Specific Heteroatom Research Articles

Conversion of high moisture biomass to hierarchical porous carbon via molten base carbonisation and activation for electrochemical double layer capacitor

Biomass-derived carbon for supercapacitors faces the challenge of achieving hierarchical porous carbon with graphitic structure and specific heteroatoms through a single-stage thermal process that minimises resource input. Herein, molten base carbonisation and activation is proposed. The process utilises the inherent moisture of Moso bamboo shoots, coupled with a low amount of KOH, to form potassium organic salts before drying. The resultant potassium salts promote in-situ activation during single-stage heating process, yielding hierarchical porous, large specific surface area, and partially graphitised carbon with heteroatoms (N, O). As an electrode material, this carbon exhibits a specific capacitance of 327F g−1 in 6 M KOH and 182F g−1 in 1 M TEABF4/AN, demonstrating excellent cycling stability over 10,000 cycles at 2 A/g. Overall, this study presents a straightforward process that avoids pre-drying of biomass, minimises base consumption, and employs single-stage heating to fabricate electrode carbon suitable for supercapacitors.

Switching between Fluorescence and Room Temperature Phosphorescence in Carbon Dots: Key Role of Heteroatom Functionalities

Herein, we have synthesized three different types of carbon dots, i.e., (a) CDs from citric acid, (b) nitrogen atom functionalized CDs from citric acid and ammonia, and (c) phosphorus atom functionalized CDs from citric acid and sodium dihydrogen orthophosphate through a simple bottom-up carbonization technique. Detailed morphological and elemental features are investigated by high-resolution transmission electron microscopy and X-ray photoelectron spectroscopy study, and it is further correlated to the ongoing photophysical properties. To investigate the specific role of the heteroatom functionalities on the room temperature phosphorescence, we have incorporated all these three types of CDs in a boric acid matrix to diminish the flexibility of surface functional groups and decrease the nonradiative relaxation processes. Various heteroatom functionalities play a very specific role to tune the afterglow properties by altering the energy gap (ΔEST) between the lowest excited singlet (S1) and triplet state (T1) and the spin–orbit coupling constant which eventually control the radiative recombination from the triplet state. Finally, a switchable fluorescence and room temperature phosphorescence have been observed depending on the specific heteroatom functionalities. A detailed temperature-dependent study has been performed to investigate the tunability between prompt fluorescence and phosphorescence properties. This is further correlated to the conversion of phosphorescence with thermally activated delayed fluorescence (TADF). Computational studies based on time-dependent density functional theory (TD-DFT) have been performed by using optimized model systems in connection to the elemental study, which nicely support our experimental findings.

Full Green Detection of Antibiotic Tetracyclines Using Fluorescent Poly(ethylene glycol) as the Sensor and the Mechanism Study.

Tetracyclines are well-known antibiotics and widely used against a variety of bacterial infections. Their monitoring and detection have been an important issue. To this end, a vast number of methods have been developed; fluorescence sensing is one of the most reported. However, most of the reported sensors are made from transition metals with sophisticated multiprocesses; polymers are hardly seen for this purpose, particularly biocompatible ones. Herein, an aqueous solution of poly(ethylene glycol) (PEG), well known for being biocompatible, is shown to emit under excitation of 280 nm, while the solutions of selected tetracyclines, namely, doxycycline (DOX) and tetracycline (TC), are non-emissive under the same conditions. In the binary solutions of PEG-DOX or PEG-TC, PEG emission is sharply quenched with high sensitivity and selectivity. PEG was then used as a sensor for DOX and TC detections in water with high performance compared to reported studies. The same tests were also done by DOX spiking in milk and tap water, demonstrating that DOX was practically fully recovered. The quenching mechanism was ascribed to the interaction between the O atoms of PEG in clusters and specific heteroatom groups on tetracycline molecules through hydrogen bonding, elucidated from FTIR and NMR analyses. Therefore, this work provides a novel, fully green, easy to operate, low cost, and reliable protocol for tetracycline monitoring and detection and opens new potential application for PEG.

