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This manuscript describes the development of a capillary electrophoresis (CE) method for the detection of acid and basic dyes and its application to real samples, blue-pen-ink strokes on office paper. First, a capillary zone electrophoresis (CZE) method was developed for the separation of basic and acid dyes, by studying the separation medium (buffer nature, pH and relative amount of additive) and instrumental parameters (temperature, voltage and capillary dimensions). The method performance was evaluated in terms of selectivity, resolution (above 5 and 2 for acid dyes and basic dyes, respectively, except for two basic dye standards), LOD (lower than 0.4 mg/L) and precision as intraday and interday RSD values of peak migration times (lower than 0.6%). The developed method was then applied to 34 blue pens from different technologies (rollerball, ballpoint, markers) and with different ink composition (gel, water-based, oil-based). A microdestructive sample treatment using a scalpel to scratch 0.3 mg of ink stroke was performed. The entire electropherogram profile allowed the visual discrimination between different types of ink and brands, being not necessary a statistical treatment. A 100% of discrimination was achieved between pen technologies, brands, and models, although non-reproducible zones in the electropherograms were found for blue gel pen samples. The two different batches of blue oil-based pens were also differentiated. Thus, this method provides a simple, microdestructive, and rapid analysis of different blue pen technologies which may complement the current analysis of questioned documents performed by forensic laboratories. [ABSTRACT FROM AUTHOR]

After demonstrating in a first paper the feasibility of SFCxSFC without decompression of the mobile phase, a modified interface has been developed in order to perform active modulation between the two SFC dimensions. In this paper, it is shown that the new interface enabled independent control of modulation parameters in SFCxSFC and performed a band compression effect of solutes between the two SFC dimensions. The effectiveness of this new modulation process was studied using a Design of Experiments. The SFCxSFC prototype was applied to the analysis of a real oil sample to demonstrate the benefits of the active modulator; in comparison to our previous results obtained without active modulation, better separation was obtained with the new interface owing to the peak compression occurring in the modulator. [ABSTRACT FROM AUTHOR]

While Reinforcement Learning (RL) has already proven successful in performing complex tasks, such as controlling large-scale epidemics, mitigating influenza and playing computer games beyond expert level, it is currently largely unexplored in the field of separation sciences. This paper therefore aims to introduce RL, specifically proximal policy optimization (PPO), in liquid chromatography, and evaluate whether it can be trained to optimize separations directly, based solely on the outcome of a single generic separation as input, and a reward signal based on the resolution between peak pairs (taking a value between [ − 1 , 1 ]). More specifically, PPO algorithms or agents were trained to select linear (1-segment) or multi-segment (2-, 3-, or 16-segment) gradients in 1 experiment, based on the outcome of an initial, generic linear gradient (ϕ s t a r t = 0.3 , ϕ e n d = 1.0 , and t g = 20 min), to improve separations. The size of the mixtures to be separated varied between 10 and 20 components. Furthermore, two agents, selecting 16-segment gradients, were trained to perform this optimization using either 2 or 3 experiments, in sequence, to investigate whether the agents could improve separations further, based on previous outcomes. Results showed that the PPO agent can improve separations given the outcome of one generic scouting run as input, by selecting ϕ -programs tailored to the mixture under consideration. Allowing agents more freedom in selecting multi-segment gradients increased the reward from 0.891 to 0.908 on average; and allowing the agents to perform an additional experiment increased the reward from 0.908 to 0.918 on average. Finally, the agent outperformed random experiments as well as standard experiments (ϕ s t a r t = 0.0 , ϕ e n d = 1.0 , and t g = 20 min) significantly; as random experiments resulted in average rewards between 0.220 and 0.283, and standard experiments resulted in average rewards of 0.840. In conclusion, while there is room for improvement, the results demonstrate the potential of RL in chromatography and present an interesting future direction for the automated optimization of separations. • Proximal policy optimization (PPO) for the direct optimization of separations. • PPO agent learned to select multi-step gradients to optimize separations of mixtures. • PPO agent improved separations based on the outcome of initial linear gradients. [ABSTRACT FROM AUTHOR]

Highlights: [•] Only a few papers reported the application of chiral ILs in enantioseparation by CE. [•] Few papers focused on chiral ILs synergistic system based on β-CD derivatives in CE. [•] Amino acid derived chiral ILs were first applied as additives in synergistic system. [•] Addition of chiral ILs has significantly improved the separation of tested drugs. [ABSTRACT FROM AUTHOR]

Abstract: Since 1980, high-speed counter-current chromatography (HSCCC) has been used for separation and purification of natural and synthetic products in a standard elution mode. In 1991, a novel elution mode called pH-zone refining CCC was introduced from an incidental discovery that an organic acid in the sample solution formed the sharp peak of an acid analyte. The cause of this sharp peak formation was found to be bromoacetic acid present in the sample solution which formed a sharp trailing border to trap the acidic analyte. Further studies on the separation of DNP-amino acids with three spacer acids in the stationary phase revealed that increased sample size resulted in the formation of fused rectangular peaks, each preserving high purity and zone pH with sharp boundaries. The mechanism of this phenomenon was found to be the formation of a sharp trailing border of an acid (retainer) in the column which moves at a lower rate than that of the mobile phase. In order to facilitate the application of the method, a new method was devised using a set of retainer and eluter to form a sharp retainer rear border which moves through the column at a desired rate regardless of the composition of the two-phase solvent system. This was achieved by adding the retainer in the stationary phase and the eluter in the mobile phase at a given molar ratio. Using this new method the hydrodynamics of pH-zone-refining CCC was diagrammatically illustrated by three acidic samples. In this review paper, typical pH-zone-refining CCC separations were presented, including affinity separations with a ligand and a separation of a racemic mixture using a chiral selector in the stationary phase. Major characteristics of pH-zone-refining CCC over conventional HSCCC are as follows: the sample loading capacity is increased over 10 times; fractions are highly concentrated near saturation level; yield is improved by increasing the sample size; minute charged compounds are concentrated and detected at the peak boundaries; and elution peaks are monitored with a pH flow meter for compounds with no chromophore. Since 1994, over 70 research papers on pH-zone-refining CCC have been published with the trends increasing in the recent years. [Copyright &y& Elsevier]

Abstract: The recent introduction of new stationary phases for liquid chromatography based on superficially porous particles, called core–shell or fused-core, dramatically improved the separation performances through very high efficiency, due mainly to reduced eddy diffusion. However, few studies have evaluated the retention and selectivity of C18 phases based on such particles, despite some retention order change reported in literature between some of these phases. The carotenoid test has been developed a few years ago in the goal to compare the chromatographic properties of C18 bonded phases. Based on the analysis of carotenoid pigments by using Supercritical Fluid Chromatography (SFC), it allows, with a single analysis, to measure three main properties of reversed phase chromatography stationary phases: hydrophobicity, polar surface activity and shape selectivity. Previous studies showed the effect of the endcapping treatment, the bonding density, the pore size, and the type of bonding (monomeric vs. polymeric) on these studied properties, and described the classification map used for a direct column comparison. It was applied to ten ODS superficially porous stationary phases, showing varied chromatographic behaviors amongst these phases. As expected, due to the lower specific surface area, these superficially porous phases are less hydrophobic than the fully porous one. In regards of the polar surface activity (residual silanols) and to the shape selectivity, some of these superficially porous phases display close chromatographic properties (Poroshell 120, Halo C18, Ascentis Express, Accucore C18, Nucleoshell C18 on one side and Aeris Wide pore, Aeris peptide and Kinetex XDB on the other side), whereas others, Kinetex C18 and Halo peptide ES C18 display more specific ones. Besides, they can be compared to classical fully porous phases, in the goal to improve method transfer from fully to superficially porous particles. By the way, the paper also report the extension of the test to other ligands such as naphtyl, cholester, phenyl-hexyl, or to the new ODS bonded phases, such as charge surface hybrid phases, High Strength Silica, and Hybrid ones, and also presents results for identical brands using different particle size, such as Luna and Synergi phases. Phenyl-hexyl and napthyl ligands show rather close properties, low hydrophobicity, high polar surface activity and specific shape selectivity, whereas, at the opposite, the cholester phase display a polymeric behavior and a high hydrophobicity. Finally, additional classical (fully porous particles) C18 bonded phases are also reported to complete the data set presented in previous papers. [Copyright &y& Elsevier]

