Aminoalkyl bonded phase

Of the other stationary phases, the amino phases have been used extensively to separate sugars and peptides the nitrile phase has found application in the separation of porphyrins. An important consideration in the use of polar bonded-phase materials is an awareness of the reactivity of the terminal functional group, for example, aminoalkyl bonded phase should not be used for the chromatography of carbonyl compounds due to possible condensation reactions and formation of Schiff s bases. 

Besides bonded phases that incorporate linear alkyl chains with 8 or 18 carbon atoms and that can be utilised between pH 2 and pH 13, there are polar stationary phases with linear chains incorporating aminopropyl, cyanopropyl, benzyl or mixed moieties. For example, aminoalkyl chains can be used for the separation of sugars. 

The aminoalkyl and the cyanopropyl bonded phases are commonly used in that they can be equally well used in either the normal phase or the reversed phase mode. The versatility of the cyanopropyl column was exploited in the development of an expert system for HPLC, allowing a single column to be used for all solutes. 

The situation for the 3-substituted compounds resembles that for the 4-substituted isoxazoles. The biologically important 4-aminoalkyl-3-hydroxyisoxazoles (see Section V) exist in the solid phase as zwitterions.288 A recent X-ray crystallographic study of 4-aminomethyl-3-hydroxy-5-methylisoxazole hemihydrate revealed sandwiches of sheets of zwitterions and water molecules held together by hydrogen bonding.277... 

---