Electrospray Ionization Time-of-flight Mass Spectrometry Research Articles

Precise Pore Engineering of Zirconium Metal-Organic Cages for One-Step Ethylene Purification from Ternary Mixtures.

One-step purification of ethylene from ternary mixtures (C2H2, C2H4, and C2H6) can greatly reduce the energy consumption of the separation process, but it is extremely challenging. Herein, we use crystal engineering and reticular chemistry to introduce unsaturated bonds (ethynyl and alkyne) into ligands, and successfully design and synthesized two novel Zr-MOCs (ZrT-1-ethenyl and ZrT-1-alkyne). The introduction of carbon-carbon unsaturated bonds provides abundant adsorption sites within the framework while modulating the pore window size. Comprehensive characterization techniques including single crystal and powder X-ray diffraction, as well as electrospray ionization time-of-flight mass spectrometry (ESI-TOF-MS) confirm that ZrT-1-ethenyl and ZrT-1-alkyne possess an isostructural framework with ZrT-1 and ZrT-1-Me, respectively. Adsorption isotherms and breakthrough experiments combined with theoretical calculations demonstrate that ZrT-1-ethenyl can effectively remove trace C2H2 and C2H6 in C2H4 and achieve separation of C2H2 from C2H4 and CO2. ZrT-1-ethenyl can also directly purify C2H4 in liquid solutions. This work provides a benchmark for MOCs that one-step purification of ethylene from ternary mixtures.

Precise Pore Engineering of Zirconium Metal‐Organic Cages for One‐Step Ethylene Purification from Ternary Mixtures

AbstractOne‐step purification of ethylene from ternary mixtures (C2H2, C2H4, and C2H6) can greatly reduce the energy consumption of the separation process, but it is extremely challenging. Herein, we use crystal engineering and reticular chemistry to introduce unsaturated bonds (ethynyl and alkyne) into ligands, and successfully design and synthesized two novel Zr‐MOCs (ZrT‐1‐ethenyl and ZrT‐1‐alkyne). The introduction of carbon‐carbon unsaturated bonds provides abundant adsorption sites within the framework while modulating the pore window size. Comprehensive characterization techniques including single crystal and powder X‐ray diffraction, as well as electrospray ionization time‐of‐flight mass spectrometry (ESI‐TOF‐MS) confirm that ZrT‐1‐ethenyl and ZrT‐1‐alkyne possess an isostructural framework with ZrT‐1 and ZrT‐1‐Me, respectively. Adsorption isotherms and breakthrough experiments combined with theoretical calculations demonstrate that ZrT‐1‐ethenyl can effectively remove trace C2H2 and C2H6 in C2H4 and achieve separation of C2H2 from C2H4 and CO2. ZrT‐1‐ethenyl can also directly purify C2H4 in liquid solutions. This work provides a benchmark for MOCs that one‐step purification of ethylene from ternary mixtures.

A rapid and accurate liquid chromatographic method for hemp compliance testing

A liquid chromatography ultraviolet (LC-UV) method, which used methanol as the organic solvent for both extraction and separation, was developed for hemp compliance testing. While published methods occasionally used methanol for separation, all of them used gradient elution which would cause baseline drifts and a subsequent high limit of quantification (LOQ), and only eight or less cannabinoids were included. Our method was characterized by a baseline separation of Δ9-tetrahydrocannabinol (Δ9-THC) and Δ9-tetrahydrocannabinolic acid (Δ9-THCA) among nineteen cannabinoids in ten minutes and a calibration between 0.04 to 50 µg/mL, making it the most effective method validated so far. However, a reproducible separation of Δ9-THCA could not be achieved with the common formate buffer system, presumably due to its adsorption onto the C18 column which could be prevented by either using acetonitrile in the organic solvent that was widely undertaken by published methods or adding 0.1 % (v/v) trifluoroacetic acid in the aqueous solvent that was achieved only in this study. While similar problems were not reported by published methods, it was speculated that the problem could be common for all C18 columns, more or less, as the stationary phase in this study was di-isobutyl-n-octadecyl-silane without any polar imbedded moieties. Additionally, while quantification of Δ9-THC at 230 nm achieved good specificity, quantification of Δ9-THCA required 269 nm for acceptable specificity, which was verified by electrospray ionization time-of-flight mass spectrometry (ESI/TOFMS), indicating no false quantification and identification of Δ9-THC and Δ9-THCA, despite the observation of ten matrix peaks in the LC-UV chromatograms and identification of three untargeted/unknown cannabinoids by ESI/TOFMS in ten samples.

