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The article focuses on the International Symposium on Hyphenated Techniques in Chromatography and Separation Technology (HTC-18), scheduled for May 28—31st, 2024, in Leuven, Belgium, serving as a significant meeting point for scientists and practitioners to exchange knowledge.

The challenges we face in troubleshooting problems with liquid chromatography (LC) separations are highly diverse. This month we take a closer look at topics that have garnered more attention recently. [ABSTRACT FROM AUTHOR]

Several new materials and columns have been introduced in recent years for size-exclusion separations of proteins. How do I know which one to choose, and which separation conditions will be the best for my protein separation?. [ABSTRACT FROM AUTHOR]

Comprehensive two-dimensional gas chromatography (GC x GC) offers significant improvement for volatile chemical separation. Selecting suitable first (¹D) and second dimension (²D) columns normally requires consideration of the chemical composition of a sample. Replacing one of these dimensions with a two-column ensemble (for example, ¹D1 + ¹D2 for the ¹D column), provided with a pressure tuning makeup gas between them, varies the relative retentions of compounds before the modulation step according to the junction pressure. This makes it possible to alter the apparent polarity of the ¹D ensemble, and this alters peak positions in the 2D GC x GC space. This article presents an account of studies that suggest this offers potential for improved operation for a GC x GC laboratory. [ABSTRACT FROM AUTHOR]

Compared to the progress made in reversed phase separations in terms of speed and efficiency, chiral chromatographers have traditionally focused on improving the selectivity of enantiomeric separations by synthetic procedures. As a result, more than 50 different types of advanced chiral stationary phase chemistries are available today. Traditionally, speed and efficiency of chiral chromatography has not received attention until recently. With the availability of superfi cially porous particles and sub-2-μm particles, sub-minute enantiomeric separations have been achieved with the help of improved particle technology with narrow size distribution, and systematic studies on packing columns. This article covers advances made in the fi eld of ultrafast chiral chromatography in the last decade. The development of instrumentation technology has also contributed immensely to making sub-second chiral separations a reality. Enantiomeric separations can now compete with the speed of sensors. Future directions and unanswered questions in the fi eld of ultrafast enantiomeric separations are highlighted. [ABSTRACT FROM AUTHOR]

LC practitioners are faced with an overwhelming number of choices for fittings that can be used to connect the components of LC systems. Users must ultimately decide which fitting technology offers the best compromise of performance and cost for each particular situation. For dedicated LC systems where system reconfiguration is infrequent-and especially for connections between instrument components excluding the column- traditional metal, ferrule-based fittings usually offer the best compromise of cost, reliability, and quality of connections. For connections to columns, particularly when changing columns frequently, reusable fittings that do not involve swaging of a metal ferrule to the capillary are very convenient. Technologies introduced by several manufacturers over the past few years have improved the design of these reusable fittings, and now enable repeated connections of high quality and at very high pressures using a single fitting. These technologies come at increased costs, but the performance gains and ease of use they provide will outweigh the costs in many practical situations. [ABSTRACT FROM AUTHOR]

Comprehensive two-dimensional liquid chromatography (LC×LC) is a powerful technique for separating highly complex samples. However, the proliferation of this technique is hindered by a range of challenges, including the possible impact of the additional separation on the detection sensitivity, concerns that mobile phase incompatibility problems will limit the applicability, and the complexity of the system and associated method development costs. This article addresses these issues and describes how modern modulators and software tools are overcoming the barriers associated with this technique. [ABSTRACT FROM AUTHOR]

The article focuses on the development in the liquid chromatography instruments with the introduction of fully porous particles rather than the old columns. It discusses how the ultra high-performance liquid chromatography (UHPLC) should be improved with separation quality and operating pressure, and analyze the separation performance while applying kinetic plot methodology.

