Jacques Crommen

Fast separation of triterpenoid saponins using supercritical fluid chromatography coupled with single quadrupole mass spectrometry

Triterpenoid saponins (TSs) are the most important components of some traditional Chinese medicines (TCMs) and have exhibited valuable pharmacological properties. In this study, a rapid and efficient method was developed for the separation of kudinosides, stauntosides and ginsenosides using supercritical fluid chromatography coupled with single quadrupole mass spectrometry (SFC-MS). The separation conditions for the selected TSs were carefully optimized after the initial screening of eight stationary phases. The best compromise for all compounds in terms of chromatographic performance and MS sensitivity was obtained when water (5-10%) and formic acid (0.05%) were added to the supercritical carbon dioxide/MeOH mobile phase. Beside the composition of the mobile phase, the nature of the make-up solvent for interfacing SFC with MS was also evaluated. Compared to reversed phase liquid chromatography, the SFC approach showed higher resolution and shorter running time. The developed SFC-MS methods were successfully applied to the separation and identification of TSs present in Ilex latifolia Thunb., Panax quinquefolius L. and Panax ginseng C.A. Meyer. These results suggest that this SFC-MS approach could be employed as a useful tool for the quality assessment of natural products containing TSs as active components.

Enantioseparation of N-derivatized amino acids by micro-liquid chromatography using carbamoylated quinidine functionalized monolithic stationary phase.

In order to obtain satisfactory column permeability, efficiency and selectivity for micro-HPLC, a capillary monolithic column containing O-9-[2-(methacryloyloxy)-ethylcarbamoyl]-10,11-dihydroquinidine (MQD) as chiral selector was re-optimized. The monolithic column was used to successfully enantioresolve a wide range of N-derivatized amino acids including alanine, leucine, methionine, threonine, phenylalanine, valine, serine, isoleucine, tryptophan, and cysteine. The influence of mobile phase parameters, such as the organic solvent type and concentration, the apparent pH, and buffer concentration, on retention and enantioseparation of N-derivatized amino acids has been investigated. 3,5-dinitrobenzoyl-amino acids and 3,5-dichlorobenzoyl-amino acids were resolved into enantiomers with exceptionally high selectivity and resolution. The chemoselectivity of the monolithic column for a multicomponent mixture of N-derivatized amino acids was also investigated. A mixture of three pairs of 3,5-dichlorobenzoyl-amino acids could be fully resolved in 22.5 min.

Development and validation of a fast SFC method for the analysis of flavonoids in plant extracts

&NA; Flavonoids from plants always show a wide range of biological activities. In the present study, a rapid and highly efficient supercritical fluid chromatography (SFC) method was developed for the separation of 12 flavonoids. After careful optimization, the 12 flavonoids were baseline separated on a ZORBAX RX‐SIL column using gradient elution. A 0.1% phosphoric acid solution in methanol was found to be the most suitable polar mobile phase component for the separation of flavonoids. From the viewpoint of retention and resolution, a backpressure of 200 bar and a temperature of 40 °C were shown to give the best results. Compared with a previously developed reverse phase liquid chromatography method, the SFC method could provide flavonoid separations that were about three times faster, while maintaining good peak shape and comparable peak efficiency. This SFC method was validated and applied to the analysis of five flavonoids (kaempferol, luteolin, quercetin, luteoloside, buddleoside) present in Chrysanthemum morifolium Ramat. from different cultivars (Chuju, Gongju, Hangju, Boju). The results indicated a good repeatability and sensitivity for the quantification of the five analytes with RSDs for overall precision lower than 3%. The limits of detection ranged from 0.73 to 2.34 &mgr;g/mL, while the limits of quantification were between 2.19 and 5.86 &mgr;g/mL. The method showed that SFC could be employed as a useful tool for the quality assessment of Traditional Chinese medicines (TCMs) containing flavonoids as active components. Graphical abstract Figure. No caption available. HighlightsA rapid and highly efficient SFC method was developed for the separation of flavonoids.The SFC method could provide separations that were about three times faster than with a previously developed HPLC method.The SFC approach can be considered as an interesting alternative to HPLC for analyzing flavonoids present in traditional Chinese medicines (TCMs).

