Equilibration technique

Empirical [65-79] Equilibration technique The most direct approach is to equilibrate the organic pollutant in the octanol/water system and measure its concentration in both phases Concentrations derived from mass balance calculation, though less time-consuming, can introduce considerably more uncertainty... 

It is important to perform both the Birch reduction of 5 and the alkylation of enolate 6 at —78 °C. Enolate 6 obtained directly from 5 at low temperatures is considered to be a kinetic enolate . A thermodynamic enolate obtained from 6 by equilibration techniques has been shown to give an opposite sense of stereoselection on alkylation. Although a comprehensive study of this modification has not been carried out, diastereoselectivities for formation of 8 were found to be greater than 99 1 for alkylations with Mel, EtI, and PhCH2Br. Thus, it should be possible to obtain both enantiomers of a target structure by utilization of a single chiral benzamide. SE... 

Miller, LA. and Bruland, K.W. (1997) Competitive equilibration techniques for determining transition metal speciation in natural waters evaluation using model data. Anal. Chim. Acta, 343, 161—181. 

The main uncertainty in the gas equilibration technique has been to judge accurately whether equilibrium has really been achieved or not. Consequently, the extent of range of error in such measurements is also difficult to estimate. It was, therefore, decided to check and re-estimate the reported data with independent techniques. 

The enthalpy of formation of YF3 was determined by Rudzitis, Feder, and Hubbard 164) using fluorine bomb calorimetry. NdCla was done by solution methods (179), and the enthalpies of formation of LaFs and PrFa were determined by Polyachenok 161) who employed an indirect equilibration technique. A recent torsion-effusion study of the vapor pressure of CeFs 115) yields second and third law values for the enthalpy of sublimation. The thermodynamics of the chlorination of rare earths with gaseous chlorine have also been investigated 144). Gibbs energies of formation were determined for CeClg by solid-state electromotive force techniques 41). 

Dinuclear complexes such as Mn2(CO)io, Cp2Mo2(CO)6, and Cp2Fe2(CO)4 serve as precursors for many organometallic complexes via reaction sequences involving formal oxidative addition across the M-M bonds, Eq. 25. Access to M-M BDE data can provide a convenient anchoring point for the determination of other M-X data. Pugh and Meyer [41] have used a redox equilibration technique that enables the determination of M-M bond strengths. 

Kim C, Manning RO, Brown RP, Bruckner JV. Use of the vial equilibration technique for determination of metabolic rate constants for dichloromethane. Toxicol Appl Pharmacol 1996 139 243-51. 

T.B. Coplen, J.D. WUdman, J. Chen (1991) Improvements in the gaseous hydrogen-water equilibration technique for hydrogen isotope ratio analysis. Anal. Chem. 63, 910-912... 

The 18O-equilibration technique was applied to several systems which undergo 1,2 alkyl or aryl shifts. The first study with a labeled sulfonate was carried out by Denney and Goldstein86 who rearranged (68) to (69) (25% scrambling of ether-180) and... 

Rapid equilibration techniques are particularly helpful to save time as the flow rate decreases, in, for example, microbore applications. Figure 9 (p. 124) shows a separation on a 1 x 50 mm column, at 0.3 mL/min, with a cycle-to-cycle inject time of 5.5 min using the parallel mode with rapid equilibration. Run in the traditional sequential manner, the corresponding cy-cle-to-cycle inject time would be in excess of 7.5 min. At lower flows, the time saving during reequilibration would be even more significant. 

The so-called batch equilibration technique is classified as pH". In this method the final (after long shaking) pH of dispersion is plotted as a function of the initial pH at constant pH and solid to liquid ratio and the plateau of the curve indicates the PZC provided that the oxide is free of soluble acids and bases. 

