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RSC Advances Sep 2023As the COVID-19 pandemic is not yet over, Pfizer has launched the novel pill Paxlovid® (Nirmatrelvir (NMV) co-packaged with ritonavir (RIT)) as an effective medication...
Tailoring two white chromatographic platforms for simultaneous estimation of ritonavir-boosted nirmatrelvir in their novel pills: degradation, validation, and environmental impact studies.
As the COVID-19 pandemic is not yet over, Pfizer has launched the novel pill Paxlovid® (Nirmatrelvir (NMV) co-packaged with ritonavir (RIT)) as an effective medication for hospitalized and non-hospitalized patients. Making pharmaceutical analysis greener and more sustainable has lately become the main direction of the research community. In this context, two fast, green, and stability-indicating chromatographic methods were designed for the neat quantitative determination of NMV and RIT in their bulk and dosage forms. Method I is deemed the first electro-driven attempt for the assay of Paxlovid®. Herein, the optimized conditions of the Micellar Electrokinetic Chromatographic (MEKC) method were 50 mM borate buffer at pH 9.2 with 25 mM sodium lauryl sulfate (SDS) being used as the background electrolyte (BGE) on a deactivated fused silica capillary (50 cm effective length × 50 μm id). Method II was an isocratic reversed-phase HPLC separation method using Zorbax-Eclipse C18 (4.6 × 250 mm, 5 μm particle size) column and 50 mM ammonium acetate buffer at pH 5 and acetonitrile as mobile phase constituents at a flow rate of 1 mL min. For the sake of simplicity and increasing sensitivity, a single wavelength of 210 nm was used for the two methods to assay both drugs. Linear correlations between peak areas and concentration were observed in the ranges of 10-200 μg mL for NMV and 5-100 μg mL RIT in both methods. The impact of versatile stress conditions such as hydrolysis, oxidation, and photolysis on the stability of NMV and RIT was studied. Fortunately, both methodologies were able to separate both drugs from their degradants. Thus, the stability indicating power of the methods was proved. The derived methods were statistically validated in agreement with the ICH guidelines. Furthermore, the environmental friendliness and sustainability of these methods were investigated and compared with the cited methods using the holistic multicriteria evaluation tools namely Hexagon, AGREE, and RGB12 metrics. Conclusively, the proposed methods offered reliable, feasible, economic, white, and stability-indicating alternatives to the cited chromatographic methods.
PubMed: 37681051
DOI: 10.1039/d3ra04186g -
Life (Basel, Switzerland) May 2024Fixed nitrogen species generated by the early Earth's atmosphere are thought to be critical to the emergence of life and the sustenance of early metabolisms. A previous...
Fixed nitrogen species generated by the early Earth's atmosphere are thought to be critical to the emergence of life and the sustenance of early metabolisms. A previous study estimated nitrogen fixation in the Hadean Earth's N/CO-dominated atmosphere; however, that previous study only considered a limited chemical network that produces NO species (i.e., no HCN formation) via the thermochemical dissociation of N and CO in lightning flashes, followed by photochemistry. Here, we present an updated model of nitrogen fixation on Hadean Earth. We use the Chemical Equilibrium with Applications (CEA) thermochemical model to estimate lightning-induced NO and HCN formation and an updated version of KINETICS, the 1-D Caltech/JPL photochemical model, to assess the photochemical production of fixed nitrogen species that rain out into the Earth's early ocean. Our updated photochemical model contains hydrocarbon and nitrile chemistry, and we use a Geant4 simulation platform to consider nitrogen fixation stimulated by solar energetic particle deposition throughout the atmosphere. We study the impact of a novel reaction pathway for generating HCN via HCN, inspired by the experimental results which suggest that reactions with CH radicals (from CH photolysis) may facilitate the incorporation of N into the molecular structure of aerosols. When the HCN reactions are added, we find that the HCN rainout rate rises by a factor of five in our 1-bar case and is about the same in our 2- and 12-bar cases. Finally, we estimate the equilibrium concentration of fixed nitrogen species under a kinetic steady state in the Hadean ocean, considering loss by hydrothermal vent circulation, photoreduction, and hydrolysis. These results inform our understanding of environments that may have been relevant to the formation of life on Earth, as well as processes that could lead to the emergence of life elsewhere in the universe.
