Polymer-initiated photogeneration of silver nanoparticles in SPEEK/PVA films: direct metal photopatterning

Cross-linking of sulfonated poly(ether-ether)ketone-poly(vinyl alcohol) (SPEEK-PVA) materials yields flexible polymer films, possessing high light-sensitivity and ion-exchange capabilities. Adsorbed Ag+ ions are photoreduced in the film under illumination (lambda = 350 nm), leading to metal nanoparticle formation in places where the film has been exposed to the light. Nanoparticles form via reduction of Ag+ by the polymeric alcohol radicals, generated in the system as a result of photochemical H-abstraction from PVA molecules by the excited carbonyl triplet state of SPEEK. Use of the films for direct metal photopatterning is demonstrated.     

Preconcentration of nickel and cobalt on algae and determination by slurry graphite-furnace atomic-absorption spectrometry

Unicellular green algae have been utilized to preconcentrate Ni(2+) and Co(2+) ions from sea-water and riverine water samples. Studies have shown that rinsing the algae with 0.12M hydrochloric acid improves the adsorption of nickel and cobalt, and the optimum range of pH of extraction is wide. The maximum extraction efficiencies were 84 and 73% for Ni and Co, respectively, at ng/ml levels. The sea-water matrix and relatively small amounts of many impurities reduce the adsorption efficiency for both nickel and cobalt. The preconcentration is achieved by mixing 6 mg of algae with 50-100 ml of sample, and subsequently isolating the algae by centrifugation. The pellet of algae is then resuspended in 1 ml of 0.08M nitric acid, and analyzed as a slurry by graphite-furnace atomic-absorption spectrometry. The values found for nickel and cobalt in riverine (SLRS-1) and sea-water (CASS-1) standard reference materials are within the limits of certification.     

Isomorphic coordination polymers of cobalt(II), zinc(II) with a flexible ligand of cis,cis,cis-1,2,3,4-cyclopentanetetracarboxylic acid and their molecular alloys: crystal structures, thermal decomposition mechanisms and magnetic properties

Three new isomorphic coordination polymers of Co(2+), Zn(2+) ions with flexible multicarboxylic acid ligand of the cis,cis,cis-1,2,3,4-cyclopentanetetracarboxylic acid (H(4)L), [Co(4)L(2)(H(2)O)(8)]·3H(2)O (1), [Zn(4)L(2)(H(2)O)(8)]·3H(2)O (2) and [Co(0.8)Zn(3.2)L(2)(H(2)O)(8)]·3H(2)O (3), have been synthesized under hydrothermal conditions and by means of controlling the pH of the reaction mixtures (with an initial pH of 6.0 for 1, 4.0 for 2, and 5.0 for 3, respectively). In the crystal of 1, two crystallographically different Co(2+) ions (Co1 and Co2) form a negatively-charged coordination polymeric chain, which contains a centrosymmetric, linear, trinuclear Co(2+) cluster (Co(3)L(2)) subunit; another crystallographically independent Co(2+) ion (Co3) coordinated to six water molecules acts as a counter ions to link the neighboring coordination polymeric chains via intermolecular H-bond interactions. The Co(2+) ions in 1 were completely and partially replaced by Zn(2+) ions to give 2 and 3, respectively. Complex 3 shows a novel molecular alloy nature, due to the random distributions of the Co(2+) and Zn(2+) ions. Three isomorphic complexes exhibit distinct thermal decomposition mechanisms. The deprotonated cis,cis,cis-1,2,3,4-cyclopentanetetracarboxylic acid ligands decompose at 420-750 °C to give the residue CoO in 1, ZnO + C in 2 and CoO + ZnO in 3. Complex 1 shows a complicated magnetic behavior with co-existence of antiferromagnetic exchange interactions between neighboring Co(2+) ions as well as strong spin-orbital coupling interactions for each Co(2+) ion; complex 3 exhibits a magnetically isolated high-spin Co(2+) ion behavior with strong spin-orbital coupling interactions.     

