Electrospray Ionization Time-of-flight Mass Spectrometry Research Articles

Spectroscopic Study of the Behavior of Mo(VI) and W(VI) Polyanions in Sulfuric-Phosphoric Acid Mixtures.

The solution chemistry of Mo(VI) and W(VI) in mixtures of sulfuric and phosphoric acids is relevant to the development of practicable hydrometallurgical processes for the recovery and separation of these two elements from low-grade scheelite ores. The behavior of Mo(VI) and W(VI) in such mixtures has been studied using X-ray absorption near-edge structure (XANES) and extended X-ray absorption fine structure (EXAFS), nuclear magnetic resonance (NMR), and small-angle X-ray scattering (SAXS) spectroscopies, along with electrospray ionization time-of-flight mass spectrometry (ESI-TOF-MS). Where applicable, these techniques have produced a self-consistent picture of the similarities and differences between the chemical speciation of Mo(VI) and W(VI) as functions of solution composition, mostly at a constant phosphorous/metal (P/M; M = Mo(VI) or W(VI)) ratio of ∼1. In dilute acidic media (0.02 mol·kg-1 H+, without H2SO4), Mo(VI) exists mostly (∼60%) as P2Mo5O236- with the remaining ∼40% as β-Mo8O264-. Under the same conditions, W(VI) is largely present as NaPW11O396- (∼80%) and P2W5O236- (∼10%), with the remainder probably occurring as isopolytungstates such as W12O4212- and some tungstophosphate dimers such as P2W18O626-. At higher acid concentrations (≲5 mol·kg-1 H2SO4), polymeric Mo(VI) anions are broken down to form the oxocations MoO22+ and Mo2O52+ and their protonated forms, with the dimers becoming increasingly dominant at higher acidities (∼80% in 5 mol·kg-1 H2SO4). In stark contrast, W(VI) polyanions do not decompose at higher acidities but instead form (∼70% in 0.6 mol·kg-1 H2SO4) a Keggin ion, PW12O403-. Further acidification with H2SO4 results in the agglomeration of this Keggin ion, forming clusters of about 50 and 100 Å in diameter that ultimately produce crystalline precipitates, which could be identified in part by their X-ray diffraction patterns. Possible application of these findings to the hydrometallurgical separation of Mo and W using acidic solutions is briefly discussed, based on a limited number of batch solvent extractions.

Perylene Diimide-Based Multicomponent Metallacages as Photosensitizers for Visible Light-Driven Photocatalytic Oxidation Reaction

Perylene Diimide-Based Multicomponent Metallacages as Photosensitizers for Visible Light-Driven Photocatalytic Oxidation Reaction

HR-LC-MS based profiling of phytochemicals from methanol extracts of leaves and bark of Myristica dactyloides Gaertn. from Western Ghats of Karnataka, India

Untargeted profiling of phytochemicals from plant extracts would aid in the exploration of various groups of compounds and assist in the identification of new bioactive compounds, reducing the redundancy in compound identification. The potential bioactive phytochemicals present in Myristica dactyloides, an endemic ethnomedicinal plant widely used in traditional treatment practices, were explored and cataloged in this study. The untargeted phytochemical profile of active methanolic leaves and bark extracts was assessed by Ultra high-performance liquid chromatography coupled to electrospray ionization and quadrupole time-offlight mass spectrometry. Preliminary screening results highlighted the high efficiency of methanolic extract as an effective antioxidant and anti-inflammatory agent, along with a remarkable amount of total phenolics and flavonoid content. Thus, the methanolic extracts of leaves and bark samples were further subjected to catalog its chemical constituents through untargeted metabolite profiling. Analysis of high-resolution liquid chromatography-mass spectrometer spectra, exhibited 3,813 and 1,797 molecular features in the ESI+ mode with clean retention time-exact mass, resulted in identifying 35 major therapeutically important common compounds for the first time in both leaves and bark extracts of M. dactyloides, fitting to major groups like lignans, neolignans, phenylpropanoids, diarylnonanoid, flavonoids, and others. Our results prove the presence of Myoinositol, Malabaricone B, Malabaricone C, Malabaricone D, and 1-(2,6-dihydroxyphenyl)- 9-(4-hydroxy-3-methoxyphenyl) nonan-1-one previously reported from M. dactyloides, along with promising chemical signatures like Monotropein, Austrobailignan 7, Fragransol B, Guaiacin, Myricanone, Nectandrin A, Argenteane, and Epicatechin to the phytochemical catalog of M. dactyloides. Furthermore, our research not only confirms the existence of previously known molecules and adds new phytochemicals, but it also sheds light on the wide application of M. dactyloides for possible bio-prospecting for a new chemical entity.