Facile synthesis of flower-like carbon microspheres for carbon dioxide capture

Among classes of porous sorbents with promise for use in mitigating carbon dioxide (CO2) emissions, carbons remain attractive due to their economical synthesis, high CO2 capacity, attractive CO2/N2 selectivity, and ease of regeneration. Here, we report a facile and scalable strategy to synthesize carbon microspheres (∼6 μm) bearing a unique, hierarchically structured flower-like morphology. These flowery carbons have specific surface areas as large as 2064 m2/g and total pore volumes ranging as high as 1 cm3/g, achieved through activation by CO2 at 900 °C. Detailed study of the textural properties and surface chemistry of these materials as a function of the activation time, primarily, and temperature, secondarily, reveals that CO2 capacity is strongly correlated to the volume of the ultra-micropores (diameters <1 nm) rather than to surface area, total pore volume, or specific N or O functionality. Ultra-micropore volume increases as a function of activation until devolving into larger micro- and meso-pores, with the optimal materials in this study showing high CO2 uptake at 1 bar spanning 4.5 mmol/g (25 °C) to 6.44 mmol/g (0 °C) and competitive CO2/N2 selectivity, as estimated by the Ideal Adsorbed Solution Theory (IAST), without any specific heteroatom doping. These carbons, derived from the simple processing of cheap precursors, also offer low isosteric heats of adsorption (20–30 kJ/mol), thereby, enabling facile temperature and pressure-swing-based cyclic regeneration. Taken together with their hierarchical structure, these materials show promise as efficient and cost-effective CO2 sorbents.

Computational Studies of Uranium Hexafluoride Interacting with Functionalized Organics. I. Screening Intermolecular Potentials between UF6 and Small Organic Functional Groups.

We report the intermolecular binding energies (IBEs) between UF6 and over 50 different functionalized small organic molecules as predicted by electronic structure calculations. Optimized geometries of UF6-molecule dimers were found at the MP2/aug-cc-pwCVDZ (non-U), cc-pVDZ-PP (U) level. IBEs were calculated using MP2 and dispersion-corrected DFT theory. We characterize the various functional groups based on the inclusion of specific heteroatoms. Those functional groups containing "nitrogen only" heteroatoms result in larger IBEs than groups containing both nitrogen and oxygen or oxygen alone. Halogen-containing and regular hydrocarbon molecules show the lowest IBEs with UF6. Nonorganic phosphoryl species are also shown to display large IBEs with UF6. These interactions are characterized in part by how much the impinging functionalized molecule distorts the UF6 from its optimal octahedral geometry. Of all the investigated groups, the amine group displayed the largest IBE values (IBE ∼ >12-14 kcal/mol for methyl amine), while hydrocarbons and perfluorocarbons both showed the weakest interactions (IBE ∼ 0.5-1.5 and 0.1-0.8 kcal/mol for methane and perfluoromethane, respectively). The study examines how the strength of the IBE is contingent on a combination of conformational deformation, stabilizing nonbonding interactions, and sterics.

(Invited) Novel Pyridine-functionalized Fullerene Derivatives toward the Efficient and Hysteresis-free Perovskite Solar Cells

Fullerene derivatives with strong electron-accepting abilities have been extensively used as electron transport layers (ETLs) of inverted (p–i–n) planar heterojunction perovskite solar cells (iPSCs); however the effect of the alkyl chains and a specific heteroatom site within the fullerene derivative on its electron transport properties has scarcely been studied. Herein,by employing pyridine carboxaldehydes bearing nitrogen sites within the pyridine moiety as a reactant, a series of novel pyridine-functionalized fullerene derivatives with variable nitrogen sites and alkyl chains length were synthesized facilely via a one-step 1, 3-dipolar cycloaddition reaction, and their molecular structures as well as molecular packing were unambiguously determined by X-ray single crystal diffraction. Despite that fullerene derivatives exhibit negligible difference in the molecular energy level and optical absorption, however, their electron transport properties are found to sensitively depend on the length of alkyl chains and nitrogen sites within the pyridine moiety. The C60-3-Py-based device shows the highest power conversion efficiency (PCE) of 17.57%. The discrepancy of the electron transport properties of fullerene derivatives is primarily due to the difference in the coordination interaction between the pyridine moiety and the Pb2+ ion of the MAPbI3 perovskite layer interaction between the pyridine moiety and the Pb2+ ion of the MAPbI3 perovskite layer.