Abstract: In this second paper of a two-part series, we demonstrate the utility of an approach to enhancing the resolution of select portions of conventional 1D-LC separations, which we refer to as selective comprehensive two-dimensional HPLC (sLC×LC), in three quite different example applications. In the first paper of the series we described the principles of this approach, which breaks the long-standing link in online multi-dimensional chromatography between the timescales of sampling the first dimension (1D) separation and the separation of fractions of 1D effluent in the second dimension. In the first example, the power of the sLC×LC approach to significantly reduce the analysis time and method development effort is demonstrated by selectively enhancing the resolution of critical pairs of peaks that are unresolved by a one-dimensional separation (1D-LC) alone. Transfer and subsequent 2D separations of multiple fractions of a particular 1D peak produces a two-dimensional chromatogram that reveals the coordinates of the peaks in the 2D separation space. The added time dimension of sLC×LC chromatograms also facilitates the application of sophisticated chemometric curve resolution algorithms to further resolve peaks that are otherwise chromatographically unresolved. This is demonstrated in this work by the targeted analysis of phenytoin in urban wastewater effluent using UV diode array detection. Quantitation by both standard addition and external calibration methods yielded results that were not statistically different from 2D-LC/MS/MS analysis of the same samples. Next, we demonstrate the utility of sLC×LC for reducing ion suppression due to matrix effects in electrospray ionization mass spectrometry through the analysis of cocaine in urban wastewater effluent. Finally, we explore the flexibility of the approach in its application to two select regions of a single 1D separation of triclosan and cocaine. The diversity of these applications demonstrates the power and versatility of the sLC×LC approach, which will benefit tremendously from further optimization and advances in valve technology that specifically address the needs of this new technique. [Copyright &y& Elsevier]

Abstract: An innovative green column-switching high-performance liquid chromatographic (HPLC) technique was developed by coupling traditional and Pb2+ ion-exclusion columns to study enzyme hydrolysis components of waste cellulosic biomass. Pure water was used as the mobile phase to separate neutral polar analytes in high salt content solution. The column-switching HPLC-RI was connected on-line to the immobilized enzyme reactor for successive on-line desalting and simultaneous analysis of six carbohydrates (cellobiose, glucose, xylose, galactose, mannose, and arabinose) in the hydrolysate of waste paper and waste tree branch by incorporating the heart-cut and the elution-time-difference techniques. Six internal standard calibration curves in the linear concentration range of 0–2000μgmL−1 were prepared. Xylitol was used as the internal standard to give excellent linear correlation coefficients (0.9984–0.9999). The limits of detection and quantification for cellobiose, glucose, xylose, galactose, mannose, and arabinose varied between 0.12–4.88 and 0.40–16.3μgmL−1, respectively, with an accuracy of 90–102% and a precision of 0.1–7.8%. Cellulose and hemicellulose contents were higher in waste paper than in waste tree branch. [Copyright &y& Elsevier]

Abstract: I-type, J-type and non-synchronous centrifuges are all coil planet centrifuges. Analysing the motion of I-type and J-type centrifuges has advanced the understanding of how to manufacture and use these centrifuges. This paper analyses the motion of non-synchronous centrifuges producing equations of motion that can be applied to all coil planet centrifuges. This has also produced simple equations to determine the critical β-values for any coil planet centrifuge. This paper also demonstrates that I-type centrifuges also have 2 critical β-values when it was thought that β-value did not influence the understanding of the processes within I-type centrifuges. For the I-type instrument both of these critical values are at bobbin radii approaching infinity. In practice this means all I-types function within one β-value range hence the unilateral distribution and type/effectiveness of the mixing is consistent. Finally the paper shows the influence that the tangential velocity has on the Archimedean screw effect and thus the unilateral distribution of the upper and lower phases in the columns of coil planet centrifuges. This explains why the maximum stationary phase retention in an I-type centrifuge is limited to 50%. [Copyright &y& Elsevier]

Abstract: Many different strategies of reversed phase high performance liquid chromatographic (RP-HPLC) method development are used today. This paper describes a strategy for the systematic development of ultrahigh-pressure liquid chromatographic (UHPLC or UPLC) methods using 5cm×2.1mm columns packed with sub-2μm particles and computer simulation (DryLab® package). Data for the accuracy of computer modeling in the Design Space under ultrahigh-pressure conditions are reported. An acceptable accuracy for these predictions of the computer models is presented. This work illustrates a method development strategy, focusing on time reduction up to a factor 3–5, compared to the conventional HPLC method development and exhibits parts of the Design Space elaboration as requested by the FDA and ICH Q8R1. Furthermore this paper demonstrates the accuracy of retention time prediction at elevated pressure (enhanced flow-rate) and shows that the computer-assisted simulation can be applied with sufficient precision for UHPLC applications (p >400bar). Examples of fast and effective method development in pharmaceutical analysis, both for gradient and isocratic separations are presented. [Copyright &y& Elsevier]

There is revived interest in the development and implementation of methods of faster GC. The paper summarises the advantages of faster GC analysis, general approaches to faster GC method development and practical aspects of fast gas chromatography with the utilisation of open tubular capillary columns with the stress on trace analysis. There are a number of ways to take the advantage of the improved speed of analysis by faster GC. Numerous options exist for pushing the speed of capillary gas chromatography (CGC) analysis. The scope of this paper is also to give an overview of the present state of faster GC instrumentation which is already available for trace analysis. The practicality of fast CGC is a function of sample preparation and the matrix interferences and how they affect the resultant resolution that may be achieved. Researchers have demonstrated the applicability of fast GC to trace and ultratrace analysis of volatile and semivolatile compounds also with narrow bore columns and difficult sample matrices (such as food, and soil extract). The main development of faster GC methods has been observed in the field of environmental analysis. Practical applications are presented. Both optimised sample preparation and experimental conditions for faster GC are the future perspective of trace analysis. [Copyright &y& Elsevier]

