Reversed-phase Conditions Research Articles

Evaluation of matrix effect in one-dimensional and comprehensive two-dimensional liquid chromatography for the determination of the phenolic fraction in extra virgin olive oils.

Olea europaea, meaning "European olive," is asmalltreebelonging to thefamilyOleaceae, occurring in theMediterranean Basin. Olive oil is an essential component of a balanced diet because of its nutritional value. Among micronutrients, phenolic compounds did show important beneficial effects for human health. The majority of the research studies on the phenol content are carried out by liquid chromatography combined to photodiode array and/or mass spectrometry detection; however, because of matrix complexity, one-dimensional liquid chromatography cannot be sometimes sufficient to obtain rewarding separations, requiring more advanced analytical techniques. In this work, comprehensive two-dimensional liquid chromatography, incorporating RP-Amide and C18 stationary phases, in the first and second dimension, respectively, both under reversed phase conditions, was investigated for the determination of the phenolic fraction in extra virgin olive oil samples. As far as detection is concerned, triple quadrupole mass spectrometry was employed under multi reaction monitoring mode offering superior selectivity and sensitivity. The reduction of matrix effects, when using comprehensive two-dimensional liquid chromatography with respect to conventional one-dimensional liquid chromatography, was assessed by comparing the slopes of calibration curves built from standard solutions and spiked olive oil samples.

Binding modes identification through molecular dynamic simulations: A case study with carnosine enantiomers and the Teicoplanin A2-2-based chiral stationary phase.

In the present study, an in silico methodology able to define the binding modes adopted by carnosine enantiomers in the setting of the chiral recognition process is described. The inter- and intramolecular forces involved in the enantioseparation process with the Teicoplanin A2-2 chiral selector and carnosine as model compound are successfully identified. This approach fully rationalizes, at a molecular level, the (S)<(R) enantiomeric elution order obtained under reversed-phase conditions. Consistent explanations were achieved by managing molecular dynamics results with advanced techniques of data analysis. As a result, the time-dependent identification of all the interactions simultaneously occurring in the chiral selector-enantiomeric analyte binding process was obtained. Accordingly, it was found that only (R)-carnosine is able to engage a stabilizing charge-charge interaction through its ionized imidazole ring with the carboxylate counter-part on the chiral selector. Instead, (S)-carnosine establishes intramolecular contacts between its ionized functional groups, that limit its conformational freedom and impair the association with the chiral selector unit.

Determination of the Metabolite Content of Brassica juncea Cultivars Using Comprehensive Two-Dimensional Liquid Chromatography Coupled with a Photodiode Array and Mass Spectrometry Detection

Plant-based foods are characterized by significant amounts of bioactive molecules with desirable health benefits beyond basic nutrition. The Brassicaceae (Cruciferae) family consists of 350 genera; among them, Brassica is the most important one, which includes some crops and species of great worldwide economic importance. In this work, the metabolite content of three different cultivars of Brassica juncea, namely ISCI Top, “Broad-leaf,” and ISCI 99, was determined using comprehensive two-dimensional liquid chromatography coupled with a photodiode array and mass spectrometry detection. The analyses were carried out under reversed-phase conditions in both dimensions, using a combination of a 250-mm microbore cyano column and a 50-mm RP-Amide column in the first and second dimension (2D), respectively. A multi (three-step) segmented-in-fraction gradient for the 2D separation was advantageously investigated here for the first time, leading to the identification of 37 metabolites. In terms of resolving power, orthogonality values ranged from 62% to 69%, whereas the corrected peak capacity values were the highest for B. juncea ISCI Top (639), followed by B. juncea “Broad-leaf” (502). Regarding quantification, B. juncea cv. “Broad-leaf” presented the highest flavonoid content (1962.61 mg/kg) followed by B. juncea cv. ISCI Top (1002.03 mg/kg) and B. juncea cv. ISCI 99 (211.37 mg/kg).