G. R. Umbreit (24) has used the gas-equilibration technique to measure several halogenated hydrocarbons, employing both flame ionization detection (FID) and electron capture (EC). Halogenated hydrocarbons included dichloromethane, chloroform, carbon tetrachloride, trichloroethylene, tetrachloroethylene, 1,1,1-trichloroethane, 1,2,2-trichlo-... 

Oil samples were analyzed for remaining low-molecular-weight hydrocarbons by equilibrating 10-20 mL of the original or surface-collected oil with 70 mL of seawater collected outside the spill area. The oil and water were hand-shaken gently and periodically for 24 hr or more to establish equilibrium, Mercuric chloride added to water samples at time of collection prevented possible biodegradation of hydrocarbons during the oil-water equilibration. This water was analyzed by the gas-equilibration technique. 

Complexation of metal ions with the carboxyl resin Complexation of the carboxyl resin was carried out towards Fe(II), Fe(III), Co(II), Ni(II) and Cu(II) ions by a batch equilibration technique. A quantity (100 mg) of the resin was stirred in an aqueous metal salt solution (0.05 mol L , 50 mL) for 24 h. The complexed resins were collected by filtration and washed with distilled water to remove uncomplexed metal ions. The concentrations of the metal salt solutions were estimated by UV spectrophotometric methods. 

Another drawback of the classical Andersen procedure is that it allows for isolation of diastereoisomerically pure (5)-(-)-menthyl p-toluene sulhnate in a poor 30% yield. An early improvement pioneered by Hebrandson employed the known racemization of sulfoxides by HCl in an epimerization/equilibration technique to increase the yield of (5)-(-)-menthyl p-toluene sulhnate to 90% from the initial (R) and (5) diastereoisomeric mixture [14]. This adaptation has been described in detail by Solladie and the proposed epimerization/equilibration is... 

Obregon MJ, Morreale de Escobar G, Escobar del Rey F, Concentrations of triiodothyronine in the plasma and tissues of normal rats as determined by radioimmunoassay Comparison with results obtained by an isotopic equilibration technique. Endocrinology 103 2145 (1978)... 

Kob] Chemical equilibrating technique between Fe-Cr-Csatd melt and Ag-Cr203 melt in equilibria with CO/CO2 atmosphere 1200-1500°C, 2.23-10.7 mass% Cr and 5.0-7.01 mass% C, liquid... 

Par] Chemical equilibration technique, atomic absorption spectroscopy, LECO thermal analyzer 1650°C, up to 5.06 mass% C and up to 0.87 mass% Cr, liquid... 

Ball] Carbon solubility measurements, Gas (CH4/H2) equilibration technique 1000-1200°C, < 1 mass% Ti, < 2 mass% C... 

The free energies of formation of some chromium carbides and ternary carbides of uranium with Cr, Mo and W were measured by the methane hydrogen equilibration technique developed earlier. 

The method developed by Hummel and Dreyer is a dynamic equilibration technique based on the fact that complexes, formed between metal ions and the ligand macromolecules, are excluded to a greater or lesser extent from the gel interior whereas the free metal ions completely permeate the gel, thus permitting a separation of the two species. 

Be sure to use a clean Pasteur pipette whenever you remove CDCI3 from its supply bottle. Avoid contaminating the stock of NMR solvent. Also be sure to fill and empty the pipette several times before attempting to remove the solvent from the bottle. If you bypass this equilibration technique, the volatile solvent may squirt out of the pipette before you can transfer it successfully to another container. 

The adsorption properties of natural clinoptilolite toward Co were investigated by batch equilibration technique [07S2], The kinetic data were fitted by pseudo-second-order reaction model, and the adsorption isotherms were defined by the Langmuir equation. The adsorption capacity of the natural clinoptilolite was decreased by the competition among the metal ions in solution. The adsorption capacity reached 2.34 mg/g for Co. The adsorption of Co was low, at low pH, but increased remarkably with increasing pH and precipitated at pH > 8. The presence of EDTA hindered the adsorption of Co on clinoptiloUte. 

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