Claire Elfakir | Université d'Orléans (Loire Valley University) (original) (raw)

Papers by Claire Elfakir

Research paper thumbnail of Determination of 20 underivatized proteinic amino acids by ion-pairing chromatography and pneumatically assisted electrospray mass spectrometry

Journal of Chromatography A, 1999

A qualitative determination of 20 underivatized proteinic amino acids by LC-MS is reported. The n... more A qualitative determination of 20 underivatized proteinic amino acids by LC-MS is reported. The need for chromatographic separation before mass spectrometry determination is demonstrated based on the study of several amino acid pairs which have some similar characteristics. Two suitable LC-MS systems are proposed for amino acid analysis. A preliminary optimization of these systems has been investigated using evaporative light scattering detection as these two detection modes have the same chromatographic requirements. The amino acid separation was achieved on a Purospher RP-18e or a 1 Supelcosil ABZ Plus column with tridecafluoroheptanoic acid or pentadecafluorooctanoic acid as volatile ion-pairing reagent in an acetonitrile-water mobile phase. In order to elute the most retained amino acids, an elution gradient based on simultaneously increasing the concentration of acetonitrile and decreasing the concentration of the ion-pairing reagent was 21 used. The detection limits of the present work (without specialized optimization) varied from 0.5 to 1 mg l .

Research paper thumbnail of Ion-pair chromatography on a porous graphitic carbon stationary phase for the analysis of twenty underivatized protein amino acids

Journal of Chromatography A, 2000

The analysis of twenty underivatized protein amino acids has been achieved on porous graphitic ca... more The analysis of twenty underivatized protein amino acids has been achieved on porous graphitic carbon packing material (Hypercarb). Five perfluoroalkyl carboxylic acids (trifluoroacetic, heptafluorobutyric, nonafluoropentanoic, tridecafluoroheptanoic and pentadecafluorooctanoic acid) have been studied as ion-pairing reagent. Several parameters (equilibration time, quantities adsorbed onto the chromatographic support, concentration and nature of the ion-pairing reagent, as well as temperature effect) have been studied leading to the complete separation of these compounds in gradient elution mode. Evaporative light scattering detector has allowed the detection of these non UV-visible absorbent molecules. The chromatographic methodology developed can also be easily coupled with pneumatically assisted electrospray mass spectrometry.

Research paper thumbnail of Evaluation of a simple and promising method for extraction of antioxidants from sea buckthorn (Hippophaë rhamnoides L.) berries: Pressurised solvent-free microwave assisted extraction

Food Chemistry, 2011

The pressurised solvent-free microwave assisted extraction (PSFME) technique has been developed a... more The pressurised solvent-free microwave assisted extraction (PSFME) technique has been developed and optimised for extraction of antioxidants from Hippophaë rhamnoides L. berries using a two-level full factorial design. The effects of factors (extraction time, irradiation power, number of cycles) and their first order interactions were evaluated from antioxidant activity of extracts using the 2,2 0 -diphenyl-1-picrylhydrazil (DPPH) free radical scavenging method, the ferric reducing ability of plasma (FRAP) assay, and the estimation of total phenolic content using the Folin-Ciocalteu method. The best extraction conditions were obtained, in a laboratory scale extractor of 50 mL filled with 4 g fresh berries, using a 1000 W microwave power applied during 50 s and repeated five cycles. PSFME was then compared to other common extraction techniques such as pressing, maceration and pressurised liquid extraction. It is appeared that PSFME leads to the most active and richest extract in phenolic content including molecules such as quercetin and isorhamnetin not extracted with other techniques. Furthermore PSFME respect green chemistry, it is rapid, cheap and does not need sample preparation and/or evaporation step.

Research paper thumbnail of Determination of 1-aminocyclopropane-1-carboxylic Acid in Apple and Peach Extracts by High Performance Liquid Chromatography Coupled to a Fluorescence Detector

Analytical Letters, 2012

A new, sensitive and simple HPLC method was described for the determination of 1-aminocyclopropan... more A new, sensitive and simple HPLC method was described for the determination of 1-aminocyclopropane-1-carboxylic acid (ACC) in apple and peach extracts. The method was based on the derivatization of ACC with fluorescamine in borate buffer systems of pH 8.0 to yield a highly fluorescent product. The experimental parameters affecting the derivatization reaction efficiency were optimized by fluorimetric analysis. Under optimum derivatization conditions, the derivative product of ACC in apple and peach extracts without extra purification was successfully chromatographed on a C-18 column by HPLC coupled to fluorescence detection. The derivative product of ACC with fluorescamine could be well separated from other concomitant substances or their derivatives that might interfere with the determination of ACC. The linearity of ACC was measured in the range of 23.82 - 238.82 µg · L with a good correlation coefficient of 0.9997. Based on signal-to-noise ratio of 3, a low detection limit of 5.0 µg · L could be reached. The proposed method was applied successfully to the determination of ACC in the crude apple and peach extracts without extra purification with low RSDs of 0.19-1.9% and good recoveries of 90.89-104.4%. The sensitive HPLC quantitative method is of great significance for the investigations of ACC metabolism in plants.

Research paper thumbnail of Porous graphitic carbon: A versatile stationary phase for liquid chromatography

Journal of Chromatography A, 2010

Chromatographic stationary phases based on porous graphitic carbon were invented 30 years ago, wh... more Chromatographic stationary phases based on porous graphitic carbon were invented 30 years ago, while columns have been commercially available for 20 years. This special occasion deserved a complete review on this material. In this paper, we describe current knowledge on graphitic carbon stationary phases, based on over 400 fundamental studies and applications.

