Dithizone Complex Research Articles

Selective cloud point extraction and preconcentration of trace amounts of silver as a dithizone complex prior to flame atomic absorption spectrometric determination

Dithizone (diphenylthiocarbazone) was used as a complexing agent in cloud point extraction for the first time and applied for selective preconcentration of trace amounts of silver. The analyte in the initial aqueous solution was acidified with sulfuric acid (pH<1) and Triton X-114 was added as a surfactant. After phase separation, based on the cloud point separation of the mixture, the surfactant rich phase was diluted with tetrahydrofuran (THF) and the analyte determined in the enriched solution by flame atomic absorption spectrometry. After optimization of the complexation and extraction conditions, a preconcentration factor of 43 was obtained for only 10 ml of sample. The analytical curve was linear in the range of 3–200 ng ml −1 and the limit of detection was 0.56 ng ml −1. The proposed method was applied to the determination of silver in water samples.

Photochromic compounds as optical limiters in the nanosecond time range: the example of mercury dithizonate complex.

Although being an efficient photochromic compound which absorbs in the blue in its stable form and in the orange in its photoactivated form, the mercury dithizonate complex is shown to be a poor optical limiter for nanosecond laser pulses at the wavelengths where both isomers absorb. Optical limiting effect, which is a consequence of reverse saturable absorption due to the photoactivated form, is demonstrated to be weak because of the back photobleaching of this form, which is important all the more as the laser intensity is high. Numerical integration of the spatiotemporal evolution of the laser beam intensity across the solution helps the understanding of the respective roles of the laser fluence and pulse duration. Finally, we draw the conclusion that photochromic compounds can only be used as optical limiters if the time constant for the back photochemical reaction is slow compared to the pulse duration.

Dithizone and carbazone complex compounds as initiators and γ -radiation anti-degradation agents for poly(methyl methacrylate)

It has been proved that lead dithizone and carbazone complex compounds act as adequate initiators and indicators for radical polymerization of methylmethacrylate. The color change observed during the polymerization process was attributed to the change in structure of the complex compounds according to tautomerization mechanism. Improvements to both polydispersity and relative crystallinity were observed in presence of lead dithizone and carbazone complex compounds. Better protection against gamma radiation was noticed ascertained through molecular mass measurements. A convincing reaction mechanism was also given.

Thermal properties of polystyrene/group IIB dithizonate films

The effect of group IIB metal dithizone complexes on the properties of polystyrene have been investigated by GPC, FTIR, X-ray diffraction, TGA and DSC. The results of GPC and X-ray diffraction analysis proved that an improvement in the polymer chain ordered was achieved due to the presence of these complexes during the bulk polymerization of styrene monomer if compared with that of pure sample. TGA thermograms showed that the thermal stability of polystyrene is enhanced with increasing complex concentration. However, mercury gives the best results followed by cadmium and zinc dithizonate. DSC scans for the different polymer samples provides a further support to the TGA data.

Resistance, accumulation and allocation of zinc in two ecotypes of the green alga Stigeoclonium tenue Kütz. coming from habitats of different heavy metal concentrations

Response to elevated Zn concentrations of two various ecotypes of the periphytic green alga Stigeoclonium tenue Kütz. was studied. An ecotype, classified as S. tenue (T), isolated from ditches containing mining water, was Zn-tolerant. It was able to grow and reproduce by zoospores at external Zn concentrations ≥15 μM. Another ecotype of this species, classified as S. tenue (S), isolated from unpolluted lake water was Zn-sensitive; its exposure to 15 μM and higher Zn concentration caused a significant decrease of chlorophyll content, inhibition of zoospore settling and, finally, death. The morphology of mature thalli of these two ecotypes cultivated under the same conditions also differed, i.e. the erect system of S. tenue (T) consisted of filaments with long, narrow cells, while the erect system of S. tenue (S) consisted of filaments with shorter, barrel-shaped cells. Therefore, S. tenue (S) thalli were more compact than thalli of S. tenue (T). S. tenue (T) exposed to 30 μM Zn for 3 weeks was able to release zoospores, while S. tenue (S) was not. The two algal ecotypes differed in the amount of intracellularly accumulated Zn and Pb. The Zn-tolerant ecotype S. tenue (T) accumulated (independently of the exposure conditions like pH and orthophosphate concentration) significantly more Zn and Pb than the Zn-sensitive ecotype. A new cytochemical method was developed to visualise intracellular Zn in algal cells. In the long-term, Zn-exposed cells of both ecotypes, pink-orange Zn–dithizone complexes were observed in peripheral vacuoles, while in cells not exposed to Zn, no deposits were present. The data obtained suggest that the Zn-tolerant ecotype S. tenue (T) is able to detoxify the excess of accumulated zinc more effectively than the sensitive ecotype, however, vacuolar Zn compartmentalisation does not seem be the main tolerance mechanism.