Ultra‐high performance separation of basic compounds on reversed‐phase columns packed with fully/superficially porous silica and hybrid particles by using ultraviolet transparent hydrophobic cationic additives

The use of the tetrabutylammonium additive was investigated in the ultra-high performance reversed phase liquid chromatographic elution of basic molecules of pharmaceutical interest. When added to the mobile phase at low pH, the hydrophobic tetrabutylammonium cation interacts with the octadecyl chains and with the residual silanols, thus imparting a positive charge to the stationary phase, modulating retention and improving peak shape of protonated basic solutes. Two sources of additive were tested: a mixture of tetrabutylammonium hydroxide/trifluoroacetic acid and tetrabutylammonium hydrogen sulfate. Retention and peak shape of eleven basic pharmaceutical compounds were evaluated on commercially available ultra-fast columns packed with octadecyl stationary phases (Ascentis Express C18 2.0μm, Acquity BEH C18 1.7μm, Titan C18 1.9μm). All columns benefit from the use of additive, especially tetrabutylammonium hydrogen sulfate, providing very symmetric peaks with reasonable retention times. Focusing on the probe compounds amitriptyline and sertraline, efficiency and asymmetry values were investigated at increasing retention factor. The trend is very different to that obtained in reversed phase conditions and the effect lies in the complex molecular interaction mechanisms based on hydrophobic and ion exchange interactions as well as electrostatic repulsion. This article is protected by copyright. All rights reserved.

Enantioselective HPLC Analysis to Assist the Chemical Exploration of Chiral Imidazolines.

In the present work, we illustrate the ability of high-performance liquid chromatography (HPLC) analysis to assist the synthesis of chiral imidazolines within our medicinal chemistry programs. In particular, a Chiralpak® IB® column containing cellulose tris(3,5-dimethylphenylcarbamate) immobilized onto a 5 μm silica gel was used for the enantioselective HPLC analysis of chiral imidazolines synthesized in the frame of hit-to-lead explorations and designed for exploring the effect of diverse amide substitutions. Very profitably, reversed-phase (RP) conditions succeeded in resolving the enantiomers in nine out of the 10 investigated enantiomeric pairs, with α values always higher than 1.10 and RS values up to 2.31. All compounds were analysed with 50% (v) water while varying the content of the two organic modifiers acetonitrile and methanol. All the employed eluent systems were buffered with 40 mM ammonium acetate while the apparent pH was fixed at 7.5. Based on the experimental results, the prominent role of π-π stacking interactions between the substituted electron-rich phenyl groups outside of the polymeric selector and the complementary aromatic region in defining analyte retention and stereodiscrimination was identified. The importance of compound polarity in explaining the retention behaviour with the employed RP system was readily evident when a quantitative structure-property relationship study was performed on the retention factor values (k) of the 10 compounds, as computed with a 30% (v) methanol containing mobile phase. Indeed, good Pearson correlation coefficients of retention factors (r - log k1st = −0.93; r - log k2nd = −0.94) were obtained with a water solubility descriptor (Ali-logS). Interestingly, a n-hexane/chloroform/ethanol (88:10:2, v/v/v)-based non-standard mobile phase allowed the almost base-line enantioseparation (α = 1.06; RS = 1.26) of the unique compound undiscriminated under RP conditions.

Enantioselective Degradation and Chiral Stability of Glufosinate in Soil and Water Samples and Formation of 3-Methylphosphinicopropionic Acid and N-Acetyl-glufosinate Metabolites.