Research paper thumbnail of Advantages of HILIC mobile phases for LC-ESI-MS-MS analysis of neurotransmitters

Research paper thumbnail of Inorganic anion determination by RPLC using evaporative light scattering detection

American laboratory

Ion-pair reversed-phase chromatography can be employed advantageously in laboratories in which on... more Ion-pair reversed-phase chromatography can be employed advantageously in laboratories in which only conventional HPLC systems are available.

Research paper thumbnail of The advantages of evaporative light scattering detection in pharmaceutical analysis by high performance liquid chromatography and supercritical fluid chromatography

Journal of High Resolution Chromatography, 1992

... 1 Introduction LC is increasingly being used in quality control analysis of raw materials for... more ... 1 Introduction LC is increasingly being used in quality control analysis of raw materials forpharmaceutical and ... analysis performed by coupling ELSD with either LC or SFC using packed columns appears very promising in pharma-ceutical analysis for control of raw ...

Research paper thumbnail of Treatment with KLEPTOSE® CRYSMEB reduces mouse atherogenesis by impacting on lipid profile and Th1 lymphocyte response

Vascular Pharmacology, 2015

The ability of pharmacological agents to target both &amp... more The ability of pharmacological agents to target both "classical" risk factors and inflammation may be key for successful outcomes in the prevention and treatment of atherogenesis. Among the promising drugs interfering with cholesterol metabolism, we investigated whether methyl beta-cyclodextrin (KLEPTOSE® CRYSMEB) could positively impact on atherogenesis, lipid profile and atherosclerotic plaque inflammation in ApoE-/- mice. Eleven-week old ApoE-/- mice were fed either a normal diet (N.D.) or a high-cholesterol diet (H.D.), resulting in different levels of hypercholesterolemia. KLEPTOSE® CRYSMEB (40mg/kg) or vehicle was intraperitoneally administrated 3 times per week in the last 16weeks before euthanasia in mice under N.D. and in the last 11weeks under H.D. Treatment with KLEPTOSE® CRYSMEB reduced triglyceride serum levels in both atherogenesis mouse models. In H.D. mice, treatment with KLEPTOSE® CRYSMEB increased HDL-cholesterol levels and reduced free fatty acids and spleen weight. In both mouse models, treatment with KLEPTOSE® CRYSMEB reduced atherosclerotic plaque size in thoraco-abdominal aortas and intraplaque T lymphocyte content, but did not induce relevant improvements in other histological parameters of vulnerability (macrophage, neutrophil, MMP-9 and collagen content). Conversely and more markedly in H.D. mice, treatment with KLEPTOSE® CRYSMEB was associated with a reduction in genetic markers of Th1-mediated immune response. In vitro, KLEPTOSE® CRYSMEB dose-dependently abrogated Th1 proliferation and IFNγ release. In conclusion, treatment with KLEPTOSE® CRYSMEB reduced atherosclerotic plaque size by improving triglyceride serum levels and Th1-mediated response. These results indicate this drug as a potential tool for blocking atheroprogression associated with different severity degrees of hypercholesterolemia.

Research paper thumbnail of New artificial standards for the HPLC analysis of natural glucosinolates

Journal of High Resolution Chromatography, 1992

Research paper thumbnail of Validation of an Ion-Interaction Chromatography Analysis of Underivatized Amino Acids in Commercial Preparation Using Evaporative Light Scattering Detection

A liquid chromatographic procedure using ion interaction reagent and evaporative light scattering... more A liquid chromatographic procedure using ion interaction reagent and evaporative light scattering detection was developed and validated for the direct quantification of 8 underivatized amino acids (threonine, lysine, valine, methionine, isoleucine, leucine, phenylalanine and tryptophan) present simultaneously in a commercial preparation. The chromatographic separation was achieved on a Purospher RP-18e column with an acetonitrile gradient and using heptafluorobutyric acid as volatile ion interaction reagent. Acceptable levels of linearity, specificity, precision, accuracy, robustness and limits of detection were achieved during the validation of the method. Detection limits varied from 1 mg.L )1 to 2 mg.L )1 depending on the amino acid being analyzed. The results of this method agree to within 98.6%-102.5% when compared to the manufacturer's certificate of analysis obtained with the standard amino acid autoanalyser method. This approach yields a simple, universal method that is well suited for amino acid analysis, when a sufficient quantity is available. Only basic LC instrumentation with an ELSD is necessary for this procedure.