Determination of trace levels of mercury in water samples based on room temperature phosphorescence energy transfer

A novel method has been developed for the sensitive determination of mercury in aqueous media by room temperature phosphorescence (RTP). The measurement principle is based on the energy transfer (ET) from a phosphor molecule (acting as a donor) to a Hg-sensitive dye (acceptor). To our acknowledgment this is the first RTP method for mercury measurement developed so far. α-Bromonaphthalene (BrN) was selected as the phosphorescent donor molecule (BrN can produce significant RTP emission in aqueous media in a β-cyclodextrin rigid microenvironment without deoxygenation).The absorption spectrum of the complex formed between mercury and the dithizone dye possesses a desirable spectral overlap with the RTP emission spectrum of the donor (BrN), giving rise to a nonradiative ET from the phosphor molecules to the mercury complex. An increase in the concentration of Hg(II) causes an increase on the concentration of the dithizone complex (acceptor) with the subsequent increase of the absorbance and, therefore, resulting in a decrease of the RTP emission. Both, RTP intensities and triplet lifetimes of the BrN decreased with increases on the Hg(II) concentration.Possible interferences present in natural waters, including different cations and anions, which could affect the analytical response, were evaluated and the analytical performance characteristics investigated. The use of phosphorescence measurements (low background noise signals) resulted in an improvement on the sensitivity of the Hg(II) detection higher than five times as compared to the molecular absorption spectrophotometric method for Hg(II) detection based on dithizone as Hg-indicator. A detection limit (D.L.) of 14ngml−1 of Hg(II) was obtained by RTP with a precision of ±4.8% for five replicates of 300ngml−1 of Hg(II). The usefulness of the method was successfully evaluated by the determination of Hg(II) in spiked natural water samples.

A new method of microvolume back-extraction procedure for enrichment of Pb and Cd and determination by flame atomic absorption spectrometry

The need for highly reliable methods for the determination of trace elements has been recognised in analytical chemistry and environmental science. A method for the trace analysis of Pb and Cd in natural waters is described. In a preconcentration step, 500 ml of an aqueous sample containing lead and cadmium were extracted into 3.5 ml of a solution containing a complexing agent (dithizone) in xylene. Subsequently, the dithizonate complexes were back-extracted into 600 μl of nitric acid solution for direct determination by flame atomic absorption spectrometry. Important microextraction parameters were optimised using spiked deionised water. The 3 σ detection limits, relative standard deviations and linear calibration graphs were, respectively, 0.39 μg l −1, 6.3% and 1.0–20.0 μg l −1 for lead and 8.2 ng l −1, 4.0% and 0.05–1.0 μg l −1 for cadmium for solvent microextraction times of 4 min and microvolume back-extraction times of 1 min. The preconcentration factors were 543- and 331-fold for lead and cadmium, respectively.

Polymerization of methylmethacrylate monomer in the presence of dithizone and carbazone complexes

It has been proved that lead dithizone and carbazone complexes act as adequate initiators for radical polymerization of methylmethacrylate and also as reliable indicators for the free-radical mechanism. Lead dithizone complex, in particular, exhibited the phenomenon of color change during the polymerization process, suggesting the use of this complex as a free-radical indicator and also as a coloring material for acrylic polymers in situ. The color change observed during the polymerization process was attributed to the change in the structure of complex compounds according to a tautomerization mechanism. The presence of lead dithizone and carbazone complexes as initiators exhibited reduced molecular mass compared to those prepared in their absence, indicating their role as regulating agents during the polymerization process. The polydispersity and tacticity parameters were measured through the present work using GPC and 1H–NMR techniques, respectively. The amorphous nature of polymer chains in both the absence and the presence of the lead dithizone and carbazone was studied using X-ray diffraction, where an increased crystallinity was observed. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 562–568, 2001

Construction of metal template polymer with covalently bound dithizone

Dithizone complexes of Co I I , Zn I I , Ni I I and Cu I I have been attached to a copolymer of styrene and acrylic acid which are then crosslinked. The metal ions are leached out leaving the ligand attached to the polymeric matrix. Absorption capacity of various metal ions in these polymeric ligands have been measured to evaluate the extent of template effect generated.