Enantioseparation of N-derivatized amino acids by micro-liquid chromatography/laser induced fluorescence detection using quinidine-based monolithic columns☆

A novel carbamoylated quinidine based monolith, namely poly(O-9-[2-(methacryloyloxy)-ethylcarbamoyl]-10,11-dihydroquinidine-co-ethylene dimethacrylate (poly(MQD-co-EDMA)), was prepared for the micro-LC enantioseparation of N-derivatized amino acids. The influence of the mobile phase composition, including the organic modifier proportion, the apparent pH and the buffer concentration, on the enantioresolution of N-derivatized amino acids was systematically investigated. Satisfactory column performance in terms of permeability, efficiency and reproducibility was obtained in most cases. The majority of the enantiomers of the tested N-protected amino acids, including 3,5-DNB, 3,5-DClB, FMOC, 3,5-DMB, p-NB, m-ClB, p-ClB and B derivatives, could be baseline separated on the poly(MQD-co-EDMA) monolithic column within 25min. A self-assembled laser induced fluorescence (LIF) detector was employed to improve sensitivity when analyzing 7-nitro-2,1,3-benzoxadiazole (NBD) derivatives of amino acids. Ten NBD-derivatized amino acids, including arginine and histidine whose enantioseparation on quinidine carbamate based CSPs has not been reported so far, were enantioresolved on the poly(MQD-co-EDMA) monolith column. It is worth noting that the d-enantiomers of NBD-derivatized amino acids eluted first, except in the case of glutamic acid. The LOD values obtained with the LIF detector were comparable to those reported using conventional LC-FL methods. The prepared poly(MQD-co-EDMA) monolithic column coupled with the LIF detector opens up interesting perspectives to the determination of trace D-amino acids in biological samples.

Influence of the linking spacer length and type on the enantioseparation ability of β-cyclodextrin functionalized monoliths.

In order to investigate the effect of the linking spacer on the enantioseparation ability of β-cyclodextrin (β-CD) functionalized polymeric monoliths, three β-CD-functionalized organic polymeric monoliths with different spacer lengths were prepared by using three amino-β-CDs, i.e. mono-6-amino-6-deoxy-β-CD, mono-6-ethylenediamine-6-deoxy-β-CD, mono-6-hexamethylenediamine-6-deoxy-β-CD, as starting materials. These amino-β-CDs reacted with glycidyl methacrylate to produce functional monomers which were then copolymerized with ethylene dimethacrylate. The enantioseparation ability of the three monoliths was evaluated using 14 chiral acidic compounds, including mandelic acid derivatives, nonsteroidal anti-inflammatory drugs, N-derivatized amino acids, and chiral herbicides under optimum chromatographic conditions. Notably, the poly(GMA-NH2-β-CD-co-EDMA) column provides higher enantioresolution and enantioselectivity than the poly(GMA-EDA-β-CD-co-EDMA) and poly(GMA-HDA-β-CD-co-EDMA) columns for most tested chiral analytes. Furthermore, the enantioseparation performance of triazole-linker containing monoliths was compared to that of ethylenediamine-linker containing monoliths. The results indicate that the enantioselectivity of β-CD monolithic columns is strongly related to the length and type of spacer tethering β-CD to the polymeric support.

Recent developments in cyclodextrin functionalized monolithic columns for the enantioseparation of chiral drugs

The use of monolithic supports containing cyclodextrins (CDs) or their derivatives as chiral stationary phases (CSPs) has drawn much attention in the field of enantioseparations. The present review summarized the recent developments in CD functionalized monolithic columns. After introducing their classification in Section 1, various strategies applied to the preparation of the three types of CD functionalized monoliths, i.e. silica based monoliths, organic polymer based monoliths and organic-silica based hybrid monoliths, are thoroughly summarized in Section 2. Particularly, three different preparation strategies for covalently immobilizing CDs onto monoliths, including multi-step strategy, single-step strategy and one-pot strategy, are discussed. In the last section, the applications of CD functionalized monoliths in chiral separation of pharmaceuticals are highlighted.

Chiral separation of acidic compounds using an O-9-(tert-butylcarbamoyl)quinidine functionalized monolith in micro-liquid chromatography.

An O-9-(tert-butylcarbamoyl) quinidine (t-BuCQD) functionalized polymeric monolithic capillary column was prepared by the in situ copolymerization method. The physicochemical properties of the optimized monolithic column were characterized by scanning electron microscopy and micro-LC. Satisfactory column permeability, efficiency, stability and reproducibility were obtained for this monolithic column. The chiral recognition ability of the resulting monolith was also evaluated using 47 N-derivatized amino acids, eight N-derivatized dipeptides, and two herbicides. Under the selected conditions, the enantiomers of all chiral analytes were baseline separated with exceptionally high selectivity and resolution using micro-LC. It is worth noting that this chiral stationary phase (CSP) containing quinidine with a tert-butyl carbamate residue as chiral selector exhibits much higher enantioselectivity and diastereoselectivity than the previously developed O-9-[2-(methacryloyloxy)-ethylcarbamoyl]-10,11-dihydroquinidine (MQD) based CSP for N-derivatized amino acids and dipeptides. These results indicate that this novel quinidine-based polymeric monolith can be used as an effective tool for the enantioseparation of chiral acidic compounds.

