Monitoring of Fe,Mn, Cu,Pb and Cd levels in two brown macroalgae from the Bulgarian Black Sea coast

Heavy metal contents (Fe, Mn, Cu, Pb and Cd) were determined in two brown macroalgal species (Cystoseira crinita and Cystoseira barbata). Samples were collected during six seasons from spring 1996 to summer 2000 from five different sites of the Bulgarian Black Sea coastal zone – Tuzlata, Ravda, Sozopol, Ahtopol and Sinemoretz. The local and seasonal metal distribution and their variations were examined.

The data obtained indicate that the two investigated species demonstrate various degrees of metal accumulation and can be used as indicators for the type and quantity of anthropogenic contamination in marine ecosystems.     

Indirect complexometric determination of small amounts of tellurium

Summary A complexometric method is proposed for the determination of small amounts of tellurium (50–350g). It is based on the reaction between Te(IV) and diethyldithiocarbamic acid (DDTC). The compound of the composition Te(DDTC)₄ obtained is extracted with CCl₄ at p_H 8.7–8.8. The yellow organic extract is shaken with copper(II)-ammonia solution, p_h 11. The organic phase, containing Cu(DDTC)₂ is then shaken with silver-ammonia solution. The Cu(II)-ions pass into the aqueous phase where they are titrated with 0.002M EDTA, using glycinethymol blue as indicator. Selenium(IV) does not interfere.

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Zusammenfassung Die Reaktion zwischen Te(IV) und Diäthyldithiocarbaminsäure (DDTC) wurde zur komplexometrischen Bestimmung kleiner Mengen Tellur (50 bis 350g benützt. Te(DDTC)₄ wird mit CCl₄ extrahiert (p_H 8,7 bis 8,8) und der gelb gefärbte organische Extrakt mit ammoniakalischer Cu(II)-Lösung bei p_h11 ausgeschüttelt. Dabei findet ein Austausch von Te(IV) gegen Cu(II) statt. Die Cu(II)-Ionen der organischen Phase werden mit ammoniakalischer Ag(I)-Lösung umgesetzt und gehen in die wäßrige Phase über, wo sie mit 0,002-m ÄDTA-Lösung gegen Glycinthymolblau titriert werden. Selen(IV) stört nicht.

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Résumé On propose une méthode complexométrique pour le dosage de petites quantités de tellure (50-350g). Elle est fondée sur la réaction entre Te-IV et l'acide diéthyldithiocarbamique (DDTC). On extrait par CCl₄ á p_H 8,7–8,8 le produit obtenu, de composition Te(DDTC)₄. On agite l'extrait organique jaune avec une solution ammoniacale de cuivre-II. Les ions cuivriques passent dans la phase aqueuse oú ils sont titrés par l'EDTA 0,002M, avec le bleu de glycinethymol comme indicateur. Le sélénium-IV n'interfére pas.

     

Extraction-spectrophotometric determination of traces of palladium by reaction between zinc(II) dibenzyldithiocarbamate and palladium(II)/2-(5-bromo-2-pyridylazo)-5-diethylaminophenol

The simple and highly sensitive determination of palladium is based on the reaction between Pd(II)/5-Br-PADAP and Zn(II) DBDTC complexes in 1,2-dichloroethane or toluene at pH 9.7. At 530 nm, the molar absorptivity is about 0.8 × 10⁵ l mol ^?1 cm ^?1. Beer's law is obeyed in the concentration range 0.1–1.2 μg ml ^?1 Pd. Relative standard deviations are 2–5%. Metal ions reacting with either of the organic reagents interfere.     

Radionuclide uptake in red macroalgae from the Bulgarian Black Sea coast

Summary Technogenic and natural radionuclide content in red macroalgae (Ceramium rubrum, Corallina officinalisand Callithamnion corymbosum) from the Bulgarian Black Sea coast, collected in the period 1992-2003, was studied by low-level gamma-spectrometry. The data show that the nuclide concentrations depend on macroalgae species and coast locations. The highest nuclide content was measured in Ceramium rubrumspecies. The ¹³⁷Cs mean value is 9.8 Bq/kg, 19.6 Bq/kg for ²²⁶Ra and 17 Bq/kg for ²¹⁰Pb. The radionuclide pollution is considerably small due to the absence of nuclear facilities along the Bulgarian Black Sea coast.     

Extraction-spectrophotometric determination of traces of copper(II), zinc(II), cadmium(II) and mercury(II) with 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol

Summary Sensitive extraction-spectrophotometric procedures are described for the complexes of Cu(II), Zn(II), Cd(II) and Hg(II) with 5-Br-PADAP using chloroform as solvent. Optimal conditions have been established for the quantitative extraction of the metal chelates and their composition and optical characteristics have been determined as well. The conditional extraction constants amount logK _ex=10, the molar absorptivities of the complexes being 10⁵ l·mole^–1·cm^–1. Job's method and equilibrium shift method indicate the molar ratios M5-Br-PADAP=12.

