Properties of chromatographic columns prepared on the basis of poly(1-trimethylsilyl-1-propyne) modified with organic bases.

This article describes the effect of modification with organic bases such as uracil (U) and polyethyleneimine (PEI) on the adsorption and chromatographic properties of poly(1-trimethylsilyl-1-propyne) (PTMSP) used as a stationary phase (SP) in packed and capillary columns. It was shown that the sorbents prepared on the basis of diatomite Chromosorb P NAW support and successively modified with 9 wt.% PTMSP and 1 wt.% U (or PEI) (PC-U and PC-PEI samples, respectively), have a mesoporous structure. The IR spectrum shows the presence of carbonyl groups in the sorbent modified with uracil. The impregnation of the Chromosorb P NAW + (9/1) wt.% PTMSP sorbent with a polyethyleneimine solution leads to the appearance in the spectrum of bands characterizing NH stretching and bending vibrations, as well as a band at 1310 cm-1 which can be attributed to CN bond vibrations. The chromatographic properties of the studied sorbents differ significantly from the properties of the initial PTMSP. Packed columns PC-U and PC-PEI, as well as capillary columns with a polyethyleneimine-modified PTMSP layer, allow one to selectively separate mixtures of polar and non-polar compounds and structural isomers of hydrocarbons. Methanol on these columns is eluted in the form of a symmetrical peak separately from propane, propylene and other associated hydrocarbon impurities in commercial (technical, target) n-butane.

Multicapillary columns with ionic liquids as stationary liquid phase.

The study demonstrates the possibility of using ionic liquids (IL) as a stationary liquid phase (SLP) for gas chromatographic (GC) multicapillary columns (MCC). Three types of IL of three classes were employed as SLP: Imidazolium, Pyridinium and Quinolinium. Dependences of the MCCs efficiency on the carrier gas flow rate were obtained. Highest efficiency was achieved on the column with 1,2-Dimethyl-3-propylimidazolium bis(trifluoromethylsulfonyl)imide (DiMPrIm). For this column, dependence of the efficiency on the sample volume has been investigated. Also the loading capacity of the MCC with DiMPrIm was determined. Separation of fatty acid esters and phenols served as an example to demonstrate that using ionic liquids as SLP for МСС make it possible to combine fast separations with high selectivity.

In situ functionalization of HPLC monolithic columns based on divinylbenzene-styrene-4-vinylbenzyl chloride.

The properties of chromatographic columns are largely determined by functional groups located on the sorbent surface. For monolithic columns, surface functional groups can be created during synthesis stage or by chemical bonding with the complete surface of the sorbent. One of sorbent modification approach is to use on-column click reactions with surface reactive groups. In this study, the surface treatment of monolithic sorbent based on divinylbenzene (DVB), styrene (St) and 4-vinylbenzyl chloride (4VBC) copolymer by heterocyclic nitrogen-containing compounds 1-methylimidazole (1MI), 2-methylimidazole (2MI), 2-methylpyridine (2 MP) and 4-methylpyridine (4 MP) is described. The reaction of nitrogen-containing heterocycles with chloromethyl fragments on the surface results in formation of ion pairs and significantly changes the selectivity of monolithic columns. The chromatographic properties of prepared columns are studied. Modified columns can be operated in reversed-phase (RP) chromatography or in hydrophilic interaction liquid chromatography (HILIC) with different composition of the mobile phase. Separation examples of various chemical substances classes are given.

Analysis of light components in pyrolysis products by comprehensive two-dimensional gas chromatography with PLOT columns.

The most successful method for pyrolysis liquids analysis is comprehensive two-dimensional gas chromatography. Columns with a stationary liquid phase are used for this purpose. However, when is necessary to analyze a gas phase containing C3-C5 hydrocarbons over a liquid pyrolysis product, the use of columns with a liquid phase in CG*CG will not result to separation of light hydrocarbons. In this case, it is necessary to use PLOT columns with a porous layer of sorbents of various nature. Today this approach with two PLOT columns in GC*GC is not described, as well as its use for the analysis of light hydrocarbons resulting from pyrolysis. This paper describes an application of two PLOT columns in GC*GC mode. This paper describes an application of two PLOT columns in GC*GC mode. The next columns of different nature that have different selectivity were used: Rt-Q-BOND, Rt-S-BOND, Rt-U-BOND (columns based on divinylbenzene styrene copolymer), column with sorbent poly- (1-trimethylsilyl-1-propyne) (PTMSP) and an Agilent GASPRO silica column. The most suitable pair of the columns was determined by finding of their orthogonality. The numerical orthogonality data was found by studying of the correlation coefficients between compounds retention time on the first and second columns. It is shown that the best combination of columns are PTMSP - GASPRO and Rt-Q-BOND - GASPRO, however, the first combination of columns allows separation at the same temperature conditions about twice as fast as the second. Examples of the separation of С3-С8 hydrocarbons in the gas phase over pyrolysis mixtures of different origin are given.