PubMed: 38792622
DOI: 10.3390/life14050601 -
The Journal of Physical Chemistry. A Mar 2024Though there is a growing body of literature on the kinetics of CIs with simple carbonyls, CI reactions with functionalized carbonyls such as hydroxyketones remain...
Though there is a growing body of literature on the kinetics of CIs with simple carbonyls, CI reactions with functionalized carbonyls such as hydroxyketones remain unexplored. In this work, the temperature-dependent kinetics of the reactions of CHOO with two hydroxyketones, hydroxyacetone (AcOH) and 4-hydroxy-2-butanone (4H2B), have been studied using a laser flash photolysis transient absorption spectroscopy technique and complementary quantum chemistry calculations. Bimolecular rate constants were determined from CHOO loss rates observed under pseudo-first-order conditions across the temperature range 275-335 K. Arrhenius plots were linear and yielded -dependent bimolecular rate constants: () = (4.3 ± 1.7) × 10 exp[(1630 ± 120)/] and () = (3.5 ± 2.6) × 10 exp[(1700 ± 200)/]. Both reactions show negative temperature dependences and overall very similar rate constants. Stationary points on the reaction energy surfaces were characterized using the composite CBS-QB3 method. Transition states were identified for both 1,3-dipolar cycloaddition reactions across the carbonyl and 1,2-insertion/addition at the hydroxyl group. The free-energy barriers for the latter reaction pathways are higher by ∼4-5 kcal mol, and their contributions are presumed to be negligible for both AcOH and 4H2B. The cycloaddition reactions are highly exothermic and form cyclic secondary ozonides that are the typical primary products of Criegee intermediate reactions with carbonyl compounds. The reactivity of the hydroxyketones toward CHOO appears to be similar to that of acetaldehyde, which can be rationalized by consideration of the energies of the frontier molecular orbitals involved in the cycloaddition. The CHOO + hydroxyketone reactions are likely too slow to be of significance in the atmosphere, except at very low temperatures.
PubMed: 38428028
DOI: 10.1021/acs.jpca.4c00156 -
Communications Chemistry Jun 2024Photolysis is an attractive method in organic synthesis to produce free radicals through direct bond cleavage. However, in this method, specific irradiation wavelengths...
Photolysis is an attractive method in organic synthesis to produce free radicals through direct bond cleavage. However, in this method, specific irradiation wavelengths of light have been considered indispensable for excitation through S-S or S-T transitions. Here we report the photoinduced homolysis of electronegative interelement bonds using light at wavelengths much longer than theoretically and spectroscopically predicted for the S-S or S-T transitions. This long-wavelength photolysis proceeds in N-Cl, N-F, and O-Cl bonds at room temperature under blue, green, and red LED irradiation, initiating diverse radical reactions. Through experimental, spectroscopic, and computational studies, we propose that this "hidden" absorption is accessible via electronic excitations from naturally occurring vibrationally excited ground states to unbonded excited states and is due to the electron-pair repulsion between electronegative atoms.
PubMed: 38834838
DOI: 10.1038/s42004-024-01208-0 -
ACS Omega Nov 2023In this study, BiOI-sensitized TiO (BiOI/TiO) nanocomposites with different levels of BiOI deposited via sequential ionic layer adsorption and reaction (SILAR) have been...
In this study, BiOI-sensitized TiO (BiOI/TiO) nanocomposites with different levels of BiOI deposited via sequential ionic layer adsorption and reaction (SILAR) have been explored for the degradation of methyl orange, 4-chlorophenol (4-CP), and crude oil in water under visible (>400 nm) irradiation with excellent degradation performance. The reaction progress for methyl orange and 4-chlorophenol was monitored by a UV-vis spectrophotometer, and the degradation of the crude oil hydrocarbons was determined by GC-MS. The BiOI/TiO heterojunction improves separation of photogenerated charges, which enhances the degradation efficiency. Evaluation of the visible-light photocatalytic performance of the synthesized catalysts against methyl orange degradation confirmed that four SILAR cycles are the optimal deposition condition for the best degradation efficiency. The efficiency was further confirmed by degrading 4-CP and crude oil, achieving 38.30 and 85.62% degradation, respectively, compared with 0.0% (4-CP) and 70.56% (crude oil) achieved by TiO. The efficiency of TiO in degrading crude oil was mainly due to adsorption along with photolysis. This study provides a simple and cost-effective alternative to traditional remediation methods requiring high energy consumption for remediation of crude oil-polluted water and refinery wastewater using visible-light photocatalysis along with adsorption.