Adsorption of some bivalent heavy metal ions from aqueous solutions by manganese nodule leached residues

The leached residue, generated after selective extraction of Cu, Ni, and Co in sulfur dioxide-ammonia leaching of manganese nodules, was characterized and batch isothermal adsorption experiments were conducted at ambient temperature to evaluate the effectiveness of the water-washed leached residue for removal of different bivalent metal ions from aqueous synthetic solutions. The effects of pH, initial metal ion concentrations, amount of adsorbent, interfering ions, and heat treatment were also investigated. The uptake of metal ions increased with increasing pH. Under identical conditions the adsorption capacity increased in the order Cd(2+)相似文献   

Investigation of Co(II) sorption on GMZ bentonite from aqueous solutions by batch experiments

In this study, a local bentonite from Gaomiaozi county (Inner Mongolia, China) was converted to Na-bentonite and was characterized by FTIR and XRD to determine its chemical constituents and micro-structure. The removal of cobalt from aqueous solutions by Na-bentonite was investigated as a function of contact time, pH, ionic strength, foreign ions and temperature by batch technique under ambient conditions. The results indicated that the sorption of Co(II) was strongly dependent on pH. At low pH, the sorption of Co(II) was dominated by outer-sphere surface complexation or ion exchange whereas inner-sphere surface complexation was the main sorption mechanism at high pH. The Langmuir, Freundlich, and D-R models were used to simulate the sorption isotherms of Co(II) at the temperatures of 293.15, 313.15 and 333.15 K, respectively. The thermodynamic parameters (∆G°, ∆S°, ∆H°) of Co(II) sorption on GMZ bentonite calculated from the temperature-dependent sorption isotherms indicated that the sorption of Co(II) on GMZ bentonite was an exothermic and spontaneous process. The Na-bentonite is a suitable material for the preconcentration and solidification of Co(II) from aqueous solutions.     

Metal Complexes of Pharmacophore-Containing Pectin with d -Elements Ions (Cu 2+ , Co 2+ , and Mn 2+ )

Spectral methods have been used to study the complexation of apple pectin modified with organic pharmacophores (nicotinic, salicylic, 5-aminosalicylic, or anthranilic acid) with Cu2+, Co2+, and Mn2+ ions in an aqueous solution. The composition and stability series of the metal complexes, corresponding to the empirical Irving–Williams series, have been established. The standard thermodynamic parameters (ΔH°, ΔG°, and ΔS°) of the complexation process have been calculated. It has been shown by means of 13C NMR and IR spectroscopy that the interaction of pharmacophore-containing pectins with d-metal ions (Cu2+, Co2+, Mn2+) occurs via the carbonyl and hydroxyl groups of the modified polymer matrices. The viscosity and thermal properties of the metal complexes have been determined.     

Magnetic circular dichroism and cobalt(II) binding equilibrium studies of Escherichia coli methionyl aminopeptidase

Equilibrium dialysis of methionyl aminopeptidase from Escherichia coli (EcMetAP) monitored by atomic absorption spectrometry and magnetic circular dichroism (MCD) shows that the enzyme binds up to 1.1 +/- 0.1 equiv of Co(2+) in the metal concentration range likely to be found in vivo. The dissociation constant, K(d), is estimated to be between 2.5 and 4.0 microM. Analysis of the temperature and magnetization behavior of the two major peaks in the MCD spectrum at 495 and 567 nm suggests that these transitions arise from Co(2+) with different ground states. Ligand field calculations using AOMX are used to assign the 495 nm peak to Co(2+) in the 6-coordinate binding site and the 567 nm peak to Co(2+) in the 5-coordinate site. This is further supported by the fact that the binding affinity of the Co(2+) associated with the 567 nm peak is enhanced when the pH is increased from 7.5 to 9.0, consistent with having an imidazole ligand from a histidine amino acid residue. On the basis of the MCD intensities, it is estimated that, when the 5-coordinate site is fully occupied, 0.1 equiv of cobalt is in the 6-coordinate site. Even when the cobalt concentration is very low, there is a small fraction of binuclear sites in EcMetAP formed through cooperative binding between the 5- and 6-coordinate Co(2+) ions. The magnetization behavior of the 6-coordinate Co(2+) MCD peak is consistent with an isolated pseudo-Kramer doublet ground state, suggesting that the cobalt ions in the binuclear sites are not magnetically coupled.     

