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In this study, a novel imidazolium-based ionic liquid (IL) coating was developed for stir bar sorptive extraction (SBSE) using a sol-gel method. The effects of different counterions, conditioning temperatures and polymer compositions were investigated. The stir bar with bis((trifluoromethyl)sulfonyl) amide 1-butyl-3-(3-(triethoxysilyl)propyl)-1H-imidazol-3-ium showed good mechanical and thermal stability with high resistance to water solubilization. The extraction efficiency of the IL-coated stir bar was evaluated on a mixture of 11 compounds presenting a wide range of polarities (log K o/w values between 0.65 and 7.21) using thermodesorption gas chromatography coupled with Orbitrap high-resolution mass spectrometry (TD-GC-Orbitrap-HRMS). The results showed that extraction yields were increased for the IL-stir bar. In contrast, the commercial polydimethylsiloxane (PDMS) stir bar resulted in decreased yields with salt addition, particularly for compounds with log K o/w > 4. SBSE of contaminants was performed on natural waters collected from France, followed by nontargeted analysis using TD-GC-Orbitrap-HRMS. The results revealed the detection of over 1,000 compounds, with 334 compounds annotated after deconvolution. The IL-stir bar with the addition of NaCl specifically extracted five times more compounds (167 compounds) than did the commercial PDMS stir bar (29 compounds) and more than 10 times more with the addition of NaCl with the PDMS stir bar (15 compounds). Various pollutants, including pesticides, personal care products, polychlorinated biphenyls (PCBs) and polycyclic aromatic hydrocarbons (PAHs), were identified. The annotations of the identified compounds were classified according to a level of confidence based on comparisons of retention indices, match library spectra and high-resolution mass filters., Competing Interests: Declaration of competing interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: MEZIANI reports financial support was provided by PHC TASSILI. If there are other authors, they declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024. Published by Elsevier B.V.)

The development of the reversed fill/flush modulator represents a significant advancement in flow-modulated, comprehensive two-dimensional gas chromatography (GC × GC). Compared to the forward flush/fill modulator, the reversed-flow modulator is less susceptible to baseline anomalies and peak tailing as a result of modulator channel overfilling or insufficient purging of high concentration analytes. Flow reversal requires the addition of a bleed capillary not present in the forward-flow modulator. Selecting the appropriate restriction of the bleed capillary is critical. If the bleed capillary is too restrictive, eluate from the first-dimension column can split between the modulator channel and second-dimension column, which also results in baseline artifacts. To gain a better understanding of the reversed-flow modulator, a comprehensive pneumatic model was developed. The model was validated by comparing calculated and measured hold-up times. The errors in calculated hold-up times were less than 1% of the measured values. The model can be used to predict first-dimension eluate splitting and determine the optimal bleed capillary dimensions to prevent its occurrence. Calculation of the modulator hold-up time can be used to determine the maximum collection time to ensure comprehensive analysis and optimal flush times for partial fill operation., (Copyright © 2018. Published by Elsevier B.V.)

New polar embedded aromatic stationary phases (mono- and trifunctional versions) that contain an amide-embedded group coupled with a tricyclic aromatic moiety were developed for chromatographic applications and described in the first paper of this series. These phases offered better separation performance for PAHs than for alkylbenzene homologues, and an enhanced ability to differentiate aromatic planarity to aromatic tridimensional conformation, especially for the trifunctional version and when using methanol instead of acetonitrile. In this second paper, a density functional theory study of the retention process is reported. In particular, it was shown that the selection of the suitable computational protocol allowed for describing rigorously the interactions that could take place, the solvent effects, and the structural changes for the monofunctional and the trifunctional versions. For the first time, the experimental data coupled with these DFT results provided a better understanding of the interaction mechanisms and highlighted the importance of the multimodal character of the designed stationary phases: alkyl spacers for interactions with hydrophobic solutes, amide embedded groups for dipole-dipole and hydrogen-bond interactions, and aromatic terminal groups for π-π interactions., (Copyright © 2017 Elsevier B.V. All rights reserved.)