Research paper thumbnail of Centrifugal partition chromatography elution gradient for isolation of sesquiterpene lactones and flavonoids from Anvillea radiata

Journal of Chromatography B, 2015

An innovative procedure coupling pressurized solvent extraction and centrifugal partition chromat... more An innovative procedure coupling pressurized solvent extraction and centrifugal partition chromatography (CPC) used in linear gradient elution mode was developed to isolate two pure germacranolides (9α-hydroxyparthenolide and 9β-hydroxyparthenolide) and to separate flavonoids (nepetin, isorhamnetin and jaceosidin) and chlorophyll pigments from aerial parts of Anvillea radiata (Coss.&Durieu). The two main germacranolides recovered using this method represent 2 and 5% of the dried plant material respectively. These molecules were extracted using accelerated solvent extraction with chloroform. After optimization of the CPC method, a two-phase solvent system composed of heptane/ethyl acetate/methanol/water (1:5:1:5 v/v/v/v) was employed in descending mode to isolate the germacranolides. Then the lower phase of a heptane/ethyl acetate/methanol/water (6:5:6:5 v/v/v/v) system was pumped in descending mode to generate a linear elution gradient, progressively decreasing the mobile phase polarity, that enabled the flavonoid compounds to be separated in the same run. The efficiency of the preparative separation was controlled through RP-HPLC analysis of the obtained fractions using UV, evaporative light scattering and mass spectrometry detection. The structural identification of the two germacranolides purified over 99% was established by (1)H NMR and (13)C NMR. The least abundant flavonoids were identified by mass spectrometry.

Research paper thumbnail of Different Ways to On-Line Hyphenate Centrifugal Partition Chromatography and Mass Spectrometry: Application to Prenylated Xanthones from Garcinia mangostana

Research paper thumbnail of Phytochemical analysis of Rosa hybrida cv. ‘Jardin de Granville’ by HPTLC, HPLC-DAD and HPLC-ESI-HRMS: Polyphenolic fingerprints of six plant organs

Phytochemistry, 2014

The Rosa hybrida cultivar 'Jardin... more The Rosa hybrida cultivar 'Jardin de Granville', a delicate clear pink flower, is here investigated through a progressive analytical strategy using complementary phytochemical screening methods in order to characterize the polyphenol content of several parts of the plant. The microwave hydro-ethanolic extract analysis of six different parts of the plant, carried out by High Performance Thin Layer Chromatography (HPTLC) and High Performance Liquid Chromatography coupled with a Diode Array Detector (HPLC-DAD) enabled initial identification of the polar molecular families present in each organ, namely tannins and flavonoids (quercetin and kaempferol derivatives). The HPLC fingerprints displayed different profiles for each organ, attesting to the original composition and potential valuation of the different plant parts. More detailed analyses of the extracts were then carried out by High Performance Liquid Chromatography coupled with electrospray ionization (ESI) mass spectrometry with a Q-TOF analyzer (ESI-HR-Q-TOF). Around 60 compounds were identified, mainly gallo-tannins, ellagi-tannins, catechin derivatives and glycoside derivatives of quercetin and kaempferol. Some compounds such as hyperoside or ellagic acid appeared to be ubiquitous and were found in abundance in each plant part. Woods were the richest organ in catechin and proanthocyanidin derivatives while kaempferol derivatives were more numerous and abundant in bud and flower parts.

Research paper thumbnail of The simultaneous determination of 1-aminocyclopropane-1-carboxylic acid and cyclopropane-1,1-dicarboxylic acid inLycopersicum esculentum by high-performance liquid chromatography?electrospray tandem mass spectrometry

Phytochemical Analysis, 2003

Varying concentrations of cyclopropane-1,1-dicarboxylic acid (CDA), an inhibitor of 1-aminocyclop... more Varying concentrations of cyclopropane-1,1-dicarboxylic acid (CDA), an inhibitor of 1-aminocyclopropane-1-carboxylic acid oxidase, added to the solid culture medium of tomato nodal shoot segments resulted in a reduction in the level of endogenous ethylene according to the concentration of inhibitor applied. Following treatment with inhibitor, plants were homogenised and the concentrations of CDA and of 1-aminocyclopropane-1-carboxylic acid (ACC) were measured simultaneously in the resulting juice using an HPLC-ESI/MS-MS method. The levels of CDA and ACC measured in the plant tissues were associated with the concentration of inhibitor added to the solid medium. The HPLC-ESI/MS-MS method described produced limits of detection of 0.8 pmol for ACC and of 4 pmol for CDA.

Research paper thumbnail of Evaporative light scattering detection for in-line monitoring of stopped-flow liquid chromatography-nuclear magnetic resonance analysis of compounds with weak or no chromophore groups

Journal of Separation Science, 2002

Evaporative light scattering detection for in-line monitoring of stopped-flow liquid chromatograp... more Evaporative light scattering detection for in-line monitoring of stopped-flow liquid chromatography-nuclear magnetic resonance analysis of compounds with weak or no chromophore groups This study demonstrates the use of the evaporative light scattering detector (ELSD) as an in-line monitoring detector for the stopped-flow liquid chromatography -nuclear magnetic resonance (LC -NMR) analysis of compounds with weak chromophore groups or none at all. The instrumentation set-up is discussed and the system is compared with the more common ultraviolet (UV) monitoring detection method. Underivatized amino acids without a UV chromophore (taurine) or with weak UV chromophores (hydroxyproline, aspartic acid, glycine, etc.) were selected as model compounds. The isocratic separation of the amino acids was achieved by using 0.5 mM pentadecafluorooctanoic acid (PDFOA) in deuterium oxide (D 2 O), on a Purospher RP-18e stationary phase column. PDFOA was particularly suitable for ion-pairing and NMR detection, due to the absence of protons in the alkyl chain, as well as the required low concentration. ELSD proved an interesting mode of chromatographic detection prior to NMR, due to its universality (no UV chromophore is needed). LC -NMR allowed the direct analysis of amino acids without the use of any particular NMR sequences (e.g. for the suppression of interfering resonances).