Development of a liquid chromatographic method with a different selectivity for the quantification of eighteen phytocannabinoids in hemp

To quantify phytocannabinoids in hemp, liquid chromatography diode array detector (LC-DAD) methods are favored, but their selectivity depends on baseline separation of all phytocannabinoids and unknown compounds in an extract. Therefore, development of a LC-DAD method with a different selectivity has become highly desirable. Currently, most LC-DAD methods use the water/acetonitrile eluting system, while this study aimed to use the water/methanol eluting system. A systematic investigation of various chromatographic parameters on LC separation of eighteen phytocannabinoids, the maximum number that has been quantified in hemp so far, plus two potential internal standards, led to a four-step isocratic mobile phase that was able to baseline separate the twenty compounds with a significantly different eluting order from published methods. Although changes in the mobile phase composition caused baseline drifts, consequent difficulty in quantification was avoided through detection at wavelengths longer than 230 nm. Subsequently, the method was validated according to the ISO 17025 guidelines, calibrated between 0.04 and 50 µg/mL, and used to analyze phytocannabinoids in nine strains of hemp flowers that were extracted using methanol between 0.04 and 50 % (w/w). Extraction recovery was tracked in real-time by spiking one of the two potential internal standards, i.e., abnormal cannabidiol (ACBD), a cannabinoid not naturally present in hemp. Method selectivity was further assessed by electrospray ionization time-of-flight mass spectrometry (ESI/TOFMS), indicating minimum interferences. In addition, five untargeted/unknown phytocannabinoids were identified by ESI/TOFMS, including two structural isomers of Δ9-tetrahydrocannabinol (Δ9-THC), two structural isomers of Δ9-tetrahydrocannabinolic acid (Δ9-THCA), and one structural isomer of Δ9-THC acetate.

Efficient and Selective Construction of 41 2 Metalla-links Using Weak C-H⋅⋅⋅Halogen Interactions.

Through a coordination-driven self-assembly method, four metalla-links and one tetranuclear monocycle were constructed with high selectivity and yield by adjusting the substituent species of the building blocks, as evidenced using X-ray crystallographic analysis, electrospray ionization-time-of-flight/mass spectrometry (ESI-TOF/MS), elemental analysis and detailed solution-state nuclear magnetic resonance (NMR) spectroscopy. Based on X-ray crystallographic analysis and independent gradient model analysis, a significant factor leading to the formation of metalla-links was the introduction of F, Cl, Br and I atoms, which generated additional weak C-H⋅⋅⋅X (X=F, Cl, Br and I) interactions. Furthermore, the dynamic conversion of metalla-links to monocyclic rings in methanol solution was systematically investigated using quantitative 1H NMR techniques.

Cucurbit[8]uril Binds Nonterminal Dipeptide Sites with High Affinity and Induces a Type II β-Turn.