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Spektralphotometrische Bestimmung von Spuren Cu(II), Zn(II), Cd(II) und Hg(II) mit 2-(5-Bromo-2-pyridylazo)-5-diethylaminophenol (5-Br-PADAP)

Zusammenfassung Einfache und empfindliche Methoden zur extraktionsspektralphotometrischen Bestimmung von Spuren Cu(II), Zn(II), Cd(II) und Hg(II) mit 5-Br-PADAP wurden beschrieben. Chloroform wurde als Extraktionsmittel verwendet. Die optimalen Bedingungen für die quantitative Extraktion der Metallchelate wurden ermittelt und deren Zusammensetzung bestimmt. Die Stabilitätskonstanten haben hohe Werte (logK _ex=10), die molare Absorption der Komplexe beträgt 10⁵1·mol^–1·cm^–1. Das Molarverhältnis der Komplexe beträgt M5-Br-PADAP=12.

     

Extraction—spectrophotometric determination of copper(II) with 4-(2-pyridylazo)resorcinol and a long-chain quaternary ammonium salt

A simple and highly sensitive extraction—spectrophotometric determination of copper (II) is described. The ion-associate formed between the copper(II)—4-(2-pyridylazo)-resorcinol (PAR) anion and tetradecyldimethylbenzylammonium chloride (TDBA) is extracted with chloroform at pH 9.7. The absorption maximum of the extracted species occurs at 510 nm, the molar absorptivity being 8.05 (± 0.07) × 10⁴ l mol^-1 cm^-1. Beer's Law is obeyed in the concentration range 0.1–0.5 μg Cu ml^-1. The composition of the ion-associate is estimated to be [Cu(PAR)₂(TDBA)₂]. The conditional extraction constant is log K'_ex ≈ 8. The interference of some cations and anions is studied. The method is suitable for analysis of waters.     

Extraction-spectrophotometric determination of zinc(ii) with 4-(2-pyridylazo)-resorcinol and a quaternary ammonium salt

A simple and sélective extraction spectrophotometric determination of zinc is described. The complex [Zn(PAR)(2)](CDBA)(2), where PAR is the 4-(2-pyridylazo)resorcinol anion and CDBA is cetyldimethylbenzylammonium ion, is extracted from a solution buffered at pH 9.7 with carbonate/bicarbonate. Beer's law is obeyed over the range 0.2-1.2 ppm zinc, the molar absorptivity being 9.2 x 10(4) 1 .mole(-1).cm(-1). The precision in this range is 0.0056 ppm. Cadmium in up to a 50-fold w w ratio may be masked with diethyldithiocarbamate.     

Extraction—spectrophotometric determination of traces of cadmium with 4-(2-pyridylazo)resorcinol and a long-chain quaternary ammonium salt

A simple and highly sensitive extraction—spectrophotometric determination of cadmium is described. The ion-associate formed between the cadmium-PAR anionic chelate and cetyldimethylbenzylammonium chloride (CDBA) is extracted with chloroform at pH 10. The absorption maximum of the extracted species occurs at 505 nm, the molar absorptivity being (9.82 ± 0.30) × 10⁴ l mol^-1 cm^-1. The optimal concentration range for measurements is 0.2–1.0 μg Cd ml^-1; Beer's law is obeyed. The composition of the ion-associate is estimated to be CdPAR₂-2CDBA. The conditional extraction constant is log K'_ex ≈ 8. The stability constant of the cadmium—PAR chelate in aqueous solution is log β₂ = 17.5 ± 0.3. Extraction with N-benzoyl-N-phenylhydroxylamine is used to avoid several interferences. Moderate amounts of zinc are masked with sodium hydroxide.     

Coupling Between the Retinal Thermal Isomerization and the Glu194 Residue of Bacteriorhodopsin†

Glu194 is a residue located at the end of F helix on the extracellular side of the light‐induced proton pump bacteriorhodopsin (BR). Currently, it is well recognized that Glu194 and Glu204 residues, along with water clusters, constitute the proton release group of BR. Here we report that the replacement of Glu194 for Gln affects not only the photocycle of the protein but also has tremendous effect on the all‐trans to 13‐cis thermal isomerization. We studied the pH dependence of the dark adaptation of the E194Q mutant and performed HPLC analysis of the isomer compositions of the light‐ and partially dark‐adapted states of the mutant at several pH values. Our data confirmed that E194Q exhibits extremely slow dark adaptation over a wide range of pH. HPLC data showed that a significantly larger concentration of all‐trans isomer was present in the samples of the E194Q mutant even after prolonged dark adaptation. After 14 days in the dark the 13‐cis to all‐trans ratio was 1:3 in the mutant, compared to 2:1 in the wild type. These data clearly indicate the involvement of Glu194 in control of the rate of all‐trans to 13‐cis thermal isomerization.