This instalment in our series on ultrahigh-pressure liquid chromatography (UHPLC) highlights its benefits in fast analysis, high-resolution separations, high performance liquid chromatography (HPLC) method development, reduced solvent and sample usage, and enhanced sensitivity and precision performance. [ABSTRACT FROM AUTHOR]

Dual flow chromatography (DFC) separations are performed with back and forth flow for rapid method development, design of experiments (DOE), quality-by-design (QbD), or high-throughput chromatographic purification. Although different than conventional unidirectional flow through chromatography, chromatographic principles still control the separations. Selectivity coefficients and Langmuir adsorption isotherms control the separation chemistry properties of the column and dictate the mobile phase conditions needed to achieve separation. However, the kinetic rates of diffusion and interaction of mobile phase molecules with the stationary phase, column channeling, and other column properties are not germane to the practice of DFC. Chromatographic conditions developed with DFC can be scaled to any size, including laboratory and industrial preparative columns. One practical use of DFC is in the pharmaceutical industry where multidimensional method development and high-throughput, parallel processing has been used to improve R&D productivity and decrease the time to manufacturing of biopharmaceutical drugs. [ABSTRACT FROM AUTHOR]

The article offers information on a study on the comparison of the separation speed of gas chromatography (GC), liquid chromatography (LC), and supercritical fluid chromatography (SFC). Topics discussed include using the kinetic plot method neglecting differences in viscous heating or extra-column band broadening; obtaining fixed length kinetic plot curves; and role of thermodynamic resistance factor in LC.

The article focuses on using the chromatography fundamentals on liquid chromatography (LC) separations in order to increase resolution (R s). Topics discussed include retention factor (k) influences on resolution, increase in K due to increase in retention time, and effect of percentage change in organic content of the mobile phase to find optimized separation.

Interfering peaks or high baseline background can compromise the results of gradient liquid chromatography (LC) separations. [ABSTRACT FROM AUTHOR]

A theme for The Chromatographic Society Diamond Jubilee Year is to increase public awareness of chromatography. Often the general public, and even chromatographers themselves, fail to appreciate the importance of chromatography. Here Tony Edge, The Chromatographic Society Vice-President, discusses just how much chromatography underpins everyday life. [ABSTRACT FROM AUTHOR]

A popular feature of The Chromatographic Society's Golden Jubilee publication was an article by Waters describing their heritage and setting out their contributions to the development of chromatography. In this special feature, some of the companies who are regular exhibitors at Society events answer questions on the current and future status of chromatography. [ABSTRACT FROM AUTHOR]

The article presents several terms related to gas chromatography. These include the Active flow technology, a concept that merge two types of column designs, the curtain flow technology and the parallel segmented flow. It notes the active site, a strong attracting site on the surface of chromatographic packing. It mentions the adsorption chromatography, a basic separation mode that relies on adsorption method to effect a separation.

The article presents suggestions to prevent the early demise of liquid chromatography (LC) columns. It is noted that somewhere around 500-600 dollars is the typical cost of reversed-phase column. It is mentioned that even though the price of an individual column still seems high, nothing much has been done to reduce the cost of analysis.

The article discusses the effect of using an injection solvent that is stronger or weaker than the mobile phase for liquid chromatography separation. Topics discussed include the allowed injection volume for a peak or a given retention and the concept of a sample plug injected in mobile phase as the injection solvent as it moves through the column. Also mentioned is the initial slowdown of molecules relative to their normal phase migration rates when the solvent is weaker than the mobile phase.

The past and future development of analytical supercritical fluid extraction (SFE) is traced in terms of experimental strategies, applications, vendor support, and timely acceptance of the existing technology. The current state of the art is compared with research activity in the 1980s. New vendor activity, in terms of automation and hyphenation with chromatographic separations, is discussed. [ABSTRACT FROM AUTHOR]

The article examines gas chromatography (GC) separations using long-distance running as a metaphor. It discusses the attributes shared by long-distance runs and chromatography separations, such as a long, narrow course and a chromatography column, runners and solute molecules, and segregation of runners into groups and the formation of discrete peaks. The basic elements of chromatography experiment, namely flow, diffusion, and retention, are explored.

In this article, the author focuses on isoseparation method based on gradient elution chromatography (LC). He discusses the nature of isocratic separation. He mentions that the method is intuitive and it can be used to make changes in separation. He states that chromatographers prefer isocratic separation method due to its intuitive nature.

