Two‐dimensional comprehensive gas chromatography is an established technique, employed for the characterization of complex samples. Broadband vacuum ultraviolet absorption spectroscopy detection has ...recently attracted a lot of attention as it is a universal detection technique characterized by good selectivity but also ease of use and amenability to coupling with two‐dimensional comprehensive gas chromatography. Vacuum ultraviolet spectroscopy is particularly interesting due to the possibility of performing spectral decomposition for species that coelute in gas chromatography analysis. This detector has quantitative capabilities, however not all species absorb vacuum ultraviolet radiation the same. Unfortunately, vacuum ultraviolet relative response factors for compounds are not always available. Methods to rapidly measure vacuum ultraviolet relative response factors and generate a large database that would allow calibration free quantitative analysis of complex mixtures are therefore of great interest. In this work, a universal methodology that permits rapid measurement of vacuum ultraviolet relative response factors is reported. It involves flow modulated two‐dimensional comprehensive gas chromatography with dual vacuum ultraviolet and flame ionization detection. In this set‐up, flame ionization detection is employed as a quantitative reference allowing to scale vacuum ultraviolet responses of investigated compounds. This approach was validated by flow measurements and by comparing relative response factors obtained for model compounds with literature data.
Comprehensive two−dimensional Gas Chromatography with Vacuum Ultraviolet detection (GC×GC/VUV) results in sizable data for which noise and baseline drift ought to be corrected. As GC×GC/VUV signal is ...acquired from multiple channels, these pre−processing steps have to be applied to data from all channels while being robust and rather fast with respect to significant size of the GC×GC/VUV data. In this study, we describe advanced GC×GC/VUV data pre−processing techniques for noise and baseline correction that are not available in commercial softwares. Noise reduction was performed on both the spectral and the time dimension. For baseline correction, a morphological approach based on iterated convolutions and rectifier operations is proposed. On the spectral dimension, much less noisy and reliable spectra are obtained. From a quantitative point of view, mentioned pre−processing steps significantly improve signal to noise ratio for analyte detection and hence improve their limit of detection (circa 6 times in this study). These pre−processing methods were integrated into plug im! platform (https://www.plugim.fr/).
The mechanisms of formation of the three-dimensional titanium phosphate πTiP and of H−TiP, a hexagonal mesotextured titanium(IV) fluorophosphate, were studied using in situ and ex situ 19F and 31P ...NMR experiments. In situ NMR indicated that the prenucleation building units (PNBU), forming the solids under hydrothermal conditions, are identical for both phases. A possible structure of the PNBU is provided. Ex situ 19F and 31P liquid NMR allowed the transformations occurring in the supernatant liquid to be followed. Two kinds of species were observed during both syntheses: reactive primary species, which are the less fluorinated titanium fluorophosphates, and passive primary species, that is, the highly fluorinated titanium fluorides and fluorophosphates, which act as a reservoir of reactive primary species by slow interconversion. πTiP crystallizes following a condensation, precipitation, dissolution, and re-crystallization process as shown by quantitative analysis of ex situ NMR of the solid state and X-ray powder diffraction. H−TiP is first mesotextured at room temperature, and then its inorganic walls redissolve and crystallize during hydrothermal aging.
The use of two-dimensional gas chromatography hyphenated with vacuum ultraviolet absorbance spectroscopy (GC×GC-VUV) is constantly finding new applications. To qualitatively and quantitively exploit ...the information obtained with this type of analysis, suitable softwares are needed. However, to date, existing multidimensional chromatography softwares are not fully adapted to this type of data and offer only limited processing capabilities. Moreover, other solutions often rely on homemade programs that are not accessible to new users. For these reasons, several data processing modules for GC×GC-VUV data were developed and were integrated into the free access plug im! software (https://www.plugim.fr/). The usage guidelines and functionalities of the proposed modules are described, and several video tutorials are supplied. The proposed modules allow to visualise and preprocess GC×GC-VUV data. The extraction of spectra for user-designed template zones is also made possible which enables their further use for both quantification and spectral decomposition. These tools result in more sensitive methods thanks to the increase of the signal-to-noise ratio through application of adapted data preprocessing.
•Data processing modules dedicated to all three possible types of GC×GC-VUV data (1D, 2D and full 3D data) were contributed.•Adapted GC×GC-VUV data preprocessing methods allowing to significantly improve signal-to-noise ratio were integrated.•Identification template creation and extraction of absorbance spectra from all template zones was made possible.•Easy mapping of sample composition trough combination of several ‘spectral filters’ was proposed.