In an effort to target polypeptides at nonterminal sites, we screened the binding of the synthetic receptor cucurbit[8]uril (Q8) to a small library of tetrapeptides, each containing a nonterminal dipeptide binding site. The resulting leads were characterized in detail using a combination of isothermal titration calorimetry, 1H NMR spectroscopy, electrospray ionization time-of-flight mass spectrometry (ESI-TOF-MS), and X-ray crystallography. The equilibrium dissociation constant values determined for the binding of Q8 to nonterminal dipeptide sites Lys-Phe (KF) and Phe-Lys (FK) were 60 and 86 nm, respectively. These are to the best of our knowledge the highest affinities reported to date for any synthetic receptor targeting a nonterminal site on an unmodified peptide. A 0.79 Å resolution crystal structure was obtained for the complex of Q8 with the peptide Gly-Gly-Leu-Tyr-Gly-Gly-Gly (GGLYGGG) and reveals structural details of the pair-inclusion motif. The molecular basis for recognition is established to be the inclusion of the side chains of Leu and Tyr residues, as well as an extensive network of hydrogen bonds between the peptide backbone, the carbonyl oxygens of Q8, and proximal water molecules. In addition, the crystal structure reveals that Q8 induces a type II β-turn. The sequence-selectivity, high affinity, reversibility, and detailed structural characterization of this system should facilitate the development of applications involving ligand-induced polypeptide folding.

Polytitanium sulfate rich with dominant-flocculated-species prepared by electrodialysis towards ceramic membrane fouling control

Ceramic membrane has always been of concern due to its high flux, fouling-resistance, and chemical-resistance. Membrane fouling is always an ever-lasting problem, and pre-coagulation is a high-recognized very effective and common methodology for membrane fouling control. Herein, a kind of high-efficient polytitanium sulfate (E-PTS) rich with dominant-flocculated-species was firstly developed by electrodialysis towards membrane fouling control. Electrodialysis well controlled the rate of polymerization among Ti-species and hydroxyl by regulating directed migration of electron through micro-interface. Both Ti-ferron and electrospray ionization time-of-flight mass spectrometry (ESI-TOF-MS) demonstrated the production of Tib and Tic as dominant-flocculated-Ti-species, accounting for 41.36 % and 42.18 %, respectively. The E-PTS had strong coagulation capability for the removal of biopolymer (BP), humic substance (HS), low molecular weight acid (LMWA), and low molecular weight neutral (LMWN) as proved by SEC-OCD-OND test. This was the very reason for the ca. 20 % higher removal efficiency of E-PTS coagulation over conventional polyaluminum chloride (PAC) and polyferric sulfate (PFS). Strong capability of coagulation with E-PTS enabled the follow-up filtration with ceramic membrane yielded large flux up to 361.0 LMH. More notable was that, continuous operation of membrane filtration for 30 h saw a stable high flux with no membrane fouling. The E-PTS pre-coagulation coupled with ceramic membrane filtration, a compact flow route, could realize both high-efficient water purification and membrane fouling control.

Nanoplastic Stimulates the Amyloidogenesis of Parkinson's Alpha-Synuclein NACore.

Environmental plastic wastes are potential health hazards due to their prevalence as well as their versatility in initiating physical, chemical, and biological interactions and transformations. Indeed, recent research has implicated the adverse effects of micro- and nano-plastics, including their neurotoxicity, yet how plastic particulates may impact the aggregation pathway and toxicity of amyloid proteins pertinent to the pathologies of neurological diseases remains unknown. Here, electrospray ionization time-of-flight mass spectrometry (ESI-TOF-MS) is employed to reveal the polymorphic oligomerization of NACore, a surrogate of alpha-synuclein that is associated with the pathogenesis of Parkinson's disease. These data indicate that the production rate and population of the NACore oligomers are modulated by their exposure to a polystyrene nanoplastic, and these cellular assays further reveal an elevated NACore toxicity in microglial cells elicited by the nanoplastic. These simulations confirm that the nanoplastic-NACore association is promoted by their hydrophobic interactions. These findings are corroborated by an impairment in zebrafish hatching, survival, and development in vivo upon their embryonic exposure to the nanoplastic. Together, this study has uncovered the dynamics and mechanism of amyloidogenesis elevated by a nanoplastic trigger, shedding a new light on the neurological burden of plastic pollution.

