Ivan Špánik

Enhanced comprehensive two-dimensional gas chromatographic resolution of polychlorinated biphenyls on a non-polar polysiloxane and an ionic liquid column series

A total of 196 out of 209 polychlorobiphenyl (PCB) congeners were resolved using GC×GC-TOFMS with a non-polar/ionic liquid column series consisting of poly(50%-n-octyl-50%-methyl)siloxane and (1,12-di(tripropylphosphonium)dodecane bis(trifluoromethansulfonyl)amide) in the first and second dimension, respectively. It has been found that 13 PCB congeners overlap in five doublets (CB12+CB13, CB62+CB75, CB70+CB76, CB97+CB125 and CB153+CB168) and one triplet (CB90+CB101+CB113). All toxic, dioxin like congeners were separated with no interferences from any PCB congener. The 109 PCBs present in Aroclor 1242 and the 82 PCBs present in Aroclor 1260 were resolved GC×GC-TOFMS analysis on this column set.

Use of full-column imaging capillary isoelectric focusing for the rapid determination of the operating conditions in the preparative-scale continuous free-flow isoelectric focusing separation of enantiomers.

A rapid, simple method is proposed here for the identification of the experimental conditions that lead to satisfactory preparative-scale isoelectric focusing enantiomer separations in continuous free-flow electrophoretic units. The method first calls for the use of a commercially available, full-column imaging capillary electrophoretic system to find the background electrolyte composition that generates the largest pI difference between the bands of the enantiomers. The method then calls for the finding of the minimum residence time that permits full development of the pH gradient across the separation chamber of the continuous free-flow electrophoretic unit by measuring the pH in the sample-free carrier electrolyte fractions collected during these runs. Finally, the quality of the predicted preparative-scale separation is verified by analyzing the enantiomer-containing collected fractions by capillary electrophoresis using a 14-sulfated, single-isomer cyclodextrin as resolving agent. The pI difference values and production rate values observed in this work agree well with the literature values that were obtained by much more time-consuming methods.

Flow-modulated comprehensive two-dimensional gas chromatography with simultaneous flame ionization and quadrupole mass spectrometric detection.

Flow-modulated comprehensive two-dimensional gas chromatography with simultaneous monitoring of the separation by flame ionization (GC × GC-FID) and quadrupole mass spectrometric (GC × GC-qMSD) detection was studied for the analysis of gasoline and kerosene samples. The acquisition frequency of the FID was 100 Hz and of the qMSD 18 Hz for the mass range m/z 40-300. The instrumental set-up is such that both one-dimensional (GC-FID and GC-qMSD) and two-dimensional separations using the same working conditions can be performed. Gasoline and kerosene samples were analyzed on the column combination HP-5MS ((1)D)+HP INNOWax ((2)D). Three modulated peaks were obtained for each hydrocarbon present above 0.1% with ca. 300 ms peak width at the base using 6 s modulation times. Modulated peaks in GC × GC-FID were thus characterized by ca. 30 points while those in GC × GC-qMSD method by 6-8 points only. The FID speed is sufficient for reliable quantitative analysis, while the qMSD scan speed is perfectly appropriate for identification purposes. Moreover, in the GC × GC-qMSD method considerably improved quality of uncorrected spectra was obtained, arising from the enhanced separation over one-dimensional GC-MSD analysis. Spectral match qualities of up to 98% were found.

On the use of ionic liquid capillary columns for analysis of aromatic hydrocarbons in low-boiling petrochemical products by one-dimensional and comprehensive two-dimensional gas chromatography.

One-dimensional and comprehensive two-dimensional flow modulated gas chromatography with simultaneous flame ionization and mass spectrometric detection were applied for the identification and quantification of benzene, toluene, ethyl benzene and xylenes (BTEX) as well as of all C9-C11 aromatic hydrocarbons in the low-boiling petroleum products gasoline, reformate and fluid catalytic cracking (FCC) samples. GC×GC experiments were performed on two reversed phase polarity column sets namely SLB-IL100 (25m×250μm i.d.×0.2μm df)+HP-5MS (5m×250μm i.d.×0.25μm df) and SLB-IL111 (30m×250μm i.d.×0.2μm df)+HP-5MS (5m×250μm i.d.×0.25μm df). The one-dimensional GC experiments were carried out on the same ionic liquid columns. The most powerful method is GC×GC on the SLB-111+HP-5MS column combination. Quantitative analysis of individual aromatic hydrocarbons (C6-C11) present in gasoline, reformate and fluid catalytic cracking (FCC) samples was performed by GC×GC-FID using the internal normalization method. Mass spectra obtained by GC×GC-qMSD were used for identification of the aromatic hydrocarbons in these samples.