Two enantiomers of glufosinate were separated under reverse-phase conditions on a chiral crown stationary phase (CROWNPAK CR(+)). An efficient and reliable chiral analytical method was developed to determine the glufosinate enantiomers and two metabolites in soil and water samples using high-performance liquid chromatography-high-resolution mass spectrometry (HPLC-HRMS). The linearities of the matrix-matched calibration curves in five water and four soil samples were good with a correlation coefficient R2 > 0.998, and the mean recoveries were 85.2-100.4%, with relative standard deviations of 1.0-7.1%. l-Glufosinate was degraded faster than d-glufosinate in four nonsterile natural soil and two nonsterile natural water samples. The degradation half-lives of the enantiomers ranged from 3.4 to 33.0 days in the soil samples, but glufosinate was stable in the five water samples, less than 22% of the applied substance degraded at the end of the experiment (100 days). Degradation in sterile soil was not enantioselective. The two enantiomers were configurationally stable in the four soil and five water samples. In most cases of glufosinate degradation in soils, the percentage of 3-methylphosphinicopropionic in relation to the parent was higher than that of N-acetyl-glufosinate. l-Glufosinate was preferentially degraded in the four soils, and formation of 3-methylphosphinicopropionic acid and N-acetyl-glufosinate was enantiomer dependent.

Enantioseparation and determination of flumequine enantiomers in multiple food matrices with chiral liquid chromatography coupled with tandem mass spectrometry.

The present work firstly described the enantioseparation and determination of flumequine enantiomers in milk, yogurt, chicken, beef, egg, and honey samples by chiral liquid chromatography-tandem mass spectrometry. The enantioseparation was performed under reversed-phase conditions on a Chiralpak IC column at 20°C. The effects of chiral stationary phase, mobile phase components, and column temperature on the separation of flumequine enantiomers have been studied in detail. Target compounds were extracted from six different matrices with individual extraction procedure followed by cleanup using Cleanert C18 solid phase extraction cartridge. Good linearity (R2 >0.9913) was obtained over the concentration range of 0.125 to 12.5 ng g-1 for each enantiomer in matrix-matched standard calibration curves. The limits of detection and limits of quantification of two flumequine enantiomers were 0.015-0.024 and 0.045-0.063 ng g-1 , respectively. The average recoveries of the targeted compounds varied from 82.3 to 110.5%, with relative standard deviation less than 11.7%. The method was successfully applied to the determination of flumequine enantiomers in multiple food matrices, providing a reliable method for evaluating the potential risk in animal productions.

LC-MS/MS method with chemical derivatization for quantitation of L-threonate in human plasma.

An LC-MS/MS-based bioanalytical method has been developed to measure the concentration of L-threonate at its endogenous level in human plasma. Following isotope dilution and protein precipitation, the samples were acetylated and chromatographed under reversed-phase conditions for baseline separation of the derivatized L-threonate and its stereoisomer D-erythronate. The method was assessed by a fit-for-purpose validation with a calibration range from 100 to 10,000 ng/mL. The intra-run coefficients of variation (CVs) were <3.6% and the inter-run CV was 3.2% for the QC samples at endogenous level. At the lower limit of quantitation, the intra-run CV was 6.1% and the average inaccuracy was -1.4%. This method provides an efficient and reliable quantitation of L-threonate and could be useful to certain biomarker investigators.

Determination of molecular mass 302 polycyclic aromatic hydrocarbons in Standard Reference Material 1597a by reversed-phase liquid chromatography and constant energy synchronous fluorescence spectroscopy

High-performance liquid chromatography with fluorescence detection is often used for the analysis of polycyclic aromatic hydrocarbons (PAHs) in environmental extracts. Since fluorescence chromatograms are usually recorded at a single set of excitation and emission wavelengths, qualitative parameters for PAH identification are restricted to characteristic retention times. The research presented here explores the use of constant energy synchronous fluorescence spectroscopy (CESFS) for the analysis of co-eluting PAHs with similar chromatographic behaviors under normal and reversed-phase conditions. Twenty-one PAH isomers with molecular mass (MM, g/mol) 302 were studied. Synchronous fluorescence spectra were recorded under stop-flow conditions with the aid of a commercial HPLC system. PAHs were extracted from a coal tar sample (Standard Reference Material 1597a) and fractionated by normal-phase liquid chromatography (NPLC). Qualitative and quantitative analysis of NPLC fractions was carried out via reversed-phase liquid chromatography-CESFS (RPLC-CESFS). Of the 21 isomers investigated in the coal tar sample, 16 were spectrally identified in the absence of matrix interference. Three of the remaining isomers were tentatively identified in the presence of moderate spectral interference. Thirteen isomers were used to investigate the accuracy of the RPLC-CESFS approach. Mass fractions statistically equivalent to the NIST reported values (P = 95%; N1 = N2 = 3) were obtained for ten isomers ranging from 2.04 (dibenzo[a,h]pyrene) to 10.41 mg/kg (naphtho[2,1-a]pyrene). The non-destructive nature of CESFS provides an additional layer of selective and accurate information to the analysis of PAH isomers with MM 302.

