Chromatographic Separations with Selected Supported Chelating Agents

In this chapter, ligands have a more focused definition than they typically do. Ligands are molecules having donor atoms with a pair of electrons that form coordinate covalent bonds with metal ions. Unidentate ligands have a single donor atom, while chelating agents have two or more donor atoms, and in attaching to the metal ions form rings that are associated with enhanced stability. Further, two kinds of chelating agents are involved: molecular and supported.

Related papers:

title: Chelex 100 as a medium for simple extraction of DNA for PCR-based typing from forensic material.
abstract: Procedures utilizing Chelex 100 chelating resin have been developed for extracting DNA from forensic-type samples for use with the PCR. The procedures are simple, rapid, involve no organic solvents and do not require multiple tube transfers for most types of samples. The extraction of DNA from semen and very small bloodstains using Chelex 100 is as efficient or more efficient than using proteinase K and phenol-chloroform extraction. DNA extracted from bloodstains seems less prone to contain PCR inhibitors when prepared by this method. The Chelex method has been used with amplification and typing at the HLA DQ alpha locus to obtain the DQ alpha genotypes of many different types of samples, including whole blood, bloodstains, seminal stains, buccal swabs, hair and post-coital samples. The results of a concordance study are presented in which the DQ alpha genotypes of 84 samples prepared using Chelex or using conventional phenol-chloroform extraction are compared. The genotypes obtained using the two different extraction methods were identical for all samples tested.

title: Studies on chelating adsorption properties of novel composite material polyethyleneimine/silica gel for heavy-metal ions
abstract: Firstly, the coordination processes of line-type polyethyleneimine with Cu 2+ , Cd 2+ and Zn 2+ were studied by using visible light absorption spectroscopy and chelation conductivity titration method, and the structures of the chelates were determined. Afterwards, polyethyleneimine (PEI) was grafted onto the surface of silica gel particles via the coupling effect of γ-chloropropyl trimethoxysilane (CP), and the novel composite adsorption material PEI/SiO 2 with strong adsorption ability towards heavy-metal ions was prepared. The chelating adsorption properties of PEI/SiO 2 for Cu 2+ , Cd 2+ and Zn 2+ were researched by both static (batch) and dynamic (flow) methods. The experiment results show that water-soluble polyamine PEI with line-type structure reacts with Cu 2+ , Cd 2+ and Zn 2+ easily and quantitatively, and water-soluble chelates with four ligands are formed. The composite material PEI/SiO 2 possesses very strong chelating adsorption ability for heavy-metal ions, and the saturated adsorption amount can reach 25.94 mg g −1 and 50.01 mg g −1 for Cu 2+ under static and dynamic conditions, respectively. The isothermal adsorption data fit to Langmuir equation, and the adsorption is typical chemical adsorption with monomolecular layer. The adsorbing ability of PEI/SiO 2 towards the three kinds of the ions follows the order of Cu 2+  > Cd 2+  > Zn 2+ . The pH value has great influence on the sorption, and at pH 6–7, the adsorption capacity is the greatest. The fact that adsorption capacity increases with temperature rising indicates the adsorbing process of PEI/SiO 2 for metal ions is endothermic. As diluted hydrochloric acid is used as eluent, the adsorbed heavy-metal ions are eluted easily from PEI/SiO 2 , and the regeneration and reuse without decreasing sorption for PEI/SiO 2 are demonstrated.

title: Extraction of Heavy Metals by 2-Mercaptoethoxy Groups Attached to Silica Gel
abstract: Silica gel is currently being used as a support for various straight chain mono- and bifunctional compounds such as amines, thiols (mercaptans), and mercaptoalochols. The current study reports the results of an investigation of a 2-mercaptoethoxy moiety covalently attached to silica gel. The condensation was effected by acid-catalyzed condensation of toluene solution of 2-mercaptoethanol and silica gel and azeotropically removing the water using a Dean-Stark tube. As a coordinating agent, this bifunctional compound was used in the removal of copper(II), cadmium(II), and lead(II) from standard aqueous solutions. Using silica gel support, the removal percentages were 91–93% for the three metals.