PubMed: 38027343
DOI: 10.1021/acsomega.3c04359 -
Environmental Science & Technology Dec 2023Dissolved organic matter (DOM) holds the largest amount of organic carbon in the ocean, with most of it residing in the deep for millennia. Specific mechanisms and...
Dissolved organic matter (DOM) holds the largest amount of organic carbon in the ocean, with most of it residing in the deep for millennia. Specific mechanisms and environmental conditions responsible for its longevity are still unknown. Microbial transformations and photochemical degradation of DOM in the surface layers are two processes that shape its molecular composition. We used molecular data (via Fourier transform ion cyclotron resonance mass spectrometry) from two laboratory experiments that focused on (1) microbial processing of fresh DOM and (2) photodegradation of deep-sea DOM to derive independent process-related molecular indices for biological formation and transformation () and photodegradation (). Both indices were applied to a global ocean data set of DOM composition. The distributions of and were consistent with increased photodegradation and biological reworking of DOM in sunlit surface waters, and traces of these surface processes were evident at depth. Increased values in the deep Southern Ocean and South Atlantic implied export of microbially reworked DOM. Photodegraded DOM (increased ) in the deep subtropical gyres of Atlantic and Pacific oceans suggested advective transport in warm-core eddies. The simultaneous application of and disentangled and assessed two processes that left unique molecular signatures in the global ocean.
Topics: Dissolved Organic Matter; Photolysis; Carbon; Mass Spectrometry; Oceans and Seas
PubMed: 38065573
DOI: 10.1021/acs.est.3c05929 -
The Journal of Physical Chemistry. A Oct 2023Sulfur oxide species (RSO) play a critical role in many fields, ranging from biology to atmospheric chemistry. Chlorine-containing sulfur oxides may play a key role in...
Sulfur oxide species (RSO) play a critical role in many fields, ranging from biology to atmospheric chemistry. Chlorine-containing sulfur oxides may play a key role in sulfate aerosol formation in Venus' cloud layer by catalyzing the oxidation of SO to SO via sulfinyl radicals (RSO). We present results from the gas-phase UV-vis transient absorption spectroscopy study of the simplest sulfinyl radical, ClSO, generated from the pulsed-laser photolysis of thionyl chloride at 248 nm (at 40 Torr of N and 292 K). A weak absorption spectrum from 350 to 480 nm with a peak at 385 nm was observed, with partially resolved vibronic bands (spacing = 226 cm), and a peak cross section σ(385 nm) = (7.6 ± 1.9) × 10 cm. From calculations at the EOMEE-CCSD/ano-pVQZ level, we assigned this band to 1A' ← XA″ and 2A' ← XA″ transitions. The spectrum was modeled as a sum of a bound-to-free transition to the 1A' state and a bound-to-bound transition to the 2A' state with similar oscillator strengths; the prediction agreed well with the observed spectrum. We attributed the vibronic structure to a progression in the bending vibration of the 2A' state. Further calculations at the XDW-CASPT2 level predicted a conical intersection between the excited 1A' and 2A' potential energy surfaces near the Franck-Condon region. The geometry of the minimum-energy conical intersection was similar to that of the ground-state geometry. The lack of structure at shorter wavelengths could be evidence of a short excited-state lifetime arising from strong vibronic coupling. From simplified molecular orbital analysis, we attributed the ClSO spectrum to transitions involving the out-of-plane π/π orbitals along the S-O bond and the in-plane orbital possessing a σ/σ character along the S-Cl bond. We hypothesize that these orbitals are common to other sulfinyl radicals, RSO, which would share a combination of a strong and a weak transition in the UV (near 300 nm) and visible (400-600 nm) regions.
PubMed: 37772907
DOI: 10.1021/acs.jpca.3c04977 -
Heliyon Jul 2023In this study, we synthesized rGO/Fe/FeO/TiO nanocomposite according to Hummer's, and straightforward sol-gel method. The FESEM, EDX, TEM, FT-IR, XRD, BET, UV spectra,...
