Séparation de produits pharmaceutiques par chromatographie en phase liquide à haute performance: Influence de l''eau. II.

The use of ternary solvent systems as mobile phases in combination with highly efficient chromatographic columns is of particular interest for the analysis of pharmaceutical and biological compounds. The solute-silanol group interactions decrease when the eluent is blended with water. Good selectivities are found with such systems.     

Analysis of alkaloids from different chemical groups by different liquid chromatography methods

Alkaloids are biologically active compounds widely used as pharmaceuticals and synthesised as secondary methabolites in plants. Many of these compounds are strongly toxic. Therefore, they are often subject of scientific interests and analysis. Since alkaloids — basic compounds appear in aqueous solutions as ionized and unionized forms, they are difficult for chromatographic separation for peak tailing, poor systems efficiency, poor separation and poor column-to-column reproducibility. For this reason it is necessity searching of more suitable chromatographic systems for analysis of the compounds.     

Systematic search for surrogate chromatographic models of biopartitioning processes

A systematic approach for identifing surrogate chromatographic models for biopartitioning processes is described. The method is based on a comparison of the system constant ratios of the solvation parameter model for biopartitioning processes and a database of system constant ratios for reversed-phase liquid chromatographic and micellar electrokinetic chromatographic systems compiled from literature sources. An acceptance filter of < or = 0.2 is applied for each difference in system constant ratio for the compared systems to provide a reasonable probability of success without outputting too many systems with limited predictive properties. Surrogate chromatographic models identified for the non-specific toxicity of neutral organic compounds to the fathead minnow and the soil-water distribution constant are tested by construction of a correlation model for the characteristic property of the biological process and the chromatographic retention factors for a structurally varied group of compounds. Although these models are not the best that could be obtained based on ranking of the differences in system constant ratios the predictive ability of the correlation models is suitable for typical applications and similar to the accepted uncertainty in the measurements of the biological property. Retention factors on the immobilized artificial membrane column (IAM PC DD 2) with 10% (v/v) methanol-water as mobile phase are able to estimate non-specific toxicity to the fathead minnow with a standard error (SE) of 0.22 log units and coefficient of determination (r2) of 0.97 for 31 compounds. Retention factors on a Bakerbond DIOL column with 20% (v/v) acetonitrile-water as mobile phase are able to estimate the soil-water distribution constant with an SE of 0.38 log units and r2 = 0.88 for 59 compounds. Other potential surrogate chromatographic models are identified for non-specific toxicity to the guppy, tadpole, Vibrio fischeri and Terahymena pyriformis as well as the plant cuticle matrix-water distribution constant. On the other hand reversed-phase chromatographic systems seem poorly suited for estimating intestinal absorption and the blood-brain distribution constant.     

Liquid chromatography in the analysis of neurotransmitters and alkaloids

Several thin-layer chromatographic (TLC) and high-performance liquid chromatographic (HPLC) systems for the determination of biogenic amine neurotransmitters, alkaloids, and the metabolites of these two groups of compounds are developed. The possibility of the interference of these compounds is investigated. In all the systems developed for neurotransmitters, the retention of alkaloids is examined and vice versa. In TLC because of different visualization procedures (a dyeing reagent for alkaloids and visible light for neurotransmitters), compounds of both the groups may be determined simultaneously without the risk of interference. In HPLC, similarly, the possibility of false diagnosis through simultaneously employing the fluorimetric and diode-array detectors can be excluded.     

Gas chromatographic characteristics and application studies of the stationary phase of CH-B-15-C-5

In this paper, separations of organic compounds, such as, n-alkanes, alcohols, ethyl asters of C(1)-C(8) carboxylic acid, halogen derivatives, position-isomers of the replacement aromatic hydrocarbon, optical isomers of ethyl lactate and isoamyl alcohol, etc. were studied using 4'-cholestenoxycarbonyl-benzo-15-crown-5 liquid crystal crown ether (CH-B-15-C-5) as stationary phase in gas-solid chromatography (GSC), general gas-liquid chromatography (GLC) and crown ether liquid crystal gas-liquid chromatography (CL-GLC). Also, the chromatographic characteristics, such as the chemical stability, thermal stability, selectivity, polarity and operating temperature range, of the CH-B-15-C-5 as stationary phase for GSC, GLC and CL-GLC systems were studied. The results showed that the polarity of this chromatographic column is mean-weak; the chemical and thermal stabilities and the selectivity are good and the operating temperature range is wide. The results of separations of organic compounds are satisfactory.     

