Ethylenediaminetetraacetic acid extraction

EDTA (ethylenediaminetetraacetic acid) extracts of soils tend in general to correlate well with plant contents, in particular with the plant-available fraction for Cd, Cu, Ni, Pb and Zn [208-210], EDTA (0.05 mol at pH 7 was used in the certification of the two soils mentioned above [197]. This test is assumed to extract both carbonate-bound and organically-bound fractions of metals and was hence considered to be suitable for calcareous soil analysis. 

The lanthanides form many compounds with organic ligands. Some of these compounds ate water-soluble, others oil-soluble. Water-soluble compounds have been used extensively for rare-earth separation by ion exchange (qv), for example, complexes form with citric acid, ethylenediaminetetraacetic acid (EDTA), and hydroxyethylethylenediaminetriacetic acid (HEEDTA) (see Chelating agents). The complex formation is pH-dependent. Oil-soluble compounds ate used extensively in the industrial separation of rate earths by tiquid—tiquid extraction. The preferred extractants ate catboxyhc acids, otganophosphoms acids and esters, and tetraaLkylammonium salts. 

It is common for acid extracting solutions to contain ligands, such as fluoride, that, when combined with metals, increase their solubility. Chelates such as ethylenediaminetetraacetic acid (EDTA), which combine with metals and either bring them into solution or keep them in solution, are also commonly used. 

Various modifying agents such as methanol, as shown in Procedure 12.3, and ethylenediaminetetraacetic acid (EDTA, a chelate) can be added to liquid C02 to either make the extraction more effective or more specific. In either case, these additives must be removed before further analysis of extracted organics is carried out. 

Ethylenediaminetetraacetic acid (EDTA) Used for fractionation of water-soluble extracts. Precipitates approximately 30% of water-soluble N Kuchroo and Fox (1982b)... 

A. r>itr>o80-tert-oetane To a 1-L, three-necked flask equipped with an addition funnel, a mechanical stirrer, and a thermometer are added 120 ml of methanol, 51.7 g of tert-octylamine (0.4 mol) and 90 mL of water containing 1.2 g (0. 0028 mol) of the tetrasodium salt of ethylenediaminetetraacetic acid and 2.52 g (0. 0076 mol) of sodium tungstate dihydrate. The solution is cooled to 15°C in an ice bath and hydrogen peroxide (361 mL of a 16% solution, 1.7 mol) (Notes 1 and 2) is added over 5 hr. The blue reaction mixture is stirred for an additional 16 hr and the product is extracted with petroleum ether (3 x 50 mL). Unreacted amine is removed by washing twice with 2 N hydrochloric acid. After the blue organic layer is washed with brine, it is dried over MgS04. Petroleum ether is removed by distillation at atmospheric pressure. Continued distillation of the product affords 29.7 g of nitroso-tert-octane... 

Official methods have been published for the determination of nitric-perchloric acid-soluble copper in soil [97] and ethylenediaminetetraacetic acid-soluble copper in soil [98]. The former method involves atomic absorption spectrometric evaluation of the acid digest and the second method involves extraction of the soil with an aqueous solution of ammonium EDTA and atomic absorption spectrometric evaluation of the extract. 

Off-line dicarbamate solvent extraction and ICP-MS analysis [317] provided part-per-trillion detection limits Cd (0.2 ppt), Co (0.3 ppt), Cu (3 ppt), Fe (21 ppt), Ni (2 ppt), Pb (0.5 ppt), and Zn (2 ppt). Off-line matrix removal and preconcentration using cellulose-immobilized ethylenediaminetetraacetic acid (EDTA) have also been reported [318]. Transition metals and rare earth elements were preconcentrated and separated from the matrix using on-line ion chromatography with a NTA chelating resin [319]. Isotope-dilution-based concentration measurement has also been used after matrix separation with a Chelex ion-exchange resin [320]. The pH, flow rate, resin volume, elution volume, and time required for isotope equilibration were optimized. A controlled-pore glass immobilized iminodiacetate based automated on-line matrix separation system has also been described [321]. Recoveries for most metals were between 62% and 113%. 