Research paper thumbnail of Conditions for rapid determination of inorganic cations in water by ion-exchange chromatography and evaporative light scattering detection

Journal of Separation Science, 2001

The simultaneous LC determination of alkali and alkaline-earth cations is possible by ion exchang... more The simultaneous LC determination of alkali and alkaline-earth cations is possible by ion exchange chromatography run in an isocratic elution mode, using a polymeric exchanger coated on a spherical silica gel, followed by evaporative light scattering detection. By using an aqueous trifluoroacetic acid (4 mM) isocratic eluent, a successful single run analysis of Na + , K + , Mg 2+ and Ca 2+ , was achieved in 6 min on a LiChrosilm IC CA 2 column. This method provides good linearity for the four calibration curves, and enables a 10 ng absolute detection limit for sodium, magnesium, and calcium and a 25 ng absolute detection limit for potassium, at a signal-to-noise ratio of 3. The repeatability determined from six injections was satisfactory for all inorganic cations studied. This methodology has been successfully applied to the direct analysis of mineral waters containing low levels of magnesium in the presence of high levels of calcium as well as low levels of potassium in the presence of high levels of sodium.

Research paper thumbnail of Liquid chromatography analysis of monosubstituted sulfobutyl ether-β-cyclodextrin isomers on porous graphitic carbon

Journal of Separation Science, 2004

The retention behaviour of the three positional isomers of monosubstituted sulfobutyl ether-beta-... more The retention behaviour of the three positional isomers of monosubstituted sulfobutyl ether-beta-cyclodextrin was investigated on a porous graphitic carbon (PGC) column. The influence of the mobile phase composition (nature and concentration of organic and electronic modifiers) was studied as well as the effect of column temperature. These hydrophilic and anionic analytes were highly retained on the PGC stationary phase compared to octadecyl bonded phases. The retention is mainly governed by a reversed-phase mechanism with electronic interaction playing a secondary role. An increase in solute retention and efficiency with temperature was observed. Successful isocratic separation with satisfactory baseline resolution of the three isomers of monosubstituted sulfobutyl ether-beta-cyclodextrin was achieved at 75 degrees C on a Hypercarb column by using ammonium acetate as electronic modifier in water-acetonitrile (83:17). The chromatographic methodology developed can be easily used for relative quantification of each isomer within a mixture and can be applied for semi-preparative purification of each one. The evaporative light scattering detector allows the detection of these non UV-visible absorbing molecules.

Research paper thumbnail of Development of an ion-pairing reversed-phase liquid chromatography method using a double detection analysis (UV and evaporative light scattering detection) to monitor the stability of Alimta®-pemetrexed preparations: Identification and quantification of l-glutamic acid as a potential degradation ...

Journal of Pharmaceutical and Biomedical Analysis, 2011

Development of an ion-pairing reversed-phase liquid chromatography method using a double detectio... more Development of an ion-pairing reversed-phase liquid chromatography method using a double detection analysis (UV and evaporative light scattering detection) to monitor the stability of Alimta ® -pemetrexed preparations: Identification and quantification of l-glutamic acid as a potential degradation product a b s t r a c t A new method based on high-performance liquid chromatography coupled to ultraviolet and evaporative light scattering detection (HPLC-UV-ELSD) was developed for the determination of l-glutamic acid, a potential degradation product of pemetrexed, and for the quantification of pemetrexed itself. This is an ion-pairing, reversed-phase method. The column was a Synergi MAX-RP C12 4 m (150 mm × 4.6 mm). The mobile phase was 1 mM tridecafluoroheptanoic acid in aqueous solution and acetonitrile under gradient elution mode. l-Glutamic acid was detected by ELSD, and pemetrexed by UV at 254 nm. Good resolution was achieved between pemetrexed and l-glutamic acid. The HPLC method was validated according to SFSTP and ICH guidelines, and applied the accuracy profile procedure with a five-level validation experimental design. For pemetrexed, the decision criteria selected consisted of the acceptability limits (±3%) and the proportion of results within the calculated tolerance intervals (95%). In conclusion, the proposed analytical procedures were validated over the selected validation domains for l-glutamic acid (0.005-0.025 mg/mL) and pemetrexed (0.4-0.6 mg/mL) and shown to provide a very effective method.

Research paper thumbnail of Characterisation of complex amphiphilic cyclodextrin mixtures by high-performance liquid chromatography and mass spectrometry

Journal of Chromatography A, 2008

It is established that amphiphilic ␤-cyclodextrins chemically modified with alkyl chains on the s... more It is established that amphiphilic ␤-cyclodextrins chemically modified with alkyl chains on the secondary face exhibit self-organisation properties yielding stable nanospheres or nanoparticles. The ability of these promising colloidal drug carriers to encapsulate drugs being partly related to the internal structure of nanosystems, precise characterisation methods are required to control their synthesis procedure. The present work describes the development of complementary analytical methods based on reversed-phase high-performance liquid chromatography (RPLC) coupled to evaporative light-scattering detection (ELSD) and electrospray ionisation-mass spectrometry (ESI-MS) to characterize various ␤-cyclodextrins enzymatically transesterified by vinyl-acyl fatty esters (the number of carbon atom in the acyl chain varying from 4 to 12). LC-ELSD has been used in a preliminary step to optimize the separation on a monolithic octadecylsiloxane-bonded silica stationary phase. A complex fingerprint was achieved for each mixture, revealing the presence of isomers unnoticed by the sole spectrometric (NMR and MS) techniques.

