Metal Stability Constants Research Articles

Determination of stability constants of metal(II)-methylcysteine and metal(II)-nitrilotriacetate-methylcysteine complexes with using a paper electrophoretic method

A method involving the use of paper ionophoresis is described for the study of the equilibria in mixed ligand complex systems in solution. Present method is based on the movement of a spot of metal ion under the electric field with the complexants added in the background electrolyte at pH 8.5. The concentration of primary ligand nitrilotriacetate (NTA) was kept constant while that of the secondary ligand methylcysteine was varied. The plot of log [methylcysteine] versus mobility were used to obtain information on the formation of mixed complexes and to calculate its stability constants. The binary equilibria metal(II)-methylcysteine and metal(II)-NTA have also been studied, since this is a prerequisite for the investigation of mixed complexes. The stability constants of the complexes Pb(II)-NTA-methylcysteine and UO2 (II)-NTA-methylcysteine were found to be 3.03 ± 0.05 and 3.42 ± 0.09 (log K values) at ionic strength 0.01 M and a temperature of 35°C.

The effect of species diversity on metal adsorption onto bacteria

In this study, we measure proton, Pb, and Cd adsorption onto the bacteria Deinococcus radiodurans, Thermus thermophilus, Acidiphlium angustum, Flavobacterium aquatile, and Flavobacterium hibernum, and we calculate the thermodynamic stability constants for the important surface complexes. These bacterial species represent a wide genetic diversity of bacteria, and they occupy a wide range of habitats. All of the species, except for A. angustum, exhibit similar proton and metal uptake. The only species tested that exhibits significantly different protonation behavior is A. angustum, an acidophile that grows at significantly lower pH than the other species of this study. We demonstrate that a single, metal-specific, surface complexation model can be used to reasonably account for the acid/base and metal adsorption behaviors of each species. We use a four discrete site non-electrostatic model to describe the protonation of the bacterial functional groups, with averaged p K a values of 3.1 ± 0.3, 4.8 ± 0.2, 6.7 ± 0.1, and 9.2 ± 0.3, and site concentrations of (1.0 ± 0.17) × 10 −4, (9.0 ± 3.0) × 10 −5, (4.6 ± 1.8) × 10 −5, and (6.1 ± 2.3) × 10 −5 mol of sites per gram wet mass of bacteria, respectively. Adsorption of Cd and Pb onto the bacteria can be accounted for by the formation of complexes with each of the bacterial surface sites. The average log stability constants for Cd complexes with Sites 1–4 are 2.4 ± 0.4, 3.2 ± 0.1, 4.4 ± 0.1, and 5.3 ± 0.1, respectively. The average log stability constants for Pb complexes with Sites 1–4 are 3.3 ± 0.2, 4.5 ± 0.3, 6.5 ± 0.1, and 7.9 ± 0.5, respectively. This study demonstrates that a wide range of bacteria exhibit similar proton and metal adsorption behaviors, and that a single set of averaged acidity constants, site concentrations, and stability constants for metal–bacterial surface complexes yields a reasonable model for the adsorption behavior of many of these species. The differences in adsorption behavior that we observed for A. angustum demonstrate that genetic differences do exist between the cell wall functional group chemistries of some bacterial species, and that significant exceptions to the typical bacterial adsorption behavior do exist.

Stability of Lead(II) Complexes of Alginate Oligomers

The current work reports on the Pb(ll) complexes formed with oligomeric uronic acids (carboxylated saccharide residues) found polymerized in the cell walls and envelopes of algae and bacteria alike. The application of partial acid hydrolysis, size-exclusion chromatography (SEC), 1H NMR, and scanned deposition stripping chronopotentiometry (SSCP) has permitted the determination of stability constants for Pb(II) with both mannuronic (M) and guluronic (G) acid oligomers ranging from the dimer to the pentamer. The determined logarithm of the stability constants range between 4.11 +/- 0.05 and 5.00 +/- 0.04 mol(-1) x dm3 for the eight oligomers studied (pH 6; I = 0.1 mol x dm(-3)). Additional experiments under the same experimental conditions employing galacturonic and glucuronic acid oligomers yielded slightly lower values (2.19 +/- 0.10 to 4.02 +/- 0.07 mol(-1) x dm3) that were expected based on their structure, whereby the monomers which were not included in the alginate oligomer series (unavailable by SEC), yielded the lowest stability constants. This work demonstrates the applicability of the SSCP technique for the determination of stability constants for metal-ligand complexes in which the ligands display relatively low molecular mass. Previous studies on heavy metal interaction with the matrix polysaccharide alginate have largely been restricted to the whole polymer that forms a gel upon binding to network bridging ions such as calcium. The results will be discussed in this context with the emphasis being placed on the relevance of these findings to processes occurring at the biointerface and results from the relevant literature.