Immobilization of cellulase in nanofibrous PVA membranes by electrospinning

Electrospinning is a nanofiber-forming process by which either polymer solution or melt is charged to high voltages. With high specific surface area and porous structure, electrospun fibrous membranes are excellent candidates for immobilization of enzymes. In this paper, immobilization of cellulase in nanofibrous poly(vinyl alcohol) (PVA) membranes was studied by electrospinning. PVA and cellulase were dissolved together in an acetic acid buffer (pH 4.6) and electrospun into nanofibers with diameter of around 200 nm. The nanofibrous membranes were crosslinked by glutaraldehyde vapor and examined catalytic efficiency for biotransformations. The activity of immobilized cellulase in PVA nanofibers was over 65% of that of the free enzyme. Nanofibers were superior to casting films from the same solution for immobilization of cellulase. The activity of immobilized cellulase descended with ascending in enzyme loading efficiency and crosslinking time, which retained 36% its initial activity after six cycles of reuse.     

Removal of Co(II) from aqueous solution by using hydroxyapatite

Herein, hydroxyapatite (HAP) was prepared by aqueous precipitation technique and was characterized by using FT-IR and XRD to determine its chemical functional groups and micro-structure. The removal of cobalt from aqueous solution to HAP was studied by batch technique as a function of various environmental parameters such as contact time, pH, ionic strength, foreign ions, fulvic acid (FA), and temperature under ambient conditions. The results indicated that the sorption of Co(II) on HAP was strongly dependent on pH and ionic strength. The presence of FA enhanced the sorption of Co(II) on HAP at low pH, whereas reduced Co(II) sorption on HAP at high pH. The Langmuir, Freundlich and D-R models were used to simulate the sorption isotherms at three different temperatures of 303.15, 323.15 and 343.15 K. The thermodynamic parameters (ΔH°, ΔS° and ΔG°) calculated from the temperature dependent sorption isotherms indicated that the sorption process of Co(II) on HAP was spontaneous and endothermic. The sorption of Co(II) was dominated by outer-sphere surface complexation and ion exchange at low pH, whereas inner-sphere surface complexation or surface precipitation was the main sorption mechanism at high pH values. The results suggest that the HAP is a suitable material in the preconcentration and solidification of Co(II) from large volumes of aqueous solutions.     

Label-free colorimetric sensing of cobalt(II) based on inducing aggregation of thiosulfate stabilized gold nanoparticles in the presence of ethylenediamine

As a sensitive and selective analytical technique, gold nanoparticles-based colorimetric sensing was characterized by its simplicity and cost-effectiveness. Specific methods have been extensively developed for different targets in diverse samples. In this study, a label-free method for sensing Co(2+) in aqueous solutions was described. The target was achieved by the induced aggregation of thiosulfate (S(2)O(3)(2-)) stabilized gold nanoparticles (AuNPs) in the presence of ethylenediamine (en). Co(2+) first reacted with en and formed complexes of Co(en)(3)(2+) in aqueous solutions, which was followed by the oxidation of Co(en)(3)(2+) to Co(en)(3)(3+) by dissolved oxygen. Co(en)(3)(3+) then attacked S(2)O(3)(2-) ligands adsorbed on the AuNPs' surfaces, forming positively charged (en)(2)CoS(2)O(3)(+) on the AuNPs' surfaces, which reduced the surface charges of AuNPs and induced the aggregation of AuNPs. The process was accompanied by a red-shift in the adsorption spectrum and a visible colour change from wine red to blue. Potential effects of relevant experimental conditions, including pH, concentrations of S(2)O(3)(2-) and en, and incubation time were evaluated for optimization of the method. The proposed method is sensitive (LOD = 0.0 4 μM or 2.36 ppb) and selective (by at least 100-fold over other metal ions except for Cu(2+)) toward Co(2+) with a linear range from 0.1 to 0.7 μM. The cost-effective method allows rapid and simple determination of the concentrations of Co(2+) ions in drinking water.     

Co2+-selective membrane electrode based on the Schiff Base NADS

A new PVC membrane electrode for cobalt(II) ions based on a recently synthesized Schiff base of 5-((4-nitrophenyl)azo)- N-(2',4'-dimethoxyphenyl)salicylaldimine is reported. The electrode exhibits a Nernstian response for Co(2+) ions over a wide concentration range (9.0 x 10(-7)-1.0 x 10(-2) M) with a slope of 29(+/-1). The limit of detection is 8.0 x 10(-7) M. The proposed sensor revealed good selectivities over a wide variety of other cations including hard and soft metals. This electrode could be used in a pH range of 3.5-6.0. It was used as an indicator electrode in potentiometric titrations of cobalt(II) ions and can be used in the direct determination of Co(2+) in aqueous solutions.     