Picosecond anisotropy of the transient absorption of the photochromic mercury dithizone complex in solution

A picosecond Kerr ellipsometry study of the transient anisotropy of the metal dithizonate Hg(HDz) 2 in solution with different organic solvents is presented. The Hg(HDz) 2 photochromic complex is one of the first organic dyes shown to exhibit photochromic proprieties. The complex exhibits reversible photochromism, changing from the normal form A (of orange-yellow colour) to the active form B (of blue colour) after excitation with 532 nm laser light. The Kerr ellipsometry signal is observed to decrease with a single exponential decay of about 100 ps, that is shown to be independent of the solvent. This indicates that the signal is dominated by the excited state lifetime of the molecule. The absence of any spectral signatures relevant to the excited states of the normal form indicates that formation of the photoisomer is a fast process with respect to the lifetime of the exited state.

Photochromic long-chain organomercury(II) dithizonate complexes in the azomethine series

The synthesis and characterization of a series­of 4 - (4′- n -alkoxybenzylideneimino)phenyl-­mercury (II) dithizonates, [CnH2n+1OC6H4CH­NC6H4Hg (Hdptc)] (H2dptc = 1,5-diphenylthiocarbazone = dithizone; n = 1, 4, 12, 14 or 18), is described. The intermediate long-chain organomercury(II) acetates were obtained by condensation of 4-aminophenylmercury(II) acetate with the appropriate 4-n-alkoxybenzaldehydes. The thermal behaviour of the complexes was studied by polarized optical microscopy and differential scanning calorimetry but revealed no mesophases. All of the complexes, however, were reversibly photochromic (yellow ⇌ blue) upon irradiation of chloroform solutions with visible light, and the half-lives of the metastable blue forms were substantially increased relative to that of the parent mercury(II) bis(dithizonate). The compounds were not photochromic in the solid state. Copyright © 2000 John Wiley & Sons, Ltd.

Synthesis, absorption spectra and semiempiric calculations on the photochromism of arylmercuric dithizonate complexes

A series of arylmercuric dithizonate complexes have been synthesized and characterized. Optical spectra of dissolved and pure compounds show transition energies around 480 nm which have been rationalized by semiempiric PM3 calculations. All complexes show a pronounced photochromism. The calculations also account for the observed blue absorption of the metastable species when an underlying geometric arrangement according to the proposal of Meriwether′s is assumed.

Complexometric determination of mercury(II) in waters by spectrophotometry of its dithizone complex

This paper presents a new method for the determination of Hg(II) in waters, using “indirect” spectrophotometric measurements of the Hg(II) dithizone complex. The reagent is a mixture of dithizone, CDTA (1,2-cyclohexylene-dinitrilo-tetraacetic acid), thiourea, ethylic alcohol and glycine. Sensitivity and working range are 0.4 μg · l−1 and 2–100 μg · l−1, respectively. A comparison of the results with those of the cold-vapor atomic absorption spectrometry shows a good correlation for different samples revealing only small interferences. The new method is well suited for on-line measurements, easy to run and has low cost equipment.

Sub-stoichiometric isotope dilution analysis for the determination of selenium by liquid scintillation counting

A sensitive and selective sub-stoichiometric isotope dilution method for the determination of trace amounts of selenium is described. The method is based on the extraction of the selenium–dithizone complex with a sub-stoichiometric amount of dithizone into toluene from 7 mol l–1 hydrochloric acid. The activity of the extracted complex was measured by liquid scintillation counting and the counting efficiency was found to be 40%. The calibration graph was linear in the range 0–10 µg of selenium in a final volume of 10 ml. As little as 0.01 µg of selenium can be determined in a total volume of 10 ml. The interferences due to several ions were overcome by using an aluminium hydroxide collection procedure.