Controllable Topological Transformations of 818 Molecular Metalla-knots by Oxidation of Thiazole-Based Ligands.

By exploiting coordination-driven self-assembly, high yields of two 818 molecular metalla-knots could be obtained using a thiazole-moiety-containing asymmetric dipyridyl ligand 2-(pyridin-4-yl)-5-(pyridin-4-ylethynyl)benzo[d]thiazole (L1 ), as confirmed using X-ray crystallographic analysis, electrospray ionization-time-of-flight/mass spectrometry (ESI-TOF/MS), and detailed liquid-state nuclear magnetic resonance (NMR) spectroscopy. To modulate the self-assembled structures, m-chloroperbenzoic acid (m-CPBA) was utilized to oxidize thiazole-based ligand L1 to N-thiazole-oxide-based ligand 2-(pyridin-4-yl)-5-(pyridin-4-ylethynyl)benzo[d]thiazole 3-oxide (L2 ), which enabled the selective construction of the corresponding tetranuclear macrocycles. Notably, two molecular metalla-knots could be topologically transformed from 818 knots to simple monocycles because the L1 alkyne bond was inert toward m-CPBA, as confirmed by liquid-state NMR spectroscopy, ESI-TOF/MS, and elemental analysis.

Tuning Solvent Composition to Enhance the Stability of Metal Clusters in Mass Spectrometry

Electrospray ionization time-of-flight mass spectrometry (ESI-TOF-MS) has been recognized as a powerful technique for studying metal clusters' chemical composition and reaction mechanisms. It is a great challenge in mass spectrometry analysis to maintain the metal cluster molecules intact without fragmentation, which is achieved in this work by using mixed solvents to change the interaction between cluster molecules and solvent molecules, further affecting the fragmentation behaviors of the metal cluster in MS. Theoretical analysis reveals that the stability of the [(C)Au6Ag2(C18H14ONP)6]4+ cluster in ESI-TOF-MS is related to the strength of the chemical bonds between its own atoms and the bonding between the solvent and the cluster molecules.

Ionic Radius Dependent Kinetic Behavior for the Self‐Assemblyand Chiral Amplification of Lanthanide Tetrahedral Cages

Comprehensive SummaryUnderstanding the kinetic process during the self‐assembly and chiral amplification of metal‐organic polyhedra (MOPs) is critical for the rational preparation of chiral MOPs. Herein, we report the ionic radius dependent kinetic processes for the self‐assembly and chiral amplification of Ln4L4‐type (Ln, Lanthanides; L, ligand) lanthanide tetrahedral cages. The chiral Eu4(LR)4 tetrahedral cage is structurally characterized by nuclear magnetic resonance (NMR), electrospray ionization time‐of‐flight mass spectrometry (ESI‐TOF‐MS), and single crystal X‐ray diffraction. Kinetic study on the stereo‐controlled self‐assembly of circularly polarized luminescence (CPL)‐active Ln4(LR)4 (Ln = LaIII, PrIII and EuIII) tetrahedra manifests that the larger ionic radius of Ln leads to faster assembly rates. Mixed‐ligand cage assembly experiments with chiral LR/S, achiral Lac and Ln (1 : 3 : 4 molar ratio) reveal that the self‐assembly and chiral amplification occur synchronously for the LaIII and PrIII cages, while two distinct steps, i.e., first self‐assembly and then chiral amplification, are observed for the EuIII cage. Such distinct kinetic behavior is attributed to different ligands exchange rates among the mixed‐ligand Ln4L4 cages. This work provides fundamental guidance for fabrication and property‐optimization of chiral lanthanide‐based molecular materials.

Hierarchical subcomponent self-assembly of covalent triple-stranded complexes with 3d-4f vertices: luminescence and magnetic properties.