Copper (II) adsorption from aqueous solution by herbaceous peat

In this research, the herbaceous peat collected from Gavurgolu peatlands, one of the biggest Turkish peatlands, was utilized as an adsorbent for the removal of copper (II) ions from aqueous solution. Adsorption experiments were conducted under various conditions, i.e., initial concentration, temperature, and pH. While the amount of Cu (II) adsorbed on the peat increased with increasing concentration of Cu (II) ions, it was not markedly affected by temperature and pH. Percentage removal was higher at lower concentration. For example, the maximum percentage removal of Cu (II) ions for initial concentration of 3 x 10(-4) M was 97.04% at 21 degrees C and pH 5.5. The adsorption capacity (Q(0)) of the peat was 4.84 mgg(-1) from Langmuir adsorption isotherm for the concentration range of 3 x 10(-4)-6 x 10(-4) M at 21 degrees C and pH 5.5. The equilibrium time of adsorption of Cu (II) ions was 150 min and independent of concentration and temperature. The amount of Cu (II) adsorbed at equilibrium time did not considerably change with temperature and pH. It was also determined that adsorption isotherm followed both Freundlich and Langmuir. Uptake mechanism of Cu (II) ions by the peat occurs via cation exchange (especially by means of Ca(2+) and Mg(2+)) as well as copper/peat complexation. Adsorption kinetic was consistent with the pseudo-second-order model.     

Formation of ternary poly(acrylic acid)-surfactant-Cu2+ complexes in aqueous solution: quenching of pyrene fluorescence and pH-controlled "on-off" emitting properties

The formation of binary and ternary complexes of poly(acrylic acid) (PAA) with N, N, N, N-dodecyltrimethylammonium chloride (DTAC) and/or Cu (2+) ions is investigated in dilute aqueous solution through turbidimetry, viscometry, and pyrene fluorescence probing. It is shown that the PAA-DTAC and PAA-Cu (2+) complexation as well as the formation of ternary PAA-DTAC-Cu (2+) complexes are controlled from the pH of the aqueous solution. A pronounced quenching of the emission of pyrene is observed when ternary PAA-DTAC-Cu (2+) complexes are formed, as a result of the close proximity of Cu (2+) ions (complexed along the polymer chain) and the probe (solubilized in the hydrophobic mixed polymer-surfactant aggregates), as indicated from the corresponding Stern-Volmer plots. A significant quenching is also observed when poly(sodium styrene sulfonate) is used instead of PAA, indicating that electrostatically bound Cu (2+) ions are still effective quenchers of the emission of the probes under similar conditions. Finally, it is demonstrated that the formation-deformation of the ternary PAA-DTAC-Cu (2+) complexes upon changing pH may act as a pH-controlled "on-off" switch of the emission of pyrene in aqueous solution.     

Incorporation of triazole into a quinoline-rhodamine conjugate imparts iron(iii) selective complexation permitting detection at nanomolar levels

Two new rhodamine based probes 1 and 2 for the detection of Fe(3+) were synthesized and their selectivity towards Fe(3+) ions in the presence of other competitive metal ions tested. The probe 1 formed a coloured complex with Fe(3+) as well as Cu(2+) ions and revealed the lack of adequate number of coordination sites for selective complexation with Fe(3+). Incorporation of a triazole unit to the chelating moiety of 1 resulted in the probe 2, that displayed Fe(3+) selective complex formation even in the presence of other competitive metal ions like Li(+), Na(+), K(+), Cu(2+), Mg(2+), Ca(2+), Sr(2+), Cr(3+), Mn(2+), Fe(2+), Co(2+), Ni(2+), Zn(2+), Cd(2+), Hg(2+) and Pb(2+). The observed limit of detection of Fe(3+) ions (5 × 10(-8) M) confirmed the very high sensitivity of 2. The excellent stability of 2 in physiological pH conditions, non-interference of amino acids, blood serum and bovine serum albumin (BSA) in the detection process, and the remarkable selectivity for Fe(3+) ions permitted the use of 2 in the imaging of live fibroblast cells treated with Fe(3+) ions.     