Apis mellifera propolis enhances apoptosis and invasion inhibition in head and neck cancer cells.

BackgroundPropolis is a resinous product accumulated from several plant sources that possess a wide range of therapeutic properties, including anti-cancer activities. However, the role of honeybee-produced propolis on head and neck squamous carcinoma (HNSCC) is not well understood. The aim of this study was to investigate the effects of Apis mellifera propolis on apoptosis and invasiveness in HNSCC cell lines.MethodsEthyl acetate extract of propolis (EAEP) was prepared from A. mellifera beehives using liquid–liquid extraction. High-performance liquid chromatography coupled with electrospray ionization-time of flight-mass spectrometry (HPLC-ESI-TOF-MS) was used to determine the flavonoids in EAEP. Isogenic HNSCC cell lines derived from primary (HN30 and HN4) and metastatic site (HN31 and HN12) were used in this study. The cytotoxicity, apoptosis, invasion, and MMP activity of EAEP on HNSCC cells were determined using an MTT assay, flow cytometry, Matrigel invasion assay, and gelatinase zymography, respectively.ResultsWe found that EAEP exhibited cytotoxic activity and induced apoptosis in the HNSCC cell lines. Furthermore, EAEP significantly decreased HNSCC cell invasion by reducing MMP-2 and MMP-9 activity. Two flavonoids, galangin and apigenin, were identified in EAEP by HPLC-ESI-TOF-MS. The results suggest that EAEP promotes apoptosis and exerts anti-invasion potential by inhibiting MMP-2 and MMP-9 activity in HNSCC cell lines. These inhibitory effects may be mediated by galangin and apigenin.

Characterization strategy of polymeric transition metal species transformation for high-purity metal recovery

The aqueous metal species with similar chemical properties are usually extracted together, limiting deep separation for high-purity metal. However, rare attention has been paid to metal speciation characterization and transformation during separation. Herein, the hydrolysis evolution of polymeric metal species was investigated systematically by electrospray ionization time-of-flight mass spectrometry (ESI-TOF-MS). The transformation evolutions were visualized with respect to characteristic vanadium species (V1, V2, V3, V4 and V10), chromium species (Cr1 and Cr2), tungsten (W1, W2, W4, W6 and W10) and molybdenum (Mo1, Mo2 and Mo4) species. The key characteristics (such as specfic pHs and concentrations) for speciation variation were revealed. The polymerization behavior of several transition metals can be semiquantitative characterized by this strategy. The sufficient speciation transformation provides a solid base for metal speciation chemistry, and guides further development of high-purity metal recovery.

Enhanced secondary organic aerosol formation from the photo-oxidation of mixed anthropogenic volatile organic compounds

Abstract. Vehicular exhaust is one of the important contribution sources of secondary organic aerosol (SOA) in urban areas. Long-chain alkanes and aromatic hydrocarbons are included in gaseous organic pollutants of vehicle emissions, representative of diesel and gasoline vehicles respectively. In this work, the SOA production from individual anthropogenic volatile organic compounds (AVOCs) (n-dodecane, 1,3,5-trimethylbenzene) and mixed AVOCs (n-dodecane + 1,3,5-trimethylbenzene) was studied with a large-scale outdoor smog chamber. Results showed that the SOA formation from the mixed AVOCs was enhanced compared to the predicted SOA mass concentration based on the SOA yield of individual AVOCs. According to the results of mass spectrometry analysis with electrospray ionization time-of-flight mass spectrometry (ESI-ToF-MS), interaction occurred between intermediate products from the two precursors, which could be the main reason for the enhanced SOA production from the mixed AVOC reaction system. The study results could improve our understanding about the contribution of representative precursors from vehicular exhaust to the formation of SOA in urban areas. This study also indicates that further studies on SOA chemistry from the mixed VOC reaction system are needed, as the interactions between them and the effect on SOA formation can give us a further understanding of the SOA formed in the atmosphere.

