Organic amine cations separation

Conventional IPC separations were achieved by adding organic amines and ammonium salts of varying chain lengths as cationic IPRs for anionic analytes and alkyl or aryl sulfonates and sulfates as anionic IPRs for cationic solutes. Since these IPRs exhibit good tensioactive properties, IPC was originally named soap chromatography [1]. 

The control of EOF is critical to the migration time precision of the separation. Among the factors affecting the EOF are buffer pH, buffer concentration, buffer viscosity, temperature, organic modifiers, cationic surfactants or protonated amines, polymer additives, field strength, and the nature of the capillary surface. 

In this type of separation the analyte cations compete with the eluent cation for ion-exchange sites and move down the eolumn at different rates. The ionic eluent selected depends on the cations to be separated, the type of separation column and on the detector. In many cases an aqueous solution of a strong acid such as hydrochloric, sulfuric or methanesulfonic acid is a satisfactory eluent. Sample cations commonly separated include the following alkali metal ions (Li, Na+, K", Rb, Cs ), ammonium, magnesium, alkaline earths (Ca, Sr +, Ba ), and various organic amine and alkano-lamine cations. Most other metal cations are separated with a weakly complexing eluent. 

As in anion chromatography, the IC separation of organic cations has long been known, or at least suspected, that its mechanism involved more than simple ion exchange. Hoffman and co-workers [9,10] have shown that two mechanisms occur in such cases ion exchange and hydrophobic interaction between the sample cations and the resin matrix. For example, these authors showed that the slopes of the linear plot of log k vs. carbon number for protonated amine cations decrease going from 30 % acetonitrile (70 % water) to 70 % acetonitrile in the eluent. This is due to lower hydro-phobic interaction in the 70 % acetonitrile. 

Neutral organic compounds that cannot exist as cations may be retained by physical adsorption but can be washed off the cation exchange colunm by a brief rinse with an organic solvent. The amine cation can then be eluted from the column with a 1 M solution of trimethylamine in methanol. The trimethylamine converts the amine cation to the free amine which is no longer retained by the cation exchanger. Because of its volatility, trimethylamine is easily removed from the eluate. After acidification, the sample amines can be separated by cation chromatography. 

In acidic solution organic amines can be separated by CE as the protonated cations. If necessary, some methanol or acetonitrile may be mixed with the aqueous BGE to enhance the solubility. For example, amino acids are zwitterions throughout much of the pH range but they have a net positive charge at very low pH values. The CE sepa-... 

Inorganic polymers can also be produced in aqueous solutions by dissolving a salt in water and heating the solution near the boiling point with dropwise addition of ammonium hydroxide [34]. This leads to cation hydrolysis and formation of mono- to polynuclear species. In another route, an aqueous solution is treated with a solution of an organic amine in a water-immiscible organic liquid. In the process, anions of the salt are extracted and hydroxyls are generated in the aqueous part [35]. This part can be separated with ease and used in emulsions. 

Abstract. Silica gel-bound crown ethers and aza macrocycles have been synthesized with the attaching arm connected to the carbon framework of the macrocycles. The interactions of these bound macrocycles with cations are almost identical to those involving the analogous free macrocycles. This has allowed for predictable cation separation, concentration, and removal processes to be performed on a small scale. Quantum mechanical calculations and NMR measurements indicate that similarly bound chiral macro-cycles will be capable of use in separating chiral organic amines. 

TBA) on the separation of protonated organic 3 = 4-tert-butylaniline, 4 = phenylpropylamine, amine cations. Electrolyte contains 50 mM 5 = pindolol, 6= metoprolol, 7 = imipramine, Tris-ethanesulfonate, pH 3, plus added 8 = laudanosine. 

Capillary zone electrophoresis provides effective separations of any charged species, including inorganic anions and cations, organic acids and amines, and large biomolecules such as proteins. For example, CZE has been used to separate a mixture of 36 inorganic and organic ions in less than 3 minutes.Neutral species, of course, cannot be separated. 

Kit for the separation of low-molecular mass organic cations like alkali metal ions, alkaline earth metal ions, and alkyl amines. Indirect UV detection is applied. 

An aspect of general interest in organometallic chemistry is the equilibrium between contact and solvent-separated ion pairs, because metal cations which are sun ounded by an individual solvent cage are expected to show different reactivity towards basic centres than those closely attached to carbanions or amines. At the same time, the anionic centre is less shielded in an SSIP than in a CIP and thus expected to be more reactive. In solution, the differentiation by NMR methods between both structural motifs relies in most cases on chemical shift interpretations and, if possible, on heteronuclear Overhauser (NOE) measurements. The latter method is especially powerful in the case of lithium organic compounds, where H, Li or even H, Li NOE can be detected by one- and two-dimensional experiments. ... 

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