Determination of stability constants of metal(II)-methionine and metal(II)-methionine-cystiene (binary and mixed) complexes using the Paper Ionophoretic Technique

Determination of stability constants of metal(II)-methionine and metal(II)-methionine-cystiene (binary and mixed) complexes using the Paper Ionophoretic Technique

Proton and metal adsorption onto bacterial consortia: Stability constants for metal–bacterial surface complexes

In this study, we conduct potentiometric titrations and metal adsorption experiments (Cd, Ca, Cu, Pb, Sr, and Zn) using bacterial consortia grown from three representative locations and sampled over the course of a year in order to determine whether bacterial diversity affects proton and metal uptake behaviors. We observe significant changes in bacterial diversity from one site to another, and from month to month during the study period. Despite these changes in diversity, all of the bacterial consortia studied exhibit similar proton and metal uptake, strongly suggesting universal adsorption behavior for the bacterial species present in these samples. We demonstrate that a single, metal-specific, averaged surface complexation model can be used to reasonably account for the acid/base and metal adsorption behaviors of each consortium. We use a four discrete site non-electrostatic model to describe the protonation of the consortia functional groups, with averaged pK a values of 3.2 + 0.2 / − 0.4, 4.8 + 0.2 / − 0.3, 6.5 + 0.3 / − 0.8, and 9.2 + 0.1 / − 0.3, and site concentrations of (1.0 ± 0.28) × 10 − 4 , (1.2 ± 0.23) × 10 − 4 , (6.12 ± 1.1) × 10 − 5 , and (9.7 ± 2.0) × 10 − 5 moles of sites per gram wet mass of bacteria, respectively. The metal adsorption data are used to constrain site-specific bacterial surface complexation models, and we determine the stability constants for the important metal–bacterial surface complexes. These calculated stability constants correlate well to known stability constants for metal–acetate complexes, yielding predictive relationships that enable the estimation of the extent of adsorption of other metals onto bacterial consortia. This study demonstrates that a wide range of bacteria exhibit similar proton and metal adsorption behaviors, and that a single set of averaged acidity constants, site concentrations, and stability constants for metal–bacterial surface complexes can be used to model the adsorption behavior.

Preferences of kanamycin A towards copper(II). Effect of the resulting complexes on immunological mediators production by human leukocytes

The widespread presence of pathogenic bacteria is a cause of permanent demand for investigating the properties of antimicrobial agents. The chemical basis of several toxic effects induced by antibiotics still remains unclear. Aminoglycosides, highly ototoxic and nephrotoxic drugs, are capable of copper(II) ions chelating. In this study we established the affinity of kanamycin A towards copper(II), in contrast with other metal ions: iron(III), nickel(II), cobalt(II) and zinc(II) by means of potentiometry. Circular dichroism spectroscopy was applied to monitor the competition of copper(II) partition between kanamycin A and human serum albumin. We show, that the drug is able to digest Cu(II) ions from HSA to some extent and comparing the stability constants for metal and antibiotic with those, obtained for the N-terminal Asp–Ala–His–Lys (DAHK) sequence, which constitutes a copper(II) binding domain within albumin, we demonstrate that the Cu(II)–kanamycin A complex formation is possible also in blood plasma. Bioassays and immunoassay were used to find out the possibility of Cu(II)–kanamycin A complexes to induce cytokines: tumor necrosis factor (TNF), interferon (IFN) and interleukin-10 (IL-10) in human peripheral blood leukocytes. The effect on the cytokines release was dose and time dependent and the interdependence between IL-10 and TNF stimulation was found. We report that Cu(II)-aminoglycoside systems can act as moderate inducers of TNF-α, IFN-α/β and IL-10 released from human leukocytes. We have also found that these complexes are non-toxic for human A549 cells.