Enantioselective retention mechanisms of dipeptides on antibiotic-based chiral stationary phases: Leucyl-leucine, glycyl-leucine, and leucyl-glycine as case studies

Chromatographic behaviors of dipeptides consisting of leucine and glycine were studied on two antibiotic-based chiral stationary phases (CSPs) with teicoplanin (Chirobiotic T) or ristocetin A (Chirobiotic R) as chiral selectors under reversed-phase conditions. The effect of mobile phase pH on the retention of stereoisomers of dipeptides was investigated and thermodynamic characteristic of adsorption were measured at different pH values. It was shown that the retention of dipeptides depends on the ionization of their molecules in the mobile phase, as different ionic forms have different affinity towards antibiotic selectors. Enantioselectivity of the bound antibiotics with respect to Leu-Leu stereoisomers was achieved via steric modulation of ion-ion interactions between the solute and the selector, while in the case of Gly-Leu enantiomers non-ionic interactions such as hydrogen bonding might play the key role. In both cases, the dipeptides terminating in D-Leu were retained stronger than their optical antipodes, whereas the enantiomers of Leu-Gly were hardly separated. The regression analysis of the retention data applying the Horvath-Melander-Molnar model revealed that different types of enantioselectivity resides in particular ionic forms of the compounds: cations are responsible for the separation of diastereomeric pairs and the anionic and zwitterionic forms have a universal enantioselectivity on the Chirobiotic T CSP, and the anions and zwitterions are the enantioselective forms for the Chirobiotic R CSP.

Enantioseparation of the racemates of a number of pesticides on a silica-based column with immobilized amylose tris(3-chloro-5-methylphenylcarbamate)

We report here the results from studies on the high-performance liquid chromatographic HPLC enantioresolution of thirty different types of pesticides on the chiral silica-based column with immobilized amylose tris(3-chloro-5-methylphenylcarbamate (ACMPC) (CHIRALPAK IG-3) under polar-organic and reversed-phase conditions measured at 20 °C. The main objective was to explore diverse polar and aqueous-based eluents for use with a single column to obtain an enantioseparation of polar pesticides usually found in environmental matrices. These pesticides included phenoxy- and aryloxyphenoxypropionic acids, imidazolinones, and diphenyl-ether herbicides; acylanilides, triazoles, and pyrimidine fungicides; chlordane and pyrethroid insecticides; organophosphorus compounds; and some metabolites and precursors. We obtained improved chromatographic enantioresolutions for seventeen of these compounds in either the polar-organic or reversed-phase modes, including six pesticides whose enantioseparation is reported for first time through the use of these chromatographic modes.