Spectral characterization of a newly synthesized fluorescent semicarbazone derivative and its usage as a selective fiber optic sensor for copper(II)

In this work photoluminescent properties of highly Cu(2+) selective organic fluoroionophore, semicarbazone derivative; bis(naphtho[2,1-b]furan-2-yl)methanone semicarbazone (BNF) was investigated in different solvents (dichloromethane, tetrahydrofuran, toluene and ethanol) and in polymer matrices of polyvinylchloride (PVC) and ethyl cellulose (EC) by absorption and emission spectrometry. The BNF derivative displayed enhanced fluorescence emission quantum yield, Q(f)=6.1 x 10(-2) and molar extinction coefficient, epsilon=29,000+/-65 cm(-1)M(-1) in immobilized PVC matrix, compared to 2.6 x 10(-3) and 24,573+/-115 in ethanol solution. The offered sensor exhibited remarkable fluorescence intensity quenching upon exposure to Cu(2+) ions at pH 4.0 in the concentration range of 1.0 x 10(-9) to 3.0 x 10(-4)M [Cu(2+)] while the effects of the responding ions (Ca(2+), Hg(+), Pb(2+), Al(3+), Cr(3+), Mn(2+), Mg(2+), Sn(2+), Cd(2+), Co(2+) and Ni(2+)) were less pronounced.     

Metal chelates of phosphonate-containing ligands-III Analytical applications of N,N,N',N'-ethylenediaminetetra(methylenephosphonic) acid

N,N*,N',N'-Ethylenediaminetetra(methylenephosphonic) acid is used as a titrant for the direct determination of Cu, Co and Ni, with murexide as indicator. Indirect titrimetric procedures are suggested for the determination of silver, mercury, zinc and cyanide and both direct and indirect methods are applied for the analysis of binary mixtures of silver (or mercury) and copper (cobalt or nickel). The stoichiometry of the reaction, interferences of some metal ions and the pH effects on the complexation reactions are discussed. The values of the equilibrium constants of the protonated CuH(n)L (n = 1, 2, 3 and 4) as well as the unprotonated CuL chelates have been measured.     

Kinetics of adsorption of the cobalt ions on the "electrolytic solution/gamma-alumina" interface

In the present work we studied, for the first time, the kinetics of adsorption of the Co(H(2)O)(6)(2+) species on the "electrolytic solution/gamma-Al(2)O(3)" interface at pH = 7 and 25 degrees C for a very broad range of Co(II) surface concentrations ranged from 0.03 to 6 theoretical Co(H(2)O)(6)(2+) surface layers. Moreover, we studied the surface dissolution of gamma-alumina in the presence of the Co(H(2)O)(6)(2+) ions in the impregnating solution, the contribution of the Co(II) desorption on the whole deposition process and the deposition isotherm. It was found that under the conditions where the deposition has taken place, the dissolution of the gamma-alumina surface is negligible even in the presence of the Co(H(2)O)(6)(2+) species in the impregnating solution. It was, moreover, inferred that the Co(II) desorption does not participate significantly to the whole deposition process. It was found that the deposition kinetics may be described by the following kinetic expression r(Co,bulk) = k'C(Co,bulk)(2), which relates the rate of disappearance of the Co(H(2)O)(6)(2+) ions from the impregnating solution, r(Co,bulk,) with their concentration C(Co,bulk). This kinetic expression may be derived assuming the following deposition scheme: nS + 2[Co(H(2)O)(6)(2+)] --> S(n) - [Co(H(2)O)(x,x)(<)(6)(2+)](2), where S represents the surface reception sites. The above expressions indicated that two Co(H(2)O)(6)(2+) ions are involved, from the side of the interface, in the reaction with the reception sites. It seems probable that the deposition step involves the simultaneous adsorption and dimerization of the two interfacial Co(H(2)O)(6)(2+) ions through (hydr)oxobridges. On the other hand, the sigmoidal form of the deposition isotherm and the dependence of the apparent rate constant, k', on the interfacial Co(II) concentration suggested that the already deposited Co(II) species may be involved in the reception sites, S, promoting the adsorption and resulting to the formation of multinuclear complexes and Co(II) surface precipitates. Finally, reasonable interface potential values for oxides were determined for the first time using kinetic results.     