Characterisation of VOC composition of Slovak monofloral honeys by GC×GC-TOF-MS

Solid phase microextraction (SPME) followed by comprehensive two-dimensional gas chromatography coupled to a time-of-flight mass spectrometer (GC×GC-TOF-MS) was used to characterise volatile organic compounds in honeys of different botanical origins. Rape, sunflower, acacia, lime, raspberry, and phacelia honeys from Slovakia were studied in detail. Up to 900 compounds were detected at the given S/N ratio of 200. The poorest VOC profiles were found for acacia and rape honeys while lime honey showed the richest VOC composition. Approximately 100 compounds were present in all honeys studied, independently of their botanical origin. They belong to various chemical classes (hydrocarbons, alcohols, aldehydes and ketones, terpenes, benzene derivatives, and compounds containing heteroatoms). The compounds found in only one type of honey were also successfully identified.

Evaluation of non-polar interactions in chiral recognition by alkylated β- and γ-cyclodextrin chiral stationary phases

The gas chromatographic separation of enantiomers of seven N-TFA-O-alkyl amino acid derivatives was studied on four different permethyl- and 2,6-di-O-methyl-3-O-pentyl-β- and -γ-CD stationary phases.It was shown that the separation of enantiomers N-TFA-O-alkyl amino acid derivatives depends both on the length of the linear alkyl chain attached to the stereogenic carbon (R 1 ) and to the ester part of the amino acid derivative (R 2 ). The cyclodextrin cavity size also affected selectivity. The separation of the amino acid derivatives decreases with increasing length of both the R 1 and R 2 alkyl chains on β-CD stationary phases, but improves on γ-CD stationary phases. The separation of enantiomers of all N-TFA-O-methyl amino acid esters, is better on the larger γ-cyclodextrin CSPs except for enantiomers of N-TFA-O-alkyl esters of alanine which are better separated on β-CD stationary phases.

The Use of Computerized Peak Deconvolution for Determination of Energy Barrier to Enantiomerization in Dynamic Gas Chromatography

Computer-assisted peak deconvolution on chromatograms obtained by GC separation of enantiomers of 1-chloro-2,2-dimethylaziridine on modified -, -, and -cyclodextrin was used to determine the peak areas of enantiomers, prior Ž. Ž . to A , B and after the separation A , A. Both Gaussian as well as A ,0 B ,0 AB exponentially modified Gaussian functions were used to approximate the peak shapes in the deconvolution procedures. Determined peak areas were used in the calculation of the rate constants and energy barriers to enantiomerization. A comparison of energy barriers determined using the deconvolution of chro- matograms with data published in the literature by classical kinetics shows differ- ences within 5%. 2001 John Wiley & Sons, Inc. J Micro Sep 12: 630636, 2000

Separation of C11C14 branched-chain alcohols by high-resolution gas chromatography on a modified β-cyclodextrin stationary phase

Abstract The separation of C 11 ue5f8C 14 branched-chain alcohols and their acetyl derivatives by gas chromatography on a fused-silica capillary column coated with heptakis (6-O- tert .-butyldimethylsilyl-2,3-di-O-diacetyl)-β-cyclodextrin dissolved in OV-1701 (1:1) was studied. It is demonstrated that the separation of positional isomers of these alcohols and their acetyl derivatives on this stationary phase is poorer than that on Carbowax 20M. Enantiomers of the alcohols were resolved on this stationary phase at temperatures below 110°C, whereas enantiomers of their acetyl derivatives were not resolved under similar conditions.

Enantioselective comprehensive two‐dimensional gas chromatography. A route to elucidate the authenticity and origin of Rosa damascena Miller essential oils

The analysis of Bulgarian and Turkish Rosa damascena Miller essential oils was performed by flow-modulated comprehensive two-dimensional gas chromatography using simultaneous detection of the second column effluent by flame ionization and quadrupole mass spectrometric detection. Enantioselective separations were obtained by running the samples on 2,3-di-O-ethyl-6-O-tert-butyldimethylsilyl-β-cyclodextrin column as the first column and on polyethylene glycol as the second column. The determination of enantiomeric or diastereomeric excess of some terpenoic solutes is a possible route for quality or authenticity control as well as for the elucidation of the country of origin.

On the determination of a detector response enhancement factor for flow modulated comprehensive two-dimensional gas chromatography.

Comparison of conventional one-dimensional gas chromatography (1D-GC) and comprehensive two-dimensional gas chromatography (GC×GC) shows that the detector signal in GC×GC is significantly enhanced. The value of this enhancement depends on the operating parameters, such as the modulation time and the non-modulated ((1)D column) and corresponding modulated ((2)D column) peak widths. Determination of the enhance factors in flow modulated GC×GC for separation of hydrocarbon samples using flame ionization detection (FM GC×GC-FID) was studied. A term named detector response enhance factor (DREF) has been designed to express the value of the signal enhancement. Two methods were used to calculate DREF: (i) employing (2)D peak height, and (ii) using a theoretical approach. Comparison of FM GC×GC-FID and 1D-GC-FID method illustrates that the DREF increases from 10 to 33 times, in 1-6s modulation time intervals.