A DNA extraction protocol that has proved useful for most ancient tissues is a modification of the protocol initially published by Blin and Stafford.20 Approximately 0.1 g of small pieces of soft tissue is added to 5 ml of extraction buffer containing 10 mM Tris-HCl (pH 8.0), 2 mM ethylenediaminetetraacetic acid (EDTA), 10 mM NaCl, 1% (w/v) sodium dodecyl sulfate (SDS), 10 mg/ml dithiothreitol (DTT), and 0.5 mg/ml proteinase K. Incubation at 37° with gentle agitation overnight will allow most or all of the tissue to go into solution. An equal volume of phenol, equilibrated with 1 M Tris-HCl (pH 8.0), is added. When the phenol is being equilibrated, care should be taken to use uncontaminated Tris buffer and to measure the pH only on aliquots that are removed from the water phase and then discarded. Two phenol extractions and one chloroform extraction are performed, and the water phase is concentrated and purified on a Centricon 30 microconcentrator (Amicon, Danvers, MA). The reten-tate can be stored frozen, preferably in a few aliquots. In all cases solutions should be manipulated with DNA-free positive displacement pipettes. 

Figure 2 Illustration of the solid phase extraction system involving the selective removal of Pb2+ from a matrix typically found in acidic high-level or low-level nuclear waste. Following selective removal of the Pb (Step 2), the column is washed to remove the solution remaining in the dead volume, and the Pb is eluted in highly purified form with a complexing agent such as citrate ion or ethylenediaminetetraacetic acid (EDTA)...

Dealuminated by extraction with ethylenediaminetetraacetic acid (EDTA). 

Prompt stabilization of ascorbic acid is especially important in the case of plasma or serum samples. Metaphosphoric acid is often used for this purpose because it also serves as a protein precipitant. Such properties are desirable in the inactivation of oxidase and the catalytic eflFect of copper. Oxalic acid is an attractive stabilizer for ascorbic acid analysis because of its lower cost and greater stability however, it is not a protein precipitant, therefore, it has a limited use for the extraction of animal tissues. The use of ethylenediaminetetraacetic acid (EDTA) in addition to the metaphosphoric acid has been recommended (96). EDTA would chelate divalent cations, and a study has shown it will stabilize ascorbic acid in the presence of copper for several days (96). Perchloric acid has been used also but because of its inherent dangerous properties its use is generally avoided. Trichloroacetic acid and EDTA also seem appropriate extractants for ascorbate in plant materials (97). 

A 250-mL, round-bottomed flask equipped with a Teflon-coated magnetic stirring bar is charged with 3.89 g (20.0 mmol) of trans-a-methylstilbene (Note T), 0.12 g (1.0 mmol) of tetrahydrothiopyran-4-one (Note 2), 90 mL of acetonitrile (Note 3) and 60 mL of aqueous 4 x 10 4 M ethylenediaminetetraacetic acid, disodium salt (Na2 EDTA) solution (Note 4). To this stirred mixture is added in portions a mixture of 18.4 g (30.0 mmol) of Oxone (Note 5) and 7.8 g (93 mmol) of sodium bicarbonate over a period of 3 hr at room temperature. A slow evolution of gas bubbles is observed (Note 6). The reaction is complete in 3.5 hr as shown by TLC analysis (Note 7). The contents of the flask are poured into a 250-mL separating funnel and extracted... 

Extraction with the solvent was followed by exhaustive extraction with water. EDA = diami-noethane or ethylenediamine DMF = N,N-dimethylformamide DMSO = dimethylsulfoxide EDTA = ethylenediaminetetraacetic acid. 

The powerful metal chelator, EDTA (ethylenediaminetetraacetic acid), is an efficient extracting agent for organically bound trace metal cations in soils at pH 6 and higher. The formation constants, for some metal-EDTA complexes in water are given below ... 

Grounding of 20 berry skins to a fine powder with liquid nitrogen Extraction with 3 volumes (v/w) of buffer pH 7.5 (Tris-HCl 0.1 M, ethylenediaminetetraacetic acid (EDTA) 5 mM, phenylmethanesulfonylfluoride ImM, 2-mercaptoethanol 2%, KC1 0.1M, sucrose 0.7M, PVPP 1%) under stirring at 4°C for lh... 

An example of a chelating ligand is ethylenediaminetetraacetic acid (H4EDTA) and its many relatives (Fig. 3.4). The six positions around Fe2+ are occupied by the two amine and four acetate groups. Chlorophyll and hemoglobin are also chelates. Chelates are quite soluble and tend to keep Fe, Zn, and Cu in solution for plant absorption. Chelates are also used to extract microelement and heavy metal ions from soils. The stability constant of theFe(III)-EDTA complex is... 

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