Well-defined 3d-4f heterometallic supramolecular architectures have attracted attention because of their applications in the field of luminescence and magnetism. However, covalent metallo-supramolecular discrete complexes, decorated with hetero-metallic vertices, have never been reported because of the difficulties in design and control. Herein, we report a series of covalent metallo-supramolecular discrete complexes with 3d-4f vertices synthesized by hierarchical subcomponent self-assembly of tris(2-aminoethyl)amine, 2,6-diformyl-p-cresol, and lanthanide ions (Ln) with different amines and transition metal ions. The programmable self-assembly process results in the formation of triple-stranded hetero-metallic covalent organic discrete complexes, namely 3a-3c-(Ln, Zn) (Ln = SmIII, EuIII, DyIII, YbIII and LuIII) and 3a'-(Dy, Co), which are characterized by nuclear magnetic resonance (NMR) analysis, electrospray ionization time-of-flight mass spectrometry (ESI-TOF-MS), and single-crystal X-ray analysis. Photophysical investigations disclose that the organic skeleton of 3a-(Ln, Zn) exhibits an excellent sensitizing ability toward SmIII, EuIII, and YbIII ions, displaying characteristic luminescence emission in both the visible and near-infrared (NIR) regions. AC susceptibility measurements of 3a'-(Dy, Co) reveal the frequency-independent performance under zero dc field, suggesting the absence of slow relaxation of magnetization. This work offers a new approach for the fabrication of discrete metallic covalent architectures with 3d-4f vertices.

Tailor-Made Poly(vinylamine) via Purple LED-Activated RAFT Polymerization of N-vinylformamide.

Photo-iniferter reversible addition-fragmentation chain transfer (PI-RAFT) polymerization of N-vinylformamide (NVF) is demonstrated by using purple light. PNVFs with predetermined molar masses and narrow molar mass distributions are obtained. High RAFT chain-end fidelity is confirmed by matrix-assisted laser desorption ionization time-of-flight (MALDI-TOF) and electrospray-ionization time-of-flight mass spectrometry (ESI-TOF-MS), and chain extension experiment. To demonstrate the potential of this approach, an original poly(N-vinylpyrrolidone)-b-poly(N-vinylformamide) (PVP-b-PNVF) diblock copolymer is synthesized and characterized by aqueous size-exclusion chromatography (SEC), asymmetric flow field-flow fractionation (A4F), and 1 H diffusion-ordered spectroscopy nuclear magnetic resonance (1 H DOSY NMR). Finally, selective hydrolysis of PNVF block to corresponding pH-responsive poly(N-vinylpyrrolidone)-b-poly(N-vinylformamide) (PVP-b-PVAm) is performed.

Enhanced Sensitivity in Comprehensive Liquid Chromatography: Overcoming the Dilution Problem in LC × LC via Temperature-Responsive Liquid Chromatography.

In comprehensive two-dimensional liquid chromatography (LC × LC), solvents of high eluotropic strength are frequently used in the first dimension (1D), which lead to peak broadening in the second dimension (2D). In the majority of the current LC × LC column combinations, analytes are less than optimally refocused upon transfer to the second column, which negatively affects sensitivity. Furthermore, the typical combination of 1 or 2.1 mm columns in the 1D paired with a 3 mm (or broader) column in the 2D leads to at least a 9- or 4-fold dilution and a corresponding loss of sensitivity when using concentration-sensitive detectors. This occurs due to the enhanced radial dilution of the analytes in a broader column, while the sensitivity problem is further exacerbated in LC × LC due to the high flow operated 2D. In this paper, we introduce a solution to neutralize and inverse this dilution problem through a reconcentrating solution using temperature-responsive liquid chromatography (TRLC) in the 1D, which is a purely aqueous separation mode. Full solute refocusing at the 2D column head is thereby obtained when TRLC is combined with reversed-phase liquid chromatography (RPLC). This is shown for the combination of a 2.1 mm I.D. TRLC column with decreasing RPLC column diameters (3-2.1-1 mm) operated at the same linear velocities, hence a resulting decrease in dilution, respectively. Ultraviolet (UV) and electrospray ionization time-of-flight mass spectrometry (ESI-TOF-MS) detection were used to determine the experimental detection limits. Sensitivity improvements with UV detection were somewhat lower than expected, but represent ∼1.5- and 3-fold sensitivity enhancement when using a 1 mm I.D. column compared to 2.1 or 3 mm I.D. columns in the 2D, respectively. This is attributed to extra-column dispersion and the poorer performance of 1 mm I.D. columns. A major benefit of the use of 1 mm I.D. columns in the 2D is that it allows split-free coupling of 2D effluent with ESI-MS (at 450 μL/min), making the coupling robust and simple. When using ESI-MS even better, albeit more variable, sensitivity enhancements were obtained on the narrower columns. The benefits of the methodology are demonstrated for paraben test solutes and for phenolic compounds in a blueberry extract by TRLC × RPLC-UV-ESI-TOF-MS.