Studies of 1,5-Bis(3,4,5-trimethoxyphenyl)- and 1,5-Bis(2-methoxy-4-methylphenyl)-3-mercaptoformazans and Their Reactions with Metal Ions

1,5-Bis(3,4,5-trimethoxyphenyl)- and 1,5-bis(2-methoxy-4-methylphenyl)-3-mercaptoformazans have been prepared and characterized, and their reactions with metal ions in a two-phase system are reported. The extraction equilibria of their metal complexes with CdII, CoII, CuII, HgII, NiII, PbII, TII and ZnII as well as their spectral characteristics are also described. The molar absorptivities of PbII and ZnII complexes with 1,5-bis(3,4,5-trimethoxyphenyl)-3-mercaptoformazan are higher than the corresponding values of their complexes with dithizone. The molar absorptivities of CuII and CdII complexes with 1,5-bis(2-methoxy-4-methylphenyl)-3-mercaptoformazan are also higher than the corresponding values of the dithizone complexes. 1,5-Bis(2-methoxy-4-methylphenyl)-3-mercaptoformazan is more efficient than dithizone in the separation of CdII from ZnII.

Spectrophotometric Determination of Copper and Silver in Glass after Extraction of Dithizonate Complexes on Polyurethane Foam

A spectrophotometric method has been described for the determination of minor or trace amount of copper and silver when present together in special glasses. The method involves selective extraction of copper dithizonate on polyurethane foam after masking of silver with chloride. Silver is extracted in ammoniacal medium after masking of copper with EDTA. Both the complexes, i.e. copper and silver dithizonates are eluted from foam with acetone. Determinations are carried out spectrophotometrically. Beer's law is obeyed for the concentration range of 0.05–2.5 μg Cu/ml at 550 nm and 0.10–6.0 μg Ag/ml at 500 nm. The method yields agreeable results.

Spectrophotometric determination of iron and cobalt with Ferrozine and dithizone

Procedures are described whereby iron (1–50 μg) and cobalt (1–25 μg) are determined spectrophotometrically, iron as iron(II) with the disodium salt of 3-(2-pyridyl)-5,6-bis(4-phenylsulfonic acid)-1,2,4-triazine (Ferrozine) and cobalt as the cobalt(III) dithizonate complex. The reduction to iron(II) prevents interference of iron(III) in the cobalt determination, and both metals can be determined in the same portion of sample solution. Removal of interference by other metal ions is described.

Direct spectrophotometric determination of trace amounts of mercury(II) in aqueous media as its dithizonate complex in the presence of a neutral surfactant

The spectrophotometric determination of mercury in aqueous solution as its dithizonate complex in the presence of Triton X-100, a neutral surfactant that renders both the ligand and the complex water soluble, is described. The molar absorptivity, specific absorptivity and Sandell sensitivity of the complex at the wavelength of maximum absorption (490 nm) were found to be 3.868 × 104 l mol–1 cm–1, 192.8 l g–1 and 5.2 ng cm–2, respectively. Beer's law was obeyed between 1 × 10–6 and 2 × 10–5M Hg2+. The interference caused by the presence of a number of common cations and anions was studied and the method was applied successfully to the analysis of a mercury-based pesticide.

Studies on Tetramethyldithizone Isomers and Their Reactions with Metal Ions

Abstract Six bis(dimethylphenyl) analogues of dithizone are prepared, characterized and their reactions with metal ions in a two phase system are reported. The extraction equilibria of their complexes with Cd(II), Co(II), Hg(II), Pb(II), Tl(I), Zn(II), and Bi(III) as well as their spectral characteristics are described. Complete extraction of these metal chelates requires higher pH’s than those needed for the unsubstituted dithizone. The molar absorptivities of Bi(III) complexes with bis(3,4-dimethylphenyl)-, and bis(3,5-dimethylphenyl) analogues are higher than the corresponding value of Bi(III) dithizonate. The molar absorptivities of Cu(II) and Hg(II) (in CCl4) complexes with bis(3,5-dimethylphenyl) analogue are also higher than the corresponding values of the unsubstituted dithizone complexes.

Zinc dithizonate staining in the cat hippocampus: Relationship to the mossy-fiber neuropil and postnatal development

The formation of a colored dithizonate complex in the vicinity of the mossy-fiber axons in the hippocampus was investigated in the cat. Two histochemical tests indicate that the dithizonate complex which is formed is zinc dithizonate. Comparison of Golgi-impregnated material with dithizonate-labeled material indicates that the zinc dithizonate staining is coextensive with the mossy-fiber neuropil throughout the hippocampus. Also, studies using the dithizone reaction with kittens show that the mossy-fiber region contains small but detectable amounts of zinc at 1 week of age and that the adult concentration of zinc in the region is not attained until 13 weeks of age or later. Taken together, the results support the notion that there is a pool of chelatable zinc uniquely associated with the mossy-fiber system of the hippocampus.