Research paper thumbnail of Determination of 20 underivatized proteinic amino acids by ion-pairing chromatography and pneumatically assisted electrospray mass spectrometry

Journal of Chromatography A, 1999

A qualitative determination of 20 underivatized proteinic amino acids by LC-MS is reported. The n... more A qualitative determination of 20 underivatized proteinic amino acids by LC-MS is reported. The need for chromatographic separation before mass spectrometry determination is demonstrated based on the study of several amino acid pairs which have some similar characteristics. Two suitable LC-MS systems are proposed for amino acid analysis. A preliminary optimization of these systems has been investigated using evaporative light scattering detection as these two detection modes have the same chromatographic requirements. The amino acid separation was achieved on a Purospher RP-18e or a 1 Supelcosil ABZ Plus column with tridecafluoroheptanoic acid or pentadecafluorooctanoic acid as volatile ion-pairing reagent in an acetonitrile-water mobile phase. In order to elute the most retained amino acids, an elution gradient based on simultaneously increasing the concentration of acetonitrile and decreasing the concentration of the ion-pairing reagent was 21 used. The detection limits of the present work (without specialized optimization) varied from 0.5 to 1 mg l .

Research paper thumbnail of Ion-pair chromatography on a porous graphitic carbon stationary phase for the analysis of twenty underivatized protein amino acids

Journal of Chromatography A, 2000

The analysis of twenty underivatized protein amino acids has been achieved on porous graphitic ca... more The analysis of twenty underivatized protein amino acids has been achieved on porous graphitic carbon packing material (Hypercarb). Five perfluoroalkyl carboxylic acids (trifluoroacetic, heptafluorobutyric, nonafluoropentanoic, tridecafluoroheptanoic and pentadecafluorooctanoic acid) have been studied as ion-pairing reagent. Several parameters (equilibration time, quantities adsorbed onto the chromatographic support, concentration and nature of the ion-pairing reagent, as well as temperature effect) have been studied leading to the complete separation of these compounds in gradient elution mode. Evaporative light scattering detector has allowed the detection of these non UV-visible absorbent molecules. The chromatographic methodology developed can also be easily coupled with pneumatically assisted electrospray mass spectrometry.

Research paper thumbnail of Evaluation of a simple and promising method for extraction of antioxidants from sea buckthorn (Hippophaë rhamnoides L.) berries: Pressurised solvent-free microwave assisted extraction

Food Chemistry, 2011

The pressurised solvent-free microwave assisted extraction (PSFME) technique has been developed a... more The pressurised solvent-free microwave assisted extraction (PSFME) technique has been developed and optimised for extraction of antioxidants from Hippophaë rhamnoides L. berries using a two-level full factorial design. The effects of factors (extraction time, irradiation power, number of cycles) and their first order interactions were evaluated from antioxidant activity of extracts using the 2,2 0 -diphenyl-1-picrylhydrazil (DPPH) free radical scavenging method, the ferric reducing ability of plasma (FRAP) assay, and the estimation of total phenolic content using the Folin-Ciocalteu method. The best extraction conditions were obtained, in a laboratory scale extractor of 50 mL filled with 4 g fresh berries, using a 1000 W microwave power applied during 50 s and repeated five cycles. PSFME was then compared to other common extraction techniques such as pressing, maceration and pressurised liquid extraction. It is appeared that PSFME leads to the most active and richest extract in phenolic content including molecules such as quercetin and isorhamnetin not extracted with other techniques. Furthermore PSFME respect green chemistry, it is rapid, cheap and does not need sample preparation and/or evaporation step.

Research paper thumbnail of Determination of 1-aminocyclopropane-1-carboxylic Acid in Apple and Peach Extracts by High Performance Liquid Chromatography Coupled to a Fluorescence Detector

Analytical Letters, 2012

A new, sensitive and simple HPLC method was described for the determination of 1-aminocyclopropan... more A new, sensitive and simple HPLC method was described for the determination of 1-aminocyclopropane-1-carboxylic acid (ACC) in apple and peach extracts. The method was based on the derivatization of ACC with fluorescamine in borate buffer systems of pH 8.0 to yield a highly fluorescent product. The experimental parameters affecting the derivatization reaction efficiency were optimized by fluorimetric analysis. Under optimum derivatization conditions, the derivative product of ACC in apple and peach extracts without extra purification was successfully chromatographed on a C-18 column by HPLC coupled to fluorescence detection. The derivative product of ACC with fluorescamine could be well separated from other concomitant substances or their derivatives that might interfere with the determination of ACC. The linearity of ACC was measured in the range of 23.82 - 238.82 µg · L with a good correlation coefficient of 0.9997. Based on signal-to-noise ratio of 3, a low detection limit of 5.0 µg · L could be reached. The proposed method was applied successfully to the determination of ACC in the crude apple and peach extracts without extra purification with low RSDs of 0.19-1.9% and good recoveries of 90.89-104.4%. The sensitive HPLC quantitative method is of great significance for the investigations of ACC metabolism in plants.

Research paper thumbnail of Porous graphitic carbon: A versatile stationary phase for liquid chromatography

Journal of Chromatography A, 2010

Chromatographic stationary phases based on porous graphitic carbon were invented 30 years ago, wh... more Chromatographic stationary phases based on porous graphitic carbon were invented 30 years ago, while columns have been commercially available for 20 years. This special occasion deserved a complete review on this material. In this paper, we describe current knowledge on graphitic carbon stationary phases, based on over 400 fundamental studies and applications.

