Martina Catani

Pirkle-type chiral stationary phase on core-shell and fully porous particles: Are superficially porous particles always the better choice toward ultrafast high-performance enantioseparations?

Pirkle-type Whelk-O1 chiral stationary phase (CSP) was prepared on 2.6μm superficially porous particles (SPPs). The chromatographic behavior of columns packed with this new CSP was compared with that of columns packed respectively with 1.8 and 2.5μm Whelk-O1 fully porous particles (FPPs). In the comparison, both thermodynamic and kinetic aspects were considered. Contrary to initial expectations, chiral columns packed with 2.6μm SPPs were quasi-comparable to those packed with 2.5μm FPPs, apparently due to larger contributions to band broadening from both eddy dispersion and, especially for the second eluted enantiomer, adsorption-desorption kinetics. These findings raise the question if SPPs, in spite of the undeniable advantages of their morphology to speed up mass transfer, are always the best choice for high-efficient ultrafast chiral separations. The last part of the work focuses on the use of short columns (10mm long) and very high flow rates to realize the separation of the enantiomers of trans-stilbene oxide (TSO) in normal phase mode in less than 1s.

Rationale behind the optimum efficiency of columns packed with new 1.9μm fully porous particles of narrow particle size distribution

Columns packed with new commercially available 1.9 fully porous particles of narrow particle size distribution (nPSD) are characterized by extremely high efficiency. Under typical reversed phase conditions, these columns are able to generate very high number of theoretical plates (in the order of 300,000plates/m and more). In this paper, we investigate the origin of the high performance of these nPSD columns by performing a series of measurements that include, in addition to the traditional determination of the van Deemter curve, peak parking, pore blocking and inverse size exclusion experiments. Two nPSD columns (both 100×3.0mm) have been considered in this study: the first one, packed with particles of 80Å pore size, is commercially available. The second one is a prototype column packed with 1.9 fully porous particles of 120Å pore size. The main conclusion of our study is that these nPSD columns are characterized by extremely low eddy dispersion, while longitudinal diffusion and mass transfer kinetics are substantially equivalent to those of other fully porous particles of similar chemistry.

Experimental evidence of the kinetic performance achievable with columns packed with new 1.9μm fully porous particles of narrow particle size distribution

Fully porous particles of narrow particle size distribution (nPSD) are now commercially available. In this paper, the kinetic performance of columns packed with these particles (1.9μm, 80Å pore size) has been investigated under typical reversed phase conditions by using a mixture of benzene derivatives as probes. The columns exhibited remarkably high efficiency (in the order of 300,000 theoretical plates per meter) and the possibility to be used at relatively high flow rates without loss of performance. These results contrast with previous studies on the same columns. Indeed we have found column efficiency comparable to that reported in previous work but, on the other hand, we could not observe the same dramatic loss of performance when columns were operated at high flow rates. The results presented in this paper, based on a set of six columns with different geometries (2.1 and 3.0 internal diameter×50, 75 and 100mm length), are not consistent with the previously proposed hypothesis that the unusually low intraparticle diffusion, which would characterize these particles, is the origin of the high efficiency of the columns. In a companion paper [1], a detailed investigation of the different terms leading to band broadening will be performed to point out the major contribution to plate height on nPSD columns.

Multi-biomarker investigation to assess toxicity induced by two antidepressants on Dreissena polymorpha

Antidepressants are one of the main pharmaceutical classes detected in the aquatic environment. Nevertheless, there is a dearth of information regarding their potential adverse effects on non-target organisms. Thus, the aim of this study was the evaluation of sub-lethal effects on the freshwater mussel Dreissena polymorpha of two antidepressants commonly found in the aquatic environment, namely Fluoxetine (FLX) and Citalopram (CT). D. polymorpha specimens were exposed to FLX and CT alone and to their mixture (MIX) at the environmental concentration of 500ng/L for 14days. We evaluated the sub-lethal effects in the mussel soft tissues by means of a biomarker suite: the activity of antioxidant enzymes superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPx) and the activity of the phase II detoxifying enzyme glutathione-S-transferase (GST). The oxidative damage was evaluated by lipid peroxidation (LPO) and protein carbonylation (PCC), while genetic damage was tested on D. polymorpha hemocytes by Single Cell Gel Electrophoresis (SCGE) assay, DNA diffusion assay and micronucleus test (MN test). Finally, the functionality of the ABC transporter P-glycoprotein (P-gp) was measured in D. polymorpha gills. Our results highlight that CT, MIX and to a lesser extent FLX, caused a significant alteration of the oxidative status of bivalves, accompanied by a significant reduction of P-gp efflux activity. However, only FLX induced a slight, but significant, increase in apoptotic and necrotic cell frequencies. Considering the variability in biomarker response and to perform a toxicity comparison of tested molecules, we integrated each endpoint into the Biomarker Response Index (BRI). The data integration showed that 500ng/L of FLX, CT and their MIX have the same toxicity on bivalves.