• Chiral extractants can be screened and designed from the field of asymmetric catalysis. • Chiral ionic liquids show great potential in enantioselective liquid-liquid extraction. • β -Cyclodextrins bonded magnetic nanoparticles as chiral extractant with high recovery. • SPINOL based phosphoric acids show high enantioselectivity of 34.6 for phenylglycinol. As the demand for enantiopure compounds increases, chiral separation has become increasingly important in many fields. Enantioselective liquid-liquid extraction is an up-and-coming technology for enantiomeric separation because it is highly efficient and easy to be scaled up. The key factor for enantioselective liquid-liquid extraction is the development of novel chiral extractants with high enantiorecognition performance. With successful studies on catalytically active metal complexes as chiral extractants, novel chiral extractants can be screened and designed from the field of asymmetric catalysis. Chiral ionic liquids, sulfobutylether- β -cyclodextrins bonded magnetic nanoparticles and 2,2′,3,3′-tetrahydro-1,1′-spirobi[indene]-7,7′-diol (SPINOL) based phosphoric acid host show unique potential ability in enantioselective liquid-liquid extraction and they deserve further study. Brief principles, extraction equipment and solvent systems in enantioselective liquid-liquid extraction are presented in the present paper, and recent progress in development of new chiral extractants in the past decade is mainly reviewed, including metal complexes, cyclodextrins, ionic liquids, tartrate acids and crown ethers. [ABSTRACT FROM AUTHOR]

• The principle of TLC-SERS combination technology is studied. • TLC-SERS technology can realize rapid separation and on-site detection of mixtures. • The practical application of TLC-SERS technology is reviewed. • The problems and challenges of TLC-SERS technology are discussed. The separation and detection of multi-component mixtures has always been a challenging task. Traditional detection methods often suffer from complex operation, high cost, and low sensitivity. Surface enhanced Raman scattering (SERS) technique is a high sensitivity, powerful and rapid detection tool, which can realize the specific detection of single substance components, but it must solve the problem that multi-component mixtures cannot be accurately determined. Thin layer chromatography (TLC) technology, as a high-throughput separation technology, uses chromatographic plate as the stationary phase, and could select different developing phases for separation experiments. The advantages of TLC technology in short distance and rapid separation are widely used in protein, dye and biomedical fields. However, TLC technology has limitations in detection ability and difficulty in obtaining ideal signal intensity. The combination of TLC technology and SERS technology made the operation procedure simple and the sample size small, which can achieve rapid on-site separation and quantitative detection of mixtures. Due to the rapid development of TLC-SERS technology, it has been widely used in the investigation of various complex systems. This paper reviews the application of TLC-SERS technology in food science, environmental pollution and biomedicine. [ABSTRACT FROM AUTHOR]

In this paper, a novel embeded elliptic cylindrical posts (ECPs) with large surface area and wide effective width, which could support more stationary phase and decrease the pressure drop, is applied on the micro-fabricated gas chromatographic (μGC) column. Compared with μGC column with cylindrical posts (CPs), the surface area and effective width of μGC column with ECPs are increased by 29% and 30%. Separation experiments are performed under the same head pressure at column inlet: in experiments of separating mixture 1, the column efficiency of the μGC column with ECPs for C9 has a 76% improvement, and the separation resolution between C8 and C9 also has a 34% improvement; in experiments of separating mixture 2, seven kinds of analytes can be identified by the μGC column with ECPs less than ten minutes, while, only six kinds can be identified by the μGC column with CPs in almost the same time. In detail, the column efficiency of the μGC column with ECPs for toluene has a 129% improvement, and the separation resolution between benzene and toluene also has a 56.4% improvement. Hence, the μGC column with the inner structures of ECPs is a valid means to improve column efficiency and resolution in a lower pressure drop. [ABSTRACT FROM AUTHOR]

Halogen bond (XB)-driven enantioseparations involve halogen-centred regions of electronic charge depletion (σ-hole) as electrophilic recognition sites. The knowledge in this field is still in its infancy. Indeed, although the influence of halogens on enantioseparation have been often considered, only recently the function of electrophilic halogens (Cl, Br, I) as enantioseparations ‘drivers’ has been demonstrated by our groups. Further to these studies, in this paper we focus on some unexplored issues. First, as XB-driven chiral recognition mechanisms are at an early stage of comprehension, a theoretical investigation based on a series of 32 molecular dynamic (MD) simulations was performed by using polyhalogenated 4,4′-bipyridines and polysaccharide-based polymers as ligands and receptors, respectively. Enantiomer elution orders (EEOs) were derived from calculations and the theoretical model accounted for some analyte- and chiral stationary phase (CSP)-dependent experimental EEO inversions. Then, the function of halogen-centred σ-holes in competitive systems, presenting also hydrogen bond (HB) centres as recognition sites, was considered. In this regard, Pirkle’s enantioseparations of halogenated compounds performed on Whelk-O1 were theoretically re-examined and electrostatic potentials (EPs) associated with both σ-holes on halogens and HB centres were computed and compared. Then, the enantioseparation of halogenated 2-nitro-1-arylethanols was performed on cellulose tris(3,5-dimethylphenylcarbamate) (CDMPC) and the influence of halogen substituents on the chromatographic results was evaluated by correlating theoretical and experimental data. [ABSTRACT FROM AUTHOR]

The use of comprehensive two-dimensional gas chromatography coupled with mass spectrometry would be a real asset for the forensic profiling of human hand odor. This paper focuses on the optimization of a comprehensive gas chromatography method using a synthetic mixture of 80 compounds representative of human hand odor composition. In order to rank the candidate column sets, instead of using a unique criterion, we used a chemometric tool called desirability which is based on Derringer functions and enables to consider several criteria simultaneously and hence to get the best compromise. Nine criteria including six orthogonality criteria were used to evaluate the quality and the efficiency of the separation. The desirability analysis lead to a straightforward ranking and an accurate overview of the results in two situations, with an objective of routine analysis and without. In both cases, the DB-1MS × DB-1701 set was found to be best suited for the separation of the considered mixture, however with different gradients. [ABSTRACT FROM AUTHOR]

With the shift of focus of the regulatory bodies, from fixed process conditions towards flexible ones based on process understanding, model-based optimization is becoming an important tool for process development within the biopharmaceutical industry. In this paper, a multi-objective optimization study of separation of three insulin variants by reversed-phase chromatography (RPC) is presented. The decision variables were the load factor, the concentrations of ethanol and KCl in the eluent, and the cut points for the product pooling. In addition to the purity constraints, a solubility constraint on the total insulin concentration was applied. The insulin solubility is a function of the ethanol concentration in the mobile phase, and the main aim was to investigate the effect of this constraint on the maximal productivity. Multi-objective optimization was performed with and without the solubility constraint, and visualized as Pareto fronts, showing the optimal combinations of the two objectives productivity and yield for each case. Comparison of the constrained and unconstrained Pareto fronts showed that the former diverges when the constraint becomes active, because the increase in productivity with decreasing yield is almost halted. Consequently, we suggest the operating point at which the total outlet concentration of insulin reaches the solubility limit as the most suitable one. According to the results from the constrained optimizations, the maximal productivity on the C 4 adsorbent (0.41 kg/(m 3  column h)) is less than half of that on the C 18 adsorbent (0.87 kg/(m 3  column h)). This is partly caused by the higher selectivity between the insulin variants on the C 18 adsorbent, but the main reason is the difference in how the solubility constraint affects the processes. Since the optimal ethanol concentration for elution on the C 18 adsorbent is higher than for the C 4 one, the insulin solubility is also higher, allowing a higher pool concentration. An alternative method of finding the suggested operating point was also evaluated, and it was shown to give very satisfactory results for well-mapped Pareto fronts. [ABSTRACT FROM AUTHOR]

