Diol bonded phase

Herman, D. P, Field, L. R., and Abbott, S., The size-exclusion chromatographic behavior of synthetic water-soluble polymers on diol bonded phase supports, /. Chromatogr. Sci., 19, 470, 1981. 

Remove the guard column before washing the analytical column, so that impurities from the guard column are not washed into the analytical column. Bare silica and cyano- and diol-bonded phases are washed (in order) with heptane, chloroform, ethyl acetate, acetone, ethanol, and water. Then the order is reversed, using dried solvents, to reactivate the column. Use 10 empty column volumes of each solvent. Amino-bonded phases are washed in the same manner as silica, but a 0.5 M ammonia wash is used after water. C18 and other nonpolar phases are washed with water, acetonitrile, and chloroform, and then the order is reversed. If this is insufficient, wash with 0.5 M sulfuric acid, and then water. 

In recent years several normal-phase HPLC methods have been reported for the quantitative analysis of tocopherols and tocotrienols (Table 11.5). The best of these methods have been able to achieve baseline separation of all four tocopherols and all four tocotrienols, as shown in Figures 11.2 and 11.3. Kamal-Eldin et al. (2000) reported the optimal baseline separation of all eight common tocols using a Diol-bonded phase column and an isocratic mobile phase of hexane/methyl tert-butyl ether (MTBE), 96 4, v/v (Figure 11.2). Similar separations were reported by Moreau et al. (2007) using the same type of column and mobile phase. Schwartz et al. (2008) reported that, with a normal-phase silica column, plastochromanol-8 in rapeseed oil eluted between y-tocopherol and 5-tocopherol. 

In normal phase HPLC, the cyano and amino columns, in conjunction with the diol bonded phase columns, are now often used in preference to unmodified silica or alumina. Whilst silica can demonstrate remarkable selectivity for the separation of closely related isomers (e.g. E/Z isomers are commonly separated on silica), some of the operational demands of silica limit its usefulness. The difficulty of manufacturing reproducible microcrystalline silica and the possible effect of trace amounts of water on... 

Diol bonded phase, 150,176 Discrimination fector, 303 Dispersion, 284... 

As expected, the aminopropyl bonded phase is more retentive toward acidic samples than either silica or cyanopropyl and diol bonded phases. For example, steroids with phenolic functional groups are more retained on the aminopropyl bonded phase (16). 

Because traditional HILIC columns such as underivatized silica, cyano-, amino-, and diol-bonded phases have hydrophilic surfaces, they are incapable of separating small molecules via hydrophobic interaction. By comparison. 

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