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• 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]

[Display omitted] • An efficient and economical adsorbent for waste gases treatment. • Remarkable enhancement of adsorption capacity by nitrated asphaltenes. • Over 2 times higher adsorption capacity for benzene comparing to Carbotrap adsorbent. • Detailed examination by inverse gas chromatography explained VOCs adsorption. • Step forward in design of adsorbents for removal of environmental pollutants. Asphaltenes isolated from bitumen possess unusual adsorption characteristics that can be further enhanced by chemical modifications to promote interactions with VOCs'. Herein, nitrated asphaltenes are used as an active layer coated on a surface of a diatomaceous earth, in order to prepare an efficient adsorbent (AsfNitro). Breakthrough experiments with benzene, pyridine, and 1-nitropropane revealed significant increase in adsorption capacity, after deposition of nitrated asphaltenes, by 26, 12, and 8 times respectively. The adsorption capacity of AsfNitro for benzene per square meter of surface area is far more superior than for other adsorbents in use. Moreover, the AsfNitro exhibited excellent efficiency. For adsorption of 1-nitropropane and pyridine, almost 100% of the adsorbent's bed was effectively used. Inverse gas chromatography measurements proved that nitrated asphaltenes were exclusively responsible for the adsorption properties, and the role of the diatomaceous earth was only to provide the surface area. Presented findings can be extended to other support materials and their inherent limitations for adsorption of VOCs can be overcome. Comparison of adsorption enthalpies demonstrated that common adsorbents e.g. activated carbons, cannot compete with AsfNitro in terms of sorbate-sorbent interactions. Additionally, contribution of chemisorption mechanism was recognized for AsfNitro, which indicate catalytic properties, and opens a new research field about asphaltenes' novel practical applications. Application of asphaltenes in adsorption processes can be an effective procedure for risk mitigation of hazardous VOCs, accompanied by effective waste management and materials' valorisation. Wasted adsorbent can be easily regenerated (without deterioration of surface properties), or blended in bitumen-aggregates mixes for road paving applications. [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]