The present paper discusses practical aspects of prototyping of microfluidic chips using cyclic olefin copolymer as substrate and the application in high-performance liquid chromatography. The developed chips feature a 60 mm long straight separation channel with circular cross section (500 μm i.d.) that was created using a micromilling robot. To irreversibly seal the top and bottom chip substrates, a solvent-vapor-assisted bonding approach was optimized, allowing to approximate the ideal circular channel geometry. Four different approaches to establish the micro-to-macro interface were pursued. The average burst pressure of the microfluidic chips in combination with an encasing holder was established at 38 MPa and the maximum burst pressure was 47 MPa, which is believed to be the highest ever report for these polymer-based microfluidic chips. Porous polymer monolithic frits were synthesized in-situ via UV-initiated polymerization and their locations were spatially controlled by the application of a photomask. Next, high-pressure slurry packing was performed to introduce 3 μm silica reversed-phase particles as the stationary phase in the separation channel. Finally, the application of the chip technology is demonstrated for the separation of alkyl phenones in gradient mode yielding baseline peak widths of 6 s by applying a steep gradient of 1.8 min at a flow rate of 10 μL/min. [ABSTRACT FROM AUTHOR]

The review is mainly focused on application of thin layer chromatography (TLC) as simple, rapid and inexpensive method for lipophilicity assessment. Among separation techniques, TLC is still one of the most popular for lipophilicity measurement. The principles and methodology of Quantitative Structure Retention Relationship (QSRR) employed to lipophilicity prediction from retention data are presented. Moreover, applications of TLC retention constants in Quantitative Structure Activity Relationship (QSAR) studies were critically overviewed. The paper concerns also bioautography as a TLC method complementary to QSAR studies. In the article, the advantages and limitations of well established and less common planar chromatography modes applied for drug discovery process were discussed. [ABSTRACT FROM AUTHOR]

In this paper we describe a strategy to estimate by CE the acidity constants (pK a ) of complex polyprotic peptides from their building peptide fragments. CE has been used for the determination of the pK a s of five short polyprotic peptides that cover all the sequence of amyloid beta (Aβ) peptides 1–40 and 1–42 (Aβ fragments 1–15, 10–20, 20-29, 25–35 and 33–42). First, the electrophoretic mobility (m e ) was measured as a function of pH of the background electrolyte (BGE) in the pH range 2–12 (bare fused silica capillary, I = 25 mM and T = 25 °C). Second, the m e s were fitted to equations modelling the ionisable behaviour of the different fragments as a function of pH to determine their pK a s. The accuracy of the pK a s was demonstrated predicting the electrophoretic behaviour of the studied fragments using the classical semiempirical relationships between m e and peptide charge-to-mass ratio (m e vs. q/M r 1/2 , classical polymer model, q = charge and M r = relative molecular mass). Separation selectivity in a mixture of the fragments as a function of pH was evaluated, taking into account the influence of the electroosmotic flow (EOF) at each pH value, and a method for the simple and rapid simulation of the electropherograms at the optimum separation pH was described. Finally, the pK a s of the fragments were used to estimate the pK a s of the Aβ peptides 1–40 and 1–42 ( t C and D 3.1, E 4.6 and Y 10.8 for acidic amino acids and t N-D 8.6, H 6.0, K 10.6 and R 12.5 for basic amino acids), which were used to predict their behaviour and simulate their electropherograms with excellent results. However, as expected due to the very small differences on q/M r 1/2 values, separation resolution of their mixtures was poor over the whole pH range. The use of poly(vinyl alcohol) (PVA) coated capillaries allowed reducing the EOF and a slight improvement of resolution. [ABSTRACT FROM AUTHOR]

The orthogonal pressurized planar electrochromatography (OPPEC) is an example of 2-D separation technique, in which two simultaneous and orthogonal processes of electrophoresis and chromatography are involved in the separation mechanism. In the case of preparative separation of substances characterized by different electrophoretic mobility, such separation system can be constantly fed with the sample solution and the separated components can be constantly collected at its outlet. In the paper, as opposed to the previous studies, we discuss the capabilities of OPPEC technique for preparative separation of substances characterized by the same electrophoretic mobility. According to the proposed solution, the separation system can be periodically fed with the sample solution and separated components can be collected alternately at its outlet. The advantages of this new approach over the column chromatography with regard to the separation of complex mixtures have been signaled. [ABSTRACT FROM AUTHOR]

In industrial liquid separation processes chromatography often has a key function in the optimization of yield and purity. For the design of an industrial system, chromatographic processes are generally simulated using mathematical models, tested and optimized at laboratory level, and then scaled up to pilot and subsequently industrial scale. To describe the system, experimental data and model data need to be fitted and extra column contribution must be determined. This paper describes the influence of extra-column volume on overall separation efficiency for lab scale and its impact on the design of large scale systems. Measurement of extra-column contribution was investigated in terms of mean retention time and variance using two different methods the commonly used zero dead volume connector and as an alternative the zero length column. Further a technique is presented to estimate extra-column contribution to band broadening for different injection volumes, velocities, and tracers based on representative measurements. When scaling up, often contribution of extra-column volume from laboratory equipment is neglected assuming to be on the safe side, however column efficiency is often lower than efficiency measured for the entire chromatographic system. Relation between system efficiency and column efficiency was investigated using laboratory data and the lumped kinetic model. Depending on the ratio of extra-column volume to retention volume in the system, deduced column efficiency was up to 20% smaller than overall system efficiency. This ratio revealed the misleading nature of the term efficiency loss, when describing influence of extra-column volume on column efficiency. A scheme, which relates the relative variance of the system to the relative extra-column volume, provided an assessment of under- or overestimation of column efficiency. In this article it is shown how scaling up a system based on laboratory data, where extra-column volume contribution is not accounted for, may severely overestimate column efficiency. This overestimation results in underestimated column dimensions at pilot and industrial scale, and hence underperformance of the industrial system. [ABSTRACT FROM AUTHOR]

• The entire OPPEC separation process can run in a fully on‐line operating mode. • There is good agreement between theory and experiment. • OPPEC periodic mode separates substances with equal electrophoretic mobility. • Successful micro-preparative separation of a real post-reaction mixture was conducted. • Advantage of OPPEC vs HPLC for productivity and eluent consumption is possible. This paper reports for the first time the coupling of a two-dimensional separation technique known as orthogonal pressurised planar electrochromatography (OPPEC) with on-line UV/VIS detection. It establishes the efficiency characteristic of a planar column used in OPPEC. The studies show that in OPPEC, all separation steps (mixture introduction, separation, and detection) can run successfully as non-separate operation, much like in HPLC, and the planar column has itself good efficiency, ensuring a relatively low plate height value. In its use, some findings of the previously proposed theoretical model concerning optimisation of preparative separation of components with the same electrophoretic mobility are verified – showing that there is a good agreement between theory and experiment. The paper also demonstrates by means of a specific example of separation of a post-reaction mixture obtained after synthesis of valine diastereomers that OPPEC can be a powerful tool used in preparative separation in that it can achieve much higher separation productivity and significantly lower eluent consumption than when using column chromatography techniques. [ABSTRACT FROM AUTHOR]