Biomass-Derived Ternary-Doped Porous Carbon Electrodes for Li-Ion Capacitors: Rational Preparation and Energy-Storage Mechanism Study

Owing to the hybrid energy-storage features, Li-ion capacitors (LICs) inherit appealing properties from secondary batteries and supercapacitors, including high power density, high energy density and good cycling stability. However, incompatible kinetics between anode and cathode limit the performance improvement of the LICs. Moreover, the energy-storage mechanisms of carbon electrodes for LICs need to be further explored. Herein, we have prepared two ginkgo leaf-derived porous carbons (GLPCs) and used them as LIC electrodes. As resourceful biomass materials, ginkgo leaves have numerous O,N,S-enriched organics (e.g., flavonoids, alkaloids and thiophenes). By direct pyrolysis of the ginkgo leaves, ternary doped GLPCs are obtained without using additional dopants. The porosities, heteroatoms and defects for the GLPCs are tailored based on electrode requirements. The GLPCs obtained at 600 and 900 °C are specifically employed as the anode and cathode materials for LICs, respectively. The GLPC electrodes show good performance in half cells and their energy-storage mechanisms are interpreted by detailed ex situ and in situ experiments. DFT calculation results reveal that only specific heteroatom doping can enhance Li+ and PF6 − storage. Because of compatible electrode kinetics, the assembled LIC using the GLPC electrodes delivers high energy (118 Wh kg−1), high power (31.6 kW kg−1) and long lifespan.

Toxic gas sensing on nanoporous carbons

Activated carbons, either synthetic, developed in our laboratory, or commercial were prepared or further modified, in order to introduce specific heteroatoms such as oxygen, nitrogen and sulfur to their matrix. Chips with thin layers of active materials were prepared and used for ammonia or hydrogen sulfide sensing. They showed high sensitivity and their response was selective. They also responded linearly to changes in various ammonia concentrations. The incorporation of specific heteroatoms to the carbons matrices was an effective means to control the type of the charge carriers, and thus the electronic and transport properties. Depending on the specific chemical arrangement of heteroatoms, materials exhibiting n- or p-type conduction were obtained. Pyridines and nitropyridines played an important role. A small amount of ammonia was oxidized to NO2 on the surface of sulfur and nitrogen co-doped carbons, due to their ability to generate superoxide ions. When adsorbed in the pore system of the carbons, it affected the electrical signal due to an increase in the population of holes as charge carriers. The synergistic effect between the heteroatoms greatly enhanced the electrical response of the chips. The mechanism governing the reversible sensing involved several processes, including specific interactions between NH3 and surface functional groups, pore-filling with NH3/NO2, and electron–hole conductivity. The structural and chemical features of the carbons were found to act either synergistically or competitively. Surface acidity, by enhancing the affinity of the carbons towards NH3 adsorption, contributed to an ammonia selective detection.

Simultaneous quantification of amoxicillin and potassium clavulanate in different commercial drugs using PIXE technique

We have demonstrated, in previous studies that Particle Induced X-ray Emission (PIXE) is one of the most rapid and accurate choices for quantification of an active ingredient, in a solid drug, from the reactions induced on its specific heteroatom using pellets made from original tablets. In this work, PIXE is used, for the first time, for simultaneous quantification of two active ingredients, amoxicillin trihydrate and potassium clavulanate, in six different commercial antibiotic type of drugs. Since the quality control process of a drug covers a large number of samples, the scope of this study was also to found the most rapid and low cost sample preparation needed to analyze these drugs with a good precision. The chosen drugs were analyzed in their tablets’ “as received” form, in pellets made from the powder of the tablets and also in pellets made from the powder of the tablets after being heated up to 70°C to avoid any molecular destruction until constant weight and removal of humidity. The quantification validity related to the aspects of each sample preparation (homogeneity of the drug components and humidity) are presented and discussed.

Distribution of Total Sulfur in Acidic, Basic, and Neutral Fractions on Brazilian Asphalt Cements and Its Relationship to the Aging Process

In this work, studies were performed in Brazilian asphaltic cements by separating fractions of maltenes and asphaltenes using nonaqueous ion exchange liquid chromatography (NIELC). Initially, three different aging processes (RTFOT, PAV, and SUNTEST) were applied to 23 different asphaltic cements for evaluating the changing of asphaltenic (12.7 ± 2.5%) and maltenic (90.6 ± 5.0%) compounds. The RTFOT+SUNTEST process was studied in a comparative way for 5 asphalt cements samples, since it caused the more pronounced changes in maltenes and asphaltenes among the asphaltic cements supplied by different Brazilian refineries. Asphaltenes presented the highest amount of polar compounds in all the studied samples, herein attributed to compounds of acidic and basic character that contain sulfur. It was also found that the aging of asphalt cement leads to an increase of the more reactive acidic (9.5–18.9%) and basic (14.6–30.9%) fraction in both asphaltenes and maltenes. As a result, a reactivity index (Ir) for asphaltic cements was calculated and proposed for classifying the studied samples regarding their aging susceptibility. It was also observed that the less reactive asphaltic cement presented the highest amount (>80%) of neutral sulfur compounds in maltenic fraction. Lastly, it was concluded that a higher content of total sulfur in asphalts does not imply necessarily in a higher chemical reactivity (susceptibility to aging) of the cement, as observed for 5 studied samples having total sulfur ranging from 1.8 to 3.4% (w/w). The presence of functional groups related to their specific heteroatoms, such as sulfur, suggest a possible way to explain a greater or lesser susceptibility of asphalts to aging.