In this study, we synthesized rGO/Fe/FeO/TiO nanocomposite according to Hummer's, and straightforward sol-gel method. The FESEM, EDX, TEM, FT-IR, XRD, BET, UV spectra, and VSM analysis were applied to determine the catalyst properties. Optimization of influence parameters on photocatalytic process performance to penicillin G degradation in aqueous media. pH (4-8), nanocomposite dose (10-20 mg/L), reaction time (30-60 min), and penicillin G concentration (50-100 mg/L) were optimized via central composite design. In the optimum condition of PCP, supplementary studies were done. As a result of the analysis, the nanocomposite was well synthesized and displayed superior photocatalytic properties for degrading organic pollutants. In addition to being magnetically separable, the synthesized rGO/Fe/FeO/TiO nanocomposite exhibits high recyclability up to 5 times. The quadratic model of optimization is based on the adjusted R(0.99), and predicated R(0.97) suggested. According to the analysis of variance test, the model was significant (F-Value = 162.95, -Value = 0.0001). Photocatalytic process is most efficiently decomposed at pH = 6.5, catalyst dose = 18.5 mg/L, reaction time = 59.1 min, and penicillin G concentration = 52 mg/L (efficiency = 96%). The chemical oxygen demand and total organic carbon decrease were 78, and 65%. The photolysis and adsorption mechanism as a single mechanism had lower performance in penicillin G degradation. Benzocaine had the greatest effect on reducing the efficiency of the process as a radical scavenger. The °OH, h and O were the main reactive oxidant species in penicillin G removal. Phenoxyacetaldehyde, Acetanilide, Diacetamate, Phenylalanylglycine, N-Acetyl-l-phenylalanine, Diformyldapsone, and Succisulfone were the main intermediates in penicillin G degradation. The results indicated the photocatalytic process with rGO/Fe/FeO/TiO nanocomposite on a laboratory scale has good efficiency in removing penicillin G antibiotic. The application of real media requires further studies.
PubMed: 37519670
DOI: 10.1016/j.heliyon.2023.e18172 -
Environmental Science & Technology Feb 2024Solar photoexcitation of chromophoric groups in dissolved organic matter (DOM), when coupled to photoreduction of ubiquitous Fe(III)-oxide nanoparticles, can...
Solar photoexcitation of chromophoric groups in dissolved organic matter (DOM), when coupled to photoreduction of ubiquitous Fe(III)-oxide nanoparticles, can significantly accelerate DOM degradation in near-surface terrestrial systems, but the mechanisms of these reactions remain elusive. We examined the photolysis of chromophoric soil DOM coated onto hematite nanoplatelets featuring (001) exposed facets using a combination of molecular spectroscopies and density functional theory (DFT) computations. Reactive oxygen species (ROS) probed by electron paramagnetic resonance (EPR) spectroscopy revealed that both singlet oxygen and superoxide are the predominant ROS responsible for DOM degradation. DFT calculations confirmed that Fe(II) on the hematite (001) surface, created by interfacial electron transfer from photoexcited chromophores in DOM, can reduce dioxygen molecules to superoxide radicals (O) through a one-electron transfer process. H nuclear magnetic resonance (NMR) and electrospray ionization Fourier-transform ion cyclotron resonance mass spectrometry (ESI-FTICR-MS) spectroscopies show that the association of DOM with hematite enhances the cleavage of aromatic groups during photodegradation. The findings point to a pivotal role for organic matter at the interface that guides specific ROS generation and the subsequent photodegradation process, as well as the prospect of using ROS signatures as a forensic tool to help interpret more complicated field-relevant systems.
Topics: Reactive Oxygen Species; Dissolved Organic Matter; Ferric Compounds; Superoxides; Photolysis
PubMed: 38294779
DOI: 10.1021/acs.est.3c08752 -
Science Advances Sep 2023Saturated fatty acids are abundant organic compounds in oceans and sea sprays. Their photochemical reactions induced by solar radiation have recently been found as an...
Saturated fatty acids are abundant organic compounds in oceans and sea sprays. Their photochemical reactions induced by solar radiation have recently been found as an abiotic source of volatile organic compounds, which serve as precursors of secondary organic aerosols. However, photoabsorption of wavelengths longer than 250 nanometers in liquid saturated fatty acids remains unexplained, despite being first reported in 1931. Here, we demonstrate that the previously reported absorption of wavelengths longer than 250 nanometers by liquid nonanoic acid [CH(CH)COOH)] originates from traces of impurities (0.1% at most) intrinsically contained in nonanoic acid reagents. Absorption cross sections of nonanoic acid newly obtained here indicate that the upper limit of its photolysis rate is three to five orders of magnitude smaller than those for atmospherically relevant carbonyl compounds.
PubMed: 37729407
DOI: 10.1126/sciadv.adj6438