Structure elucidation of volatile aromatic isomers at trace level has long been considered as an elusive task, due to their structural similarities and similar polarities, even with the aid of many spectroscopic techniques such as mass spectrometry and nuclear magnetic resonance (NMR) spectroscopy. Single-crystal X-ray diffraction (SCD) is recognized as one of the most powerful structural elucidation techniques. The recently developed crystalline sponge method overcomes the intrinsic limitation of SCD that the target molecules must be single crystals, being able to analyze non-crystalline and trace-amount compounds without any special treatment. In order to investigate whether the crystalline sponge method could be used for the structure elucidation of closely related isomers or other volatile and even oily compounds in complex mixtures at trace level, we combined HPLC separation with the crystalline sponge method for X-ray crystallographic analysis. In this paper, two pairs of volatile aromatic isomers including cis / trans isomers of asarone and positional isomers of carvacrol and thymol, as well as the main volatile component in essential oil extracted from Acorus Tatarinowii , were first isolated by HPLC and encapsulated into the crystalline sponge then elucidated by X-ray crystallographic analysis. Direct observation of these volatile compounds by X-ray crystallography was achieved using only microgram quantities without crystallization or derivatization. Unambiguous identification of these compounds was realized without reference standards. This strategy offers a promising platform capable of providing high-confidence detailed structural information of closely related isomers as well as other volatile and even oily compounds in complex mixtures in microgram quantities. [ABSTRACT FROM AUTHOR]

This paper reports for the first time, a method for simultaneous determination of naphazoline (NPZ) and zinc (Zn) using an analytical separation technique (capillary electrophoresis with capacitively coupled contactless conductivity detection -CE–C 4 D). A single run is possible every 55 s (sampling rate = 65 h −1 ). The separation by CE–C 4 D was achieved on a fused silica capillary (50 cm length − 10 cm effective, 50 μm i.d.) with a background electrolyte (BGE) composed by 20 mmol L −1 of 2-(morpholin-4-yl)ethane-1-sulfonic acid (MES) and 20 mmol L −1 of histidine (HIS) (pH 6.0). Detection limits were estimated at 20 and 30 μmol L −1 and recovery values for spiked samples were 98 and 102% for NPZ and Zn, respectively. The developed procedure was compared to HPLC (NPZ) and FAAS (Zn) and no statistically significant differences were observed (95% confidence level). [ABSTRACT FROM AUTHOR]

High performance liquid chromatography (HPLC) is a kind of efficient separation technology and has been used widely in many fields. Micro-sized porous silica microspheres as the most popular matrix have been used for fast separation and analysis in HPLC. In this paper, the monodisperse large-porous silica microspheres with controllable size and structure were successfully synthesized with polymer microspheres as the templates and characterized. First, the poly(glycidyl methacrylate-co-ethyleneglycol dimethacrylate) microspheres (P GMA-EDMA ) were functionalized with tetraethylenepentamine (TEPA) to generate amino groups which act as a catalyst in hydrolysis of tetraethyl orthosilicate (TEOS) to form Si-containing low molecular weight species. Then the low molecular weight species diffused into the functionalized P GMA-EDMA microspheres by induction force of the amino groups to form polymer/silica hybrid microspheres. Finally, the organic polymer templates were removed by calcination, and the large-porous silica microspheres were obtained. The compositions, morphology, size distribution, specific surface area and pore size distribution of the porous silica microspheres were characterized by infrared analyzer, scanning-electron microscopy, dynamic laser scattering, the mercury intrusion method and thermal gravimetric analysis, respectively. The results show that the agglomeration of the hybrid microspheres can be overcome when the templates were functionalized with TEPA as amination reagent, and the yield of 95.7% of the monodisperse large-porous silica microspheres can be achieved with high concentration of polymer templates. The resulting large-porous silica microspheres were modified with octadecyltrichlorosilane (ODS) and the chromatographic evaluation was performed by separating the proteins and the digest of BSA. The baseline separation of seven kinds of protein standards was achieved, and the column delivered a better performance when separating BSA digests comparing with the commercial one currently available. The high column efficiency and good reproducibility present that the large-porous silica microspheres obtained can be used as a matrix for peptide and protein separation. [ABSTRACT FROM AUTHOR]

The chirality of herbicides has been the focus of research. However, there is little information on the enantioseparation of amide herbicides with different chiral elements. In this study, the need for different chiral stationary phases (CSPs), mobile phases, temperatures and flow rates for the separation of napropamide, acetochlor and propisochlor was discussed in detail and compared to metolachlor. Resolution of C-chiral enantiomers was easier than that of axial-chiral enantiomers. Metolachlor and acetochlor could achieve baseline separation only on AY-H and AS-H columns, respectively. Propisochlor had satisfactory separations on OD-H and AS-H columns. Napropamide was separated on OJ-H, AY-H and AS-H columns. Both the structures of the compounds and CSPs and the interactions between them played significant roles in the enantioseparations. Molecule dockings were also used to elucidate the separation mechanisms. C-chiral enantiomers had perfect symmetry in their optical properties, whereas the axial-chiral enantiomers did not. The elution order for napropamide, acetochlor and propisochlor, with a single chiral location, was R- prior to S -. These results were the first that compare the enantioseparations of four amide herbicides with different chirality, and they provided the absolute configurations for the herbicides. The paper also illustrated certain mechanisms for enantioseparations. [ABSTRACT FROM AUTHOR]

Gas chromatography (GC) is a superior separation technique for many compounds. However, fractionation of a GC eluate for analyte isolation and/or post-column off-line analysis is not straightforward, and existing platforms are limited in the number of fractions that can be collected. Moreover, aerosol formation may cause serious analyte losses. Previously, our group has developed a platform that resolved these limitations of GC fractionation by post-column infusion of a trap solvent prior to continuous small-volume fraction collection in a 96-wells plate (Pieke et al., 2013 [17]). Still, this GC fractionation set-up lacked a chemical detector for the on-line recording of chromatograms, and the introduction of trap solvent resulted in extensive peak broadening for late-eluting compounds. This paper reports advancements to the fractionation platform allowing flame ionization detection (FID) parallel to high-resolution collection of a full GC chromatograms in up to 384 nanofractions of 7 s each. To this end, a post-column split was incorporated which directs part of the eluate towards FID. Furthermore, a solvent heating device was developed for stable delivery of preheated/vaporized trap solvent, which significantly reduced band broadening by post-column infusion. In order to achieve optimal analyte trapping, several solvents were tested at different flow rates. The repeatability of the optimized GC fraction collection process was assessed demonstrating the possibility of up-concentration of isolated analytes by repetitive analyses of the same sample. The feasibility of the improved GC fractionation platform for bioactivity screening of toxic compounds was studied by the analysis of a mixture of test pesticides, which after fractionation were subjected to a post-column acetylcholinesterase (AChE) assay. Fractions showing AChE inhibition could be unambiguously correlated with peaks from the parallel-recorded FID chromatogram. [ABSTRACT FROM AUTHOR]

Supercritical fluid chromatography (SFC) has recently benefited of new instrumentation, together with the availability of many ultra-high performance columns (sub −2 μm fully porous particles or sub −3 μm superficially porous particles), rendering it more attractive than ever. Most of these columns commonly used in SFC were initially developed for HPLC use, with an increasing number of stationary phases specifically designed for SFC. While the availability of different stationary phase chemistries is an advantage to achieve successful SFC separations, selecting a column for method development remains difficult. For this reason, we have previously developed a classification of stationary phases dedicated to SFC use. It is based on linear solvation energy relationships (LSER) with Abraham descriptors (for neutral species). While current interest in SFC is strong in the pharmaceutical industry, the need to take account of interactions occurring with ionisable species is pressing. We have previously shown how a modified version of the solvation parameter model, adapted to take account of ionic and ionizable species, could be applied to the characterization of SFC systems. In the present paper, based on this modified LSER model, and on the analysis of 109 neutral and ionisable species, we propose an improved classification of 31 ultra-high performance stationary phases to facilitate method development with SFC. [ABSTRACT FROM AUTHOR]