Identification of 2-aminothiazolobenzazepine metabolites in human, rat, dog, and monkey microsomes by ion-molecule reactions in linear quadrupole ion trap mass spectrometry.

2-Aminothiazolobenzazepine (2-ATBA), 7-[(1-methyl-1H-pyrazol-4-yl)methyl]-6,7,8,9-tetrahydro-5H-[1,3]thiazolo[4,5-h][3]benzazepin-2-amine, is a D2 partial agonist that has demonstrated antipsychotic effects in a rodent in vivo efficacy model. The metabolite profile showed that 2-ATBA is mainly metabolized by oxidation. However, identification of the oxidation site(s) in the 2-aminothiazole group presents a challenge for the traditional metabolite identification methods such as liquid chromatography/mass spectrometry and NMR due to the lack of unique tandem mass spectrometry fragmentation patterns for ions with the 2-aminothiazole group oxidized at different sites and the lack of stability for purification or reference standard synthesis. We describe the characterization of the oxidized heteroatoms of the 2-aminothiazole group via gas-phase ion-molecule reactions (GPIMR) in a modified linear quadrupole ion trap mass spectrometer. The GPIMR reagents used were dimethyl disulfide, tert-butyl peroxide, and tri(dimethylamino)borane. Each reagent was introduced into the ion trap through the helium line and was allowed to react with the protonated metabolites. The ionic ion-molecule reaction products and their fragmentation profiles were compared with the profiles of the ionic ion-molecule reaction products of protonated reference compounds that had specific heteroatom functionalities. The oxidized 2-aminothiazole metabolite of 2-ATBA showed a similar GPIMR profile to that of the reference compounds with a tertiary N-oxide functionality and distinct from the profiles of the reference compounds with N-aryl hydroxylamine, nitroso, or pyridine N-oxide functionalities. This study demonstrates the feasibility of fingerprinting the chemical nature of oxidized nitrogen functional groups via GPIMR profiling for metabolite structure elucidation.

Review of Sublimation Thermodynamics of Polycyclic Aromatic Compounds and Heterocycles

This review details sublimation vapor pressure and thermodynamic data on 85 polycyclic aromatic compounds and heterocycles from the early 1900s through 2012. These data were collected using a variety of vapor pressure measurement techniques, from effusion to gas saturation to inclined-piston manometry. A brief overview of each measurement technique is given; these methods yield reproducible sublimation vapor pressure data for low volatility organic compounds such as polycyclic aromatic compounds and heterocycles. Several conclusions can be drawn from this literature survey, specifically that there remains a dearth of data on the sublimation thermodynamics (and fusion thermodynamics) of heteroatomic high molecular weight aromatic compounds, inhibiting a holistic understanding of the effect of specific heteroatoms and substituent position on the thermodynamics of these compounds. However, we can clearly see from the data that there are a variety of potential intermolecular interactions at work that generally tend to increase the enthalpy of sublimation and decrease the vapor pressure of a substituted polycyclic aromatic compound/polycyclic heterocycles versus its parent compound.

A Quantum Alloy: The Ligand-Protected Au25–xAgx(SR)18 Cluster

Recent synthetic advances have produced very small (sub-2 nm), ligand-protected mixed-metal clusters. Realization of such clusters allows the investigation of fundamental questions: (1) Will heteroatoms occupy specific sites within the cluster? (2) How will the inclusion of heteroatoms affect the electronic structure and chemical properties of the cluster? (3) How will these very small mixed-metal systems differ from larger, more traditional alloy materials? In this report we provide experimental and computational characterization of the ligand-protected mixed-metal Au25–xAgx(SC2H4Ph)18 cluster (abbreviated as Au25–xAgx, where x = 0–5 Ag atoms) compared with the unsubstituted Au25(SC2H4Ph)18 cluster (abbreviated as Au25). Density functional theory analysis has predicted that Ag heteroatoms will preferentially occupy sites on the surface of the cluster core. X-ray photoelectron spectroscopy revealed Au–Ag state mixing and charge redistribution within the Au25–xAgx cluster. Optical spectroscopy and nonaqueous electrochemistry indicate that Ag heteroatoms increased the cluster lowest unoccupied molecular orbital (LUMO) energy, introduced new features in the Au25–xAgx absorbance spectrum, and rendered some optical transitions forbidden. In situ spectroelectrochemical experiments revealed charge-dependent Au25–xAgx optical properties and oxidative photoluminescence quenching. Finally, O2 adsorption studies have shown Au25–xAgx clusters can participate in photomediated charge-transfer events. These results illustrate that traditional alloy concepts like metal-centered state mixing and internal charge redistribution also occur in very small mixed-metal clusters. However, resolution of specific heteroatom locations and their impact on the cluster’s quantized electronic structure will require a combination of computational modeling, optical spectroscopy, and nonaqueous electrochemistry.