Untargeted LC-MS-based metabolomics revealed specific metabolic changes in cotyledons and roots of Ricinus communis during early seedling establishment under salt stress

Early seedling development is one of the most crucial period of the plant's life cycle, which is highly susceptible to adverse environmental conditions, especially those impose by salt stress. Castor plant (Ricinus communis) is a famous non-edible oilseed and salt-resistant crop worldwide. However, the specific metabolic responses in the cotyledons and roots of this species during seedling establishment under salt stress are still not clearly understood. In the present study, 16 d castor seedlings were treated with 150 mM NaCl for 6 d, and the metabolite profiling of cotyledons and roots was conducted using liquid chromatography (LC) combined with electrospray ionization time-of-flight mass spectrometry (ESI-TOF-MS). The Principal Component Analysis (PCA) results showed that the metabolites were great differed in cotyledons and roots under salt stress. There were 38 differential metabolites, mainly including fatty acid, nucleic acid and organic acids in the cotyledons, but only 19 differential metabolites, mainly including fatty acid and organic acids in the roots under such condition. Furthermore, Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis revealed that flavone and flavonol biosynthesis, pantothenate and CoA biosynthesis, citrate cycle and carotenoid biosynthesis were the common metabolic pathways in response to salt stress in the two organs. Salt stress caused metabolite process alteration mainly on carbon and nitrogen metabolisms, and the carbon allocation from root to cotyledon was increased. Additionally, changes of amino acids and nucleic acids profiles were only found in the cotyledons, and the roots could enhance the activity of antioxidant enzyme systems to scavenge ROS under salinity. In conclusion, the present research provides an improved understanding on specific physiological changes in the cotyledons in castor early seedlings, and explores their interaction under salt stress.

The influence mechanism of HCO3− on fluoride removal by different types of aluminum salts

In order to study the influence mechanism of HCO3− on the fluoride removal by AlCl3 and Al13, the residual fluoride concentration, residual aluminum concentration and pH value in coagulation effluent were measured at different HCO3− concentrations. Electrospray ionization time-of-flight mass spectrometry (ESI-TOF-MS) was used to analyze the aluminum species in the supernatant after coagulation, and the flocs collected were analyzed by nuclear magnetic resonance (NMR) and X-ray photoelectron spectra (XPS). The results show that AlCl3 is used as a coagulant, when the concentration of HCO3− increases from 100 mg/L to 300 mg/L, Al3+ and HCO3− are double hydrolyzed to form Al(OH)3 alum flower after adding AlCl3, and the removal rate of fluoride rapidly increases from 9.55 % to 78.0 %. When the concentration of HCO3− increases from 300 mg/L to 1000 mg/L, the precipitation of Al(OH)3 will gradually dissolve to form Al(OH)4− and the removal rate of fluoride drops from 78.0 % to 56.2 %. When Al13 is used as a coagulant, with the increase of HCO3− from 100 mg/L to 1000 mg/L, its double hydrolysis with Al-F complexes is enhanced, resulting in the formed Al6F2, Al7F2 and Al9F3 gradually dissociate, and the removal rate of fluorine decreases from 78.8 % to 59.4 %.

Polymerization and Transformation of Tungsten(VI) Species in Acidic Aqueous Solution by Electrospray Ionization Time-of-Flight Mass Spectrometry

Deep understanding of the polymerization and transformation of tungstate species in aqueous solution is of great significance for hydrometallurgical and chemical separation processes, such as solvent extraction, membrane separation and crystallization. In order to study the polymerization and transformation of tungstate species, the semi-quantitative characterization method of electrospray ionization time-of-flight mass spectrometry (ESI-TOF-MS) was developed. In this paper, the tungsten speciation in simulative leaching solution was investigated in detail between pH 2.5 and 7 under various conditions (e.g. acid species, initial concentration, pH), and the results indicated that HCl was more conducive than HNO3 for the polymerization of tungsten at the same pH, and HAc accelerated the polymerization of tungsten species, especially in acid solution at lower pH; the morphological changes of each tungsten species tended to be consistent with the increase of tungsten concentration; pH strongly influenced the distribution of tungsten species. Then, the polymerization and transformation laws of tungstate species are summarized. W1 (monomers) are dominant species in weak acid and neutral solution, and aggregate into oligomeric species (e.g. W2, W4, W6). Transformations also exist among W2, W4 and W6. The polymerization process from W4 and W6 species to higher poly-tungstate (W10–12) was observed with the consumption of H+. This work aims to understand the polymerization and transformation of tungsten speciation using ESI-TOF-MS, which should provide useful information for the understanding and optimizing of industrial production and environmental processes, building a bridge between micro tungsten speciation and macro industrial applications.