Future perspectives in high efficient and ultrafast chiral liquid chromatography through zwitterionic teicoplanin-based 2-μm superficially porous particles

With the aim of pushing forward the limits of high efficient and ultrafast chiral liquid chromatography, a new Chiral Stationary Phase (CSP) has been prepared by covalently bonding the teicoplanin selector on 2.0μm Superficially Porous Particles (SPPs). An already validated bonding protocol, which permits to achieve teicoplanin-based CSPs exhibiting zwitterionic behaviour, has been employed to prepare not only the 2.0μm version of the CSP but also two other analogous CSPs based, respectively, on 2.7μm SPPs and 1.9μm Fully Porous Particles (FPPs). The kinetic performance of these CSPs has been compared through the analysis of both van Deemter curves and kinetic plots by employing in-house packed columns of 4.6mm internal diameter and different lengths (20, 50 and 100mm). In particular on the columns packed with 2.0μm SPPs, extremely large efficiencies were observed for both achiral (>310,000 theoretical plates/meter, N/m; hr: 1.61) and chiral compounds (>290,000 N/m; hr: 1.72) in HILIC conditions. Thanks to their efficiency and enantioselectivity, these CSPs were successfully employed in ultrafast chiral separations. As an example, the enantiomers of haloxyfop were baseline resolved in about 3s, with a resolution higher than 2.0, (flow rate: 8mL/min) on a 2cm long column packed with the 2.0μm chiral SPPs.

New insights into perfluorinated adsorbents for analytical and bioanalytical applications

Perfluorinated (F-) adsorbents are generally prepared by bonding perfluoro-functionalized silanes to silica gels. They have been employed for a long time essentially as media for solid-phase extraction of F-molecules or F-tagged molecules in organic chemistry and heterogeneous catalysis. More recently, this approach has been extended to proteomics and metabolomics. Owing to their unique physicochemical properties, namely fluorophilicity and proteinophilicity, and a better understanding of some fundamental aspects of their behavior, new applications of F-adsorbents in the field of environmental science and bio-affinity studies can be envisaged. In this article, we revisit the most important features of F-adsorbents by focusing, in particular, on some basic information that has been recently obtained through (nonlinear) chromatographic studies. Finally, we try to envisage new applications and possibilities that F-adsorbents will allow in the near future.

New frontiers and cutting edge applications in ultra high performance liquid chromatography through latest generation superficially porous particles with particular emphasis to the field of chiral separations

AbstractAbout ten years after their introduction to the market (happened in 2006), the so-called second generation superficially porous particles (SPPs) have undoubtedly become the benchmark as well as, very often, the preferred choice for many applications in liquid chromatography (LC), when high efficiency and fast separations are required. This trend has interested practically all kinds of separations, with the only exception of chiral chromatography (at least so far). The technology of production of base SPPs is advanced, relatively simple and widely available. The deep investigation of mass transfer mechanisms under reversed-phase (RP) and normal-phase (NP) conditions for achiral separations has shown the advantages in the use of these particles over their fully porous counterparts. In addition, it has been demonstrated that SPPs are extremely suitable for the preparation of efficient packed beds through slurry packing techniques. However, the research in this field is in continual evolution. In this article, some of the most advanced concepts and modern applications based on the use of SPPs, embracing in particular ultrafast chiral chromatography and the design of SPPs with engineered pore structures or very reduced particle diameter, are revised. We describe modern trends in these fields and focus on those aspect where further innovation and research will be required. Graphical AbstractWord cloud of cutting edge applications of superficially porous particles in liquid chromatography

Continuous ion-exchange resin catalysed esterification of eugenol for the optimized production of eugenyl acetate using a packed bed microreactor