Effect of the crosslinker type on the enantioseparation performance of β-cyclodextrin functionalized monoliths prepared by the one-pot approach.

Low column efficiency for enantioseparations in capillary liquid chromatography (CLC) is a major problem commonly encountered with β-cyclodextrin (β-CD) functionalized polymer-based monoliths. In order to investigate the effect of the crosslinker type on enantioseparation performance, three commonly used crosslinkers, i.e. 1,4-bis(acryloyl)piperazine (PDA), ethylene dimethacrylate (EDMA) and N,N-methylenebisacrylamide (MBA), were copolymerized using the one-pot approach with glycidyl methacrylate-mono-6-amino-6-deoxy-β-CD (GMA-NH2-β-CD) as functional monomer. The three monolithic columns, including poly(GMA-NH2-β-CD-co-PDA) and poly(GMA-NH2-β-CD-co-MBA), as well as the previously reported column poly(GMA-NH2-β-CD-co-EDMA) were systematically compared with respect to morphology, permeability, β-CD density, retention mechanism and efficiency. The enantioseparation ability of each column was evaluated using 14 chiral compounds, including mandelic acid derivatives, profens, N-derivatized amino acids, and herbicides, as test substances. The β-CD-functionalized monolith with MBA as crosslinker was found to exhibit higher polarity, higher column efficiency and better enantioseparation performance than those with PDA or EDMA as crosslinker.

Determination of phenolic acids in extra virgin olive oil using supercritical fluid chromatography coupled with single quadrupole mass spectrometry

HIGHLIGHTSA rapid, sensitive and efficient SFC‐MS method was developed for the separation of 12 phenolic acids.The analysis time with the SFC method was about three times shorter than using HPLC.The SFC‐MS method was successfully applied to the analysis of phenolic acids in extra virgin olive oils. ABSTRACT Phenolic acids represent one third of the total phenolic compounds in extra virgin olive oil (EVOO) and contribute greatly to the biological and sensory properties of EVOO. In the present research, an analytical method based on supercritical fluid chromatography coupled with single quadrupole mass spectrometry (SFC‐MS) was developed for the analysis of phenolic acids in EVOOs. The chromatographic and MS conditions were optimized in terms of selectivity, peak shape and sensitivity. Satisfactory separation of 12 phenolic acids was achieved within 20min on a Platisil CN column (250mm×4.6mm, 5&mgr;m) using 7% (v/v) water and 0.5% (v/v) formic acid in MeOH as mobile phase additives at the backpressure of 140bar and temperature of 60°C. The developed method was validated by evaluating the linearity, sensitivity, repeatability, intermediate precision and accuracy. The limits of detection (LODs) and limits of quantification (LOQs) of the SFC‐MS method for phenolic acids ranged from 0.03 to 5.00&mgr;g/mL and 0.08 to 15.0&mgr;g/mL, respectively. The relative standard deviations (RSDs) for intraday and interday precision were lower than 9.91% and the recoveries ranged from 80.2 to 117% and 80.9 to 118% for low‐level and high‐level concentrations of standards spiked in olive oil, respectively. Compared to an HPLC method, the SFC method was about three times faster and provided better selectivity. Finally, the SFC‐MS method was successfully employed for the quantitative analysis of phenolic acids in EVOOs. Differences in individual and total phenolic acid contents were observed between six varieties.

Effect of fabrication strategy on the enantioseparation performance of β-cyclodextrin-functionalized polymethacrylate monoliths: A comparative evaluation

To evaluate the effect of the preparation strategy on the enantioseparation performance of β-cyclodextrin-functionalized monoliths, a series of β-cyclodextrin-functionalized organic polymeric monolithic columns were prepared through two-step, single-step, and one-pot approaches, using the same cyclodextrin, linker-spacer, and crosslinker. Physicochemical characterization of the columns was carried out by determining the morphology, β-cyclodextrin density, permeability, and chromatographic efficiency. For each type of monolithic column, the enantioresolution of 22 chiral compounds, including mandelic acid derivatives, nonsteroidal anti-inflammatory drugs, N-derivatized amino acids, and herbicides, was comparatively studied under optimum chromatographic conditions. The β-cyclodextrin-functionalized monolithic columns prepared through the one-pot approach exhibited higher enantioresolution for most chiral compounds, and they have the advantage of good controllability and simple preparation. On the other hand, the enantioresolution obtained on columns prepared through the single-step approach was quite unsatisfactory, and therefore the effect of using different linking spacers and crosslinkers was studied. A significant improvement of enantioresolution for 2-chloro-mandelic acid was obtained by using N,N-methylenebisacrylamide instead of ethylene dimethacrylate as the crosslinker in the single-step preparation.