Ion-exchange chromatography (IEX) is universally accepted as the optimal method for achieving process scale separation of charge variants of a monoclonal antibody (mAb) therapeutic. These variants are closely related to the product and a baseline separation is rarely achieved. The general practice is to fractionate the eluate from the IEX column, analyze the fractions and then pool the desired fractions to obtain the targeted composition of variants. This is, however, a very cumbersome and time consuming exercise. A mechanistic model that is capable of simulating the peak profile will be a much more elegant and effective way to make a decision on the pooling strategy. This paper proposes a mechanistic model, based on the general rate model, to predict elution peak profile for separation of the main product from its variants. The proposed approach uses inverse fit of process scale chromatogram for estimation of model parameters using the initial values that are obtained from theoretical correlations. The packed bed column has been modeled along with the chromatographic system consisting of the mixer, tubing and detectors as a series of dispersed plug flow and continuous stirred tank reactors. The model uses loading ranges starting at 25% to a maximum of 70% of the loading capacity and hence is applicable to process scale separations. Langmuir model has been extended to include the effects of salt concentration and temperature on the model parameters. The extended Langmuir model that has been proposed uses one less parameter than the SMA model and this results in a significant ease of estimating the model parameters from inverse fitting. The proposed model has been validated with experimental data and has been shown to successfully predict peak profile for a range of load capacities (15–28 mg/mL), gradient lengths (10–30 CV), bed heights (6–20 cm), and for three different resins with good accuracy (as measured by estimation of residuals). The model has been also validated for a two component mixture consisting of the main mAb product and one of its basic charge variants. The proposed model can be used for optimization and control of preparative scale chromatography for separation of charge variants. [ABSTRACT FROM AUTHOR]

The separation of enantiomeric chiral nanotubes that can form non-covalent complexes with an unlike stability upon adsorption of chiral molecules is a process of potential interest in different fields and applications. Using fully atomistic molecular dynamics simulations, we report in this paper a theoretical study of the adsorption and denaturation of an oligopeptide formed by 16 chiral amino acids having a helical structure in the native state on both the inner and the outer surface of the chiral (10, 20) and (20, 10) single-walled carbon nanotubes having an opposite handedness, and of the armchair (16, 16) nanotube with a similar diameter for comparison. In the final adsorbed state, the oligopeptide loses in all cases its native helical conformation, assuming elongated geometries that maximize its contact with the surface through all the 16 amino acids. We find that the complexes formed by the two chiral nanotubes and the chosen oligopeptide have a strongly unlike stability both when adsorption takes place on the outer convex surface of the nanotube, and when it occurs on the inner concave surface. Thus, our molecular simulations indicate that separation of chiral, enantiomeric carbon nanotubes for instance by chromatographic methods can indeed be carried out using oligopeptides of a sufficient length. [ABSTRACT FROM AUTHOR]

Centrifugal Partition Chromatography (CPC) is a purification technique using a biphasic liquid system. As a preparative separation technique, scale-up is of primary concern. Once the separation is optimized on a lab-scale instrument, the scale-up transfer is quite straightforward simply using the instrument volume ratio as the linear transfer factor, thanks to the absence of solid support. Such linear transfer underestimates the performances of large-scale CPC rotors that are usually better than that of small rotors. It means that more material than predicted by the linear estimation could be purified. A fully practical method based on experimental observations is proposed. The first step is to determine experimentally the free space volume available between the two peaks of interest doing two analytical separations, one with the small analytical CPC instrument, giving Δ V 1 , and the second with the large preparative one, giving Δ V 2 . The second step is to determine on the small CPC instrument how much material can be loaded to reach the maximum mass load still giving the required purity and recovery ratio of the desired compound. Then, an accurate prediction of the maximal quantity of sample that the large-scale rotor can purify is simply obtained by multiplying the maximum mass load on the analytical CPC instrument by the free-space between peaks Δ V 2 /Δ V 1 ratio. For demonstration purposes, the method is applied to the transfer of the CPC separation of a synthetic three-GUESS-compound mixture from a 35 mL-rotor to a semi-prep 239-mL rotor. The paper addresses also the operating condition optimization depending on industrial production strategy (maximal load per run or maximal productivity). [ABSTRACT FROM AUTHOR]

The high performance separation and enrichment of polar phenols from aqueous matrices is often difficult due to the strong interactions between phenols and water. In this paper, carboxylated solid carbon spheres (SCSs-COOH) were, for the first time, used as a novel coating material in the solid-phase microextraction (SPME) of polar phenols at ultra-trace levels in environmental water samples. Gas chromatography coupled with tandem mass spectrometry (GC–MS/MS) was applied for sample quantification and detection. The novel SCSs-COOH-coated fiber exhibited good thermal stability (>330 °C) and higher extraction efficiency than commercial fibers in the extraction of phenols. The Plackett–Burman design was employed to optimize the extraction factors affecting the extraction efficiency through a response surface methodology. A possible phenol extraction mechanism enabled by the SCSs-COOH-coated fiber is proposed. Under the optimized conditions, low detection limits (0.26–2.63 ng L −1 ), a wide linear range (1–1000 ng L −1 ), good repeatability (2.00–9.02%, n = 5) and excellent reproducibility (2.08–8.55%, n = 3) were achieved. The developed method was validated against several environmental water samples, with satisfactory results being obtained each case. [ABSTRACT FROM AUTHOR]

The purification of therapeutic peptides is most often performed using one or more reversed phase chromatography steps. This ensures high purities while keeping the costs of purification under control. In this paper, a doped reversed phase chromatographic material is tested and compared to traditional reversed phase materials. The doping consists of adding limited amounts of ion exchange ligands to the surface of the material to achieve orthogonal separation and increase the non-hydrophobic interactions with the surface. These ionic groups can either be attractive (opposite charge), or repulsive (same charge) to the peptide. The benefit of this new doped reversed phase material is shown through increases in selectivity in diluted conditions and yield and productivity in overloaded (i.e. industrial) conditions. It is the conjectured that all performance characteristics should increase using repulsive doping groups, whereas these characteristics should decrease when using attractive doping groups. This conjecture is shown to be true through several examples, including purifications of industrially relevant peptide crudes, in industrially relevant conditions. Moreover, the effect of ionic strength and organic modifier concentration was explored and shown to be in line with the expected behavior. [ABSTRACT FROM AUTHOR]

Dual-opposite-injection capillary electrophoresis (DOI-CE) is a separation technique that utilizes both ends of the capillary for sample introduction. Depending on the individual electrophoretic mobilities of the analytes of interest and the migration distance that each analyte travels to the detection window, the elution order of analytes in a DOI-CE separation can vary widely. One consequence of a variable elution order is that co-detection of oppositely charged analytes becomes possible under certain experimental conditions. While several approaches currently exist to avoid co-detection, they are often time consuming and inefficient. This paper describes a systematic approach to easily avoid co-detection by analyzing the net mobilities of the analytes of interest to aid in choosing appropriate capillary lengths for a particular separation. Simulated electropherograms that highlight various aspects of this new approach are shown. An electropherogram from the literature is replicated and the derived relationship is applied to show the potential advantages of this new approach. [ABSTRACT FROM AUTHOR]