Mechanism of fluoride removal by AlCl3 and Al13: The role of aluminum speciation

Coagulation is an important defluorination process. However, because of the poor sedimentation properties, conventional coagulants often result in limited defluorination performance and excessive residual aluminum. In this study, AlCl3 and the highly-positively-charged molecule [AlO4Al12(OH)24(H2O)12]7+ (Al13) was utilized to treat fluoride-containing water. By comparison, the role of aluminum speciation in fluoride removal was elucidated. Under initial pH of 6.0, 7.0 and 8.0, the highest defluorination efficiencies of high-fluoride water ([F−]0 = 8.0 mg/L) were 78.2%, 71.6% and 83.2% at Al13 dosage of 20 mg/L, 40 mg/L and 50 mg/L. Combined with detailed investigations of the chemical compositions of flocs, along with electrospray ionization time-of-flight mass spectrometry (ESI-TOF-MS) analysis of residual aluminum, the defluorination mechanisms of both coagulants were discussed. In acidic conditions, both coagulants hydrolyzed and formed various Al clusters, among which transient Al (Alts) was the intermediate of the other clusters. The coprecipitation of high-polymerized Al and F− contributed most of the defluorination rate. While under neutral and alkaline conditions, hydrogen bonding and ion exchange together with coprecipitation were the main roles for Al13. The effects of AlCl3 were merely physical actions, and were affected by the decreased pH. This work provides new insights into the coagulation and defluorination process.

Changes in redox state of albumin before and after kidney transplantation in patients with end-stage renal disease

ObjectivesCardiovascular disease is one of the major causes of death in patients with end-stage kidney disease who have undergone kidney transplantation. Since the complication of cardiovascular disease in patients with chronic kidney disease is strongly linked to oxidative stress, understanding the oxidative stress condition after kidney transplantation would be of great importance for the prevention of cardiovascular disease. This study examined whether improvement of renal function after kidney transplantation has an impact on the redox state of the Cys34 residue of albumin that reflects the level of oxidative stress in blood. Design & methodsWe enrolled 23 patients with end-stage renal failure who received kidney transplantation. All patients were followed for 180 days after transplantation. The fractions of albumin isoforms were determined by the electrospray ionization time-of-flight mass spectrometry (ESI-TOFMS) method. ResultsSerum creatinine decreased significantly immediately after kidney transplantation, suggesting successful transplantations. The ESI-TOFMS method identified three albumin isoforms cysteinylated at the Cys34 residue (Cys-Cys34-albumin) and the three corresponding albumin isoforms without Cys34 cysteinylation. The fraction of total Cys-Cys34-albumin decreased transiently after kidney transplantation, and was followed by an elevation at day 7 and gradual decrease thereafter until day 180. Meanwhile, reduced albumin concentration did not change until day 14 after kidney transplantation, then showed a significant increase compared to pre-transplant level at day 30 and remained stably elevated until day 180. ConclusionsActual reduced albumin levels were found to exceed pre-transplant levels on or after day 30 following kidney transplantation unlike immediate restoration of renal function. Renal function was recovered immediately following kidney transplantation, but reduced albumen concentration increased above the pre-transplant levels only from day 30 after transplantation.

