Enantioselective separation of amino acids as biomarkers indicating life in extraterrestrial environments

Traces of prebiotic amino acids, i.e., the building blocks of proteins, are excellent biomarkers that could provide evidence of extinct or extant life in extra-terrestrial environments. In particular, characterization of the enantiomeric excess of amino acids gives relevant information about the biotic or abiotic origin of molecules, because it is generally assumed that life elsewhere could be based on either l or d amino acids, but not both. The analytical procedures used in in-situ space missions for chiral discrimination of amino acids must meet severe requirements imposed by flight conditions: short analysis time, low energy consumption, robustness, storage for long periods under extreme conditions, high efficiency and sensitivity, automation, and remote-control operation. Such methods are based on gas chromatography, high-pressure liquid chromatography, and capillary electrophoresis, usually coupled with mass spectrometry; of these, gas chromatography–mass spectrometry (GC–MS) is the only such combination yet used in space missions. Preliminary in-situ sample derivatization is required before GC–MS analysis to convert amino acids into volatile and thermally stable compounds. The silylation reagent most commonly used, N-(tert-butyldimethylsilyl)-N-methyltrifluoroacetamide, is unsuitable for detection of homochirality, and alternative derivatization techniques have been developed that preserve the stereochemical configuration of the original compounds and are compatible with spaceflight conditions. These include the reagent N,N-dimethylformamide dimethylacetal, which has already been used in the Rosetta mission, a mixture of alkyl chloroformate, ethanol, and pyridine, a mixture of perfluorinated anhydrides and perfluoro alcohols, and hexafluoroacetone, the first gaseous derivatizing agent. In all the space instruments, solvent extraction of organic matter and chemical derivatization have been combined in a single automatic and remote-controlled procedure in a chemical reactor. Liquid-based separation systems have been used in space missions. In particular, microchip capillary electrophoresis, based on microfluidic lab-on-a-chip systems, enables high-performance chemical analysis of amino acids with low mass and volume equipment and low power and reagent consumption. Coupling with laser-induced fluorescence detectors results in ultra-low limits of detection. This critical review describes applications of the on-board instruments used in the Rosetta mission to comets and in the more recent Mars exploration program, i.e., the Mars Science Laboratory and ExoMars missions.

Stability Studies of UV Laser Irradiated Promethazine and Thioridazine after Exposure to Hypergravity Conditions

Pharmaceuticals carried into space are subjected to different gravitational conditions. Hypergravity is encountered in the first stage, during spacecraft launching. The stability of medicines represents a critical element of space missions, especially long-duration ones. Therefore, stability studies should be envisaged before the implementation of drugs for future deep space travel, where the available pharmaceuticals would be limited and restocking from Earth would be impossible. Multipurpose drugs should be proposed for this reason, such as phenothiazine derivatives that can be transformed by optical methods into antimicrobial agents. Within this preliminary study, promethazine and thioridazine aqueous solutions were exposed to UV laser radiation that modified their structures and generated a mixture of photoproducts efficient against particular bacteria. Subsequently, they were subjected to 20 g in the European Space Agency’s Large Diameter Centrifuge. The aim was to evaluate the impact of hypergravity on the physico-chemical and spectral properties of unirradiated and laser-irradiated medicine solutions through pH assay, UV-Vis/FTIR absorption spectroscopy, and thin-layer chromatography. The results revealed no substantial alterations in centrifuged samples when compared to uncentrifuged ones. Due to their stability after high-g episodes, laser-exposed phenothiazines could be considered for future space missions.     

Microemulsion electrokinetic chromatography – or solvent-modified micellar electrokinetic chromatography?

An overview of the microemulsion electrokinetic chromatography technique and its fields of applications in analytical chemistry are given. The separation mechanisms involved are discussed and the technique is compared to solvent-modified micellar electrokinetic chromatography.     

Raman spectra of pure biomolecules obtained using a handheld instrument under cold high-altitude conditions

A handheld Raman spectrometer (Ahura First Defender) was tested for the unambiguous identification of biomolecules (pure amino acids, carboxylic acids, saccharides and trehalose) in the solid state under outdoor conditions (including moderate climate conditions as well as cold temperatures and high altitudes). The biomolecules investigated represent important objects of interest for future exobiological missions. Repetitive measurements carried out under identical instrumental setups confirmed the excellent reliability of the Raman spectrometer. Raman bands are found at correct wavenumbers ±3 cm⁻¹ compared with reference values. This testing represents the first step in a series of studies. In a preliminary, challenging investigation to determine the detection limit for glycine dispersed in a powdered gypsum matrix, 10% was the lowest content confirmed unambiguously. Clearly there is a need to investigate further the detection limits of Raman spectroscopic analyses of biomolecules in more complex samples, to demonstrate the usefulness or disqualify the use of this technique for more realistic outdoor situations, such as eventual future missions to Mars.     