Natural variation and drought-induced differences in metabolite profiles of red oak-leaf and Romaine lettuce play a role in modulating the interaction with Salmonella enterica

Nutrients on produce surfaces are vital for successful enteric pathogen colonisation. In this study, we investigated natural variation in metabolite profiles of Romaine ‘Parris Island Cos’ and red oak-leaf lettuce ‘Mascara’ under regular and restricted watering conditions. We also investigated the impact of plant drought stress on the Salmonella – lettuce association. Salmonella Newport and Typhimurium were able to persist at higher levels on regularly watered Romaine than red oak-leaf lettuce. Drought treatment to lettuce impaired epiphytic Salmonella association, with S. Newport and Typhimurium being differentially affected. A higher log reduction of both serotypes was measured on drought-subjected red oak-leaf lettuce plants than controls, but S. Typhimurium was unaffected on water deficit-treated Romaine lettuce (p < 0.05). To assess Salmonella interaction with leaf surface metabolites, leaf washes collected from both cultivars were inoculated and found to be able to support S. Newport growth, with higher levels of Salmonella retrieved from Romaine washes (p < 0.05). The lag phase of S. Newport in washes from water restricted red oak-leaf lettuce was prolonged in relation to regularly-watered controls (p < 0.05). Untargeted plant metabolite profiling using electrospray ionization time-of-flight mass spectrometry (ESI-TOF-MS) revealed natural variation between Romaine and red oak-leaf lettuce profiles for leaf tissue and leaf washes. Metabolite profile shifts were detected in both lettuce types in response to drought stress, but more unique peaks were detected in red oak-leaf than Romaine lettuce after drought treatment. Variation between the two cultivars was in part attributed to naturally higher levels of flavonoids and anthocyanins in red oak-leaf lettuce compared to Romaine. Moreover, red oak-leaf, but not Romaine lettuce, responded to drought by inducing the accumulation of proline, phenolics, flavonoids and anthocyanins. Drought stress, therefore, enhanced the functional food properties of red oak-leaf lettuce. Salmonella growth dynamics in lettuce leaf washes suggested that natural variation and drought-induced changes in metabolite profiles in lettuce could partly explain the differential susceptibility of various lettuce types to Salmonella, although the primary or secondary metabolites mediating this effect remain unknown. Regulated mild water stress should be investigated as an approach to lower Salmonella contamination risk in suitable lettuce cultivars, while simultaneously boosting the health beneficial quality of lettuce.

Molecular docking and antihypertensive effects of a novel angiotensin-I converting enzyme inhibitory peptide from yak bone.