From a mononuclear FeL2 complex to a Fe4L4 molecular square: Designed assembly and spin-crossover property

By introduction of a new Fe(L1)2 spin-crossover (SCO) unit into the polynuclear system, a nano-scale Fe4(L2)4 molecular square architecture is designed through coordination-directed self-assembly strategy. Both the mononuclear Fe(L1)2 and tetranuclear Fe4(L2)4 complexes have been structurally confirmed by 1H nuclear magnetic resonance (NMR), electrospray ionization time-of-flight mass spectrometry (ESI-TOF-MS), and temperature-dependent single crystal X-ray diffraction studies. Variable-temperature magnetic susceptibility measurements reveal the presence of an abrupt SCO behavior with a thermal hysteresis width of 4 K for Fe(L1)2. By clear contrast, Fe4(L2)4 undergoes a gradual spin transition behavior with enlarged thermal hysteresis width and higher spin transition temperature.

Analysis of spectrometry and thermodynamics of the metallothionein in freshwater crab Sinopotamon henanense for its binding ability with different metals.

The metal binding nature of heterologously expressed metallothionein of Sinopotamon henanense (ShMT) had been demonstrated previously. In this study, we analysed the stoichiometry of ShMT yielded invivo and exchange reactions of the Zn-ShMT with Cd2+, Pb2+ and Cu2+invitro via electrospray ionization time-of-flight mass spectrometry (ESI-TOF-MS), circular dichroism (CD) spectroscopy, inductively coupled plasma mass spectrometry (ICP-MS), and isothermal titration calorimetry (ITC). The results of ESI-TOF-MS analyses showed that metal-ShMT synthesized invivo had three major forms, namely Zn15-, Cd9-, and Pb5-ShMT. The ITC analyses of exchange reactions demonstrated that Zn-ShMT exhibited up to 6, 6, and 7 binding sites for Cd2+, Pb2+ and Cu2+. By the analyses of the UV and CD spectra in the substitution experiments showed that the geometric structural stability of metal-ShMT could be influenced when excess of over 6, 6, or 7 equivalents of Cd2+, Pb2+, or Cu2+ were added into Zn-ShMT. Although both the reconstructed apo-ShMT and substituted Zn-ShMT with three metal ions fitted the same M6Ⅱ- and M7Ⅰ-ShMT binding models for divalent and monovalent metals, the differences in their thermodynamic data suggested that discrepancies exit in their physiological functions. These results suggested that ShMT yielded invivo had a higher storage capability for Zn2+ and a uptake ability for Cd2+, and Zn-ShMT was more easy to release Zn2+ as well as to uptake Cd2+, Cu2+, or Pb2+. The results presented in this work will be very valuable to understand the function(s) of ShMT not only in a normal physiological condition but also in the presence of non-essential metals in crabs.

UV irradiation of Cu-based complexes with aliphatic amine ligands as used in living radical polymerization

The effect UV irradiation on Cu(II)-based complexes with aliphatic amine ligands is investigated. Four aliphatic amines are used as ligands and Cu(II)Br2 as the metal source for the formation of catalyst complexes that can be used for the photoinduced Cu-RDRP of methyl acrylate. Different characterization techniques such as transient electronic absorption spectroscopy (TEAS), ultraviolet–visible (UV–Vis) spectroscopy, electrospray ionization time of flight mass spectrometry (ESI-ToF-MS) and cyclic voltammetry (CV) are applied in order to provide insights into the catalyst behaviour upon photo-irradiation. The excited-state dynamics, the electrochemical behaviour of the Cu(II)/Cu(I) redox couples and the detection of different species upon complexation of the ligand to the metal center (before and after UV irradiation) are further depicted in the quality of the obtained polymers.

Hierarchical self-assembly of 3D amphiphilic discrete organoplatinum(II) metallacage in water

Here we described the design and synthesis of a discrete 3D amphiphilic metallacage 4, in which the tetragonal prismatic frameworks act as the hydrophobic cores and the poly(ethylene glycol) (PEG) chains as the hydrophilic tails. The structure of 4 was characterized by 1H NMR, 31P NMR and electrospray ionization time-of-flight mass spectrometry (ESI-TOF-MS). Notably, 4 with its long PEG tails was subsequently ordered into micelles at a low concentration (1.20 × 10−6 mol/L) in water. As the concentration and cultivation time increased, the micelles can further self-assembly into nanofibers and nanoribbons. Considering the dynamic property of the coordination bond, these structures show reversible transformation under external stimuli.