Comprehensive two-dimensional chromatography necessitates additional nomenclature over and above that used In classical one dimensIonal (10) chromatography. The use of two (or more) columns requires various parameters on these separate dimensions to be adequately identified. This Is achieved by use of a superscript preceding the respective symbol. Also, the process of coupling different dimensions leads to sp.ciftc terminology, which we report here. A number of recent examples where specific nomenclature related to retention indices, estimation of first dimension retention times, and the definition of modulation ratio, are included. This article and its predecessor alms to establish a basis for suitable nomenclature and conventions in this rapidly advancing area. [ABSTRACT FROM AUTHOR]

Solid-phase microextraction (SPME) was originally introduced as a solvent-free sample preparation technique ideally suited for analysis of fragrance compounds and environmental pollutants requiring gas chromatographic (GC) analysis. Introduction by thermal desorption into a standard GC injector helped to make this technique widely used. Its applicability for additional compound classes including pesticides, drugs and endogenous chemicals requiring liquid chromatographic (LC) analysis was demonstrated later, where the desorption of extracted analyte into a minimal volume of solvent compatible for injection into LC instrumentation was employed. Recently, new SPME sorbent phases have been introduced to further broaden the range of applications of the technology, and facilitate both on-site and in vivo sampling and sample preparation for dynamic living systems. This article briefly introduces the theory relevant to such applications and provides examples of its use. [ABSTRACT FROM AUTHOR]

The article discusses the development of a gas chromatography/mass spectrometry (GC-MS) analyser to address the need for more sensitive catalyst poisoner analysis. It combines the power of chromatographic separation and backflush/Dean's heart-cut capabilities of a classic oxygenate analyser. Its suitability for catalyst poisoner analysis is evaluated by direct injection of oxygenate standard. It is found to have the capability to expand the application range of catalyst contaminants analyser.

The article focuses on the selection of column types in solving problems related to liquid chromatography (LC) separations. According to the author, in selecting column types, users could change the stationary phase from C18 columns to embedded polar phase and they could also use the column database on the website of the U.S. Pharmacopoeia. It also concludes that to leverage gains, change is more effective if it employs a different stationary phase and foreknowledge of selectivity differences.

The article offers tips on the application of ultrahigh-pressure liquid chromatography (UPLC) system. It mentions the tips to maintain the cleanliness of UPLC columns including the need to locate the source of particulate matter and the observation for microbial growth. It notes the effects of pressure on the UHPLC system such as faster separations on higher pressure for columns.

Monolith pioneer, Frantisek Svec, brings readers up to date on the latest developments in monoliths for use in chromatography. Breakthroughs in the organic monoliths include phases for small molecule separations, nanoparticle-modified surfaces, new approaches to polymeric monoliths and design of monolithic layers. Less common inorganic monoliths are highlighted. Finally, commercial sources for monolith technology are covered for those who would like to purchase rather than synthesize their columns. [ABSTRACT FROM AUTHOR]

The combination of the small particle size and narrow particle size distribution coupled with the significantly shorter diffusion path provided by the Kinetex core-shell particle results in a material that yields significantly increased column efficiencies and chromatographic resolution. This is a significant benefit for separation scientists looking to increase efficiency and chromatographic resolution, especially for complex separations containing many compounds and very closely eluting compounds so that accurate identification and quantification can be achieved. [ABSTRACT FROM AUTHOR]

Detectors are another link in the chain of signals that a chromatographic analysis generates. After separation, a detector transduces the chemical signals of eluted analytes to an electrical signal that is then recorded and measured. The identities and amounts of analytes are determined from this information. This month in "GC Connections", John Hinshaw examines the environment, set-up and operating conditions necessary to ensure high gas chromatography detector performance and reliability. [ABSTRACT FROM AUTHOR]

Various modes of capillary electrochromatography (CEC) for the separation of enantiomers on immobilized cyclodextrin derivatives are described. The following techniques have been used: (i) open-tubular electrochromatography (o-CEC), (ii) packed electrochromatography (p-CEC) and (iii) monolithic electrochromatography (rod-CEC). Three different strategies to prepare enantioselective cyclodextrin-coated chiral monoliths are described. The advantages and disadvantages of the various methods are outlined. [ABSTRACT FROM AUTHOR]

Many HPLC analyses could be performed at lower expenditure. This could involve a combination of reducing the analysis time, reducing the resolution between critical peaks, and lowering the consumption of mobile phase. Successfully optimizing the method in such instances - as well as in situations where it is necessary to transfer the method to Another laboratory that lacks the same selection of Columns - can save the analyst time and money. [ABSTRACT FROM AUTHOR]

