Unexpected differences between planar and column liquid chromatographic retention of 1-acenaphthenol enantiomers controlled by supramolecular interactions involving β-cyclodextrin at subambient temperatures.

We report the results of experimental work focusing on host-guest supramolecular complex creation between macrocyclic compound (β-cyclodextrin) and 1-acenaphthenol enantiomers (racemic mixture) in liquid phase composed of 35% acetonitrile in water (v/v) at different temperatures ranging from 0 to 90 °C. Experimental setup involved several analytical protocols based on classical non-forced flow planar chromatography (RP-18 TLC plates), micro-TLC (RP-18 W HPTLC plates), column chromatography (HPLC with C-18 and C-30 stationary phases), as well as UV-Vis spectrophotometry and optical microscopy. It has been found that under various planar chromatographic conditions (stationary plates type, chamber shape and volume, development mode, and saturation) non-typical retention properties (extremely high retention) of 1-acenaphthenol at subambient temperatures can be observed.

A novel miniaturized extraction capillary for determining gaseous formaldehyde by high-performance liquid chromatography.

A novel miniaturized sample extraction capillary was developed to provide a simple and sensitive method for analyzing gaseous formaldehyde (FA) using conventional high-performance liquid chromatography (HPLC). The extraction capillary was prepared by packing silica gel particles in a stainless steel capillary with a 1.6-mm o.

Needle-type extraction device for the purge and trap analysis of 23 volatile organic compounds in tap water.

We developed a rapid determination technique for trace volatile organic compounds (VOCs) in tap water by introducing a novel needle-type extraction device coupled to a purge-and-trap method. To extract a wide range of VOCs, a new extraction needle containing particles of divinylbenzene and activated carbon was developed in this study. During the active sampling of the headspace gas in a glass vial by the extraction needle, pure N2 gas was used for purging the aqueous sample.

An abnormal temperature dependence of alkylpyrazines' retention in reversed-phase liquid chromatography.

Retention behaviors of pyrazine and alkylpyrazines on various stationary phases in reversed-phase liquid chromatography were examined. An abnormal temperature effect on the retention of alkylpyrazines with a mobile phase consisting of acetonitrile and water was observed when changing the column temperature. On the other hand, no similar trend was found with a methanol-water mobile phase.

High-temperature separations on a polymer-coated fibrous stationary phase in microcolumn liquid chromatography.

Novel polymer-coated fiber-packed microcolumns in liquid chromatography (LC) have been developed. Typical polymeric materials, such as polydimethylsiloxane and polyethyleneglycol, which are conventional stationary phases of capillary columns in gas chromatography (GC), have been employed as coating materials onto the surface of fine filaments. Packed longitudinally with a bundle of polymer-coated filaments into a stainless-steel capillary of 0.

Novel fire investigation technique using needle extraction in gas chromatography.

A novel fire investigation technique using a needle extraction device was studied. Using a polymer particle-packed needle device, air samples containing volatile organic compounds (VOCs) generated from fire accelerants, gasoline and kerosene were extracted effectively, and subsequent gas chromatographic (GC) analyses were successfully carried out. Carpet and wood samples were spiked with gasoline and kerosene, followed by monitoring of the time-variation profiles of emitted VOCs up to 48 h.

Retention behavior on aminoethyl-modified poly(p-phenylene terephthalamide) fiber stationary phases in gas chromatography.

Surface derivatization of Kevlar, poly(p-phenylene terephthalamide), fiber has been studied along with the evaluation of the surface characteristics of the chemically-modified fiber as the stationary phase in packed-capillary gas chromatography (GC). Several experimental parameters in the derivatization reaction have been optimized, and the retention behavior of the surface-derivatized fibrous stationary phase has been investigated using various standard solutes, such as alkanes, alcohols and alkylbenzenes. By introducing aminoethyl functional groups onto the surface of the fibrous material, a specific selectivity for polar solutes has been observed.

Rapid temperature-programmed separation and retention prediction on a novel packed-capillary column in gas chromatography.

Novel packed-capillary columns for gas chromatography were developed with a thin-wall stainless-steel capillary of 1.0 mm i.d.

Determination of volatile organic compounds for a systematic evaluation of third-hand smoking.

Third-hand smoking was quantitatively evaluated with a polymer-packed sample preparation needle and subsequent gas chromatography-mass spectroscopy analysis. The extraction needle was prepared with polymeric particles as the extraction medium, and successful extraction of typical gaseous volatile organic compounds (VOCs) was accomplished with the extraction needle. For an evaluation of this new cigarette hazard, several types of clothing fabrics were exposed to sidestream smoke, and the smoking-related VOCs evaporated from the fabrics to the environmental air were preconcentrated with the extraction needle.