Research paper thumbnail of Advantages of HILIC mobile phases for LC-ESI-MS-MS analysis of neurotransmitters

Research paper thumbnail of Inorganic anion determination by RPLC using evaporative light scattering detection

American laboratory

Ion-pair reversed-phase chromatography can be employed advantageously in laboratories in which on... more Ion-pair reversed-phase chromatography can be employed advantageously in laboratories in which only conventional HPLC systems are available.

Research paper thumbnail of The advantages of evaporative light scattering detection in pharmaceutical analysis by high performance liquid chromatography and supercritical fluid chromatography

Journal of High Resolution Chromatography, 1992

... 1 Introduction LC is increasingly being used in quality control analysis of raw materials for... more ... 1 Introduction LC is increasingly being used in quality control analysis of raw materials forpharmaceutical and ... analysis performed by coupling ELSD with either LC or SFC using packed columns appears very promising in pharma-ceutical analysis for control of raw ...

Research paper thumbnail of Treatment with KLEPTOSE® CRYSMEB reduces mouse atherogenesis by impacting on lipid profile and Th1 lymphocyte response

Vascular Pharmacology, 2015

The ability of pharmacological agents to target both &amp... more The ability of pharmacological agents to target both "classical" risk factors and inflammation may be key for successful outcomes in the prevention and treatment of atherogenesis. Among the promising drugs interfering with cholesterol metabolism, we investigated whether methyl beta-cyclodextrin (KLEPTOSE® CRYSMEB) could positively impact on atherogenesis, lipid profile and atherosclerotic plaque inflammation in ApoE-/- mice. Eleven-week old ApoE-/- mice were fed either a normal diet (N.D.) or a high-cholesterol diet (H.D.), resulting in different levels of hypercholesterolemia. KLEPTOSE® CRYSMEB (40mg/kg) or vehicle was intraperitoneally administrated 3 times per week in the last 16weeks before euthanasia in mice under N.D. and in the last 11weeks under H.D. Treatment with KLEPTOSE® CRYSMEB reduced triglyceride serum levels in both atherogenesis mouse models. In H.D. mice, treatment with KLEPTOSE® CRYSMEB increased HDL-cholesterol levels and reduced free fatty acids and spleen weight. In both mouse models, treatment with KLEPTOSE® CRYSMEB reduced atherosclerotic plaque size in thoraco-abdominal aortas and intraplaque T lymphocyte content, but did not induce relevant improvements in other histological parameters of vulnerability (macrophage, neutrophil, MMP-9 and collagen content). Conversely and more markedly in H.D. mice, treatment with KLEPTOSE® CRYSMEB was associated with a reduction in genetic markers of Th1-mediated immune response. In vitro, KLEPTOSE® CRYSMEB dose-dependently abrogated Th1 proliferation and IFNγ release. In conclusion, treatment with KLEPTOSE® CRYSMEB reduced atherosclerotic plaque size by improving triglyceride serum levels and Th1-mediated response. These results indicate this drug as a potential tool for blocking atheroprogression associated with different severity degrees of hypercholesterolemia.

Research paper thumbnail of New artificial standards for the HPLC analysis of natural glucosinolates

Journal of High Resolution Chromatography, 1992

Research paper thumbnail of Validation of an Ion-Interaction Chromatography Analysis of Underivatized Amino Acids in Commercial Preparation Using Evaporative Light Scattering Detection

A liquid chromatographic procedure using ion interaction reagent and evaporative light scattering... more A liquid chromatographic procedure using ion interaction reagent and evaporative light scattering detection was developed and validated for the direct quantification of 8 underivatized amino acids (threonine, lysine, valine, methionine, isoleucine, leucine, phenylalanine and tryptophan) present simultaneously in a commercial preparation. The chromatographic separation was achieved on a Purospher RP-18e column with an acetonitrile gradient and using heptafluorobutyric acid as volatile ion interaction reagent. Acceptable levels of linearity, specificity, precision, accuracy, robustness and limits of detection were achieved during the validation of the method. Detection limits varied from 1 mg.L )1 to 2 mg.L )1 depending on the amino acid being analyzed. The results of this method agree to within 98.6%-102.5% when compared to the manufacturer's certificate of analysis obtained with the standard amino acid autoanalyser method. This approach yields a simple, universal method that is well suited for amino acid analysis, when a sufficient quantity is available. Only basic LC instrumentation with an ELSD is necessary for this procedure.

Research paper thumbnail of Centrifugal partition chromatography elution gradient for isolation of sesquiterpene lactones and flavonoids from Anvillea radiata

Journal of Chromatography B, 2015

An innovative procedure coupling pressurized solvent extraction and centrifugal partition chromat... more An innovative procedure coupling pressurized solvent extraction and centrifugal partition chromatography (CPC) used in linear gradient elution mode was developed to isolate two pure germacranolides (9α-hydroxyparthenolide and 9β-hydroxyparthenolide) and to separate flavonoids (nepetin, isorhamnetin and jaceosidin) and chlorophyll pigments from aerial parts of Anvillea radiata (Coss.&Durieu). The two main germacranolides recovered using this method represent 2 and 5% of the dried plant material respectively. These molecules were extracted using accelerated solvent extraction with chloroform. After optimization of the CPC method, a two-phase solvent system composed of heptane/ethyl acetate/methanol/water (1:5:1:5 v/v/v/v) was employed in descending mode to isolate the germacranolides. Then the lower phase of a heptane/ethyl acetate/methanol/water (6:5:6:5 v/v/v/v) system was pumped in descending mode to generate a linear elution gradient, progressively decreasing the mobile phase polarity, that enabled the flavonoid compounds to be separated in the same run. The efficiency of the preparative separation was controlled through RP-HPLC analysis of the obtained fractions using UV, evaporative light scattering and mass spectrometry detection. The structural identification of the two germacranolides purified over 99% was established by (1)H NMR and (13)C NMR. The least abundant flavonoids were identified by mass spectrometry.