Solvent system selection is the first step toward a successful counter-current chromatography (CCC) separation. This paper introduces a systematic and practical solvent system selection strategy based on the nonrandom two-liquid segment activity coefficient (NRTL-SAC) model, which is efficient in predicting the solute partition coefficient. Firstly, the application of the NRTL-SAC method was extended to the ethyl acetate/ n -butanol/water and chloroform/methanol/water solvent system families. Moreover, the versatility and predictive capability of the NRTL-SAC method were investigated. The results indicate that the solute molecular parameters identified from hexane/ethyl acetate/methanol/water solvent system family are capable of predicting a large number of partition coefficients in several other different solvent system families. The NRTL-SAC strategy was further validated by successfully separating five components from Salvia plebeian R.Br. We therefore propose that NRTL-SAC is a promising high throughput method for rapid solvent system selection and highly adaptable to screen suitable solvent system for real-life CCC separation. [ABSTRACT FROM AUTHOR]

The present paper presents the mathematical expressions for the concentration enhancement which can be expected when applying a subsequent retentive trapping and strong eluent remobilization process in a packed trap column connected to the end of an analytical separation column. The established expressions for the optimal loading times, trap dimensions and expected concentration enhancement are illustrated and confirmed using numerical simulations of the trapping and release process. These simulations also provide a direct insight in how the bands are deformed and sharpened during the different steps of the process. The simulations, as well as the established expressions, for example show that in the backward elution mode the loading time should exceed a minimum value to allow the strong eluent front to fully overtake the remobilized band as this is the necessary condition to get a completely sharpened peak (in both the backward and the forward elution modes). The simulations also show it is very critical that this occurs as close as possible to the trap exit, as the bands are most sensitive to band broadening once they have been sharpened. The refocusing traps should hence be filled with particles producing the smallest possible plate heights, and connected to the detector using very short and small i.d. connection tubing. It was also found that, if there would be no band broadening in the trap, the achievable concentration enhancement would be the same for either a strong or weakly retaining trap. The true advantage of a high retention in the trap is that it leads to small trap volumes, which in turn minimizes the distance the band has to travel to reach the detector. This then minimizes the band broadening (inevitable in practice) and helps keeping a high concentration enhancement. [ABSTRACT FROM AUTHOR]

Separation of polar alkaloids by countercurrent chromatography (CCC) is challengeable due to their close partition behaviors in solvent system. In this paper, a two-stage method for isolation of epiberberine, jatrorrhizine, palmatine, coptisine, and berberine from Rhizoma coptidis was presented. The first stage separation performed on CCC was based on the principle of reactive extraction. Trifluoroacetic acid was acted as a modulator to selectively react with alkaloids, which changed their partition coefficients in solvent system. Purified epiberberine and other partially separated targets were eluted by ammonium adjusted mobile phase. In the second stage, four alkaloids were purified in pH-zone-refining CCC mode. All the targets collected were over 97% pure determined by HPLC. The method developed demonstrates performing of reactive extraction on standard CCC as an option for separation of polar alkaloids from medicinal plants. [ABSTRACT FROM AUTHOR]

Polysaccharide-derived selectors are often used in the separation of enantiomers by supercritical fluid chromatography (SFC). Their recognition patterns are normally investigated with alcohols and acetonitrile as modifiers. The present paper describes the results of a research program designed by Pfizer and Chiral Technologies Inc. to explore the potential of other solvents (i.e. ethyl acetate, tetrahydrofuran, dichloromethane) in SFC by using a series of polysaccharide-derived supports with broad solvent versatility (CHIRALPAK IA, IB, IC, ID, IE and IF). The contribution of such extended solvent range to the overall success rate, as well as to overcome racemization, solubility and stability issues was confirmed by using standard non-proprietary samples and research molecules. Elution patterns with such lower polarity solvents, compared to alcohols, and the role of the different additives were also investigated. [ABSTRACT FROM AUTHOR]

In hydrophobic interaction chromatography (HIC), interactions between buried hydrophobic residues and HIC surfaces can cause conformational changes that interfere with separations and cause yield losses. This paper extends our previous investigations of protein unfolding in HIC chromatography by identifying protein structures on HIC surfaces under denaturing conditions and relating them to solution behavior. The thermal unfolding of three model multidomain proteins on three HIC surfaces of differing hydrophobicities was investigated with hydrogen exchange mass spectrometry (HXMS). The data were analyzed to obtain unfolding rates and Gibbs free energies for unfolding of adsorbed proteins. The melting temperatures of the proteins were lowered, but by different amounts, on the different surfaces. In addition, the structures of the proteins on the chromatographic surfaces were similar to the partially unfolded structures produced in the absence of a surface by temperature as well as by chemical denaturants. Finally, it was found that patterns of residue exposure to solvent on different surfaces at different temperatures can be largely superimposed. These findings suggest that protein unfolding on various HIC surfaces might be quantitatively related to protein unfolding in solution and that details of surface unfolding behavior might be generalized. [ABSTRACT FROM AUTHOR]

This paper reports a simple chromatographic system to separate lipids classes as well as their molecular species. By the use of phenyl coated silica as stationary phase in combination with a simple mobile phase consisting of methanol and water, all tested lipid classes elute within 30 min. Furthermore, a method to accurately predict retention times of specific lipid components for this type of chromatography is presented. Common detection systems were used, namely evaporative light scattering detection (ELSD), charged aerosol detection (CAD), electrospray mass spectrometry (ESI-MS), and UV detection. [ABSTRACT FROM AUTHOR]

Aggregates of monoclonal antibody (mAb) therapeutics, due to their perceived impact on immunogenicity, are recognized as a critical quality attribute by the regulatory authorities as well as the industry. Hence, removal of aggregates is a key objective of bioprocessing. At present, this is achieved by a combination of two or more orthogonal chromatographic steps with possible modalities of ion exchange, hydrophobic interaction and mixed mode. A two-stage chromatographic purification process consisting of ion-exchange and hydrophobic interaction modes is proposed in this paper for effective and efficient control of aggregates for a mAb therapeutic. The proposed scheme does not require any intermediate processing of the process stream. Further, baseline separation is achieved for monomer and aggregates resulting in robust performance. This was possible because the proposed operational scheme allowed for an addition of selectivities of the two chromatography modes vs. the traditional two column scheme where part of the separation of aggregates achieved by the first column is lost upon pooling. The proposed process scheme yielded improved separation of aggregates (0% vs. 1–2%) at >95% recovery and reduced overall process time (6 h vs . 14 h) for a typical application. Further, clearance of host cell proteins was also shown to have improved with the suggested process scheme. Successful implementation of the proposed scheme has been demonstrated for two different monoclonal antibody therapeutic products. [ABSTRACT FROM AUTHOR]

This paper presents a photografting process of monolithic silica capillary columns based on the ene-thiol click chemistry. This study is performed on a “generic” vinyl-functionalized silica monolith ( H min 6 ± 1 μm). The photoclick reaction is investigated using different thiol monomers (octadecanethiol, cysteine and sodium mercaptoethanesulfonate) to prepare capillary columns dedicated to various chromatographic modes (reversed-phase, HILIC and strong cation exchange). Whatever the monomer used, the photografting reaction is achieved in less than 5 min with a relatively high thiol monomer content. This allows preparing highly retentive and efficient monolithic columns while avoiding polymerization and/or column clogging. In addition to the aforementioned properties (duration, versatility, efficiency), this photo-triggered chemical reaction allows addressing several appropriate surface functionalizations inside a single monolithic column in order to prepare nanovolume multimodal capillary columns. A multimodal biphasic monolithic column with a 1 cm length cation-exchange segment followed by a 9 cm length reversed-phase segment (SCX-RP) is prepared through two successive photografting reactions using a UV-mask to localize the reactions. This multimodal biphasic column is investigated using a model sample for the selective fractionation and separation of cationic and neutral compounds and is applied to the on-line preconcentration and separation of β-blockers. [ABSTRACT FROM AUTHOR]