The ring-air technique: An alternative to the ring-oven technique in circular thin-layer chromatography

A technique is described in which a ring of air is used to produce sample concentration by solvent evaporation on high-performance thin-layer chromatography plates. The technique is compared to the ring-oven technique and both are evaluated by using a dye mixture. Both techniques are employed to reduce the size of relatively large spots on the plates in an attempt to match the resolution obtained from small spots in circular chromatography.     

Centrifugal partition chromatography – A review of recent applications and some classic references

Countercurrent chromatography, based on liquid–liquid partitioning, has many technological variants. One of them is centrifugal partition chromatography, introduced by Wataru Murayama and Kanichi Nunogaki in 1982. This technique, like other countercurrent chromatography techniques, is based on the phenomenon of liquid–liquid partitioning between two immiscible liquid phases that stay at equilibrium. But the significant difference between this technique and others is the retention mechanism of stationary phase. In the case of centrifugal partition chromatography, this mechanism is based on hydrostatic force, formed by the centrifugal field in the rotor in one‐axis centrifuge. Sometimes that allows more control of stationary phase, for example, when aqueous two‐phase and other difficult solvent systems are used. However, the efficiency of the separation in centrifugal partition chromatography is also affected by a variety of parameters dependent on the sample properties in the solvent system, physical properties of the solvent system, parameters of the instrument, and the method. This article includes also recent ideas for improvements to the technique and broadening its application (e.g., (multiple) dual‐mode or elution–extrusion procedure, pH‐zone‐refining centrifugal partition chromatography, ion‐exchange centrifugal partition chromatography, online and offline coupling of centrifugal partition chromatography).     

Real-time control of column switching in multidimensional gas chromatography

In chromatography the separation power expressed in terms of peak capacity can be greatly enhanced by multidimensional techniques. The most important aspect of multidimensional chromatography is the precise location of the heart-cut window. Very often the reliability of this positioning is ensured by applying relatively large heart-cuts; this reduces the intrinsic selectivity offered by the technique. The best way of locating peaks in chromatography is by means of retention indices. This technique can also be used in multidimensional chromatography. A method is described whereby the heartcut window in multidimensional gas chromatography (MDGC) can be defined precisely.     

High-performance affinity chromatography

High-performance affinity chromatography is a new technique for the fast and efficient purification of biologically active molecules. It combines the biospecificity of affinity chromatography with the high speed and resolution obtained in high-performance liquid chromatography. In particular, the immobilization of ligands to different silica derivatives and their suitability for high-performance affinity chromatography are discussed.     

Phosphorescence in liquid solutions: a promising detection principle in liquid chromatography and flow injection analysis

A new detection technique for liquid chromatography and flow injection analysis has been developed. The technique is based on the phosphorescence of biacetyl in various eluents. It can be applied in two modes, i.e. sensitized and quenched phosphorescence. Especially the latter is widely applicable for instance to non-absorbing compounds as measured in ion chromatography.     

Biomonitoring of xenobiotics by planar chromatography (thin-layer chromatography)

The classical chromatographic technique, thin-layer chromatography (TLC), has been outpaced for some time by the more recent techniques of high-performance liquid chromatography (HPLC) and gas chromatography (GC). Recently, improved TLC layers, reliable spotting devices, new derivatization reagents, sophisticated chromatographic equipment and simple mathematical procedures for evaluation have become available and accepted. There seems to be a trend in many laboratories to re-introduce this classical but still young technique for quantitative analysis. Some of the facets involved and experiences from our laboratory are discussed in this article.     

高效液相色谱技术在代谢组学研究中的应用

高效液相色谱技术逐渐广泛应用于代谢组学的研究中。迄今为止,该技术已经在不同生理状态的生物体液的代谢指纹谱分析中得到了应用。本文评述了传统高效液相色谱技术、毛细管技术和超高效液相色谱等技术在代谢组学的应用。     

Simultaneous correlation chromatography,a new technique applied to calibration in high-performance liquid chromatography

Simultaneous correlation chromatography (SCC) is introduced as a technique capable of analyzing several different samples simultaneously on the same chromatographic column. The theoretical basis of the technique is outlined and a computer simulation demonstrates the feasibility of the method. The advantages and potential of the technique are discussed. The technique is applied experimentally in a calibration procedure for high-performance liquid chromatography. During the calibration, unknown sample and calibration standards are processed under the same conditions, resulting in very accurate calibration. Other applications are outlined.     

