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The integration of semi-packed columns in gas chromatography has garnered significant interest in recent years. This review investigates various aspects of semi-packed columns, encompassing their fundamental concept, fabrication process, coating techniques, and exploration of various designs employed in gas chromatography. Diverse applications of semi-packed columns in gas chromatography are presented to showcase their practical significance and potential. By examining the current state of research and advancements in semi-packed column technology, this review aims to provide valuable insights for researchers seeking to enhance the capabilities of gas chromatography systems using innovative column designs. [ABSTRACT FROM AUTHOR]

• Micro pillar array column has been used in high pressure gas chromatography. • Carrier gas pressure as high as 60 bar was used for gas and liquid analysis. • HETP value as low as 14 µm has been obtained in few seconds. • Carrier gas nature was used to tune the selectivity. Micro pillar array column with interpillar distance of 2.5 µm for pillars diameter of 5 µm has been introduced in high pressure gas chromatographic systems for online industrial analysis. Separation of gas mixtures have been performed under carrier gas pressure as high as 60 bar using rotating valve for gas injection without sample decompression stage prior to injection. A very low intrinsic height equivalent to a theoretical plate value of 14 µm has been obtained in few seconds. Instead of conventional gas chromatography, carrier gas nature such as helium, argon and carbon dioxide and pressure can be used to tune the selectivity. Liquid hydrocarbon samples have been successfully introduced in the column using a septum based split/splitless injector modified to work up to 40 bar. Separations of VOCs and gasoline samples have been successfully performed. [ABSTRACT FROM AUTHOR]

• Semi-packed columns known as "µPAC™" with 2.5 µm pillar-pillar distance were tested in high-pressure gas chromatography. • A flow prediction tool based on geometrical parameters of the semi-packed column was introduced and exhibit good agreement with experimental values. • A comparative analysis of hydrodynamics, performance, and loading capacity between two semi-packed columns with different cross section was conducted. • The effect of carbon dioxide as carrier gas on semi-packed columns was investigated. Hydrodynamics, efficiency, and loading capacity of two semi-packed columns with different cross sections (NANO 315 µm x 18 µm; CAP 1000 µm x 28 µm) and similar pillar diameter and pillar-pillar distance (respectively 5 µm and 2.5 µm) have been compared in high-pressure gas chromatography. A flow prediction tool has been first designed to determine pressure variations and hold-up time across the chromatographic system taking into account the rectangular geometry of the ducts into the semi-packed columns. Intrinsic values of Height Equivalent to Theoretical Plate were determined for NANO and CAP columns using helium as carrier gas and similar values have been obtained (30 µm) for the two columns. Loading capacity of semi-packed columns were determined for decane at 70 °C using helium, and the highest value was obtained from CAP column (larger cross section and stationary phase content). Finally, significant HETP improvement (down to 15 µm) and peak shape were observed when carbon dioxide was used as carrier gas, suggesting mobile phase adsorption on stationary phase in high pressure conditions. [ABSTRACT FROM AUTHOR]

80% vinyltrimethoxysilane-based hybrid silica monoliths (80-VTMS), which have been initially developed for separation in reversed-phase liquid chromatography, have been investigated in high pressure gas chromatography separations (carrier gas pressure up to 60 bar) and compared to silica monolithic columns. The behavior of both silica and 80-VTMS monolithic columns was investigated using helium, nitrogen and carbon dioxide as carrier gas. The efficiency of 80-VTMS monolithic columns was shown to vary differently than silica monolithic columns according to the temperature and the carrier gas used. Carrier gas nature was a significant parameter on the retention for both silica and vinyl columns in relation to its adsorption onto the stationary phase in such high pressure conditions. The comparison of retention and selectivity between 80-VTMS monoliths and silica was performed under helium using the logarithm of the retention factor according to the number of carbon atoms combined to Kovats indexes. The very good performances of these columns were demonstrated, allowing the separation of 8 compounds in less than 1 min. [ABSTRACT FROM AUTHOR]

Nano-gravimetric detector (NGD) has been recently introduced as miniaturized gas chromatography detector. The NGD response is based on an adsorption-desorption mechanism of compounds between the gaseous phase and the NGD porous oxide layer. The NGD response was characterized by hyphenating NGD in-line with FID detector and a chromatographic column. Such method led to the full adsorption-desorption isotherms of several compounds in a single run. Langmuir model was used to describe the experimental isotherms, and the initial slope of the isotherm (Mm.K T) obtained at low gas concentration was used to compare the NGD response for different compounds (good repeatability was demonstrated with a relative standard deviation lower than 3%). The column-NGD-FID hyphenated method was validated using alkane compounds according to the number of carbon atoms in the alkyl chain and to the NGD temperature (all results agreed with thermodynamic relations associated to partition coefficient). Furthermore, relative response factor to alkanes, for ketones, alkylbenzenes, and fatty acid methyl esters have been obtained. These relative response index values led to easier calibration of NGD. The established methodology can be used for any sensor characterization based on adsorption mechanism. [Display omitted] • A Nano-gravimetric detector response model was successfully developed. • A hyphenated system was used for fast characterization of NGD detector. • Several adsorption isotherms were obtained in a single chromatographic run. • The proposed methodology to plot isotherms exhibited good repeatability. • Relative response to alkanes were determined for easier calibration of the detector. [ABSTRACT FROM AUTHOR]

In order to analyze light hydrocarbons mixtures with silica monolithic columns, a conventional gas chromatograph was modified to work with carrier gas pressure as high as 60 bar. To understand hydrodynamic flow and retention with short columns (less than 30 cm), special attention was required due to the temperature difference between the oven area and the FID detector which contain a significant length of the column. Efficiency and selectivity using various carrier gases (helium, nitrogen and carbon dioxide) at different inlet pressure for different oven temperature were studied. Carrier gas nature was a very significant parameter: on one side, linked to adsorption mechanism for gases like nitrogen and carbon dioxide onto the stationary phase modifying retention and selectivity, on the other side in relation to the minimum theoretical plate height which was as low as 15 μm (66 000 plate m −1 ) using carbon dioxide as carrier gas. The chromatographic system was then used to separate methane, ethane, ethylene, acetylene, propane, cyclopropane, and butane in less than 30 s. [ABSTRACT FROM AUTHOR]

Abstract: The polar organic chemical integrative sampler (POCIS) was relatively recently developed to trap hydrophilic organic micropollutants in aquatic environments. The aim of this article is to compile information from numerous references involving the POCIS in order to discuss the evaluation of time-weighted average concentrations (e.g., calibration methods, sampling rates, performance and reference compounds) and to review critically the different in situ applications (e.g., screening or quantifying micropollutants, and coupling to toxicity tests), application domains (e.g., molecules analyzed, and sampling media) and analytical protocols (e.g., processing, analysis, and exposure duration). [Copyright &y& Elsevier]