A novel angiotensin-converting enzyme (ACE) inhibitory peptide ser-ala-ser-val-ile-pro-val-ser-ala-val-arg-ala (SASVIPVSAVRA) was purified and identified from yak bone by Electrospray Ionization-Time of Flight-Mass Spectrometry (ESI-TOF-MS). Results in vitro showed that the peptide exhibited strong ACE inhibition activities with an IC50 of 54.22 μM. Molecular docking results showed the binding between the peptide SASVIPVSAVRA and ACE mainly driven by van der Waals forces, hydrogen bonds and metal receptor. Interestingly, the ACE inhibition activities of the peptide increased about 19% after digestion, but none of its metabolites showed stronger activity than it. The in vivo experiment showed that the antihypertensive effect of peptide SASVIPVSAVRA at dose of 30 mg/kg is nearly equal to Captopril at dose of 10 mg/kg to spontaneously hypertensive rats (SHRs). The antihypertensive effect mechanism of SASVIPVSAVRA should be further studied through plasma metabolomics and bioanalysis. Structure analysis of amino acids and peptides produced during digestion may help better understand the antihypertensive effect of peptides.

Potency testing of up to twenty cannabinoids by liquid chromatography diode array detector with optional electrospray ionization time-of-flight mass spectrometry

The growing popularity of Cannabis sativa L. and its widespread use for medical and recreational purposes have created an urgent demand of accurate and reliable analytical methods to identify and quantify a growing number of cannabinoids. To meet this demand, a liquid chromatography diode array detector (LC-DAD) method has been developed, validated, and applied in analysis of cannabinoids in nine samples of plant materials of marijuana, six samples of marijuana cigarettes, five samples of hemp flowers, one sample of hemp cigarette, and two samples of Δ8-tetrahydrocannabinol (Δ8-THC) fortified hemp flowers. The method has achieved significant improvements over published methods, which was characterized of 20 targeted cannabinoids, 18 quantified cannabinoids, baseline resolution among quantified cannabinoids, a low limit of quantification (0.02 μg mL−1), a wide linear range (0.02–25 μg mL−1 or 0.04–50% (w/w)), a unique experiment to track the recovery of sample preparation in real time by spiking abnormal cannabidiol (CBD), and a well-assessed specificity by electrospray ionization time-of-flight mass spectrometry (ESI/TOFMS). Precision and accuracy were assessed using quality control (QC) samples at three concentration levels, i.e., 0.02, 0.5, and 12.5 μg mL−1, in triplicates with inter-day and intra-day precision of less than 15% relative standard deviation (RSD) and accuracy of less than ±15% relative error, therefore meeting the requirements by the ISO 17025 standards. Additionally, ESI/TOFMS has discovered seven unknown cannabinoids, including one structural isomer of cannabigerol (CBG), one structural isomer of cannabinolic acid (CBNA), four structural isomers of Δ9-THC, and one structural isomer of Δ9-THC acetate. Furthermore, it uncovered that one of the two samples of Δ8-THC fortified hemp flowers contained 5.16% (w/w) Δ9-THC, an alarm to the current Δ8-THC craze by the public.

Development of a validated method for rapid quantification of up to sixteen cannabinoids using ultra-high-performance liquid chromatography diode-array detector with optional electrospray ionization time-of-flight mass spectrometry detection