Chromatographic models for the sorption of neutral organic compounds by soil from water and air.

The solvation parameter model is used to construct models for the estimation of the soil-water and soil-air distribution constants and to characterize the contribution of fundamental intermolecular interactions to the underlying sorption processes. Wet soil is shown to be quite cohesive and polar but relatively non-selective for dipole-type, lone-pair electron and hydrogen-bond interactions. Using a comparison of system constant ratios chromatographic systems employing reversed-phase liquid chromatography on polar bonded phases are shown to provide suitable models for estimating soil-water distribution constants. No suitable gas chromatographic models were found for the soil-air distribution constant but the requirements for such a system are indicated. Models are also provided for adsorption at the air-water interface. Estimation methods based on either the solvation parameter model or chromatographic model reproduce experimental distribution constants for a wide variety of compounds with a similar error (0.2-0.3 log units) to that expected in the experimental data.     

The Use of an α-Cyclodextrin Mobile Phase in the Thin-Layer Chromatographic Separation of Ortho,Meta, and Para Substituted Phenols

Abstract

An aqueous solution of α-cyclodextrin (cyclohexaamylose) is demonstrated to be a very effective mobile phase in thin-layer chromatographic separations. The chromatographic behaviors of twenty-six substituted phenolic and naphtholic compounds using polyamide thin-layer stationary sheets are described. The R_f values were found to be dependent upon both the structural features of the phenolic compounds and the concentration of α-cyclodextrin in the mobile phase. A possible mechanism that accounts for the observed chromatographic behavior is presented. The advantages and disadvantages of the aqueous α-cyclodextrin mobile phase over the traditional pure or mixed organic solvent systems typically employed are discussed.     

Comprehensive chromatographic separations in proteomics

In such a complicated field as proteomic analysis, scientists are more and more challenged in implementing separation systems capable to provide enhanced separation power, as well as sensitivity of detection for adequate identification and, to a lesser extent, quantification of the separated compounds. To address such issues, several combinations of different separation modes have been investigated in comprehensive liquid chromatographic platforms, in which the entire sample eluted from the first dimension is subjected to a secondary chromatographic separation. The different applications exploited for comprehensive LC analysis of intact or digested proteins are the focus of this review, in which advantages and disadvantages of the different columns combinations, interfaces, and operating modes are pointed out. The combination with mass spectrometry as part of the total system is stressed, and illustrated in more detail. Theoretical concerns and practical requirements will be briefly discussed, as well.     

超临界流体色谱在金属络合物和金属有机化合物中的分析应用

超临界流体色谱（SFC）在色谱分离过程中能在较低的温度下分析对热不稳定性的化合物,包括金属络合物和金属有机化合物。本文总结了近来文献报道的各种过渡金属、重金属、镧系和锕系以及铅、汞和锡的金属有机化合物的SFC分离,还讨论了SFC检测系统和金属有机化合物的溶解度的测定。     

Use of borohydride reduction in the separation of estrogen carbonyls

The chromatographic behavior of the estrogen carbonyls, equilenin, equilin, and estrone, and their respective sodium borohydride reduction products has been studied. The separation of the 17 alpha-hydroxy reduced compounds is superior to the separations achieved for the parent carbonyls using both reversed-phase and normal-phase systems. The reductions appear quantitative by the chromatographic systems used but other work indicates that a small quantity of 17 alpha-hydroxy isomer is produced. The separations developed here have been used in the identification of 9-dehydroestrone, an impurity in estrone, and in the identification of the estrogens in a commercial aqueous suspension of estrogenic substances.     

Multiple preparative chromatography. II. Dual-step system

Summary The capacity of dual-step preparative chromatographic separation systems is considered. It is shown that dualstep separation makes it possible to enhance the capacity of preparative installations as compared with single- and dual-stage purification of the compounds.     

Derivatization in mass spectrometry --7. On-line derivatisation/degradation

The review describes on-line derivatization/degradation methods employed in mass spectrometry to solve some structural and analytical problems. Advantages and applications of various positions of reaction systems connected mainly to a mass spectrometer or a gas chromatograph/mass spectrometer are considered. Among these are reaction systems connected directly to the mass spectrometer (reaction mass spectrometry, pyrolysis-mass spectrometry or direct pyrolysis-mass spectrometry); flash-heaters as reactors in gas chromatography/mass spectrometry (GC/MS); in-line chemical reactors located before the chromatographic column [pre-column derivatization/degradation with the use of catalytic reactions, pyrolysis (pyrolysis-GC/MS), degradation in elemental analyzers-isotope ratio mass pectrometry (EA-IRMS)]; on-column derivatization and deuteration; reactor located between the chromatographic column and a mass spectrometer [post-column catalytic derivatization, gas chromatograph-combustion-isotope ratio mass spectrometer (GC-c-IRMS)]. Post-column derivatization in high performance liquid chromatography/mass spectro-metry is briefly mentioned. Application of such on-line methodology to structure elucidation of low molecular mass compounds and polymers, to the determination of isotope ratios of the most common elements, to the investigation of catalytic reactions is discussed..     