Application of the “inverted chirality columns approach” for the monitoring of asymmetric synthesis protocols

In the present study, the “Inverted Chirality Columns Approach (ICCA)” was applied to follow an asymmetric synthetic reaction, namely, the addition of butan-2-one to trans-β-nitrostyrene, catalysed by (S)-proline, leading to the formation of 3-methyl-4-phenyl-5-nitro-2-pentan-2-one. The ICCA method was applied to overcome the lack of pure enantiomeric standards.The two widely employed (R,R)- and (S,S)-Whelk-O1 chiral stationary phases (CSPs), incorporating fully synthesized enantiomeric chiral selectors, were profitably used for this purpose. The enantioselective analysis with the two CSPs was performed under optimized reversed-phase conditions with a water/acetonitrile (60/40, v/v) eluent.In the probe reaction under investigation, a diastereomeric excess >90% was found according to a well-established reaction mechanism, thus affording the enantiomer couple (3S,4R)-3-methyl-4-phenyl-5-nitropentan-2-one and (3R,4S)-3-methyl-4-phenyl-5-nitropentan-2-one as the main product. Therefore, the attention was exclusively focused on this enantiomers pair.Rather similar retention and separation factor [1.12 with (R,R)-Whelk-O1 and 1.13 with (S,S)-Whelk-O1] values as well as resolutions [2.06 with (R,R)-Whelk-O1 and 2.30 with (S,S)-Whelk-O1] were produced by the two enantiomeric CSPs.Applying the ICCA concept allowed to identify the two enantiomers-related peaks in the chromatograms, ultimately indicating a 65-to-35 enantiomeric per cent ratio. Electronic circular dichroism (ECD) and high-resolution mass spectrometry analyses of the two peaks collected during the enantioselective analyses further confirmed the enantiomeric nature of the identified compounds. The (3S,4R) < (3R,4S) enantiomer elution order with the (R,R)-Whelk-O1 was fully disclosed thanks to ECD studies coupled with in silico quantum mechanical simulations. As expected, reversed elution order turned out with (S,S)-Whelk-O1.

Utility of dry load injection for an efficient natural products isolation at the semi-preparative chromatographic scale

Semi-preparative HPLC is one of the main techniques used for the purification of natural products (NPs). Generally, the sample has to be solubilized in organic solvent and injected on column through a loop valve. Since the solubility of crude natural extracts is often limited, a high solvent volume is needed for injection. This significantly compromises the resolution and increases the risk of overpressure in the system. To overcome this problem, a dry load injection procedure was developed to ensure optimum resolution even at high sample loading. The approach was first validated with a representative mixture of NPs standards, and successfully applied to two representative crude plant extracts: the dichloromethane extract of Annacardium occidentale and the methanolic extract of Hypericum perforatum. In all cases, the dry loading injection setup enabled an efficient introduction of the samples in the semi-preparative HPLC system. Different overload conditions of the columns were tested and the results demonstrated the robustness of the method and the possibility of applying it with a limited loss of resolution compared to liquid injection and without increasing pressure. The chromatographic resolutions were close to those obtained at the analytical level and separation were of much better quality when compared to liquid injection. This approach is especially relevant when purifying compounds isolated with high resolution from extracts that are poorly soluble in low volume of injection solvent due to the presence of lipophilic compounds and are thus not compatible for loop injection in typical reversed phase conditions. In addition, the dry load setup was also found to be useful when relatively polar components have to be separated in reversed phase conditions. In this case, loop injection with methanol generates strong peak distortion and broadening, while the dry load injection affords symmetrical peaks.

In-situ photopolymerized C4-functionalized organosilicon monoliths for reversed-phase protein separation in nano-liquid chromatography