This article investigates the different methods that can be used to compare the performance of liquid chromatography (LC) columns to assess the advantage of using them at high pressures and/or high temperatures. The main focus is on the kinetic plot method. This method, which is based on two simple equations, allows the user to transform the more common Van Deemter curve into a curve describing the ultimate separation speed as a function of the required plate number, or the required peak capacity or the required resolution. [ABSTRACT FROM AUTHOR]

Sub-2 pm particle liquid chromatography (LC) columns were applied to generate fast and high-resolution separations for a wide range of chemical compounds ranging from small molecules to high-molecular- weight polymers. Examples include separation of styrene-acrylonitrile (SAN) copolymers, ultra-fast analysis of additives and high-resolution oligomer separations of epoxy resins. In addition ultra-fast LC separations at critical conditions (LCCC) are shown for solid epoxy oligomers. The effect of column coupling on separation efficiency is investigated for high-resolution oligomer separations. Advantages and limitations of high-temperature operation are discussed and a perspective on future developments in high-speed LC is presented. [ABSTRACT FROM AUTHOR]

The article examines some of the improved resolution of liquid chromatographers methods for its faster separation. Equation 1 has been used to develop a separation with the necessary resolution, where it will adjust the column parameters to increase or decrease resolution to fit the target value of marginal separation. It is useful to spend a little extra time during the method development to obtain a method with more resolution and trade some excess resolution for shorter run times.

The article examines several activities of some leading separation science research institutes in Austria. One group is the Institute Chemistry and Radiochemistry which simplifies sample preparation technique to isolate trace components from complex environmental to allow interference-free chromatographic measurements. Other groups include the Institute of Analytical Chemistry, Institute of Chemistry-Analytical Chemistry, and Center for Analytical Chemistry.

The article presents the activities related to chromatography within research institutes in Northern Europe. The research team of the Vytautas Magnus University in Kaunas Lithuania which is led by Audrius Maruška is focusing on the development and evaluation of stationary phases and microseparation. The research group of Susanne K Wiedmer at the University of Helsinki in Finland is focusing on the deeper understanding of the interactions taking place in biomembranes.

This article describes the factors that affect the selection of columns for two-dimensional (2D) LCxLC separations. The maximum increase in peak capacity compared with single-dimension (1D) separations is obtained by using "orthogonal" systems employing various combinations of separation mechanisms to provide as different separation selectivities as possible for the sample compounds in the first and in the second dimension systems. To obtain best results, matching the chemistry of the stationary phase, column dimensions and mobile phases in the first and in the second dimensions is essential for successful separations, especiall for comprehensive LCXLC. [ABSTRACT FROM AUTHOR]

The article discusses various research performed in separation science by research groups in France. One research investigates on the screening of metal/ligand using separation techniques and the development of new supports-based metal affinity. Another research group aims to discover and characterize new peptides and work on the analysis of complex mixtures. A research team intends to develop analytical systems for the analysis of complex samples and organic mixtures.

Over the years, LC instrumentation has undergone continuous development in pursuit of greater performance. More recently, the focus of progress has been on shorter run times, as a direct response to greater user demand to perform faster chromatographic analyses, particularly for their LC-MS applications. This has led to separations on short (30–50 mm) columns with a small internal diameter (i.d. ∼2.0 mm), packed with small particle size phases (1.5–3.0 pm). The trend for smaller column particle size has now reached a practical limit on current hardware and innovative technological solutions for further gains in performance are required. Several manufacturers offer fast LC instruments designed for greater productivity, while maintaining low carryover, high sample capacity, resolution and reliability. With ultra-fast run times of under 1 minute, these companies have achieved increased throughput using contrasting technological approaches. Here we examine the background to this current trend, the current state of analytical instrumentation and the possible future ways forward. [ABSTRACT FROM AUTHOR]

Size-exclusion chromatography (SEC) — also known as gel permeation chromatography (GPC) — is the standard technique used to characterize macromolecules in solution. In this article GPC is employed to measure membrane performance parameters such as retention behaviour, pore size and molar mass cut-off. This method relies on the filtration behaviour of the membranes. The applicability to different kinds of membranes is described. [ABSTRACT FROM AUTHOR]