Due to the recent legalization of medical and recreational Cannabis in many countries in the world, there has been an increasing demand for accurate quantification of a growing number of cannabinoids. To meet this challenge, a method for rapid quantification of up to sixteen cannabinoids using ultra-high-performance liquid chromatography diode-array detector (UHPLC-DAD) has been developed, validated and used in the analysis of hemp concentrates. While published LC-UV methods were usually for twelve or less cannabinoids and might not achieve baseline separation of some critical pairs of cannabinoids, e.g., CBG/CBD (cannabigerol/cannabidiol) and Δ9-THC/Δ8-THC (tetrahydrocannabinol), in this study a systematic separation optimization led to a resolution of 1.7 for both pairs. The linear calibration range of all cannabinoids were between 0.02 to 25 µg/mL in methanol, leading to the quantification of 0.1 to 125% (w/w) individual cannabinoids in hemp concentrates after they were mixed with methanol at 20 µg/mL and analyzed after ultrasonication, centrifugation and filtration. The analytical results showed that none of the nine analyzed samples contained any of the seven acidic cannabinoids, but all the nine neutral cannabinoids were detected, with average content ranging from 0.10 to 93.23% (w/w) and RSD (relative standard deviation) values from 0.3 to 11.2% in triplicates. Particularly, two hemp concentrates, i.e., delta 8 hemp distillate and delta 8 hemp shatter contained 9.35 and 11.33% (w/w) Δ9-THC, respectively. While published recovery experiments were limited by the unavailability of cannabinoid-free matrix and the high cost of cannabinoid standards, this problem was solved by spiking abnormal CBD, a cannabinoid not naturally present in Cannabis plants and commercially available with a reasonable price, into the samples. The obtained average recovery ranged from 94.8 to 103.6% with RSD values from 1.5 to 9.0% in triplicates for the nine analyzed samples. Electrospray ionization time-of-flight mass spectrometry (ESI/TOFMS) confirmed the good specificity of the UHPLC-DAD method, i.e., without any false positive identification of individual cannabinoids, and discovered six untargeted cannabinoids that were structural isomers of Δ9-THC in the nine hemp concentrate samples.

Innovative synthesis of polytitanium chloride by electrodialysis: Identification of Ti-based hydroxyl polymers and coagulation performance

Biocompatibility of titanium (Ti) and recycling of the coagulated sludge to produce functional nanoparticles make the popularization of Ti-based coagulants highly attractive. Slow alkaline titration (SAT) method was commonly used to synthesize polytitanium coagulants, but cannot control the formation of dominant flocculation species due to the fast hydrolysis. We propose the innovative preparation of Ti-based coagulants by electrodialysis (ED) to control the directional transfer of electrons and regulate the rate of the micro-interface reaction. An efficient polytitanium chloride (PTC) was successfully prepared by ED method with TiCl4 as precursor, denoted as E-PTC. Results from electrospray ionization time-of-flight mass spectrometry (ESI-TOF-MS) proved the generation of the Ti-based hydroxyl polymers with various degrees of polymerization benefiting from the controllable migration of ions during ED process. The predominant Ti-based species changed from the small/median polymers to the large ones with increasing ED period. This was evidenced by Ti-Ferron assay that high Tib (34.35%) and Tic (47.05%) fractions were obtained in E-PTC after 8 h of ED period. The resulting E-PTC had stronger coagulation capability for both surface water and municipal wastewater treatment than the conventional ones. Compared with the conventional Al-based and Fe-based coagulants, E-PTC achieved 15% to 30% higher removal of organic matter, and produced the flocs with larger size, faster growth rate, better dewaterability, stronger strength and recoverability. This study provided the efficient ED method for the preparation of Ti-based coagulants with superior flocculation performance.

Self-Assembly of [3]Catenane and [4]Catenane Based on Neutral Organometallic Scaffolds

Transition metal-mediated templating and self-assembly have shown great potential to construct mechanically interlocked molecules. Herein, we describe the formation of the bimetallic [3]catenane and [4]catenane based on neutral organometallic scaffolds via the orthogonality of platinum-to-oxygen coordination-driven self-assembly and copper(I) template–directed strategy of a [2]pseudorotaxane. The structures of these bimetallic [3]catenane and [4]catenane were characterized by multinuclear NMR {1H and 31P} spectroscopy, electrospray ionization time-of-flight mass spectrometry (ESI-TOF-MS), and PM6 semiempirical molecular orbital theoretical calculations. In addition, single-crystal X-ray analyses of the [3]catenane revealed two asymmetric [2]pseudorotaxane units inside the metallacycle. It was discovered that tubular structures were formed through the stacking of individual [3]catenane molecules driven by the strong π–π interactions.