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• Facile method for effective modification of asphaltenes by nitro groups. • Surface properties are determined by inverse gas chromatography (IGC). • Nitrated asphaltenes exhibits outstanding adsorption properties. • Nitrated asphaltenes are comparable with activated carbon, zeolites and alumina. • IGC revealed changes in the Lewis acid-base properties of aphaltenes by nitration. A novel nitrated asphaltene-derived adsorbent (Asf-Nitro) was prepared using facile isolation and modification procedures. The successful modification was confirmed by Fourier-transform infrared spectroscopy (FTIR). The nitrated adsorbent was evaluated in terms of dispersive and specific interactions, Lewis acid-base properties and adsorption isotherms by means of inverse gas chromatography (IGC). Nitration was found to be extremely effective in enhancing adsorption properties of asphaltenes towards variety of chemical compounds. Asf-Nitro adsorbent exhibits superior dispersive interactions (197.50 ± 1.12 mJ m−2 at 423 K), as compared to unmodified asphaltenes, which are comparable with activated carbons, zeolites or alumina. Examination of the specific interactions revealed a shift from basic to acidic character of the surface, what will be beneficial for adsorption of alkaline gases. Additionally, adsorption isotherms revealed that developed surface properties of the Asf-Nitro results in more than doubled monolayer adsorption capacity. Obtained results demonstrates the applicability of the asphaltene-derived materials in adsorption processes as highly effective and low cost adsorbents. This studies revealed a highly effective adsorption of environmentally important VOCs, e.g. n -butanol (odorous compound), trichloromethane (chlorinated hydrocarbon) and benzene (carcinogenic). [ABSTRACT FROM AUTHOR]

• Unprecedented selectivity towards volatile organic compounds (VOCs). • NADES based approach for separation techniques. • Comparable performance and stability with commercially available phases. • Green analytical chemistry approach for gas chromatography. • High applicability in environmental analysis. The paper presents a new kind of stationary phase for gas chromatography based on deep eutectic solvents (DES) in the form of a mixture of L-proline (protonated with hydrochloric acid) as a hydrogen bond acceptor (HBA) and xylitol as a hydrogen bond donor (HBD) in a molar ratio of HBA:HBD 5:1. DES immobilized on a silanized chromatographic support was tested by gas chromatography (GC) in order to determine its resolving power for volatile organic compounds. Studies have demonstrated the suitability of this type of DES as a stationary phase for GC. The Rohrschneider-McReynolds constants were determined for the synthesized DES, revealing that it is a polar stationary phase (Σ(ΔI) = 1717). The selectivity of DES is influenced by the presence of hydroxyl groups in the xylitol structure capable of forming hydrogen bonds of a donor nature and the proton acceptor properties of the protonated L-proline structure. The presence of additional interactions is brought about by the presence of the carboxyl group. As a result, the retention of alcohols is several times higher (200-670%) than the expected value based on their boiling points. A significant increase in retention (400-970%) was also found for pyridine derivatives. The developed DES stationary phase is characterized by very good repeatability of retention and stability (up to 140°C). The efficiency of the prepared columns (6300-11300 theoretical plates/m) and the selectivity of the DES stationary phase are competitive with the commercial products. [ABSTRACT FROM AUTHOR]

• First deep eutectic solvents (DES) based GC stationary phase • Unexpected selectivity towards volatile organic compounds (VOCs) • High applicability of developed DES in separation techniques The paper presents the first application of deep eutectic solvents (DES) as stationary phases for gas chromatography. DES obtained by mixing tetrabutylammonium chloride (TBAC) as a hydrogen bond acceptor (HBA) with heptadecanoic acid being a hydrogen bond donor (HBD) in a mole ratio of HBA:HBD equal to 1:2 was characterized by its ability to separate volatile organic compounds (VOCs). The Rohrschneider – McReynolds constants determined reveal that the synthesized DES is a stationary phase of medium polarity. A detailed retention characteristic was determined for a number of groups of chemical compounds, including aromatic hydrocarbons, alcohols, ketones, sulfides and thiophene derivatives. The synthesized DES was found to have a high selectivity towards alcohols. At the same time, the investigated stationary phase was found to have specific interactions with some analytes. For example, a stronger retention was observed for 1-hexanol and 1-heptanol compared to other alcohols. Retention times of these two alcohols are longer by 191% and 300%, respectively, relative to the expected value based on their boiling point. Such an increased retention is caused by a synergistic effect of various kinds of interactions – the possibility of formation of hydrogen bonds between the DES and the hydroxyl group of alcohols and hydrophobic interactions of alkyl chains of the DES with the alkyl chain of alcohols. The ability to modify properties of DESs by replacement of HBA or HBD with a different chemical compound or by dissolving in DES macromolecular substances makes the proposed stationary phase highly flexible. In addition to using the developed DES in chromatographic techniques, the retention data collected indicate the possibility of its application to other separation techniques, i.e. extractive distillation. [ABSTRACT FROM AUTHOR]