In this study, polyhedral oligomeric silsesquioxane (POSS)-based capillary monoliths with short alkyl chain ligand in the form of butyl (C4) were synthesized via two different polymerization routes, namely UV-initiated free radical copolymerization of methacrylate-derivatized POSS (POSS-MA) with butylmethacrylate (BMA) and UV-initiated thiol-methacrylate copolymerization of POSS-MA with butanethiol (BT). An organosilicon monolith with a pore size distribution lying on both mesoporous and macroporous scales, a lower mean pore size and a higher specific surface area was obtained with UV-initiated thiol-methacrylate polymerization. Both monoliths were then comparatively evaluated for gradient separation of proteins under reversed phase conditions in nano-liquid chromatography. The chromatographic performance was defined in terms of peak-resolution and peak capacity. Four carbon (C4) functionalized-poly(POSS-MA) monolith produced by UV-initiated thiol-methacrylate polymerization exhibited better separation performance with higher peak resolutions and peak capacities. Both, the morphological characterization of monoliths and the results of gradient separation of proteins showed that thiol-methacrylate polymerization was more suitable for the synthesis of C4 functionalized organosilicon based stationary phases for reversed-phase protein separation. The monolith prepared by thiol-methacrylate polymerization was also successfully applied for impurity analysis of two important hormones, namely insulin and genotropin. A comparison with a commercial poly(styrene-co-divinylbenzene) monolith documented the good chromatographic performance of the new BT-attached poly(POSS-MA) monolith.

Immobilized Cellulose-Based Chiralpak IC Chiral Stationary Phase for Enantioseparation of Eight Imidazole Antifungal Drugs in Normal-Phase, Polar Organic Phase and Reversed-Phase Conditions Using High-Performance Liquid Chromatography

Due to the remarkable enantioselective performances of polysaccharide derivatives, immobilized cellulose-based columns have high enantioseparation ability, which can be applied under various mobile phase conditions. In the present work, a cellulose-derived chiral stationary phase (CSP), namely Chiralpak IC was evaluated for enantioseparation of eight imidazole antifungal drugs (miconazole, econazole, isoconazole, sulconazole, butoconazole, fenticonazole, sertaconazole, and ketoconazole) in three mobile phase modes: normal-phase mode, polar organic mode and reversed-phase mode. The factors that affected the enantioseparation were investigated and optimized. Results indicated that the Chiralpak IC column possessed good enantioselectivity in three modes, with all analytes being successfully resolved. In addition, the mechanism of enantioseparation was preliminarily discussed based on the molecular structures and retention behavior of the enantiomers.

Homochiral metal-organic framework immobilized on silica gel by the interfacial polymerization for HPLC enantioseparations

Herein, we reported a homochiral metal-organic frameworks (HMOF) [Nd3(D-cam)8(H2O)4Cl]n and prepared four novel chiral stationary phases (CSPs) in which two CSPs were fabricated by interfacial polymerization (IP). Some analytes were used to evaluate the separation performance of the two CSPs packed column. Moreover, the two CSPs also were tested under normal phase (NP), reverse phase (RP) and polar organic phase (POP) chromatography conditions and showed high column efficiency and selectivity especially for α-amino acids. Which seventeen and thirteen racemates were separated by the two CSPs (CSP-1, CSP-2). In contrast, only five and eight chiral compounds were separated in the CSP-3 and CSP-4, respectively. The experimental results showed that the HMOF [Nd3(D-cam)8(H2O)4Cl]n based novel CSPs possessed of good recognition ability for chiral separation in high-performance liquid chromatography (HPLC).

Retention of Fluorescent Amino Acid Derivatives in Ion-pairing Reversed-phase Liquid Chromatography.

Recent studies have shown that pillar array columns enable fast and quantitative analysis of amino acids. However, hydrophilic amino acids still cannot be retained on pillar array columns since they have limited retention ability. Ion-pairing liquid chromatography is a promising means of increasing analyte retention. In this study, the effects of ion-pairing reagents on the retention of eight hydrophilic amino acids (histidine, asparagine, glutamine, serine, arginine, aspartic acid, glycine, and glutamic acid) derivatized with 4-fluoro-7-nitro-2,1,3-benzoxadiazole (NBD-F) under reversed-phase conditions on a conventional ODS column were studied. Among the ion-pairing reagents investigated, tetraheptylammonium bromide proved to be the most effective for increasing analyte retention. With a mobile phase consisting of 20 mM citrate buffer (pH 6.3)-acetonitrile (100:40, v/v) and 2 mM tetraheptylammonium bromide, the retention times of the eight NBD-amino acids-except NBD-arginine-were longer than 19.4 min, which was the retention time of NBD-valine when eluted without an ion-pairing reagent. As NBD-valine was well retained on pillar array columns, the chromatographic conditions may thus be applied in the analysis of hydrophilic amino acids using pillar array columns.