Recent methodological and instrumental development in MEKC

The review gives an update about the methodological and instrumental developments in micellar electrokinetic capillary chromatography as a type of CE analytical technique. Here, the last two years development of the technique are particularly presented. Recent approaches to improve sensitivity are discussed. Newly introduced concentration techniques and experimental methods for verification of the different mechanisms and processes of micellar electrokinetic chromatography analysis are highlighted. A theoretical model to explain changes in separation and electrophoretic mobility order of fully charged analytes are demonstrated. Modern approaches for improving compatibility of micellar electrokinetic capillary chromatography to mass spectrometry are also reported.     

Preparative argentation reversed-phase high performance liquid chromatography

In this study, a preparative chromatography method named preparative argentation reversed-phase high performance liquid chromatography (Ag-RP-HPLC) was developed by adding silver ion to the mobile phase of preparative HPLC. Firstly, an analytical Ag-RP-HPLC method was developed, and the effects of silver content and acid content in the mobile phase on the column efficiency were studied. Based on the method of linear amplification, a preparative Ag-RP-HPLC technique with optimized separation conditions was developed. The new technique was applied successfully to the separation of the unsaturated aliphatic acid amide isomers contained in Asarum forbesii Maxim. Compared with the commonly used technique of argentation normal phase chromatography, this method with little solvent consumption is simple, fast, efficient, and flexible for the isolation and purification of the unsaturated compounds.     

Safer Solvent Blends for Food,Dye, and Environmental Analyses Using Reversed-Phase High Performance Liquid Chromatography

Chromatographia - Liquid chromatography (LC) is a technique widely used to identify and quantify organic compounds in a complex mixture. Typical operations of high-performance liquid chromatography...     

亲和色谱纯化蛋白质新进展

通过对３５篇文献的综述,介绍了亲和色谱技术的新进展     

Characterization and classification of stationary phases in HPLC and SFC – a review

Packed column supercritical fluid chromatography (pSFC) is an attractive technique in drug discovery related analysis because it offers several advantages over the more commonly used high-performance liquid chromatography (HPLC) technique. The environmental-friendly CO₂ mobile phase, the high-throughput capacity, the increased efficiency and the lower operational costs give SFC additional benefits over HPLC in analysis related to drug development. The latter technique is well established and has been used for decades in the pharmaceutical industry. On the other hand, SFC is still in its infancy, even though the technique has been known for decades and researchers are still discovering the possibilities and limitations of this technique.     

Thermal aqueous liquid chromatography—the TALC technique

Thermal Aqueous Liquid Chromatography (TALC) using pure water as a mobile phase should be a very attractive technique promoting the use of liquid chromatography in routine analysis, either in the laboratory or in future on-line process control. This simple form of chromatography, the selectivity of which depends on the fixed phase only, would allow the use of flame ionization as an almost universal, low-cost detector in liquid chromatography. The potential of the TALC technique is illustrated by selected examples.     

Measurement of anions in ambient particulate matter by ion chromatography: A novel sample preparation technique and development of a generic uncertainty budget

A novel sample preparation technique for the measurement of anions in particulate matter by ion chromatography is presented. The technique uses the eluant from the ion chromatography analysis stage to perform the extraction of the anions from the particulate matter. The demonstrated advantages of the new technique are manifold: faster sample throughput, minimised sample preparation, and a matrixed-matched sample for analysis. The repeatability of the technique has been tested using nominally identical ambient particulate matter samples (sub-sampled from one large filter) and the uncertainty of the technique has been estimated. The uncertainty estimate is transferable to other similar methods used to measure ions in particulate matter. Real data obtained using the new method are also presented.     

Complementary information from isotachophoresis and high-performance liquid chromatography in peptide analysis

Reversed-phase high-performance liquid chromatography is a valuable analytical technique to support the synthesis, isolation and purification of peptides, as is illustrated by some critical separations. In addition to this technique, capillary isotachophoresis can give useful information on the purity determination of peptides and on the presence of ionic compounds of a non-peptidic nature. With regard to the latter aspect, isotachophoresis proved to be a suitable technique as a check on the effective removal of salts after preparative high-performance liquid chromatography.