Modeling heavy metal uptake by sludge particulates in the presence of dissolved organic matter

The uptake of the seven heavy metal ions Cd(II), Co(II), Cr(III), Cu(II), Ni(II), Pb(II), and Zn(II) by sludge particulates in single-metal systems was investigated. Results showed that under acidic and neutral pH conditions, the uptake of all heavy metals by sludge particulates increases with the increase of pH. However, in the alkaline pH region, the uptake of Cu(II), Ni(II), and Co(II) decreases with the increase of pH, primarily due to the high dissolved organic matter (DOM) concentration in high pH conditions. Based on chemical reactions among heavy metal, sludge solids, and DOM, a mathematical model describing metal uptake as functions of DOM and pH was developed. The stability constants of metal–sludge and metal–DOM complexes can be determined using this model in conjunction with experimental metal uptake data. Results showed that, for the secondary sludge sample collected from Baltimore Back River Wastewater Treatment plant on March 1997, the stability constants of Cu(II)–sludge complex ( log K S ) and Cu(II)–DOM complex ( log K L ) are 5.3±0.2 and 4.7±0.3, respectively; for Ni(II), they are 4.0±0.2 and 3.9±0.2, respectively. Results also showed that under neutral and low pH conditions (pH<8), the DOM effects on metal uptake for all heavy metals are insignificant. Therefore, the DOM term in the model can be ignored. Results showed that, for the secondary sludge sample collected from Baltimore Back River Wastewater Treatment plant on December 1996, the estimated log K S values of metal–sludge complexes for Cd(II), Co(II), Cr(III), Cu(II), Ni(II), Pb(II), and Zn(II) are, respectively, 3.6±0.2, 3.0±0.1, 5.5±0.1, 4.8±0.1, 3.1±0.1, 5.1±0.1, and 4.4±0.3.

Metal-ion recognition. Modeling the stability constants of some mixed-donor macrocyclic metal ion complexes—a simple model

A procedure for modeling the stability constants of the Zn(II), Cd(II), Ag(I) and Pb(II) complexes of an extended series of 17-membered, mixed-donor macrocycles incorporating nitrogen, oxygen and/or sulfur donor atoms is presented. The ligands fall into two categories—those incorporating a symmetrical arrangement of their donor atom set (9 examples) and those in which the donor set has an unsymmetrical arrangement (5 examples). Metal stability constants for the former have been reported previously while corresponding data for the latter was determined as part of the present investigation. Initial computations were based on the 1:1 stability constants for the systems incorporating a symmetrical arrangement of their donor atom set. The approach employed was to assume that the overall free energy for metal complexation can be partitioned into the sum of contributions from individual metal–donor interactions. Thus for a given metal ion type, the log K data corresponding to each of these ligand systems were employed to derive parameters that are characteristic of the respective metal ion–donor bond types present. The parameterisation derived from the above (previously reported) stability data was then employed to compute log K values for the complexes of both the symmetrical and unsymmetrical ligand series. In general, quite good agreement with the experimentally determined log K values for both series of complexes was obtained. The procedure thus points the way for the prediction of metal complex stabilities for other systems that incorporate closely related ligand types.

Determination of protonation- and metal complex stability constants for a chelating monomer and its immobilized in polymer resin

An improved method is described for the calculation of complex stability constants for metal–ligand complexes considering ligands immobilized in resin phase. The applicability of it has been proved for N′-benzylethylene diamine N, N, N′-triacetic acid monomer (BEDTA) and for the ion exchange resin developed in the authors laboratory immobilizing this with styrene divinyl benzene. Calcium and magnesium metal ion complexes were investigated. Electrochemical and flame photometric measurements were used to collect equilibrium concentration data. The procedure worked out included the measurement of the quantity of resin bound water. Using these and the other experimentally gathered values and the improved way of calculation metal ligand complex stability constants were determined in aqueous media. Ion exchange chromatographic separation of calcium and magnesium ions was performed with a resin containing column for separation and optimized eluent.

Ligand-Modified Colloid Enhanced Ultrafiltration. Use of Nitrilotriacetic Acid Derivatives for the Selective Removal of Lead from Aqueous Solution