title: Extraction of Selected Heavy Metals Using Modified Clays
abstract: In the present study, attapulgite, kaolinite, and montmorillonite KSF were modified using azeotropic distillation to condense 2-mercaptoethanol with the clay material. The resulting product was used as a coordinating agent to remove selected metal ions, e.g., copper(II), cadmium(II), silver(I), nickel(II), and lead(II) ions from standard aqueous solutions. Batch systems were used, and samples were shaken for two hours, and following filtration, metal content of the filtrate was measured by atomic absorption spectrometry. Without adjusting the pH, better than 90% of the metal ions could be removed.

title: Removal of heavy metal ions from aqueous solutions using dithiooxamides supported on silica gel
abstract: Silica gel was used as a support for N, N'‐ didodecyldithiooxamide, a bidentate chelating agent with sulfur and nitrogen donor atoms. Aqueous solutions of five heavy metals (0.03 M copper, lead, nickel, silver, and zinc solutions) were treated with silica gel (control) and loaded silica gel. Resulting solutions were analyzed using atomic absorption spectroscopy. Using silica gel alone (control), the percent metal extracted was 3.2+0.9 (Cu), 16.3 ±1.6 (Ni), 3.9±1.2 (Pb), 13.6 ± 4.8 (Ag), and 4.8± 1.8 (Zn). Using silica‐supported chelating agent, the percent removal was 99.1±0.3 (Cu), 70.7±1.7 (Ni), 29.1±1.7 (Pb), 83.5±0.7 (Ag), and 6.5±1.9 (Zn). The results did not correlate with the “softness”; parameter for type a or type b metals.

title: EXTRACTION OF HEAVY METALS BY MERCAPTANS ATTACHED TO SILICA GEL BY A CORKSCREW MECHANISM
abstract: Saturated, straight chain mercaptans were attached to silica gel and used as coordinating agents for removal of cadmium(II), copper(II), lead(II), and nickel(II) ions from standard solutions. It is believed that the mercaptans become wedged in the silica pores, but are available for reaction. Four thiols were used, viz., 1-hexanethiol, 1-dodecanethiol, 1-hexadecanethiol, and 1-octadecanethiol. Standard solutions of metals (1.57 mM) were stirred with the supported mercaptans for two hours, and at 25°C, and the sample supernatants were analyzed using atomic absorption spectrometry. At pH = 8, the percent removal was 99 (Cd), 91.5 (Cu), 80.8 (Pb), and 97 (Ni). It was possible to acidify the metal-containing solids, and regenerate the supported chelating agents.

title: Comparison of effectiveness of removal of nuisance anions by metalloligs, metal derivatives of Octolig®
abstract: The present study describes the effectiveness of removal of selected aqueous anions by several metalloligs, i.e., metal derivatives of a commercially available immobilized ligand, IMLIG, Octolig®. This material consists of polyethylenediamine moieties covalently bound to a high-surface area silica gel (CAS Registry number = 404899-06-5). The metals involved are copper, cobalt, iron, nickel, manganese, and thorium. The nuisance anions, studied as aqueous solutions, were arsenate, orthophosphate, selenite, sulfate, nitrate, and nitrite. All six metalloligs tested were able to remove arsenate (280 ppb, > 99% removal) effectively. The effectiveness for other anions varied, but all anions were removed by one metallolig or another. For example, for Colbaltilig, in deionized water samples, removal was 96% for 20.9 ppm NO3-N, 98% for 29.6 ppm sulfate (as sodium sulfate). For Cuprilig, removal was 98% for 9.82 ppm boron as boric acid, > 99% for Cr as 212 ppm dichromate, 97% for P as 10 ppm HPO4-P, and 90% for sulfate as 29 ppm sulfate. Removal of nitrate by Cobaltilig appeared to be adversely affected by the presence of sulfate. Manganilig and Nickelig were able to remove > 97% of 10 ppm P as Na2HPO4. Mechanisms of interaction are proposed that suggest six types of behavior and several classes of materials are represented by these metalloligs.

title: Comparative ease of separation of mixtures of selected nuisance anions (nitrate, nitrite, sulfate, phosphate) using Octolig®
abstract: Mixtures of sodium salts of nitrate, nitrite, sulfate, and phosphate were prepared in relative amounts present in atomic waste containers with a view to effect removal by chromatography over Octolig®, commercially available material with polyethylenediamine moieties covalently attached to high-surface area silica gel. Separation was attempted using aqueous solutions and column chromatography with Octolig®. It is presumed that this material is capable of removing the anions by means of encapsulation. Matrix effects were tested by varying the relative concentrations. Rates of elution were varied 5-fold without adverse effect. The order of selectivity was found to be phosphate > sulfate > nitrite > nitrate through experiments altering the volume and relative concentrations. Quantitative removal of all anions (375 ppm of each) could be achieved given reasonable volumes of Octolig®. An effort at regeneration by altering the pH of the eluant indicated the stability of the encapsulated anions.