Dinuclear transition metal complexes with direct metal-metal interactions have the potential to generate unique reactivities and properties. Using asymmetric triazine ligands HN
3
t
BuR (R = Et,
i
...Pr,
n
Bu) featuring different alkyl substituents at 1,3-N centers, we report here the first rational synthesis of 'tetragonal lantern' type Fe(
ii
) triazenides Fe
2
(N
3
t
BuR)
4
R = Et (
1
),
i
Pr (
2
),
n
Bu (
3
) having an exceptionally short Fe-Fe distance (2.167-2.174 Å). Unlike the previously reported lantern structures with related amidinate or guanidinate ligands, highly air-sensitive
1-3
show a lower spin ground state, as indicated by Mössbauer,
1
H NMR and DFT studies.
We synthesized novel homoleptic dimeric complexes of the general formula Fe
2
(N
3
t
BuR)
4
(R = Et,
i
Pr,
n
Bu) having the shortest Fe(
ii
)-Fe(
ii
) bond (2.167-2.174 Å) reported to date and a low-spin ground state.
Dinuclear transition metal complexes with direct metal-metal interactions have the potential to generate unique reactivities and properties. Using asymmetric triazine ligands (HN3BuR)-Bu-t (R = Et, ...Pr-i, Bu-n) featuring different alkyl substituents at 1,3-N centers, we report here the first rational synthesis of 'tetragonal lantern' type Fe(ii) triazenides Fe-2((N3BuR)-Bu-t)(4) R = Et (1), Pr-i (2), Bu-n (3) having an exceptionally short Fe-Fe distance (2.167-2.174 & Aring;). Unlike the previously reported lantern structures with related amidinate or guanidinate ligands, highly air-sensitive 1-3 show a lower spin ground state, as indicated by M & ouml;ssbauer, H-1 NMR and DFT studies.
Since the beginning of the 2000's, comprehensive GC x GC chromatography brought a totally new way to characterize complex matrices. This disruptive technique is well adapted to fuels and rapidly ...gained importance in R & D laboratories of oil (and related) companies. Therefore, this analytical tool has been applied to many aspects of refining and especially the challenge of reducing the sulfur content in fuels. The present article reviews the use of comprehensive GC x GC for understanding the nature of sulfur compounds in refinery products (from gasoline to VGO) and their catalytic conversion through various catalytic processes such as HDS, AOTS, ODS. Various types of detectors (universal or specific) as well as FIT GC x GC have been applied and can be combined in order to get a better description of the S compounds in oil products.
Zeolites are promising candidate materials for water-based thermochemical heat storage applications. In this study, 13X and LiX commercial zeolites of different shapes were investigated due to their ...high thermal stability and storage capacities. Composite materials were prepared by impregnating matrices of 13X zeolite beads (13X(b)), 13X zeolite powder (13X(p)), or LiX beads (LiX(b)) with CaCl
2
, MgSO
4
and LiCl salts (5 wt%). The different zeolites and zeolite@salt composites were characterized using N
2
and H
2
O sorption isotherms, X-ray diffraction and NMR. The heat and water storage capacities were studied by TG-DSC analysis, as well as the hydration kinetics and the stability over time of the storage capacity. The Dubinin-Astakhov model was applied to the water sorption isotherms in order to better understand the sorption process. It turns out that zeolite shaping has a strong impact on hydration kinetics; moreover, the presence of an inert binder reduces the sorption capacity of 13X(b) compared to 13X(p). The pure zeolites and composites present a very high reversibility of water and heat storage capacities, with a good preservation of storage capacities after 50 simulated cycles of hydration in a water saturated environment. Salt incorporation impacts the porosity (especially for beads) and the environment of the zeolite component, as well as the water sorption behavior, kinetics and process, with a greater influence for LiCl based composites. The impregnation of 13X(b) and LiX(b) zeolites negatively affects the sorption capacities of the composites. This is due to blockage of the zeolite pores, which limits the accessibility of the zeolite structure for water vapor and decreases the contribution of the host matrix to the storage capacity to an extent that is not offset by the relatively small amount of salt added to the system.
13X zeolite in powder displays higher storage performances and faster hydration kinetics than 13X in beads. Salt-doped zeolite composite in powder form presents lower pore blockage and higher storage performances than composites in beads.
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•Review on comprehensive GC×GC for the characterization of S compounds in fuels.•S compounds in middle distillates and VGO, identification and kinetics.•Specific and universal ...detectors for GC×GC.
Since the beginning of the 2000’s, comprehensive GC×GC chromatography brought a totally new way to characterize complex matrices. This disruptive technique is well adapted to fuels and rapidly gained importance in R&D laboratories of oil (and related) companies. Therefore, this analytical tool has been applied to many aspects of refining and especially the challenge of reducing the sulfur content in fuels. The present article reviews the use of comprehensive GC×GC for understanding the nature of sulfur compounds in refinery products (from gasoline to VGO) and their catalytic conversion through various catalytic processes such as HDS, AOTS, ODS. Various types of detectors (universal or specific) as well as HT GC×GC have been applied and can be combined in order to get a better description of the S compounds in oil products.
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