Research paper thumbnail of Different Ways to On-Line Hyphenate Centrifugal Partition Chromatography and Mass Spectrometry: Application to Prenylated Xanthones from Garcinia mangostana

Research paper thumbnail of Phytochemical analysis of Rosa hybrida cv. ‘Jardin de Granville’ by HPTLC, HPLC-DAD and HPLC-ESI-HRMS: Polyphenolic fingerprints of six plant organs

Phytochemistry, 2014

The Rosa hybrida cultivar 'Jardin... more The Rosa hybrida cultivar 'Jardin de Granville', a delicate clear pink flower, is here investigated through a progressive analytical strategy using complementary phytochemical screening methods in order to characterize the polyphenol content of several parts of the plant. The microwave hydro-ethanolic extract analysis of six different parts of the plant, carried out by High Performance Thin Layer Chromatography (HPTLC) and High Performance Liquid Chromatography coupled with a Diode Array Detector (HPLC-DAD) enabled initial identification of the polar molecular families present in each organ, namely tannins and flavonoids (quercetin and kaempferol derivatives). The HPLC fingerprints displayed different profiles for each organ, attesting to the original composition and potential valuation of the different plant parts. More detailed analyses of the extracts were then carried out by High Performance Liquid Chromatography coupled with electrospray ionization (ESI) mass spectrometry with a Q-TOF analyzer (ESI-HR-Q-TOF). Around 60 compounds were identified, mainly gallo-tannins, ellagi-tannins, catechin derivatives and glycoside derivatives of quercetin and kaempferol. Some compounds such as hyperoside or ellagic acid appeared to be ubiquitous and were found in abundance in each plant part. Woods were the richest organ in catechin and proanthocyanidin derivatives while kaempferol derivatives were more numerous and abundant in bud and flower parts.

Research paper thumbnail of The simultaneous determination of 1-aminocyclopropane-1-carboxylic acid and cyclopropane-1,1-dicarboxylic acid inLycopersicum esculentum by high-performance liquid chromatography?electrospray tandem mass spectrometry

Phytochemical Analysis, 2003

Varying concentrations of cyclopropane-1,1-dicarboxylic acid (CDA), an inhibitor of 1-aminocyclop... more Varying concentrations of cyclopropane-1,1-dicarboxylic acid (CDA), an inhibitor of 1-aminocyclopropane-1-carboxylic acid oxidase, added to the solid culture medium of tomato nodal shoot segments resulted in a reduction in the level of endogenous ethylene according to the concentration of inhibitor applied. Following treatment with inhibitor, plants were homogenised and the concentrations of CDA and of 1-aminocyclopropane-1-carboxylic acid (ACC) were measured simultaneously in the resulting juice using an HPLC-ESI/MS-MS method. The levels of CDA and ACC measured in the plant tissues were associated with the concentration of inhibitor added to the solid medium. The HPLC-ESI/MS-MS method described produced limits of detection of 0.8 pmol for ACC and of 4 pmol for CDA.

Research paper thumbnail of Evaporative light scattering detection for in-line monitoring of stopped-flow liquid chromatography-nuclear magnetic resonance analysis of compounds with weak or no chromophore groups

Journal of Separation Science, 2002

Evaporative light scattering detection for in-line monitoring of stopped-flow liquid chromatograp... more Evaporative light scattering detection for in-line monitoring of stopped-flow liquid chromatography-nuclear magnetic resonance analysis of compounds with weak or no chromophore groups This study demonstrates the use of the evaporative light scattering detector (ELSD) as an in-line monitoring detector for the stopped-flow liquid chromatography -nuclear magnetic resonance (LC -NMR) analysis of compounds with weak chromophore groups or none at all. The instrumentation set-up is discussed and the system is compared with the more common ultraviolet (UV) monitoring detection method. Underivatized amino acids without a UV chromophore (taurine) or with weak UV chromophores (hydroxyproline, aspartic acid, glycine, etc.) were selected as model compounds. The isocratic separation of the amino acids was achieved by using 0.5 mM pentadecafluorooctanoic acid (PDFOA) in deuterium oxide (D 2 O), on a Purospher RP-18e stationary phase column. PDFOA was particularly suitable for ion-pairing and NMR detection, due to the absence of protons in the alkyl chain, as well as the required low concentration. ELSD proved an interesting mode of chromatographic detection prior to NMR, due to its universality (no UV chromophore is needed). LC -NMR allowed the direct analysis of amino acids without the use of any particular NMR sequences (e.g. for the suppression of interfering resonances).