Selection of the porous layer open tubular columns for separation of light components in comprehensive two-dimensional gas chromatography.

Up to the present, comprehensive two-dimensional gas chromatography was commonly performed using combinations of columns with stationary liquid phases. There are singular examples with a porous layer open tubular (PLOT) column used only in the second dimension. However, GC × GC systems with two PLOT columns are not reported in the literature. Our work describes the application of two PLOT columns in the GC × GC mode. In the first and second dimensions we used columns with the sorbents based on organic porous polymers with different selectivity: Rt-Q-BOND (nonpolar column consist of 100% divinylbenzene-styrene), Rt-S-BOND (intermediate polar column, which contain 4-vinylpyridine), Rt-U-BOND (polar column based on divinylbenzene - ethylene glycol dimethylacrylate copolymer), DVB-VIm (divinylbenzene-vinylimidazole copolymer), a column PTMSP with poly-(1-trimethylsilyl-1-propyne) sorbent, and a GASPRO column with porous silica as a stationary phase. The degree of orthogonality was calculated for five different combinations of columns, where a column with the porous polymer was used in the first dimension, and GASPRO column - in the second dimension. Orthogonality was estimated from the correlation coefficient of retention times in the first and second dimensions. Examples of the separation of C1-C5 hydrocarbons on a combination of PTMSP - GASPRO and Rt-Q-BOND - GASPRO columns are reported. It is shown that not only light hydrocarbons but also compounds belonging to different chemical classes can be separated with the use of PLOT columns.

The properties of capillary columns with sorbents based on poly-(1-trimethylsilyl-1-propyne) modified with nitrous oxide.

In this work, we report the study of properties of capillary columns with a porous layer of the functionalized polymer prepared via oxidation of poly-(1-trimethylsilyl-1-propyne) (PTMSP) by nitrous oxide. It was shown that the double CC bonds of polymer reacted with nitrous oxide with formation of ketone, carbonyl and hydroxyl groups. The increase in number of those groups in polymer changed a polarity of PTMSP. The change in polarity of polymer led to the selectivity of separations, including oxygen-containing substances. The polarity values were calculated for the prepared columns. It was shown that the total polarity according to McReynolds (ΔI) was lower than that for known porous polymers. The examples of separations of aliphatic and aromatic hydrocarbons, oxygen- and halogen-containing substances were presented.

The properties of capillary columns with silica organic-inorganic MCM-41 type porous layer stationary phase.

In this work, we report the method of capillary columns preparation for gas-solid chromatography with a porous layer of MCM-41 type silica sorbent. The porous layer was synthesized by the sol-gel method inside the column. Scanning electron microscopy (SEM) measurements were performed to obtain information about the porous layer. The loading capacity of the prepared columns was investigated. An adsorbent selectivity was changed by using different relative contents of organic-inorganic precursors: vinyltriethoxysilane (VTEOS) and tetraethoxysilane (TEOS). Properties of the columns prepared are discussed. Separating examples of C1-C4 hydrocarbons and some other compounds are presented.

Sol-gel multicapillary columns for gas-solid chromatography.

In this work, we report the method for the preparation of multicapillary columns (MCCs) for gas-solid chromatography. The porous layer adsorbent is formed on capillary walls by the hydrolysis of aluminum alkoxide in the presence of polypropylene glycol (PPG) and HCl. Porosity and selectivity of the adsorbent depend on reaction conditions and the concentration of PPG. Sol-gel MCCs are well suited for high-speed chromatographic analysis of light hydrocarbons by gas-solid chromatography. Nine-component mixtures of C1-C4 hydrocarbons are separated within 8-12 s. The efficiency of 25-30 cm long alumina sol-gel MCCs consisting of approximately 1400 capillaries of 40 microm diameter is up to 2500-3000 theoretical plates.