Chroamtographic behaviour of un-sulphated and sulphated oligoethyleneglycol nonylphenyl ether surfactants in normal-phase liquid chromatographic systems containing water

2008

227

144

Hydrophilic interaction chromatography (HILIC) is becoming increasingly popular for separation of polar samples on polar columns in aqueous-organic mobile phases rich in organic solvents (usually ACN). Silica gel with decreased surface concentration of silanol groups, or with chemically bonded amino-, amido-, cyano-, carbamate-, diol-, polyol-, or zwitterionic sulfobetaine ligands are used as the stationary phases for HILIC separations, in addition to the original poly(2-sulphoethyl aspartamide) strong cation-exchange HILIC material. The type of the stationary and the composition of the mobile phase play important roles in the mixed-mode HILIC retention mechanism and can be flexibly tuned to suit specific separation problems. Because of excellent mobile phase compatibility and complementary selectivity to RP chromatography, HILIC is ideally suited for highly orthogonal 2-D LC-LC separations of complex samples containing polar compounds, such as peptides, proteins, oligosaccharides, drugs, metabolites and natural compounds. This review attempts to present an overview of the HILIC separation systems, possibilities for their characterization and emerging HILIC applications in 2-D off-line and on-line LC-LC separations of various samples, in combination with RP and other separation modes.

Section: Introductionmentioning

confidence: 99%

Stationary phases for hydrophilic interaction chromatography, their characterization and implementation into multidimensional chromatography concepts

2008

227

144

“…Recently, zwitterionic sulfobetaine stationary phases [11] have been introduced for separations in the HILIC mode. Early applications of HILIC focused mainly on the carbohydrate, amino acid, oligonucleotide, peptide and protein analysis [12][13][14][15], but many low-molecular polar compounds, such as drugs, toxins, plant extracts [1,[16][17][18], non-ionic [19] and ionic [20] surfactants, can be also separated in the HILIC mode.…”

Section: Introductionmentioning

confidence: 99%

Dual hydrophilic interaction‐RP retention mechanism on polar columns: Structural correlations and implementation for 2‐D separations on a single column

Hájek

Škeříková

et al. 2010

We investigated the retention of phenolic acid and flavone antioxidants on five polar columns in buffered aqueous ACN mobile phases. All columns show mixed retention mechanism: RP in highly aqueous mobile phases and normal phase (hydrophilic interaction LC, HILIC) in mobile phases with high concentration of ACN. The Silica Hydride and the ZIC HILIC sulfobetaine zwitterionic columns show rather limited retention in the RP mode. The Luna HILIC column shows higher retention in both the HILIC and the RP modes in comparison to the PEG and DIOL columns. We characterized the selectivity of various HILIC systems using linear solvation energy relationship model with molecular structure descriptors characterizing selective molecular size, dipole-dipole and proton-donor/proton-acceptor interactions and we investigated the effects of the mobile phase composition on the linear solvation energy relationship characteristics of the separation phase systems to select suitable conditions for orthogonal HILIC separations in combination with RP systems. Dual retention mechanism offers possibilities for using complementary selectivity in the HILIC and the RP modes for sequential 2-D separations of natural antioxidants on a single Luna HILIC column. Column equilibration time of 15 min between alternating RP and HILIC gradient runs is sufficient for reproducible results.

“…Since its introduction, HILIC applications have expanded to include many low‐molecular polar compounds, such as drugs, toxins, plant extracts and other compounds important to food and pharmaceutical industries 1, 17–19. Non‐ionic 20 and ionic 21 surfactants can be also separated in the HILIC mode.…”

Section: Introductionmentioning

confidence: 99%

Utilization of dual retention mechanism on columns with bonded PEG and diol stationary phases for adjusting the separation selectivity of phenolic and flavone natural antioxidants

Hájek

2009

The retention of phenolic acid and flavone antioxidants was investigated on three columns with bonded PEG, hydroxy (DIOL) and mixed oxyethylene-hydroxy (Luna HILIC) stationary phases in buffered aqueous ACN mobile phases. All columns show mixed retention mechanism: reversed phases in highly aqueous mobile phases and normal phases (HILIC, hydrophilic interaction LC) in mobile phases with high concentration of ACN, showing characteristic U-shape retention versus mobile phase composition plots. Equations enabling description and prediction of retention of sample compounds over the full mobile phase composition range were compared. Dual retention mechanism offers possibilities for using differences in selectivity between the two separation modes on a single column to improve the separation of natural antioxidants. The Luna HILIC column shows larger HILIC retention range, enhanced retention, improved selectivity and better peak symmetry in comparison to the PEG and DIOL columns.