Breath acetone analysis with miniaturized sample preparation device: in-needle preconcentration and subsequent determination by gas chromatography-mass spectroscopy.

A new approach to the determination of human breath acetone with particle-packed sample preparation needle was developed. The extraction needle was packed with a copolymer of methacrylic acid and ethylene glycol dimethacrylate as the extraction medium. For the analysis of breath sample, exhaled breath was collected in a sampling bag, and 50 mL of the breath sample was extracted with the needle-type sample preparation device followed by analysis using gas chromatography-mass spectrometry (GC-MS).

Development of novel fiber-packed needle interface for off-line reversed-phase liquid chromatography-capillary gas chromatography.

For two-dimensional reversed-phase liquid chromatography-gas chromatography (2D RPLC-GC), a specially-designed needle packed with a polymer-coated fibrous stationary phase was introduced as a novel interface. The bundle of synthetic fibers coated with polydimethylsiloxane (PDMS) was packed into the head section of the needle, and served as the extraction medium. Using the post-column dilution of the LC eluent by water and subsequent extraction with the needle interface, the analyte was successfully concentrated to the PDMS phase on the fibrous support in the needle.

Rapid determination of ethylene oxide with fiber-packed sample preparation needle.

Fiber-packed sample preparation device was applied to the simultaneous derivatization/preconcentration of ethylene oxide (EO) in air samples. The polymer-coated filaments were packed longitudinally into the needle, and hydrogen bromide (HBr) was loaded onto the filaments in the preconditioning process. Simultaneous derivatization with HBr in the needle was made during the sampling process of the gaseous EO, and the corresponding derivatized analyte, 2-bromoethanol, was desorbed by passing a small amount of methanol through the extraction needle in the heated gas chromatograph (GC) injector.

Fiber-packed needle-type sample preparation device designed for gas chromatographic analysis.

A miniaturized sample preparation technique that uses a fine-fiber-packed needle as the extraction medium is reviewed, especially in relation to its application to the analysis of volatile organic compounds by gas chromatography. When the needle was packed longitudinally with a bundle of fine filaments (12 microm o.d.

Modeling of retention of adrenoreceptor agonists and antagonists on polar stationary phases in hydrophilic interaction chromatography: a review.

Retention prediction models for reversed-phase liquid chromatography (RPLC) have been extensively studied owing to the fact that RPLC remains the most widely used chromatographic technique especially in the field of pharmaceutical and biomedical analyses. However, RPLC is not always the method of choice for the analysis of some compounds that have high polarity. Hydrophilic interaction chromatography (HILIC) has been gaining interest in the last few years as an alternative option to RPLC for the analysis of polar and hydrophilic analytes.

Effects of alcohols on CE enantioseparation of basic drugs with native gamma-CD as chiral selector.

The effects of alcohol on the CE enantioseparation of selected basic drugs with gamma-CD as the chiral selector was investigated. The enantioseparation behavior of the analytes with gamma-CD in the absence and presence of different alcohols specifically methanol, ethanol, 2-propanol (IPA), and 2-methyl-2-propanol (TBA), the relationship of enantiomeric resolution (R(s)) values with either hydrophobicity or bulkiness of the alcohols, as well as the effect of these alcohols on interaction of the analytes with gamma-CD were studied. Results showed that hydrophobicity and/or bulkiness of alcohols have an influence on the enantioresolution of most of the analytes based on the relatively high correlation coefficients (R) obtained between R(s) versus log P and between R(s) versus ovality (i.

Multiple linear regression and artificial neural network retention prediction models for ginsenosides on a polyamine-bonded stationary phase in hydrophilic interaction chromatography.

The development of retention prediction models for the seven ginsenosides Rf, Rg1, Rd, Re, Rc, Rb2, and Rb1 on a polyamine-bonded stationary phase in hydrophilic interaction chromatography (HILIC) is presented. The models were derived using multiple linear regression (MLR) and artificial neural network (ANN) using the logarithm of the retention factor (log k) as the dependent variable for four temperature conditions (0, 10, 25, and 40 degrees C). Using stepwise MLR, the retention of the analytes in all the temperature conditions was satisfactorily described by a two-predictor model wherein the predictors were the percentage of ACN (%ACN) in the mobile phase and local dipole index (LDI) of the compounds.

