Hydrophilic Interaction Chromatography HILIC

Additional modes of HPTC include normal phase, where the stationary phase is relatively polar and the mobile phase is relatively nonpolar. Silica, diol, cyano, or amino bonded phases are typically used as the stationary phase and hexane (weak solvent) in combination with ethyl acetate, propanol, or butanol (strong solvent) as the mobile phase. The retention and separation of solutes are achieved through adsorp-tion/desorption. Normal phase systems usually show better selectivity for positional isomers and can provide orthogonal selectivity compared with classical RPLC. Hydrophilic interaction chromatography (HILIC), first reported by Alpert in 1990, is potentially another viable approach for developing separations that are orthogonal to RPLC. In the HILIC mode, an aqueous-organic mobile phase is used with a polar stationary phase to provide normal phase retention behavior. Typical stationary phases include silica, diol, or amino phases. Diluted acid or a buffer usually is needed in the mobile phase to control the pH and ensure the reproducibility of retention times. The use of HILIC is currently limited to the separation of very polar small molecules. Examples of applications... 

M. Yang and R.Thompson, A retention and selectivity model for hydrophilic interaction chromatography HILIC, submitted to J. Chrom. A (Aug 2006). 

In hydrophilic interaction chromatography (HILIC), LC is performed on a non-modified silica column, using an aqueous-organic mobile phase. Compared to reversed-phase LC, the retention order is reversed, i.e., highly polar analytes are more strongly retained. For ESI-MS applications, basic compounds can be eluted... 

Reversed-phase LC (RPLC) is applied most often in LC-MS, although attention is also paid to the use of hydrophilic interaction chromatography (HILIC, Ch. 11.7.3) and the need for chiral separations (see Ch. 11.7.4). 

Hydrophilic interaction chromatography (HILIC) is a variation of normal-phase chromatography in which solutes are retained on a polar bonded phase under high concentrations (80-90%) of organic solvent and released during a gradient to a more aqueous solvent. The organic mobile phase usually causes at least partial denaturation of proteins. 

Applications of click chemistry are already far too numerous to acknowledge by even offering an example fi om each area herein. Some of these areas include dendrimers, polypeptides, polymeric materials, conformationally restricted macrocycles, new ligand designs, and carbohydrates. One representative procedure is provided below. A related study describes sugar-based silica gels for use as hydrophilic interaction chromatography (HILIC) for separation of monosaccharides. ... 

Figure 3.8 Structural analysis of a post-translationally modified peptide by MALDI-MS/MS. Porcine membrane dipeptidase, a GPi-anchored glycoprotein, was in-gel-digested by trypsin. The C-terminal CPi-anchored peptide was recovered from the peptide mixture by hydrophilic interaction chromatography (HiLiC) and then analyzed...

Hydrophilic interaction chromatography (HILIC) is particularly used for strongly polar compounds, that is, if these have a low retention at RP chromatography or... 

Generally, the applications in food metabolomics reported in the literature are conducted using reverse-phase LC. However, the combination of hydrophilic interaction chromatography (HILIC) gives the possibility of a better separation of polar compounds, extending food metabolic information. 

The other recent approach to use of LC-MS for analysis of PSP toxins (Dell Aversano 2005) exploits the unique properties of hydrophilic interaction chromatography (HILIC, Section 4.4.2c) that are ideally suited to these highly polar analytes. Moreover, the high organic content of the mobile phase leads to ready evaporation of the charged electrosprayed droplets and thus high ionization efficiency. 

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