A green scalable flow-synthesis process for the production of eugenyl acetate, an eugenol derivative with potential applications in food and medicinal chemistry, was developed. Through batch experiments, the anion-exchange resin Amberlyst A-21 was recognized as a suitable catalyst for the esterification of eugenol with acetic anhydride. Next, the process was switched from batch- to flow-mode by using a packed-bed microreactor integrated in an instrumental platform that permitted at the same time continuous control of the main process parameters (flow rate, feed mixture composition, temperature) and the on-line HPLC analysis of the reactor effluent. Thanks to this apparatus, a number of experiments with different reaction conditions have been easily performed to evaluate the effects of temperature and reagent molar ratios on eugenyl acetate production. The results have been used to carry out a central composite rotatable experimental design (CCRD) whose derived response surface model (RSM) suggested an optimal temperature and acetic anhydride to eugenol molar ratio of 95 °C and 3 : 1, respectively. The goodness of these theoretically deduced parameters has been experimentally confirmed obtaining, with a flow rate of 40 μL min−1, a 95% conversion. The Amberlyst A-21 packed-bed microreactor also demonstrated good long-term stability ensuring, under the above optimized conditions, a high and stable conversion (over 93%) for prolonged reaction times.

Unmatched kinetic performance in enantioselective supercritical fluid chromatography by combining latest generation Whelk-O1 chiral stationary phases with a low-dispersion in-house modified equipment

This proof-of-concept work investigates the ultimate kinetic limits reachable in chiral supercritical fluid chromatography (SFC) with modern columns and advanced technological solutions. A commercial equipment (Waters Acquity UPC2) has been in-house modified to minimize its overall extra-column variance through a series of technical adjustments including low-volume connecting tubings, reduced-volume flow cell, an in-house made external column oven, external low-dispersion injection system, and electronic temperature controller. Compared to the original (as-shipped) configuration, the extra-column variance on the low-dispersion equipment was reduced by more than 97%, from about 85 to slightly more than 2 μL2 (measured at 2.0 mL/min). This was mainly achieved thanks to the occurrence of fully developed turbulent regime with a proper selection of capillary i.d. at significantly smaller flow rates (1.5-4 mL/min; CO2/methanol 80/20, v/v; 35 °C; back pressure regulator (BPR), 105 bar) than in entry-1 configuration. Ultrahigh efficiency columns of different geometries in-house packed with latest generation sub-2 μm UHPC-FPP-Whelk-O1 Chiral Stationary Phase (CSP) have been employed under sub- and supercritical fluid conditions. By carefully modulating the length and the internal diameter of connecting tubings in the function of column geometry, state of the art efficiencies (estimated in roughly 300 000 theoretical plates/m with reduced HETP of roughly 1.85) have been obtained on 4.6 mm i.d. chiral columns. Remarkably, for 3.0 mm × 100 mm (i.d. × length) columns, the efficiency gain on the fully modified SFC system (compared to an instrumental configuration where only the standard injector was replaced by the low-dispersion one) was greater than 90% for compounds with a retention factor of 1 and as large as 25% for retention factors of 2.5.

A campus sustainability initiative: Indoor air quality monitoring in classrooms

The presence of contaminants in indoor environments can affect the health of occupants and expose them to several kind of risks (respiratory diseases, allergies, skin/eyes/throat irritation, etc.). During winter season, in addition, concentration of chemicals indoor increases in new or refurbished buildings due to limited ventilation and energy-efficient insulation (windows, doors, walls, etc.) with accentuated negative effects on health. Recent studies have demonstrated that concentration of some air pollutants indoor can exceed that found outdoor. The impacts of indoor air quality on occupant health and comfort are ultimately determined by levels of contaminants and comfort parameters (i.e., temperature, humidity and metabolic substances). It is well known that most of chemicals accumulating indoor are volatile or semi-volatile organic compounds (VOCs and SVOCs, respectively) and their presence is either as gas mixture in indoor air or adsorbed on airborne particulate matter and settled dust. This work represents an initiative of sustainability on campus in which available low-cost technology has been employed to continuously monitor basic parameters, such as carbon dioxide, humidity and temperature inside classrooms of the University of Ferrara. There are a number of relationships that could be useful in discussing carbon dioxide and indoor air quality, such as the impact of carbon dioxide on occupant negative perception of the indoor environment (i.e., low comfort level, high relative humidity levels, body odour) or the relationship between carbon dioxide concentration and the concentration of other indoor contaminants. In this work, carbon dioxide concentration has been used as an indicator of indoor air quality due both to its use as tracer gas for air change rate estimation and to its adverse effects on students performance and productivity (e.g., concentration, learning ability, specific mental tasks). The study has been conducted on different typologies of classrooms (in terms of maximum number of allowed occupants, indoor volume, architectonic structure, etc.) during teaching activities with the purpose to evaluate, on the one side, if air quality and comfort are appropriate for teaching/learning activities (according to WHO guidelines) and, on the other, to establish whether air ventilation rate is adequate or implementation is required. Acquired data can thus also be useful in defining good practices that help creating and maintaining healthy indoor environments.