title: Effectiveness of removal of aqueous perchlorate by Cuprilig, a copper(II) derivative of Octolig®
abstract: The present study describes the effectiveness of removal of perchlorate ion by Octolig® a commercially available immobilized ligand, IMLIG, and by Cuprilig, the cupric ion derivative of this material. Octolig® consists of polyethylenediamine moieties covalently bound to a high-surface area silica gel (CAS Registry number = 404899–06-5). Perchlorate in drinking water is a nuisance anion that escapes from firms that produce rocket fuel, batteries, and fireworks and becomes a contaminant of groundwater. It may also be a natural component of the environment. Perchlorate ion can interfere with thyroid function and may also cause birth defects. Perchlorate contamination of water supplies is serious because of the difficulty in removing it, especially in the western United States where a combination of drought and water shortages exacerbate the problems of supplying safe drinking water to an increasing population. In this study, aqueous solutions were passed over a chromatography column containing samples of Cuprilig. Test water contained 70 μ g perchlorate/L and effluent was below detection level (< 1 μ g/L. Equally good results were obtained for Octolig® in deionized water and in well water. Analyses were performed by a commercial laboratory. Mechanisms of interaction are proposed.

title: Removal of selected nuisance anions by Octolig®
abstract: Octolig®, a commercially available immobilized ligand (IMLIG), has been studied for its effectiveness in removing nuisance anions. The material consists of polyethylenediamines covalently linked to high surface-area silica, and has a high affinity for transition metal ions. Previous research indicated that anions could be removed quantitatively from aqueous solutions using the metal derivatives of Octolig® as packing in column chromatography. The present study focused on the results with Octolig® alone. Quantitative removals (> 99%) were obtained for arsenate, chromate, paramolybdate, selenious acid, and fluoride. Boric acid was not removed by under similar conditions, but previously the copper(II) derivative of Octolig® had been partially successful. A mechanism of removal is proposed.

title: Removal of BPA model compounds and related substances by means of column chromatography using Octolig®
abstract: Octolig®, a polyethylenediimine ligand covalently attached to high-surface area silica gel, was used to study the removal of phenolic compounds from aqueous samples by column chromatography. Model phenolic compounds of Bisphenol A (BPA), 4-isopropylphenol and 4-(t-butyl) phenol, were selected for this study due to their similarities in pKa and log P values. The percent removal of these compounds by Octolig® was 26 ± 2 and 22 ± 2, respectively. Furthermore, the three isomers of nitrophenol were investigated as well as additional phenolic compounds, such as amoxicillin and five phenolic dyes. These compounds have a pKa range of 2–10.2. The compounds that have pKa values less than 8.3 were able to be completely removed by Octolig®, yet compounds with pKa values of 8.3 and higher resulted in approximately 20–26% removal.