In ligand-modified, colloid-enhanced ultrafiltration (LM-CEUF), a ligand that selectively complexes target ions (e.g., lead) also associates with a water-soluble colloid, such as a surfactant micelle or polyelectrolyte. The colloid, associated ligand, and target ion are then concentrated using ultrafiltration, producing a filtrate with a low concentration of the target ion. Dialysis, ultrafiltration, and potentiometric titration experiments have been used to investigate the effectiveness of four nitrilotriacetic acid (NTA) derivatives in the removal of lead from aqueous solution through LM-CEUF. The ligands are 2-phenyl nitrilotriacetic acid (PNTA), 2-[N, N-di-(carboxymethyl)]amino-octanoic acid (HNTA), 2-[N,N-di-(carboxymethyl)]amino-dodecanoic acid (DNTA), and 2-[N,N-di-(carboxymethyl)]amino-3-sulfopropionic acid (SNTA). The colloids used were the cationic polyelectrolyte poly(diallyldimethylammonium chloride) (PDADMAC) and the cationic surfactant cetylpyridinium nitrate (CPNO3). In equilibrium dialysis and ultrafiltration (UF) experiments, SNTA and PDADMAC systems provided effective lead removal. In semiequilibrium dialysis and UF experiments, DNTA and CPNO3 systems also provided effective lead removal. The effects of pH, ionic strength, competing ions, and colloid concentration were investigated for each ligand system. Ligand protonation constants and ligand–metal stability constants were obtained for SNTA in both water and solutions of PDADMAC and for DNTA in solutions of CPNO3. Ligand regeneration through pH adjustment and metal precipitation with various anions was also demonstrated.

Comparison of the acid-base behaviour and metal adsorption characteristics of a gram-negative bacterium with other strains

Thermodynamic parameters for proton and metal adsorption onto a gram-negative bacterium from the genus Enterobacteriaceae have been determined and compared with parameters for other strains of bacteria. Potentiometric titrations were used to determine the different types of sites present on bacterial cell walls. Stability constants for adsorption of Pb, Cu and Zn to specific sites were determined from batch adsorption experiments at varying pH with constant metal concentration. Titrations revealed 3 distinct acidic surface sites on the bacterial surface, with p K values of 4.3±0.2, 6.9±0.5 and 8.9±0.5, corresponding to carboxyl, phosphate and hydroxyl/amine groups, with surface densities of 5.0±0.7×10 −4, 2.2±0.6×10 −4 and 5.5±2.2×10 −4 mol/g of dry bacteria. Only carboxyl and phosphate sites are involved in metal uptake, yielding the following intrinsic stability constants: Log K carboxyl: Zn=3.3±0.1, Pb=3.9±0.8, and Cu=4.4±0.2, Log K phosphoryl: Zn=5.1±0.1 and Pb=5.0±0.9. The deprotonation constants are similar to those of other strains of bacteria, while site densities are also within an order of magnitude of other strains. The similarities in surface chemistry and metal stability constants suggest that bacteria may be represented by a simple generic thermodynamic model for the purposes of modelling metal transport in natural environments. Comparison with oxide-coated sand shows that bacteria can attenuate some metals to much lower pH values.

Humic acids from coals of the North-Bohemian coal field: II . Metal-binding capacity under static conditions

The interactions of metal cations (Al, Ba, Ca, Cd, Co, Cr, Cu, Fe, Mg, Mn, Ni, Pb, Zn) with solid humic acids (HAs) were investigated in a batch arrangement. The sorption of metals on the surface of HAs depends strongly on the pH — sorption decreases with decreasing pH. The metal-binding capacities estimated from the metal–humate binding model range from ca. 0.4 mmol/g (Fe, Ni, Zn) to 1.7 mmol/g (Pb). Of the examined metal cations, Pb 2+ binds most strongly to solid HAs. The order of the metal–humate binding strength is consistent with series found in the literature and is based on the stability constants of metal–humate complexes. In comparison with coal-derived HAs, soil HAs from chernozem (and also low molecular weight HAs) exhibited markedly higher metal-binding capacities, whereas the capacity of oxyhumolite (the raw material for HA production) was lower.

Seasonal variability in the kinetics of Cu, Pb, Cd and Hg accumulation by macroalgae