Swift Quantification of &lt;i&gt;Fenofibrate&lt;/i&gt; and &lt;i&gt;Tiemonium methylsulfate&lt;/i&gt; Active Ingredients in Solid Drugs Using Particle Induced X-Ray Emission

The quantification of active ingredients (AI) in drugs is a crucial and important step in the drug quality control process. This is usually performed by using wet chemical techniques like LC-MS, UV spectrophotometry and other appropriate organic analytical methods. However, if the active ingredient contains specific heteroatoms (F, S, Cl…), elemental IBA like PIXE and PIGE techniques, using small tandem accelerator of 1-2 MV, can be explored for molecular quantification. IBA techniques permit the analysis of the sample under solid form, without any laborious sample preparations. In this work, we demonstrate the ability of the Thick Target PIXE technique for rapid and accurate quantification of both low and high concentrations of active ingredients in different commercial drugs. Fenofibrate, a chlorinated active ingredient, is present in high amounts in two different commercial drugs, its quantification was done using the relative approach to an external standard. On the other hand, Tiemonium methylsulfate which exists in relatively low amount in commercial drugs, its quantification was done using GUPIX simulation code (absolute quantification) The experimental aspects related to the quantification validity (use of external standards, absolute quantification, matrix effect,...) are presented and discussed.

Group 6 Carbon Monoxide-Releasing Metal Complexes with Biologically-Compatible Leaving Groups

A series of carbon monoxide-releasing molecules (CO-RMs) based on the M(CO)(5) framework (M = Cr, Mo, W) is reported. The metal carbonyl anions [MCl(CO)(5)](-) are shown to be highly versatile precursors to Group 6 pentacarbonyl complexes containing amino-ester groups, namely, [M(CO)(5)(NH(2)CH{R}CO(2)R')]. The structures of five of the complexes, including an enantiomeric pair based on (R) and (S)-alanine, were determined by single crystal X-ray diffraction. These species exhibit rapid CO-release, as shown by a myoglobin-based assay. The rate of release is affected by the nature of both the metal and the amino-ester employed. A mechanistic study shows that a common intermediate is formed corresponding to loss of the amino-ester from the metal. In addition, a further series of potential CO-RMs have been prepared based on Fischer-type carbenes complexes, which contain either amino esters or amino acids. The amino esters and amino acids are introduced into the coordination sphere of the metal by a nucleophilic substitution reaction at the carbene carbon atom. The Michael addition of NH(2)CH(2)CO(2)Et across the triple bond in [Cr(CO)(5)(═C{OMe}-C≡CPh)] affords crystallographically characterized [Cr(CO)(5)(═C{OMe}-(Z)-CH═C{Ph}NHCH(2)CO(2)Et)]. The rate of CO-release from the carbene complexes depends primarily on the specific heteroatom connected to the carbene center. Rapid CO-release is observed in the case of sulfur- and methoxy-stabilized carbenes whereas in the case of amino-substituted carbenes, release is far more sluggish. This may be correlated with the electrophilic character at the carbene carbon atom.

Ion Beam Analysis and PD-MS As New Analytical Tools for Quality Control of Pharmaceuticals: Comparative Study from Fluphenazine in Solid Dosage Forms