Remarkable effect of the preparation technique on the state of cobalt ions in BEA zeolites evidenced by FTIR spectroscopy of adsorbed CO and NO, TPR and XRD

The state of cobalt in two BEA zeolites was studied by XRD, TPR, and FTIR spectroscopy using CO and NO as probe molecules. One of the samples, CoAlBEA (0.4 wt % of Co), was prepared by conventional ion exchange and the other, CoSiBEA (0.7 wt % Co), by a two-step postsynthesis method involving dealuminated SiBEA zeolite. The introduction of Co into SiBEA leads to an increase of unit cell parameters of the BEA structure and to the consumption of silanol groups in vacant T-sites of the dealuminated zeolite. In contrast, no structural changes are observed after incorporation of cobalt into AlBEA by ion-exchange. The reduction temperature of cobalt in CoSiBEA zeolite (1130 K), is much higher than for CoAlBEA and indicates a strong interaction of cobalt ions with SiBEA. Low-temperature CO adsorption on CoAlBEA results in (i) H-bonded CO, (ii) Co(3+)-CO adducts (2,208 cm(-1)) and (iii) a small amount of Co(2+)-CO complexes (2,188 cm(-1)). In agreement with these results, NO adsorption leads to the appearance of (i) NO(+) (2,133 cm(-1), formed with the participation of the zeolite acidic hydroxyls), (ii) Co(3+)-NO (1932 cm(-1)), and (iii) a small amount of Co(2+)(NO)(2) dinitrosyls (nu(s) = 1,898 and nu(as) = 1,814 cm(-1)). Low-temperature CO adsorption on CoSiBEA leads to formation of two kinds of Co(2+)-CO adducts (2,185 and 2,178 cm(-1)). No Co(3+) cations are detected. In line with these results, adsorption of NO reveals the existence of two kinds of Co(2+)(NO)(2) dinitrosyls (nu(s) = 1,888 and nu(as) = 1,808 cm(-1) and nu(s) = 1,878 and nu(as) = 1,799 cm(-1), respectively).     

Photophysical properties of sulfonated dihydroxy phosphorus(V) tetrabenzotriazacorrole

The photosensitizing properties of a novel phthalocyanine analogue, sulfonated dihydroxy phosphorus(V) tetrabenzotriazacorrole [P(OH)2TBCSn] and a non-sulfonated one [P(OH)2TBC] are reported in this paper. Different from other phthalocyanine derivatives, P(OH)2TBCSn shows little aggregation in aqueous solution. The fluorescence quantum yield (PhiF) of P(OH)2TBCSn is lower than that of the non-sulfonated one. Studies of triplet state photophysics show that the presence of peripheral substituents on the macrocycle enhances the quantum yield of the triplet state. The sulfonated derivative, P(OH)2TBCSn, has a longer triplet lifetime (tauT = 0.234 ms) and higher singlet oxygen quantum yield (PhiDelta = 0.88) than P(OH)2TBC. Together with the ground-state absorption properties, the photosensitizing properties of the new compound suggest that it may be used as an excellent photosensitizer for photodynamic therapy (PDT).     

Analytical-kinetical study on the quinalizarin-hydrogen peroxide indicator reaction for Co2+ determination

Summary By a kinetic study of the indicator reaction of quinalizarin with hydrogen peroxide, catalysed by Co²⁺ ions, the optimum conditions necessary for determining traces of the catalyst have been found. These conditions are: pH=12.0 (sodium tetraborate-sodium hydroxide buffer), wavelength of measurement 565 nm,c (H₂O₂)/c(R)=200, temperature=25° C, Co²⁺ concentration range 1×10^–8-2×10^–7 M. A mechanism similar to that for enzymatic reactions, involving the occurrence of two intermediate complexes, gives a good explanation for the optimal conditions found.

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Analytisch-kinetische Untersuchung der Indikator-Reaktion von Chinalizarin mit Wasserstoffperoxid zur Co(II)-Bestimmung

Zusammenfassung Durch eine kinetische Untersuchung der Indikator-Reaktion von Chinalizarin mit Wasserstoffperoxid, die durch Co(II)ionen katalysiert wird, wurden die optimalen Bedingungen für die Bestimmung von Spuren des Katalysators ermittelt: pH=12,0 (Natriumtetraborat-Natriumhydroxid); Wellenlänge: 565 nm;c (H₂O₂)/c(R)=200; Temperatur=25° C; Konzentrationsbereich von Co(II): l·10^–8 bis 2·10^–8 M. Ein Reaktionsmechanismus ähnlich wie für enzymatische Reaktionen einschließlich zwei Zwischenprodukt-Komplexe bieten eine gute Erklärung für die gefundenen Optimalbedingungen.