In this paper we determine acid dissociation constants, limiting ionic mobilities, complexation constants with β-cyclodextrin or heptakis(2,3,6-tri-O-methyl)-β-cyclodextrin, and mobilities of resulting complexes of profens, using capillary zone electrophoresis and affinity capillary electrophoresis. Complexation parameters are determined for both neutral and fully charged forms of profens and further corrected for actual ionic strength and variable viscosity in order to obtain thermodynamic values of complexation constants. The accuracy of obtained complexation parameters is verified by multidimensional nonlinear regression of affinity capillary electrophoretic data, which provides the acid dissociation and complexation parameters within one set of measurements, and by NMR technique. A good agreement among all discussed methods was obtained. Determined complexation parameters were used as input parameters for simulations of electrophoretic separation of profens by Simul 5 Complex. An excellent agreement of experimental and simulated results was achieved in terms of positions, shapes, and amplitudes of analyte peaks, confirming the applicability of Simul 5 Complex to complex systems, and accuracy of obtained physical–chemical constants. Simultaneously, we were able to demonstrate the influence of electromigration dispersion on the separation efficiency, which is not possible using the common theoretical approaches, and predict the electromigration order reversals of profen peaks. We have shown that determined acid dissociation and complexation parameters in combination with tool Simul 5 Complex software can be used for optimization of separation conditions in capillary electrophoresis. [ABSTRACT FROM AUTHOR]

This paper reports a novel fluorescence chiral derivatization–liquid chromatography (LC) method for the analysis of d - and l -lactic acids (LAs) using 4-(4,6-dimethoxy-1,3,5-triazin-2-yl)-4-methylmorpholinium chloride (DMT-MM) as an enantioseparation enhancer. In this method, the dl -LAs were fluorescently derivatized with ( S )-(+)-4-( N , N -dimethylaminosulfonyl)-7-(3-aminopyrrolidin-1-yl)-2,1,3-benzoxadiazole [( S )-(+)-DBD-APy] in the presence of DMT-MM as a condensing agent. These conditions resulted in the hydroxyl group of the LA derivative being etherified by the triazine unit of DMT-MM, producing sterically bulky diastereoisomers. The resulting fluorescent diastereoisomers of d - and l -LAs could be discriminated and successfully enantioseparated through reversed-phase LC. The enhancement effect of the derivatization agent DMT-MM when using seven other commercially available chiral amines was also demonstrated. Finally, this method was successfully applied to quantification of dl -LAs in foodstuffs (yogurts and fermented milk drinks). [ABSTRACT FROM AUTHOR]

Abstract: This work focuses on the development and experimental evaluation of micromachined chromatographic columns for use in a commercial gas chromatography (GC) system. A vespel/graphite ferrule based compression sealing technique is presented using which leak-proof fluidic interconnection between the inlet tubing and the microchannel was achieved. This sealing technique enabled separation at temperatures up to 350°C on a μGC column. This paper reports the first high-temperature separations in microfabricated chromatographic columns at these temperatures. A 2m microfabricated column using a double Archimedean spiral design with a square cross-section of 100μm×100μm has been developed using silicon microfabrication techniques. The microfabricated column was benchmarked against a 2m 100μm diameter commercial column and the performance between the two columns was evaluated in tests performed under identical conditions. High temperature separations of simulated distillation (ASTM2887) and polycyclic aromatic hydrocarbons (EPA8310) were performed using the μGC column in temperature programmed mode. The demonstrated μGC column along with the high temperature fixture offers one more solution toward potentially realizing a portable μGC device for the detection of semi-volatile environmental pollutants and explosives without the thermal limitations reported to date with μGC columns using epoxy based interconnect technology. [Copyright &y& Elsevier]

Abstract: This paper reviews critically LC–MS approaches for toxicological drug screening using (ultra) high performance liquid chromatography (UHPLC) coupled to low and high resolution mass spectrometry (HRMS) published since 2010. A concluding discussion focuses on progress and current status of sample workup, separation by HPLC vs. UHPLC, MS detection modes and their specificity, universality of LC–MS libraries, and validation necessary of LC–MS for screening methods. Finally, a discussion on what the future holds for LC–MS drug screening in clinical and forensic toxicology completes this review article. [Copyright &y& Elsevier]

Abstract: In the recent years, new molecules have appeared in the illicit market, claimed to contain “non-illegal” compounds, although exhibiting important psychoactive effects; this heterogeneous and rapidly evolving class of compounds are commonly known as “New Psychoactive Substances” or, less properly, “Smart Drugs” and are easily distributed through the e-commerce or in the so-called “Smart Shops”. They include, among other, synthetic cannabinoids, cathinones and tryptamine analogs of psylocin. Whereas cases of intoxication and death have been reported, the phenomenon appears to be largely underestimated and is a matter of concern for Public Health. One of the major points of concern depends on the substantial ineffectiveness of the current methods of toxicological screening of biological samples to identify the new compounds entering the market. These limitations emphasize an urgent need to increase the screening capabilities of the toxicology laboratories, and to develop rapid, versatile yet specific assays able to identify new molecules. The most recent advances in mass spectrometry technology, introducing instruments capable of detecting hundreds of compounds at nanomolar concentrations, are expected to give a fundamental contribution to broaden the diagnostic spectrum of the toxicological screening to include not only all these continuously changing molecules but also their metabolites. In the present paper a critical overview of the opportunities, strengths and limitations of some of the newest analytical approaches is provided, with a particular attention to liquid phase separation techniques coupled to high accuracy, high resolution mass spectrometry. [Copyright &y& Elsevier]

Abstract: A method for the determination of five polyether ionophores in urban sewage sludge has been developed. The extraction of compounds was performed by pressurised liquid extraction using acetone, while florisil was used for in-cell clean-up to minimise the matrix effect in the sludge extracts. An amide polar-embedded reversed-phase column was used for the chromatographic separation with a rapid-resolution liquid chromatograph coupled to a tandem mass spectrometer. Moreover, several clean-up strategies such as in-cell and on-cell clean-up and solid-phase extraction clean-up, among others, were tested and their results are discussed in the present paper. Recoveries (10 and 250μg/kg in dry weight (d.w.), n =6) were close to 90%, repeatability and reproducibility (%RSD, 10 and 250μg/kg (d.w.), n =6) were less than 10% and12%, respectively. Limits of detection (LODs) and limits of quantification (LOQs) ranged between 0.5 and 1μg/kg (d.w.) and between 1 and 5μg/kg (d.w.), respectively. The method was applied to samples collected in five sewage treatment plants in Catalonia. Monensin and narasin were determined in some sludge samples at concentrations from

Abstract: Chromatographic modelling can be used to describe and further understand the behaviour of biological species during their chromatography separation on adsorption resins. Current modelling approaches assume uniform rate parameters throughout the column. Software and hardware advances now allow us to consider what can be learnt from modelling at bead level, enabling simulation of heterogeneity in bead and packed bed structure due to design or due to changes during operation. In this paper, a model has been developed to simulate at bead level protein loading in 1.5μl microfluidic columns. This model takes into account the heterogeneity in bead sizes and the spatial variations of the characteristics of a packed bed, such as bed void fraction and dispersion, thus offering a detailed description of the flow field and mass transfer phenomena. Simulations were shown to be in good agreement with published experimental data. [Copyright &y& Elsevier]