In order to evaluate the potential of accelerator based analytical techniques ((particle induced X-ray emission (PIXE), particle induced gamma-ray emission (PIGE), and particle desorption mass spectrometry (PD-MS)) for the analysis of commercial pharmaceutical products in their solid dosage form, the fluphenazine drug has been taken as a representative example. It is demonstrated that PIXE and PIGE are by far the best choice for quantification of the active ingredient (AI) (certification with 7% precision) from the reactions induced on its specific heteroatoms fluorine and sulfur using pellets made from original tablets. Since heteroatoms cannot be present in all types of drugs, the PD-MS technique, which makes easily the distinction between AI(s) and excipients, has been evaluated for the same material. It is shown that the quantification of AI is obtained via the detection of its protonated molecule. However, calibration curves have to be made from the secondary ion yield variations since matrix effects of various nature are characteristics of such mixtures of heterogeneous materials (including deposits from soluble components). From the analysis of solid tablets, (either transformed into pellets and even as received), it is strongly suggested that the physical state of the grains in the mixture is a crucial parameter in the ion emission and accordingly for the calibration curves. As a result of our specific (but not optimized) conditions the resulting precision is <17% with an almost linear range extending from 0.04 to 7.87 mg of AI in a tablet made under the manufacturer conditions (the commercial drug product is labeled at 5 mg).

Elemental Speciation by Parallel Elemental and Molecular Mass Spectrometry and Peak Profile Matching

Trace elemental speciation in complex, real-world matrixes is a daunting task because of the low concentration of metals/metalloids and the correspondingly high molecular chemical noise. We constructed a liquid chromatography parallel elemental and molecular mass spectrometry (PEMMS) system and evaluated the use of peak elution profiles to identify trace molecular species containing specific heteroatoms, using the case of Se in yeast. We demonstrate that it is possible to use the HPLC-inductively coupled plasma (ICP)MS peak profile (retention time, width) to identify candidate ions with matching peak profiles in the molecular MS data. Proof of principle was demonstrated by C18 separation of three Se-amino acid standards (0.005-15 ppm as Se). The molecular MS (atmospheric pressure chemical ionization time-of-flight, APCI-TOF-MS) data set was converted into selected ion chromatograms of 0.05 Th width. ICPMS and APCI-TOF-MS ion chromatograms were fit by the Haarhoff-VanderLinde function using the following parameters: area, retention time, width, and skew. The ICPMS fit parameters were more reproducible than the APCI-TOF-MS fit parameters from run to run, and the APCI-TOF-MS signal was expected to limit correlation in most circumstances. Retention time and width were found to correlate well between the two MS systems for APCI-TOF-MS peaks with signal-to-fit-error (S/FE) of >25. Correction factors for differences in flow path length and peak broadening were required. The normalized correction factors were species and concentration independent and were stable from run to run. The skew parameter was found to be highly susceptible to noise and was not generally useful in matching ICPMS and APCI-TOF-MS peaks. An artificially noisy sample was generated by spiking 30 ppb Se-methionine (SeMet) and 5 ppb Se-methylselenocysteine (SeMSC) with unselenized yeast extract and run by PEMMS. The PEMMS software was able to detect four molecular MS peaks associated with SeMet and two for SeMSC, while filtering out >40 coeluting spectral peaks associated with chemical noise in each sample. In summary, we have demonstrated that correlated information in peak shape between parallel detectors can facilitate detection of trace elemental species in complex matrixes.

On the direct quantification of celecoxib in commercial solid drugs using the TT-PIXE and TT-PIGE techniques

The quantification of the active ingredient (AI) in drugs is a crucial and important step in the drug quality control process. This is usually performed by using wet chemical techniques like LC–MS, UV spectrophotometry and other appropriate organic analytical methods. In the case of an active ingredient contains specific heteroatoms (F, S, Cl, etc.,), elemental IBA technique can be explored for molecular quantification. IBA techniques permit the analysis of the sample under solid form, without any laborious sample preparation. This is an advantage when the number of sample is relatively large.In this work, we demonstrate the ability of the thick target PIXE (TT-PIXE) and the TT-PIGE techniques for rapid and accurate quantification of celecoxib in commercial drugs. The experimental aspects related to the quantification validity are presented and discussed.

Redetermination of σ+ constants for heteroaromatic rings. Oxygen-17 chemical shifts of trifluoroacetyl substituents and solvolytic reactivities of heteroaromatic analogs of 1-tert-butylbenzyl halides

Abstract

Synthèses photochimiques diastéréosélectives de complexes à liaison fer-métal du groupe 14

The diastereomeric Fe *(MR 3(CO)(P *R 1R 2R 3)Cp complexes (M  Si, Ge and Sn, R  aryl or methyl) are synthesized by photolysis of the prochiral Fe(MR 3(CO) 2Cp, precursors in the presence of the corresponding racemic phosphorus III ligands. Asymmetric induction at iron is observed if the phosphorus atom is bound to a group containing a specific heteroatom (nitrogen or oxygen).