New polar embedded aromatic stationary phases of different functionalities (mono- and trifunctional) and on different silica supports (Fully Porous Particle (FPP) and Superficially Porous Particle (SPP)) were synthesized to determine the impact of the functionality on the retention process and the selectivity towards aromatic compounds. A full experimental characterization was performed using a combination of techniques (elemental analysis, thermogravimetric measurements, infrared spectroscopy and solid-state NMR) to differentiate unambiguously the mono- and trifunctional Stationary Phases (SP). Commercially available columns with either an aromatic group or a polar embedded group were compared to the new stationary phases. The latter presented enhanced affinity for polycyclic aromatic hydrocarbons (PAH) structures compared to alkylbenzenes, especially when using methanol instead of acetonitrile as the organic modifier., (Copyright © 2017 Elsevier B.V. All rights reserved.)

Supercritical Fluid Chromatography is frequently used to efficiently handle separations of enantiomers. The separation of basic analytes usually requires the addition of a basic additive in the mobile phase to improve the peak shape or even to elute the compounds. The effect of increasing the concentration of 2-propylamine as additive on the elution of a series of basic compounds on a Chiralpak-AD stationary phase was studied. In this study, unusual additive concentrations ranging from 0.3% to 10% of 2-propylamine 2-propylaminein the modifier were explored and the effect on retention, peak shape, selectivity and resolution was evaluated. The addition of a large quantity of additive allowed to drastically improve the selectivity and the resolution, and even enantiomers elution order reversal was observed by changing the concentration of basic additive. The role of the ratio additive/modifier appeared a key to tune the enantioselectivity. Finally, the impact of these drastic conditions on the column material was evaluated., (Copyright © 2017 Elsevier B.V. All rights reserved.)

This study aims at modelling and predicting solute retention in capillary Gas Chromatography (GC) and Flow Modulation comprehensive GC (FM-GCxGC). A new thermodynamic model, taking into account the effects of temperature and pressure, is proposed to describe the variation of the equilibrium partition constant of a solute during its elution. This retention model was challenged with the classical one, and both were applied to: (i) stationary phase film thickness indirect estimation; (ii) retention time (RT) prediction of a set of 11 model polycyclic aromatic hydrocarbons (PAHs) on the SLB-IL60 and DB-35MS columns, in temperature-programmed mode. Film thickness determination led to values about 2 times lower than those indicated by column nominal dimensions, whatever the employed model. Prediction of retention times in GC led to 0.84 and 0.26% mean errors using the classical and the extended models, respectively. Prediction in GCxGC gave 5.5 and 0.44% mean errors in 1st dimension RTs, and 7.3 and 2.2% mean errors in 2nd dimension RTs, using the classical and the extended models, respectively., (Copyright © 2017 Elsevier B.V. All rights reserved.)

This study reports the impact of thermal pretreatment between 400 and 1100°C on superficially porous silica particles (e.g. core-shell, fused-core; here abbreviated as SPP silica). The different thermally pretreated SPP silica (400°C, 900°C and 1100°C) were chemically bonded with an octadecyl chain under microwave irradiation. The bare SPP silica, thermally untreated and pretreated, as well as the chemically bonded phases (CBPs) were fully characterized by elemental analysis, diffuse reflectance infrared Fourier transform spectroscopy (DRIFT), and solid state cross polarization magic angle spinning (CP-MAS) (29)Si NMR. The chromatographic properties of the overall set of C18-thermally pretreated SPP silica stationary phases were determined using the Tanaka test. Complementary, the simplified Veuthey test was used to deeply study the silanol activity, considering a set of 7 basic solutes with various physicochemical properties. Both tests were also performed on different commercial SPP silica columns and different types of bonding chemistry (C18, Phenyl-hexyl, RP-amide, C30, aQ). Multivariate data analyses (hierarchical cluster analysis and principal component analysis) were carried out to define groups of stationary phases with similar chromatographic properties and situate them in relation to those commercially available. These different C18-thermally pretreated SPP silicas represented a wide range of stationary phases as they were spread out along the score plot. Moreover, this study highlighted that the thermal pretreatment improved the chemical stability of the SPP silica compare to untreated SPP silica and untreated porous silica. Consequently, higher thermal pretreatment can be applied (up to 900°C) before functionalization without destruction of the silica matrix. Indeed, a significantly lower dissolution of the thermally pretreated SPP silica under aggressive conditions could allow the use of the corresponding functionalized stationary phases at high temperature (60°C) with good lifetime of the columns., (Copyright © 2015 Elsevier B.V. All rights reserved.)