A chromatographic study on the retention behavior of the amylose tris(3-chloro-5-methylphenylcarbamate) chiral stationary phase under aqueous conditions.

In this study, the retention properties of the immobilized polysaccharide-derived Chiralpak IG-3 chiral stationary phase under aqueous-organic conditions were investigated. A systematic evaluation of the retention factors of the enantiomers of the chiral sulfoxide oxfendazole, endowed with anthelmintic activity and selected as test compound, was carried out changing progressively the water content in hydro-organic eluents containing methanol, ethanol or acetonitrile. From the results obtained with acetonitrile/water mobile phases and the associated retention plots, clear U-shape retention dependencies, indicative of the interplay of both hydrophilic interaction liquid chromatography and reversed-phase modes, were highlighted. A U-turn point of retention mechanism was recorded in correspondence of the acetonitrile/water 100:40 v/v mobile phase. Retention was significantly affected by small percentages of trifluoroacetic acid or diethylamine additives incorporated in the mobile phase. It is worth emphasizing that the basic additive was more effective in reducing retention in the reversed-phase region, while the action of acid additive was more pronounced in the hydrophilic interaction liquid chromatography region. Finally, either in the transition from hydrophilic interaction liquid chromatography to reversed-phase conditions or after additive addition, the enantioselectivity did not vary significantly.

Synthesis and evaluation of a pentafluorobenzamide stationary phase for HPLC separations in the reversed phase and hydrophilic interaction modes.

A pentafluorobenzamide stationary phase was synthesized by an easy method with no intermediate purification steps. Physicochemical characterization (elemental analysis, fourier transform infrared spectroscopy, 29 Si and 13 C nuclear magnetic resonance spectroscopy) confirmed the presence of pentafluorobenzamide functionalization on the surface of the silica particles. The pentafluorobenzamide stationary phase proved to be quite versatile as it can be used in two different modes in liquid chromatography: reversed phase and hydrophilic interaction liquid chromatography. Chromatographic characterizations in both modes confirmed the multiple interactions established by the new stationary phase, such as hydrogen bonding and π-π and ion-exchange interactions. The pentafluorobenzamide stationary phase was successfully employed for the separation of nucleosides and antihypertensive drugs under hydrophilic interaction liquid chromatography conditions, as well as pesticides and benzodiazepine using reversed phase conditions. The stationary phase showed significant potential when compared with commercial columns.

Modelling the enantioresolution capability of cellulose tris(3,5-dichlorophenylcarbamate) stationary phase in reversed phase conditions for neutral and basic chiral compounds

To the best of our knowledge, the prediction of the enantioresolution ability of polysaccharides-based stationary phases in liquid chromatography for structurally unrelated compounds has not been previously reported. In this study, structural information of neutral and basic compounds is used to model their enantioresolution levels obtained from an immobilised cellulose tris(3,5-dichlorophenylcarbamate) stationary phase in reversed phase conditions. Thirty-four structurally unrelated chiral drugs and pesticides, from seven families, are studied. Categorical enantioresolution levels (RsC, 0 = no baseline enantioresolution and 1 = baseline enantioresolution) are established from the experimental enantioresolution values obtained at a fixed experimental conditions. From 58 initial structural variables, three topological parameters (two of them connected to the chiral carbon), and six molecular descriptors (one of them also related with the chiral carbon), are selected after a discriminant partial least squares refinement process. The molar total charge of the molecule at the working pH is the most important variable. The relationships between RsC and the most important structural variables and the drug/pesticide family are evaluated. An explicit model is proposed to anticipate the RsC levels, which provides 100% of correct anticipations. A criterion is introduced to alert about the compounds that should not be anticipated.