Abstract Here it is demonstrated that both Porphyra spp. and Enteromorpha spp. of macro-algae display similar and very marked seasonal variations in their concentration factor (CF) of Cu, Pb, Cd and Hg in field conditions. The CF variations are specific for each metal and reproducible over several years. The way variations in the biological activity affect the equilibrium and kinetics of the interaction between trace metals and live algae was studied in vitro. Natural seawater was used as the culture medium. Voltammetry was used for the determination of natural organic ligands and trace metals except Hg, which was determined by mercury cold vapour after on-line pre-concentration. Titrations with the relevant metal demonstrated that the maximum binding capacity of the algae was not significantly dependent on the season for Pb (ca. 100 μmol gdry algae−1), Cd (ca. 50 μmol g−1) and Hg (80–100 μmol g−1). Marked seasonal variations were observed for Cu (ca. 40 μmol g−1 in January; 70 μmol g−1 in May; and 100 μmol g−1 in August). The conditional stability constants of metal–algae complexation sites were seasonally independent and similar for both algae: logKMS′=8.5±0.3 (Cu), 5.6±0.2 (Pb), 5.3±0.2 (Cd) and 18.0±0.3 (Hg). Exudates with a strong Cu complexing capacity (logK′CuL=12.47±0.06) were determined in cultures with added Cu, Pb or Cd concentrations, and identified by cathodic stripping voltammetry (CSV) as cysteine or glutathione. All the tested metals promoted the liberation of exudates, both cysteine- and glutathione-like ligands were exuded in the presence of Cu, only cysteine-like ligands in the presence of Pb, and only glutathione-like ligands in the presence of Cd, the rise depending of the season of the year, particularly for Cu. Highest levels were produced in the presence of added Pb. When exposed to either 1- or 100-μM total dissolved metal concentrations, the metal uptake, and its rate, varied with the season and the algae.

Stability Constants of Metal–Humic Acid Complexes and Its Role in Environmental Detoxification

Humic acid with hydroxyl-, phenoxyl-, and carboxyl-reactive groups can form coordination compounds with metals. The ion-exchange equilibrium method using Dowex AG 50W-X8, 20-25 mesh Na+ form was used to determine stability constants of complexes formed between humic acid (isolated from the soil) 50–250 μg (≈3×10−5–15×10−5 mol/liter) and metal salts solution 200 μg at pH 3.5. The stability constant (log K) for different metal–humic acid complexes indicated the following order of the stabilities of complexes formed between humic acid and metal ions: Cu>Fe>Pb>Ni>Co>Ca>Cd>Zn>Mn>Mg. The data on stability constants demonstrated substantial deviation from Irwing–Williams series reported for divalent ions. The molar humic acid/metal ratios were also calculated. Some of the factors affecting the stability constants such as cation exchange capacity of humus soil, molecular radius, and molecular surface area of humic molecules were also estimated. The significance of the data to predict the behavior of these complexes in the environment is discussed.

Soft- and Hard-Modeling Approaches for the Determination of Stability Constants of Metal–Peptide Systems by Voltammetry

The Zn2+–glutathione system is studied as a model for metal–peptide systems where some critical factors must be considered when using voltammetric techniques for the determination of stability constants. These factors are the presence of side reactions (in this case, both the protonation of glutathione and the hydrolysis of Zn2+), the association–dissociation rates of the complexes compared with the time scales of the measurements (which makes the complexes electrochemically labile or inert), and the electron transfer kinetics on the electrode surface (which makes the metal ion reduction reversible or irreversible). For the study of these factors, three data treatment approaches have been applied: (i) the electrochemical hard-modeling approach (modelization of both chemical equilibrium and electrochemical processes), (ii) a chemical hard-modeling approach (modelization of chemical equilibria only, based on the least-squares curve-fitting program SQUAD), and (iii) a previously developed model-free soft-modeling approach based on multivariate curve resolution with a constrained alternating least-squares optimization. By analyzing differential pulse polarographic data obtained under different experimental conditions, the influence of the mentioned factors on every approach is discussed and, if possible, the corresponding stability constants are computed. The results of this study showed the potential usefulness of voltammetry in combination with hard- and soft-modeling data analysis for the study of peptide complexation equilibria of metal ions such as Zn which have neither relevant spectroscopic properties nor proper isotopes for NMR measurements.

Determination of stability constants for metal–ligand complexes using the voltammetric oxidation wave of the anion/ligand and the DeFord and Hume formalism

The voltammetric oxidation peaks for anions and other ligands that react at the Hg electrode can be used for the determination of stability constants of metal–ligand complexes using the DeFord and Hume formalism. Metal–ligand complexes with known stability constants that span the range of log β=2.9–5.9 were determined using the oxidation wave of the ligand as metal was varied. For the larger stability constants, it was possible to titrate concentrations of metal to ligand that are smaller than the ligand concentration and obtain reliable data ( β j C x j approaches 1 in this case) indicating that an excess of titrant is not required to obtain reliable β values. Data reduction with different versions of the Solver tool (included with Microsoft Excel) is discussed and blind use of these programs without knowledge of the physical chemistry of the system is discouraged. The use of Solver gives β values that are in agreement with previous work that used (non)linear regression to evaluate each F n ( X) versus [ X] function.

