 ppm, 1-g samples must be taken and the time required is then about 3 hr; 0.4 ppm of sulphur has been determined with a standard deviation of 0.13 ppm. The accuracy of the method seems to be well within the random error.     

Determination of trace amounts of Germanium in CdS

Summary By an indirect method germanium can be determined by application of flameless atomic-absorption spectrometry to germanomolybdic acid. With this procedure some difficulties inherent in the AAS determination of Ge can be avoided and the detection limits are improved. Furthermore there is an amplification reaction because of the 121 MoGe ratio in the germanomolybdic acid. Determination of Ge at the ppm level in CdS is possible and results for this are reported.

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Zusammenfassung Germanium kann auf indirektem Wege durch Anwendung der flammenlosen Atomabsorptions-Spektrometrie auf Germanomolybdänsäure bestimmt werden. Damit können einige Schwierigkeiten vermieden werden, die der Germaniumbestimmung mit Hilfe der AAS anhaften, außerdem werden so die Nachweisgrenzen verbessert. Darüber hinaus handelt es sich hier infolge des Verhältnisses MoGe=121 in der Germanomolybdänsäure um eine Verstärkungsreaktion. Die Bestimmung von ppm-Mengen Germanium in CdS ist auf diesem Wege möglich. Über Ergebnisse wurde berichtet.