This article reveals the first liquid chromatography (LC) separations performed on a microfabricated pillar array column under pressure-driven conditions. The pillars were non-porous and produced using a Bosch-type deep reactive ion etch (DRIE) to pattern the surface of a silicon wafer and had a diameter of approximately 5 pm. Two different packing densities were compared: one similar to the packing density of a packed bed (external porosity of approximately 49%) and one similar to the packing density of monolithic columns (external porosity of approximately 70%). The most densely packed pillar array yielded plate heights between 0.9–4.9 μm (depending on the degree of retention of the employed coumarin test compounds). This is considerably smaller than for a packed bed column filled with particles with the same diameter, demonstrating the large potential advantages of ordered pillar array columns compared with the much more random structure of packed beds. The main obstacle to developing this new type of column technology at the moment is the lack of reproducible coating procedures. [ABSTRACT FROM AUTHOR]

This article describes and compares a number of approaches to increase the speed of liquid chromatographic separations. On a standard LC column, a gain of a factor two in the run time (from 10 to 5 minutes) was achieved by increasing the flow-rate two-fold. On a monolithic column, a column operated at high temperature (120 °C) and a short column, flow-rates could be increased typically five-fold, resulting in run times in the order of 2 minutes. This was accompanied by a sometimes considerable loss in separation efficiency. A combination of a very short run time and unaffected separation efficiency was realized on a UPLC system, designed for use at higher pressure. By working at approximately 800 bar, the analytes could be well separated within 30 seconds. [ABSTRACT FROM AUTHOR]

Capillary gas chromatography (GC) is a well-established separation technique. Rick Parmely reviews some of the capillary column basics by investigating a standard test mixture and observing some of the chromatographic effects that can affect peak response, peak shape and column bleed. He provides guidelines for obtaining the best performance from a capillary column. He discusses peak tailing, column overload, ghost peaks and column bleed and speculates on "when to give up." He concludes with a set of fundamental steps to be used in achieving better GC analyses. [ABSTRACT FROM AUTHOR]

This article presents an overview of the work performed to define generic separation strategies and methods in chiral method development using capillary electrochromatography as a separation technique. Polysaccharide chiral stationary phases were found suitable for this purpose. Two separate strategies were defined, one for acidic and one for non-acidic substances. These strategies were evaluated and found applicable on structurally diverse molecules, showing their generic character. [ABSTRACT FROM AUTHOR]

This article discusses the contents of a gas chromatography method. A chromatography method consists of three major parts including sample preparation, component separation and data handling. A chromatography method should capture a snapshot of all the information that would be necessary to recreate the analysis at a later date. There will always be instrument dependent disparities in the contents of a method. Different instruments are controlled in different ways, and there is imperfect cross-model uniformity in the name, number, range and function of many instrument parameters. Modern data systems have the capability to provide much of the information and store it in appropriate places.

Focuses on the offer of high separation power by modern planar chromatographic techniques. Application of two-dimensional planar arrangements, chromatoplates with different properties; Potential of multidimensional planar chromatographic techniques.

Focuses on separation efficiency of capillary gas chromatography, complemented by hardware and detectors. Complexity of resolution on any chromatographic phase; Exacerbation of compounds present at trace amounts; Use of selective element specific detectors for positive compound identification.

Discusses calibration in chromatography. Importance of residual standard deviation in estimating the prediction interval and uncertainty of the result; Determination of the standard deviation of a signal at its lowest and highest concentration.

Part II. Investigates the baseline disturbances in chromatographic systems with refractive index detection using acetonitrile-water mixtures on amino-phase columns. Role of minor fluctuations in the column thermostat in causing composition fluctuations in the column effluent; Correlation between the magnitude of these composition fluctuations and the time derivative of the temperature fluctuations.

Ecdysteroids are insect moulting hormones that regulate metamorphosis. Coincidentally, these compounds also show therapeutic benefits in both humans and animals. Some, particularly 20-hydroxyecdysone, are found at surprisingly high levels in certain plants, which have subsequently been subjected to intensive research as the possibility of their use in health preparations is investigated. Research on plant ecdysteroids (phytoecdysteroids) includes the analysis of known and new substances (hitherto unknown ecdysteroids), and isolation of known and new compounds. In this article the use of high performance liquid chromatography, thin-layer chromatography and classic column chromatography of ecdysteroids will be discussed. [ABSTRACT FROM AUTHOR]