B. Herbreteau

High performance liquid chromatography of raw sugars and polyols using bonded silica gels

SummaryBonded silica columns have been evaluated for their ability to separate carbohydrates and polyols. Mobile phases consisting of dichloromethane/methanol produced the best separations in comparison with the acetonitrile/water mixtures commonly used with amino columns. Of all the bonded phases tested, LiChrospher Diol silica provided the best separations, and selectivities were not very different from those obtained on the most popular system using an amino bonded phase and acetonitrile/water as eluent. In addition, diol columns with a dichloromethane/methanol eluent offer excellent stability with no Schiff’s base formation of reducing sugars. Using an evaporative light scattering detector, low limit detection is obtainable (20 ng of glucose from a column) and gradient elution is quite feasible.

Controle de certains systemes de chromatographie liquide haute performance à láide d'un détecteur évaporatif à diffusion de lumière

Abstract The quasi universal character of the light scattering detection of microparticles permits in the case of sugar analysis to choose the column and to control its evolution as a function of time. A simple test is proposed to induce the beginning of the regeneration of resinous CA2+. LiChrosorb Diol support is preferred to aminopropyl silica to realize at the same time a gradient elution and a good sensitivity (30–50 ng).

Subcritical fluid chromatography of monosaccharides and polyols using silica and trimethylsilyl columns

Efficient subcritical fluid chromatography (SubFC) analysis of twelve monosaccharides and polyols on silica and trimethylsilyl (TMS)-bonded silica stationary phases is proposed. Mobile phase composition was studied using CO2-methanol, CO2-methanol-water, CO2-methanol-water-triethylamine in order to obtain high efficiency and resolution. By adjusting the column temperature to 60°C and the flow-rate to 5 ml min−1, a complete separation of eight monosaccharides and polyols is obtained in less than 10 min. Using silica and TMS columns, retentions of carbohydrates and polyols in SubFC are compared with those of some glycolipids. It was found that carbohydrate retention increases when water is added to the eluent, whereas the retention of glycolipids decreases.

Chiral supercritical fluid chromatography on porous graphitic carbon using commercial dimethyl β-cyclodextrins as mobile phase additive

Using dimethylated-beta-cyclodextrin mixtures (MeCD) as chiral selectors in CO2-polar modifier mobile phase and porous graphitic carbon as solid-phase, chiral supercritical (or subcritical) fluid chromatography was performed. The adsorbed quantity of MeCD onto the porous graphitic carbon (Hypercarb) was measured for various chiral selector concentrations using the breakthrough method with evaporative light scattering detector. The effects of MeCD concentration in the mobile phase, the nature of the polar modifier, the outlet pressure, the column temperature and the nature of the commercial MeCD mixture on the retention and the enantioselectivities were studied. For a given solute, the enantioselectivity is greatly dependent on the commercial MeCD mixture used. The retention mechanism was also studied. From the data, we find that the dominant mechanism for the chiral discrimination is the diastereoisomeric complexation in the mobile phase.

Analysis of sugars by supercritical fluid chromatography using polar packed columns and light-scattering detection

Abstract The application of supercritical fluid chromatography (SFC) with polar packed columns and light-scattering detection for the analysis of sugars is reported. Cyano-, diol- and nitro-bonded silicas were used with carbon dioxide-methanol mobile phases and a comparison of sugar retention was carried out. These SFC systems showed different selectivites from that found in high-performance liquid chromatography. The association of a constant flow-rate of carbon dioxide and a variable flow-rate of methanol affords the elution of mono-, di- and trisaccharides in the same analysis without baseline drift.

Supercritical fluid chromatography of carbohydrates

Abstract Supercritical fluid chromatography (SFC) is a relatively new technique applied to polar solutes such as carbohydrates about 10 years ago. The developments in the SFC of carbohydrates are summarized and a comparison between capillary and packed column SFC is presented. High-efficiency capillary columns are suitable only for derivatized carbohydrates since various packed columns are well adapted for non derivatized mono-, di- and trisaccharides and provide complementary selectivities.

Analysis of partially methylated cyclodextrins by subcritical fluid and liquid chromatography

Abstract Liquid and subcritical chromatographic analyses using evaporative light scattering detection were used to investigate the composition of various commercial dimethylated β-cyclodextrins (β-CD). The chromatographic fingerprints better depict the complexity of each mixture than the degree of substitution. The elution order is reversed when subcritical fluid chromatography is used instead of LC on apolar stationary phases (TMS and phenyl columns). Concerning the RPLC analysis of methylated β-CD, a phenyl-bonded silica column offers selectivities that are different from those obtained using a classical C18-bonded silica column. With regard to the more complex mixtures, SubFC allows one to obtain richer methylated β-CD fingerprints than does LC.

High-performance liquid chromatography and supercritical fluid chromatography of monosaccharides and polyols using light-scattering detection: Chemometric studies of the retentions

Abstract Twelve sugars and polyols were analyzed using high-performance liquid chromatographic (HPLC) and supercritical fluid chromatographic (SFC) systems with silica and bonded silica stationary phases with the help of an evaporative light-scattering detector. The separation capacities of the two techniques are discussed. The retention data were studied using different chemometric methods (automatic classification, factor analysis). They clearly show that SFC and HPLC have the same retention process for these compounds and that is the sum of only two mathematically independent physico-chemical phenomena.

Electrospray mass spectrometry and supercritical fluid chromatography of methylated β-cyclodextrins

Five commercial dimethylated beta-cyclodextrin (DM-beta-CD) samples were analysed by electrospray (or ionspray) mass spectrometry (ESI-MS) and supercritical fluid chromatography (SFC) with evaporative light scattering detection. A silica and a nitro-bonded silica were selected using CO2-methanol-acetonitrile-water and CO2-methanol as mobile phase, respectively. An extensive optimisation scheme was performed for mobile phase selection. Both SFC systems were used for analyses of complex DM-beta-CD samples. Peak identifications were made using off-line ESI-MS. Commercial DM-beta-CDs are impure mixtures of homologues and isomers and analysis reveals that every manufacturer produces a different mixture.

Preliminary studies of supercritical-fluid chromatography on porous graphitic carbon with methylated cyclodextrin as chiral selector

SummaryDimethylated-β-cyclodextrins dynamically adsorbed on porous graphitic carbon have been used as chiral selectors in chiral supercritical-(or subcritical-) fluid chromatography. The kinetics of adsorption and desorption were studied with CO2-methanol+dimethylated-β-cyclodextrins and CO2-methanol as mobile phases. The system was proved to be stable and reproducible and to afford rapid enantiomer separations especially when performed with 95:5 CO2-methanol+dimethylated-β-cyclodextrin as mobile phase. The versatility of the chiral system enabled the use of a variety of chiral selectors. It was found that enantiomer separation can vary largely as a function of the composition of commercial dimethylated-β-cyclodextrin mixture.