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A comparative assessment is performed of the separation capability of three types of PLOT capillary columns: PTMSP032 (poly(1-trimethylsilyl-1-propyne)), Rt-Q-BOND (polydivinylbenzene), GS-GasPro (silica), and it is studied of the possibility of their use for the determination of impurities in commercial (target, technical) n-butane. Satisfactory separation of alkanes, alkenes, arenes and methanol was achieved on PTMSP032 and Rt-Q-BOND columns. The effect of the main component amount of the mixture on the separation of trace amounts of hydrocarbons and methanol is studied. It is shown that the macrozone (> 99%) of n-butane is selectively separated from the accompanying impurities. With an increase in the injected sample volume, the resolution for the peaks of C1–C2 hydrocarbons and the structural isomers of o-, m-, and p-xylenes on the PTMSP032 column is significantly higher than on the Rt-Q-BOND column. A comparative assessment of the precision of the measurements of the hydrocarbons and methanol retention times on PTMSP032 and Rt-Q-BOND is characterized by a relative standard deviation (RSD) of not more than 0.3%.

Features of the dead (void) volume V0 determination of chromatographic columns with organic sorbents were considered. Two monolithic columns were studied: based on divinylbenzene – styrene ...

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.

For the first time in this work, two methods of modification of poly(1-trimethylsilyl-1-propyne) (PTMSP) and the possibilities of its application for the determination of catalytic reaction products are described. Aging of PTMSP is determined by three mechanisms: physical, chemical and mechanical effects. Free volume decreases, texture characteristics change, and partial oxidation of the polymer takes place in the structure of PTMSP. The chromatographic behavior of PTMSP, which was used for 18 months, differs significantly from the properties of the freshly prepared polymer. Thermal stability and chemical inertness are the main requirements for chromatographic materials. Therefore, two methods were used to stabilize the aging process. The first method consisted of preparing a mixed phase by adding disubstituted polyacetylene poly(1-phenyl-1-propyne) (PPP) to PTMSP. The resulting sorbent Chromosorb Р NAW + 10 wt% (97% PTMSP + 3% PPP) is efficient for solving a wide range of chromatographic tasks such as simultaneous analysis of hydrocarbons and sulfur-containing inorganic gases, analysis of chlorine-substituted methanes in CCl4 and thiophene in benzene, separation of hydrocarbons and aromatic compounds. It should be noted, the low selectivity of separation of oxygen-containing components on this sorbent. A second method of PTMSP modification, namely the oxidation treatment with nitrous oxide, is proposed. It was shown that the polymer is oxidized by means of its C=C double bond with the formation of ketone, carbonyl and hydroxyl groups. The increase in number of those groups in the polymer changed the polarity of PTMSP. The change in polarity of polymer led to the selectivity of separations, including oxygen-containing substances. Examples of separations of aliphatic and aromatic hydrocarbons, oxygen- and halogen-containing substances are presented. Chromatographic characteristics of the sorbent Chromosorb P NAW + 10 wt% (97% PTMSP + 3% PPP) and PTMSP oxidized by nitrous oxide are stable in the temperature range from 30 to 220 °C for at least 1.5 years of continuous operation.

Monolithic chromatographic columns for HPLC based on divinylbenzene-styrene both with 1-vinylimidazole and with 4-vinylpyridine are prepared. The monoliths were synthesized in glass tubes with the ...

During the synthesis of 4-hydroxy-3-methoxybenzaldehyde (vanillin) several byproducts are formed in the reaction mixture, so the development of a method for the end product selective extraction from process solutions is an important stage of the used technology. This task can be solved by non-ionogenic sorbents application. The equilibrium and kinetic characteristics of vanillin uptake by hypercrosslinked non-ionogenic polymer material MN-202 (Purolite International Ltd) are studied. Applying the procedure of variable concentration, hydroxybenzaldehyde sorption isotherm for the studied sorbent has been obtained. It is well described by Langmuir equation with high value of correlation coefficient. In the system of aromatic aldehyde and non-ionogenic sorbent the stacking interactions between benzene ring of hydroxybenzaldehyde and styrene-divinylbenzene matrix have the main impact. Based on vanillin uptake kinetic curves at various temperatures and initial aldehyde concentration 6 mmol/dm3 the time of equilibrium attainment in the studied system has been determined. It is shown that sorption equilibrium is reached faster with temperature increase but the total capacity regarding vanillin is not changed in the considered temperature range. The nitrogen adsorption/desorption isotherms for MN-202 polymer have been measured before and after vanillin uptake. The changes in specific surface area and pores volume of the studied hypercrosslinked sorbent after vanillin sorption have been revealed. Pores distribution of non-ionogenic sorbent according to the sizes before vanillin uptake and after its sorption has been evaluated using the method of Barrett-Joyner-Halenda (BJH). MN-202 specific surface area has been calculated using the experimental data by the equation of Brunauer-Emmet-Teller. The represented low temperature (77 K) nitrogen adsorption/desorption isotherms for the sorbent samples before and after vanillin uptake belong to the IV type according to IUPAC classification, common for mesoporous materials. The specific surface area and pores volume of polystyrene polymer decrease significantly after vanillin sorption. At the same time the average size of pores in the structure increases that deals with the filling of considerable part of sorbent micro pores with sorbate molecules.

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.

The possibility to use multicapillary gas-chromatography column (MCC) as the second-dimension column in comprehensive two-dimensional gas chromatography (GC × GC) has been demonstrated. Dependences of the efficiency on the carrier gas volumetric flow rate were studied for capillary columns (CC) HP-5 and ZB-WAX of length 5 m and multicapillary columns of length 0.25 m with stationary phases OV-73 and Carbowax 20 M. For standard capillary columns, the maximum efficiency is reached at a flow rate below 2 mL/min. In the GC × GC mode, a capillary column is operated at a flow rate strongly exceeding the optimal value. Therewith, the efficiency of standard capillary column decreases several-fold, to 1570 theoretical plates for HP-5 and 1000 theoretical plates for ZB-WAX. In the case of multicapillary columns that are used in this paper, the maximum efficiency is reached at the carrier gas velocities above 60 mL/min. This allows MCC to be used as the second-dimension column in GC × GC at the optimal flow rate, thus reaching a maximum efficiency of 5900 theoretical plates for MCC with the OV-73 stationary phase and 2800 theoretical plates with Carbowax 20 M. The GC × GC separation of aliphatic and aromatic compounds was used to demonstrate that high efficiency of MCC enhances peak resolution in the second dimension as compared to standard capillary column. MCC was shown to be superior in separation of the components with close retention times and substantially differing concentrations.

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 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.

Multicapillary columns (MCCs) for gas chromatography make it possible to perform high-speed analysis of the mixtures of gaseous and volatile substances at a relatively large amount of the loaded sample. The study was performed using PLOT MCCs for gas-solid chromatography (GSC) with different stationary phases (SP) based on alumina, silica and poly-(1-trimethylsilyl-1-propyne) (PTMSP) polymer as well as porous polymers divinylbenzene-styrene (DVB-St), divinylbenzene-vinylimidazole (DVB-VIm) and divinylbenzene-ethylene glycol dimethacrylate (DVB-EGD). These MCCs have the efficiency of 4000-10000 theoretical plates per meter (TP/m) and at a column length of 25-30cm can separate within 10-20s multicomponent mixtures of substances belonging to different classes of chemical compounds. The sample amount not overloading the column is 0.03-1μg and depends on the features of a porous layer. Examples of separations on some of the studied columns are considered.

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.

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 μm diameter is up to 2500–3000 theoretical plates.