Determination of Stability Constants of Metal Complexes by Capillary Electrophoresis

The stability constants of several divalent first row transition and trivalent lanthanide metal complexes were determined by capillary electrophoresis (CE) methods. Four different approaches, i.e. direct formation, ligand exchange, metal exchange and metal-ligand double exchange were developed. To verify if these CE methods are indeed applicable, the stability constant of CuHEDTA was re-determined to be 17.47 ± 0.20 (consistent with the published 17.50) using the CuEDTA and ZnHEDTA metal-ligand double exchange approach. The stability constants of lanthanide (Ce3+ and Eu3+) and transition metal (Ni2+ and Zn2+) complexes of an aminopolycarboxylate ligand, DO2A (1,7-dicarboxymethyl-1,4,7,10-tetraazacyclododecane) were measured under the direct complex formation condition. The stability constant of the NiDO2A complex was determined by the ligand exchange method using 1,4,8,11-tetraazaundecane (2,3,2-tet) as the competing ligand. The stability constant of CuDO2A complex was determined by the metal exchange method using Zn2+ ion as the competing metal ion, and complex formation competitions of Ni2+ and Cu2+ between DO2A and 2,3,2-tet were studied by the metal-ligand double exchange method. Effects of experimental conditions and the advantages and limitations of these CE methods are discussed.

Electromigration behavior of metal ions in the presence of complexing polymer

Electromigration behavior of metal ions in the presence of high concentrations of polyethylene glycol as a complexing agent was investigated under acidic non-buffered conditions. Simulation of the isotachophoretic steady state of the system containing the neutral polymer was performed. Both the complexation and the influence of viscosity on the electrophoretic mobility were taken into account. Good agreement between the calculated results and the experimentally obtained values was achieved. Based on the theoretical model, a new approach for the estimation of polymer–metal stability constants from experimental isotachophoretic data was proposed. Stability constants of Li +, Na +, Cs +, Mg 2+, Sr 2+, Mn 2+, Co 2+, Ni 2+, Zn 2+, Pb 2+, Lu 3+ and Y 3+ ions with polyethylene glycol were determined.

Metal–sulfide complexation in seawater

The conditional stability constants of metal–sulfide complexes were determined in pH 8 seawater at various salinities, by flow-analysis with detection by cathodic stripping voltammetry (FA-CSV). Two methods were used. The first method was titration of the sulfide by metal with detection of the free sulfide by FA-CSV. The titrant metals were Ag+, Cd2+, Co2+, Fe2+, Mn2+, Pb2+, Zn2+, Cr3+ and Al3+. This method was suitable for comparatively weak complexes (log K<∼8). The second method took advantage of ligand competition between sulfide and 8-hydroxyquinoline (oxine) for free metal ions. The ability of the oxine to form electroactive complexes with Cu2+, Cd2+, Pb2+, Zn2+, Co2+ and Ni2+, was used to detect the concentration of the metal–oxine complexes in equilibrium with sulfide. More stable complexes could be detected by this method. The two independent methods could be compared for some metals showing good agreement. The stability of the sulfide complexes with copper was found to be much greater than previously determined, in line with theoretical prediction. The high stability, greater than that for Ag+, suggests that copper may be complexed by sulfide as copper(I) rather than copper(II). Complex stability with Co2+ and Cd2+ is also greater than found before, but the difference is smaller. The stability constants were used to calculate the speciation of sulfide at realistic sulfide and metal concentrations similar to those present in the open ocean. At a sulfide concentration of 0.5 nM and a copper concentration of 1 nM in seawater, the major form of sulfide is copper(II) monobisulfide (Cu(HS)+) representing 99% of the total sulfide. In the presence of natural organic complexing ligands a smaller percentage (28%) of sulfide was bound to copper, the remainder occurring as bisulfide, whereas copper was then 71% complexed by organic matter. The new data and the calculations confirm the potential importance of sulfide as a complexing ligand in seawater, more important than major anions and competing effectively with natural organic ligands.

Synthesis, Characterization, and Alkali Metal Stability Constants of a New Bis(phosphotriester) Macrobicyclic Polyether Cryptand

Synthesis, Characterization, and Alkali Metal Stability Constants of a New Bis(phosphotriester) Macrobicyclic Polyether Cryptand