Ammonium a-hydroxyisobutyrate

Fig. 3. The elution of tnpositive actinide and lanthanide ions. Dowex-50 ion-exchange resin was used with ammonium a-hydroxyisobutyrate as the eluant.

Figure 15.8 Original elution data corresponding to the discovery of mendelevium, February 18, 1955. The curves for einsteinium-253 (given the old symbol E253) and californium-246 are for a-particle emission. (Dowex 50 ion exchange resin was used, and the eluting agent was ammonium a-hydroxyisobutyrate.)...

Fig. 14.11 Elution of Irivalenl lanthanide and actinide ions on a Dowex 50 calion-exchange resin with an ammonium a-hydroxyisobutyrate eluant. The band for is predicted. (From Katz. J. J. Morss, L. R. Seaborg. G. T. In The Chemistry of the Actinide Elements. Katz. J. J. Morss, L. R. Seaborg,...

Figure 5. Elution of nobelium from a heated (80°C) Dowex 50 X 12 cation-exchange column with 1.9M ammonium a-hydroxyisobutyrate (pH 4.8) (26)...

Separation factors (relative to Cm) for ammonium a-hydroxyisobutyrate cation exchange of trivalent lanthanides and actinides from Smith and Hoffman (1956), Choppin et al. (1956), and Choppin and Silva... 

Fig. 10.2 HPLC elution curve of Bk and Ce using 0.5 M ammonium a-hydroxyisobutyrate on a cation-exchange column [54]. Reproduced with permission of the authors and Pergamon Press.)...

Fig. 14.3 Elution of tripositive lanthanide and actinide ions on Dowex SO cation-exchange resin and ammonium a-hydroxyisobutyrate eluant. Lr band (dashed line) is predicted.

Fig. 21.12 Separation of the trivalent oxidation states of the transplutomum elements Am-Md by elution from the cation-exchange resin Dowex 50 sulfonated polystyrene 12% crosslinked) with a 0.4m ammonium a-hydroxyisobutyrate solution at 87°C [192],...

The later chemical work of Silva et was done with the Berkeley 65 s, 261 isotope, and this longer half-life enabled a rapid cation-exchange operation to be undertaken. The material was loaded on to Dowex 50 resin and eluted with ammonium a-hydroxyisobutyrate. Despite complications caused by the daughter No having a very similar alpha spectrum to Rf, it was concluded that Rf eluted in much the same fraction as Hf and Zr tracers, in contrast to actinide tracers which were not eluted in these conditions. 

The reaction is mn for several hours at temperatures typically below 100°C under a pressure of carbon monoxide to minimise formamide decomposition (73). Conversions of a-hydroxyisobutyramide are near 65% with selectivities to methyl a-hydroxyisobutyrate and formamide in excess of 99%. It is this step that is responsible for the elimination of the acid sludge stream characteristic of the conventional H2SO4—ACH processes. Because methyl formate, and not methanol, is used as the methylating agent, formamide is the co-product instead of ammonium sulfate. Formamide can be dehydrated to recover HCN for recycle to ACH generation. 

Acesulfame-K, dulcin, saccharin Cl8 column Acetonitrile 50 mM a-hydroxyisobutyric acid, pH 4.5 (2.2 3.4, v/v) with 2.5 mM hexadecyltrimethyl-ammonium bromide UV—233 nm 65... 

Capillary electrophoresis Capillary electrophoresis (CE) is used to analyze sodium, potassium, calcium, and magnesium in water samples. The detection is conducted by reverse absorbance measurements. Sufficient separation of the four cations is established with an electrolyte solution of 5 mM imidazole/6.5 mM a-hydroxyisobutyric acid/2 mM 18-crown-6 ether of pEI 4.1 [42]. CE with a contactless conductometric detector is used to determine small anions and cations in water samples from different sources. 2-(N-Morpholino)ethanesulfonic acid/histidine-based (Mes/Elis) electrolytes are used for direct conductivity detection of anions and cations, while ammonium acetate is used for indirect conductivity determination of alkylammonium salts. Eor the simultaneous separation procedure, involving dual-opposite end injection, an electrolyte consisting of 20 mM Mes/EIis, 1.5 mM 18-crown-6 and 20 mM cetyltri-methylammonium bromide provides baseline separation of 13 anions and cations in less than 6 min [43]. Also CE with a capacitively coupled... 

Rare earths Dowex-50 5% ammonium citrate, pH 3-3.5, or 0.2-0.4 M a-hydroxyisobutyric acid, pH 4.0-4.6, or 0.025 M ethylene-diaminetetraacetic acid (EDTA)... 

The ACH process has been improved by Mitsubishi Gas [332]. Acetone cyanohydrin is first hydrolyzed to 2-hydroxyisobutylamide with a Mn02 catalyst the amide is then reacted with methyl formate to produce the methyl ester of 2-hydroxyisobutyric acid, with co-production of formamide (this reaction is catalyzed by sodium meth-oxide). The ester is finally dehydrated with an Na-Y zeolite to methyl methacrylate. Formamide is converted into cyanhydric acid, which is used to produce acetone cyanohydrin by reaction with acetone. The process is elegant, since it avoids the co-production of ammonium bisulfate, and no net income of HCN is present. However, there are many synthesis steps, and a high energy consumption. 

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