Automated gas chromatographic method for the determination of residual solvents in bulk pharmaceuticals

A generalized gas chromatographic method is described for the determination of a wide variety of residual solvents and other volatile impurities in bulk pharmaceuticals. The method employs a highly selective graphitized carbon-black stationary phase, which is demonstrated to retain compounds on the basis of a linear combination of their boiling points and molecular volumes (i.e., molecular weight divided by density). An autosampler is utilized to optimize injection precision and to provide for high sample throughput. Analytical data from replicate determinations of seven representative compounds are reported, and it is shown that calibration of the chromatographic systems against external standards produces comparable results to those obtained by standard addition techniques.     

Retention time prediction of compounds in Grob standard mixture for apolar capillary columns in temperature-programmed gas chromatography

This paper presents an extension of a previous investigation in which the behavior of nonpolar compounds in temperature-programmed gas chromatographic runs was predicted using thermodynamic (entropy and enthalpy) parameters derived from isothermal runs. In a similar manner, entropy and enthalpy parameters were determined for a Grob standard mixture of compounds with widely varying chemical characteristics. These parameters were used to predict the retention times and chromatographic behaviors of the compounds on four gas chromatography capillary columns: three that had phenyl-based stationary phases (with degrees of substitution of 0%, 5% and 50%) and one with (50%) cyanopropyl substitution. The predictions matched data empirically obtained from temperature-programmed chromatographic runs for all of the compounds extremely well, despite the wide variations in polarity of both the compounds and stationary phases. Thus, the results indicate that such simulations could greatly reduce the time and material costs of chromatographic optimizations.     

Chemometrics for the analysis of chromatographic data in metabolomics investigations

Metabolomics aims to better understand biological systems through the chemical analysis of an organism's metabolic profile. One common method of analysis is mass spectrometry preceded by chromatographic separations. Samples produced by metabolomics investigations can contain hundreds to thousands of compounds, which can put great strain on the instrumental analysis. In order to improve these analyses, the data analysis must not be overlooked. The ever‐evolving field of chemometrics provides many useful tools for the analysis of chromatographic data. These include methods for preprocessing data to extract a maximum amount of information from the data as well as pattern recognition in order to find the compounds that vary the most in relation to the perturbation to the biological system under study. This article aims to highlight and provide future outlooks on current chemometric methods for chromatographic‐based metabolomics investigations. Copyright © 2014 John Wiley & Sons, Ltd.     

Two-dimensional high resolution GLC environmental analysis,preliminary results

Summary The current status of gas chromatographic procedures and instrumentation for the analysis of volatile environmental contaminants is discussed. Design features of gas chromatographic systems, capable of transferring portions of eluting compounds from one gas chromatographic column into another are also discussed. A prototype two-dimensional gas chromatograph has been built and tested. The system is composed of two separate gas chroamtographs, which are joined by a common heated interface. A combination of off-line valves and restrictors (Deans' switches) serves to change carrier gas flow directions. Compounds selected for cutting are transferred to the second gas chromatograph and held in an intermediate trap. The effluents from the second column are detected by FID/ECD, operated in parallel. Important parameters which effect sample transfer between the systems have been studied to serve as basis for a semiautomated instrument to be built. Some applications with synthetic mixtures are demonstrated.     

Design of simulated moving bed and Varicol processes for preparative separations with a low number of columns

Simulated moving bed (SMB) chromatography has received significant attention in the last decade, particularly as regards the production of very valuable products, such as enantiomerically pure pharmaceutical compounds. Recent applications in the pharmaceutical industry use SMB systems containing a low total number chromatographic columns, usually four to eight. This paper deals with the modeling and simulation of SMB systems with only four, five and six columns. In particular, two modeling strategies, the equivalent true moving bed and the real SMB models, are compared for these units in terms of separation regions and system productivity. Also, the recently proposed Varicol process is analyzed and compared with the classical SMB operation, and the advantages of this new operation mode are shown for systems using a low number of columns.