Mixtures by ion exchange

Riickert, M., Wohlfarth, M., and Bringmann, G., Characterization of protein mixtures by ion-exchange chromatography coupled on-line to nuclear magnetic resonance spectroscopy, ]. Chromatogr. A, 840, 131, 1999. 

The amino-acid composition usually is obtained by complete acid hydrolysis of the peptide into its component amino acids and analysis of the mixture by ion-exchange chromatography (Section 25-4C). This procedure is complicated by the fact that tryptophan is destroyed under acidic conditions. Also, asparagine and glutamine are converted to aspartic and glutamic acids, respectively. 

Torres, E. A., and Peterson, E. A. (1992). Purification of complex protein mixtures by ion-exchange displacement chromatography using spacer displacers.. Chromatogr. 604, 39-46. 

The template condensation of [Co( L869)2] + with formaldehyde and nitromethane in aqueous solution, followed by separation of the reaction mixture by ion-exchange chromatography, is represented in Schemes 4-7-4-9. Branched routes of successive transformations result in the formation of four main products, [Co(L872)]3+ to [Co(L875)] + [63, 64]. 

Intermediate, partially coordinated tren complexes of the type [Cr(trenH)(ox)OH2], [Cr(trenH2)(ox)(OH2)2], and [Cr(trenH3)(ox)(OH2)3] were isolated from the reaction mixture by ion exchange chromatography. The acid-independent rate data for the stepwise unwinding of the tren molecule are collected in Table 5.7. Fission of the first Cr-N bond in the strained tren complex occurs 20 times faster than in the less strained a-[Cr(trien)(ox)] ion, and subsequent reactions are much slower. From studies in concentrated hydro-... 

Hydrolysis 10 mmol of the phosphate salt are dissolved by swirling with Dowex AG50W-X8 (H ) in 200 mL of water. After filtration, the pH is adjusted to 6.0, acid phosphatase (150 U EC 3.1.3.2) is added and the mixture is incubated at 25 CC until complete conversion, as monitored by TLC (48 h). The solution is desalted by ion exchange, concentrated in vacuo, and the residue is crystallized from ethanol to give colorless crystals of D-sorbosc yield 1.6g (89%). 

Derivatization Dissolve less than 1 mg of methyl or ethyl ester in 1 ml of freshly distilled pyrrolidine and 0.1 ml of acetic acid. Heat the mixture in a sealed or capped tube (able to withstand high temperatures) at 100° for 30 min. Cool the reaction mixture to room temperature and add 2 ml of methylene chloride. Wash the methylene chloride extract with dilute HC1, followed by ion exchange water. Dry the methylene chloride extract with anhydrous magnesium sulfate.1... 

Ion chromatography can be used in unique ways and by appropriate modification can often be applied to the separation of mixtures where the components themselves do not ionize or do not normally produce interactive ions in aqueous solution. A good example of this type of separation is afforded by the analysis of saccharide mixtures using ion exchange interactions. An illustration of such a separation is given in figure 15. 

Catalysts were prepared from an alkali form of ferrierite, NaK-FER, with a Si/Al = 9 (TOSOH Co., Japan). The monometallic Co-HFER (3 wt. % Co) was obtained by ionexchanging the NH4-FER form with a Co(CH3COO)2 solution. The bimetallic Co/Pd-HFER sample (0.3 wt. % of Pd, 3wt. % Co) was then prepared by ion-exchanging it with a solution of Pd(NH3)4(N03)2. Further details are given elsewhere [10], UV-Vis/RDS spectra were carried out on a Varian Cary 5000 UV-VIS-NIR spectrophotometer. H2-TPR experiments were performed using samples of 130 mg of catalyst, under a mixture of 5% H2/Ar from RT to 1000°C (7.5°C min"1). 

Oligonucleotides have also been separated by ion-exchange chromatography of yeast ribonucleic acid treated either with acid216 or with ribonuclease.209 Alkaline hydrolysis of the fission products obtained with the latter gives rise to pyrimidine nucleoside 3-phosphates and mixtures of purine nucleoside 2- and 3-phosphates. Bone phosphomonoesterase196 followed by alkaline hydrolysis gives pyrimidine nucleosides and purine... 

Loss of catalytic complex by dissolution from the support This can either occur to physically bound catalysts (physisorbed, entangled in a polymer, hydro-gen-bonded), when the reaction medium has too-good solvent properties. The catalyst complex can also be dissolved from ionically bound species by ion exchange with electrolytes in the reaction mixture, or when the covalent bond to the support is broken (e.g., by hydrolysis). In the case of SIB catalysts, a good solvent such as ethanol can displace a salen-type ligand from the metal. 

In systems with two oxo moieties, electrophilic attack occurs at the nitrogen of the cyclic amide. As an illustration, triazidiridine dione 32 was converted in good yield to the salt 16 upon treatment with Mel and followed by ion exchange (Equation 4) <2005H(65)1629>. Similar reactivity was observed with substrate 33, but in this case a 3/1 mixture of O-acylated and iV-acylated products 34 and 35 was obtained (Equation 5) <1997J(P1)2223>. 

Ion-pair liquid chromatography can be applied to compounds separated by ion-exchange liquid chromatography, and mixtures of ionic and non-ionic compounds are easily separated. The latter separation is difficult by ion-exchange liquid chromatography. Anions can be separated by reversed-phase ion-pair liquid chromatography (Figure 4.18). 

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