Development of retention prediction models for adrenoreceptor agonists and antagonists on a polyvinyl alcohol-bonded stationary phase in hydrophilic interaction chromatography.

Retention prediction models based on multiple linear regression (MLR) and artificial neural network (ANN) for adrenoreceptor agonists and antagonists chromatographed on a polyvinyl alcohol-bonded stationary phase under hydrophilic interaction chromatography were described. The models showed the combined effects of solute structure and mobile phase composition on the retention behavior of the analytes. Using stepwise MLR, the retentions of the studied compounds were satisfactorily described by a five-predictor model; the predictors being the %ACN, the logarithm of the partition coefficient (log D), the number of hydrogen bond donors (HBD), the desolvation energy for octanol (FOct), and the total absolute atomic charge (TAAC).

Retention prediction modeling of ginsenosides on a polyvinyl alcohol-bonded stationary phase at subambient temperatures using multiple linear regression and artificial neural network.

The development of retention prediction models for the seven ginsenosides (Rf, Rg1, Rd, Re, Rc, Rb2 and Rb1) on a polyvinyl alcohol (PVA)-bonded stationary phase at subambient temperatures is presented. The models were derived using multiple linear regression (MLR) and artificial neural network (ANN) using the logarithm of the retention factor (log k) as the dependent variable. Using stepwise MLR, the retention of the analytes under all temperature conditions was satisfactorily described by a three-predictor model; the predictors being the percentage of acetonitrile (%MeCN) in the mobile phase, the number of hydrogen bond donors (HBD) and the ovality (Ov) of the compounds.

Fast separation and quantification of C60 and C70 fullerenes using thermostated micro thin-layer chromatography.

Thermostated micro planar chromatography was applied for systematic separation studies of C60 and C70 fullerenes using n-alkanes as mobile phases on TLC and HPTLC plates coated with polyamide, silica gel, aluminum oxide as well as two types of octadecylsilica (C18) sorbents. Retention data were collected at constant temperature at 20 degrees C (+/-0.05 degrees C) using an unsaturated chamber mode with an eluent, such as n-pentane, n-hexane and n-heptane.

Simultaneous enantioseparation and sensitivity enhancement of basic drugs using large-volume sample stacking.

Simultaneous enantioseparation with sensitive detection of four basic drugs, namely methoxamine, metaproterenol, terbutaline and carvedilol, using a 20-mum ID capillary with native beta-CD as the chiral selector was demonstrated by the large-volume sample stacking method. The procedure included conventional sample loading either hydrodynamically or electrokinetically at longer injection times without polarity switching and EOF manipulation. In comparison to conventional injections, depending on the analyte, about several hundred- and a thousand-fold sensitivity enhancement was achieved with the hydrodynamic and the electrokinetic injections, respectively.

Retention behavior of ginsenosides on a poly(vinyl alcohol)-bonded stationary phase in hydrophilic interaction chromatography.

The influences of the organic component of the mobile phase and the column temperature on the retention of ginsenosides on a poly(vinyl alcohol) (PVA) bonded stationary phase operated under hydrophilic interaction chromatographic mode were investigated. The retention of the ginsenosides was found to increase with increasing amount of acetonitrile (MeCN) in the mobile phase, which is typical of hydrophilic interaction chromatographic behavior. It was also found that the retention of the analytes was highly affected by the type of the organic modifier used.

Retention prediction of adrenoreceptor agonists and antagonists on a diol column in hydrophilic interaction chromatography.

Retention prediction models using multiple linear regression (MLR) and artificial neural networks (ANN) were developed for adrenoreceptor agonists and antagonists chromatographed on a diol column under hydrophilic interaction chromatographic (HILIC) mode at three pH conditions (3.0, 4.0 and 5.

Retention prediction of adrenoreceptor agonists and antagonists on unmodified silica phase in hydrophilic interaction chromatography.

The development of retention prediction models for adrenoreceptor agonists and antagonists chromatographed on an unmodified silica stationary phase under the hydrophilic interaction chromatographic (HILIC) mode at three pH conditions (3.0, 4.0 and 5.

Fiber-packed needle for dynamic extraction of aromatic compounds.

A fiber-packed needle was developed as a novel extraction device for gas-chromatographic analysis of trace organic compounds in aqueous samples. In the extraction device, a bundle of the polymer-coated filaments as the sorbent material was longitudinally packed into a specially designed needle. The extraction was made by pumping the aqueous sample solution into the needle extraction device, and the subsequent desorption process was carried out with a flow of desorption solvent through the needle in a heated gas chromatograph injector.