Research paper thumbnail of Conditions for rapid determination of inorganic cations in water by ion-exchange chromatography and evaporative light scattering detection

Journal of Separation Science, 2001

The simultaneous LC determination of alkali and alkaline-earth cations is possible by ion exchang... more The simultaneous LC determination of alkali and alkaline-earth cations is possible by ion exchange chromatography run in an isocratic elution mode, using a polymeric exchanger coated on a spherical silica gel, followed by evaporative light scattering detection. By using an aqueous trifluoroacetic acid (4 mM) isocratic eluent, a successful single run analysis of Na + , K + , Mg 2+ and Ca 2+ , was achieved in 6 min on a LiChrosilm IC CA 2 column. This method provides good linearity for the four calibration curves, and enables a 10 ng absolute detection limit for sodium, magnesium, and calcium and a 25 ng absolute detection limit for potassium, at a signal-to-noise ratio of 3. The repeatability determined from six injections was satisfactory for all inorganic cations studied. This methodology has been successfully applied to the direct analysis of mineral waters containing low levels of magnesium in the presence of high levels of calcium as well as low levels of potassium in the presence of high levels of sodium.

Research paper thumbnail of Liquid chromatography analysis of monosubstituted sulfobutyl ether-β-cyclodextrin isomers on porous graphitic carbon

Journal of Separation Science, 2004

The retention behaviour of the three positional isomers of monosubstituted sulfobutyl ether-beta-... more The retention behaviour of the three positional isomers of monosubstituted sulfobutyl ether-beta-cyclodextrin was investigated on a porous graphitic carbon (PGC) column. The influence of the mobile phase composition (nature and concentration of organic and electronic modifiers) was studied as well as the effect of column temperature. These hydrophilic and anionic analytes were highly retained on the PGC stationary phase compared to octadecyl bonded phases. The retention is mainly governed by a reversed-phase mechanism with electronic interaction playing a secondary role. An increase in solute retention and efficiency with temperature was observed. Successful isocratic separation with satisfactory baseline resolution of the three isomers of monosubstituted sulfobutyl ether-beta-cyclodextrin was achieved at 75 degrees C on a Hypercarb column by using ammonium acetate as electronic modifier in water-acetonitrile (83:17). The chromatographic methodology developed can be easily used for relative quantification of each isomer within a mixture and can be applied for semi-preparative purification of each one. The evaporative light scattering detector allows the detection of these non UV-visible absorbing molecules.

Research paper thumbnail of Development of an ion-pairing reversed-phase liquid chromatography method using a double detection analysis (UV and evaporative light scattering detection) to monitor the stability of Alimta®-pemetrexed preparations: Identification and quantification of l-glutamic acid as a potential degradation ...

Journal of Pharmaceutical and Biomedical Analysis, 2011

Development of an ion-pairing reversed-phase liquid chromatography method using a double detectio... more Development of an ion-pairing reversed-phase liquid chromatography method using a double detection analysis (UV and evaporative light scattering detection) to monitor the stability of Alimta ® -pemetrexed preparations: Identification and quantification of l-glutamic acid as a potential degradation product a b s t r a c t A new method based on high-performance liquid chromatography coupled to ultraviolet and evaporative light scattering detection (HPLC-UV-ELSD) was developed for the determination of l-glutamic acid, a potential degradation product of pemetrexed, and for the quantification of pemetrexed itself. This is an ion-pairing, reversed-phase method. The column was a Synergi MAX-RP C12 4 m (150 mm × 4.6 mm). The mobile phase was 1 mM tridecafluoroheptanoic acid in aqueous solution and acetonitrile under gradient elution mode. l-Glutamic acid was detected by ELSD, and pemetrexed by UV at 254 nm. Good resolution was achieved between pemetrexed and l-glutamic acid. The HPLC method was validated according to SFSTP and ICH guidelines, and applied the accuracy profile procedure with a five-level validation experimental design. For pemetrexed, the decision criteria selected consisted of the acceptability limits (±3%) and the proportion of results within the calculated tolerance intervals (95%). In conclusion, the proposed analytical procedures were validated over the selected validation domains for l-glutamic acid (0.005-0.025 mg/mL) and pemetrexed (0.4-0.6 mg/mL) and shown to provide a very effective method.

Research paper thumbnail of Characterisation of complex amphiphilic cyclodextrin mixtures by high-performance liquid chromatography and mass spectrometry

Journal of Chromatography A, 2008

It is established that amphiphilic ␤-cyclodextrins chemically modified with alkyl chains on the s... more It is established that amphiphilic ␤-cyclodextrins chemically modified with alkyl chains on the secondary face exhibit self-organisation properties yielding stable nanospheres or nanoparticles. The ability of these promising colloidal drug carriers to encapsulate drugs being partly related to the internal structure of nanosystems, precise characterisation methods are required to control their synthesis procedure. The present work describes the development of complementary analytical methods based on reversed-phase high-performance liquid chromatography (RPLC) coupled to evaporative light-scattering detection (ELSD) and electrospray ionisation-mass spectrometry (ESI-MS) to characterize various ␤-cyclodextrins enzymatically transesterified by vinyl-acyl fatty esters (the number of carbon atom in the acyl chain varying from 4 to 12). LC-ELSD has been used in a preliminary step to optimize the separation on a monolithic octadecylsiloxane-bonded silica stationary phase. A complex fingerprint was achieved for each mixture, revealing the presence of isomers unnoticed by the sole spectrometric (NMR and MS) techniques.