The development of new efficient conversion processes to transform heavy petroleum fractions into valuable products, such as diesel, requires improved chemical knowledge of the latter. High-temperature comprehensive gas chromatography (HT-GC × GC) has proven to be a powerful technique for characterizing such complex samples. This paper reports on an evaluation of the performances of four different differential flow modulators, including two original ones that have not been previously described in the literature, in terms of dispersion, peak intensity, peak capacity and overloading. These modulators, all of which are based on Agilent capillary flow technology (CFT), are forward fill/flush (FFF) differential flow modulators with an integrated collection channel or an adjustable channel (new) and reverse fill/flush (RFF) differential flow modulators with an integrated collection channel (new) or an adjustable channel. First, the optimization of the collection channel dimensions is described. Second, an RFF and an FFF differential flow modulator possessing the same collection channel were compared. The reverse differential flow modulation significantly reduced band broadening compared to forward differential flow modulation, and the peak intensity doubled for every modulated peak when an RFF differential flow modulator was used. Then, an RFF differential flow modulator and CO2 dual-jet modulator were compared. Whereas the percentages of separation space used were similar (61% with the HT-GC × GC method using a cryogenic modulator and 59% with the method using an RFF differential flow modulator), the peak capacities were at least three times more important with differential flow modulation due to the greater length of the column used in the second dimension. The results demonstrate that the RFF differential flow modulator is an excellent tool for studying heavy petroleum cuts. It demonstrates the best performances and it is the most versatile modulator. In its two-plate version, it gives more flexibility regarding the set of columns, the flow rates and the modulation periods that can be used compared with the others., (Copyright © 2015 Elsevier B.V. All rights reserved.)

New polyethylene-glycol-based sol-gels containing cyclodextrin or calix[6]arene derivatives have been synthesized. An original method for sol-gel preparation and capillary column coating, which consumes smaller quantities of selectors and allows for control of their amounts in the stationary phase, is reported herein. The new stationary phases exhibited excellent column efficiencies over a large range of temperatures and thermal stability up to 280°C. The cyclodextrin derivative generally showed the best separation factors for aromatic positional isomers. The calix[6]arene derivative exhibited the best selectivity for the polychlorobiphenyl congeners and some polycyclic aromatic hydrocarbon isomers. The relationship between the structure and the chromatographic properties of the selectors is discussed. The tert-butyl groups on the upper rim of the calix[6]arene were found to possibly play an important role in the recognition of solutes. The incorporation of the cyclodextrin derivative into the sol-gel matrix did not affect its enantioselective recognition capabilities., (Copyright © 2013 Elsevier B.V. All rights reserved.)

Original mixed selectors were synthesized by coupling a single L-valine diamide moiety on permethylated β-cyclodextrin. The structures of the new selectors were designed to limit the interactions between the L-valine derivative and cyclodextrin by removing the amino acid moiety from the cyclodextrin cavity by means of an amide linkage on mono-6-amino permethylated β-CD or the insertion of a carboxymethyl group. The accessibility of the amino acid group moiety was thus facilitated. The new mixed selectors exhibited better enantioselectivity than Chirasil-L-Val for half (selector based on mono-6-amino permethylated β-CD) or more (selector with the carboxymethyl group) of the 41 amino acid derivatives. Molecular modeling confirmed that these results could be attributed to an increase in the distance between the chiral center of the amino acid and the cyclodextrin cavity allowing better access of the amino acid moiety. These new mixed chiral selectors demonstrated a novel enantioselective capability with the successful separation of more than 90 racemic mixtures among the 105 chiral compounds tested. These mixed selectors exhibited enhanced enantioselectivity in comparison to binary selectors previously described with respect to both enantiomer resolution and the number of separated chiral compounds. Moreover, an improvement of the enantioseparation factors compared to the corresponding 'parent phases' for the amino acid derivatives was observed in many cases. These mixed selectors should therefore be considered some of the most versatile selectors for chiral gas chromatography., (Copyright © 2012 Elsevier B.V. All rights reserved.)