title: Pharmaceuticals in the environment : sources, fate, effects and risks
abstract: General Aspects.- Pharmaceuticals in the Environment - A Brief Summary.- Special Characteristics of Pharmaceuticals Related to Environmental Fate.- Sources, Occurrence and Fate.- Drug Production Facilities - An Overlooked Discharge Source for Pharmaceuticals to the Environment.- Substance Flows Associated with Medical Care - Significance of Different Sources.- Pharmaceutical Residues  Consequences and Perspectives.- Antibiotics in the Environment.- Veterinary Antibiotics in Dust: Sources, Environmental Concentrations, and Possible Health Hazards.- Fate of Veterinary Medicines Applied to Soils.- Pharmaceuticals as Environmental Contaminants: Modeling Distribution and Fate.- Environmental Exposure Modeling: Application of PhATE(TM) and Great-ER to Human Pharmaceuticals in the Environment.- Exposure Assessment Methods for Veterinary and Human-Use Medicines in the Environment: PEC vs. MEC Comparisons.- Effects.- Effects of Pharmaceuticals on Aquatic Organisms.- Another Example of Effects of Pharmaceuticals on Aquatic Invertebrates: Fluoxetine and Ciprofloxacin.- Effects of Antibiotics and Virustatics in the Environment.- Realizing the Potential Benefits of Small Animal Models for the Aquatic Hazard Assessment of Human Pharmaceuticals: A Conceptual Approach.- On the Ecotoxicology of Pharmaceutical Mixtures.- Chronic Mixture Toxicity of Pharmaceuticals to Daphnia - The Example of Nonsteroidal Anti-Inflammatory Drugs.- The Ecotoxicological Effects of Pharmaceuticals (Antibiotics and Antiparasiticides) in the Terrestrial Environment - a Review.- Odorants - Potent Substances at Minor Concentrations: The Ecological Role of Infochemicals.- Risk Assessment.- European Developments in the Environmental Risk Assessment of Pharmaceuticals.- The State and the Future Development/Perspective of Environmental Risk Assessment of Medicinal Products for Human Use: Aspects of Its Regulations in Japan.- Deterministic and Probabilistic Environmental Risk Assessment for Diazepam.- Comparison of Prospective and Retrospective Environmental Risk Assessments of Human Pharmaceuticals.- Methodological Aspects Concerning the Environmental Risk Assessment for Medicinal Products Research  Risk Management.- Strategies for Reducing the Input of Pharmaceuticals into the Environment.- Cost Action 636 Xenobiotics in the Urban Water Cycle - A Network for Collaboration within Europe.- Removal of Pharmaceutical Residues from Contaminated Raw Water Sources by Membrane Filtration.- Photooxidation as Advanced Oxidation Treatment of Hospital Effluents.- Pharmaceuticals and Environment: Role of Community Pharmacies.- Mitigation of the Pharmaceutical Outlet into the Environment - Experiences from Sweden.- Pharmaceutical Waste.

title: Influence of operational parameters on electro-Fenton degradation of organic pollutants from soil
abstract: The combination of the Fenton's reagent with electrochemistry (the electro-Fenton process) represents an efficient method for wastewater treatment. This study describes the use of this process to clean soil or clay contaminated by organic compounds. Model soil of kaolinite clay polluted with the dye Lissamine Green B (LGB) was used to evaluate the capability of the electro-Fenton process. The effects of operating parameters such as electrode material and dye concentration were investigated. Operating in an electrochemical cell under optimized conditions while using electrodes of graphite, a constant potential difference of 5 V, pH 3, 0.2 mM FeSO4· 7H2O, and electrolyte 0.1 M Na2SO4, around 80% of the LGB dye on kaolinite clay was decolorized after 3 hours with an electric power consumption around 0.15 W h g−1. Furthermore, the efficiency of this process for the remediation of a real soil polluted with phenanthrene, a typical polycyclic aromatic hydrocarbon, has been demonstrated.

title: FOOD DYE DEBATE RESURFACES
abstract: ARTIFICIAL COLORS have been making processed foods look more appealing for decades. But renewed fears about a link between the consumption of chemically synthesized dyes and behavioral problems in children have prompted regulators to take a closer look at the safety of color additives in food. An expert panel, convened by the Food & Drug Administration, grappled with dozens of studies on the behavioral effects of food dyes at a two-day meeting late last month in Silver Spring, Md. Despite compelling anecdotal evidence from people who claimed that their behavior or their children’s behavior has been adversely affected by particular food dyes, the committee concluded that the scientific evidence is inadequate to support a link between synthetic food dyes and behavioral problems, such as hyperactivity. By a vote of 8-6, the committee recommended that FDA not require warning labels on food products containing artificial dyes. Currently, such dyes must be listed by name on food ...

title: Food dyes impair performance of hyperactive children on a laboratory learning test.
abstract: Forty children were given a diet free of artificial food dyes and other additives for 5 days. Twenty of the children had been classified as hyperactive by scores on the Conners Rating Scale and were reported to have favorable responses to stimulant medication. A diagnosis of hyperactivity had been rejected in the other 20 children. Oral challenges with large doses (100 or 150 milligrams) of a blend of FD & C approved food dyes or placebo were administered on days 4 and 5 of the experiment. The performance of the hyperactive children on paired-associate learning tests on the day they received the dye blend was impaired relative to their performance after they received the placebo, but the performance of the nonhyperactive group was not affected by the challenge with the food dye blend.