Antioxidant capacity and prebiotic effects of Gracilaria neoagaro oligosaccharides prepared by agarase hydrolysis

Gracilaria is a genus of red algae widely cultivated in Asia and is notable for its economic importance as food ingredients. Neoagaro oligosaccharides (NAOSs) are products of Gracilaria that have excellent water solubility, antioxidant activity and prebiotic effect. In this study, Gracilaria crude polysaccharide was treated with agarase and hydrolyzed into NAOSs with different degrees of polymerization (DP). The compositions of the hydrolyzed NAOSs were analyzed by electrospray ionization-time of flight-mass spectrometry and thin layer chromatography. The antioxidant capacity and prebiotic effects of NAOSs with different DPs were investigated and the results showed that DP could affect the antioxidant capacity of NAOSs. The prebiotic effects of NAOSs with different DP were evaluated based on the influence on the growth of four intestinal bacteria. NAOSs promoted the growth of Lactobacillus delbrueckii subsp. bulgaricus and Sterptococcus thermophilus. The protective effect of Gracilaria NAOSs in simulated gastrointestinal juice was also studied. Finally, NAOSs with best prebiotic effects were used in Procambarus feeding experiment and exhibited promotion effect on Procambarus growth. The present study showed that Gracilaria NAOSs can be utilized as antioxidant and prebiotic additive, which had a considerable potential in food and feed industry.

Light-Responsive Serinol-Based Polycarbonate and Polyester as Degradable Scaffolds.

Stimuli-responsive self-immolative aliphatic polycarbonates (APCs) and polyesters (APEs) have attractive advantages for biomedical and pharmaceutical applications. In the present work, polycondensation of o-nitrobenzyl-protected serinol was explored as a simple route to obtain light-responsive polycarbonate (LrPC) and polyester (LrPE). By exposure to UV light, these polymers decomposed rapidly and completely into oligomers and small molecules, as detected by size exclusion chromatography (SEC), UV/vis, and 1H nuclear magnetic resonance (NMR) spectroscopies. The degradation mechanism of serinol-based APC and APE was investigated with the help of the Boc-protected model APC and APE, showing that the APC underwent intramolecular cyclization, accompanied by intermolecular transcarbamation, and degraded into oxazolidinone and 2-aminopropanol terminated oligourethanes. Different from APC, the degradation process of serinol-based APE has been proven by electrospray ionization time-of-flight mass spectrometry (ESI-ToF-MS) to follow intramolecular cyclization of the functional amine group with the remote ester group, forming a ten-membered cyclic degradation compound. Further processing of the serinol-based polymers was performed by preparation of nanoparticles (NP). With light-responsive characteristics, a drug delivery system could be potentially obtained enabling a controllable drug release. Based on this strategy, a variety of self-immolative polymers responsive to different triggers can be prepared by polycondensation without the limit of ring-opening polymerization and will expand the family of biodegradable polymers.

Monitoring the Bioactive Compounds Status in Olea europaea According to Collecting Period and Drying Conditions

Polyphenols and triterpenoids in olive have relevant importance both in the physiology of the plant and the nutritional and biological value of its products. Olive leaf extracts are of special interest for their numerous health-promoting properties. The present research is investigating the occurrence of phytochemicals in supercritical fluid extracts from leaves with regard to collection time and drying temperature. The phytochemical profiles of the olive leaf extracts were determined by reversed-phase high-performance liquid chromatography (HPLC) coupled to electrospray ionization time-of-flight mass spectrometry (ESI-TOF-MS) detection. The main extracted phytochemicals were phenols and terpenoids. A significant variation in the amounts of the different components was observed as a function of the different drying temperature and collecting time (p < 0.05). Among samples, the maximal contents of polyphenols and secoiridoid derivatives were found in the extracts from olive leaves collected in November and dried at 120 °C, whereas triterpenoids showed the highest content in fresh leaves collected in August.

Novel method for characterization of aqueous vanadium species: A perspective for the transition metal chemical speciation studies.

Identification the polymerization nature of vanadium bearing solution is difficult, yet it is of great environmental concern due to the possible carcinogenic effects as well as high-value sustainable necessities. Thus, seeking for simple and efficient characterization methods of tracking vanadium species is in urgent demand. In this work, high-resolution electrospray ionization time-of-flight mass spectrometry (ESI-TOF-MS) coupled with thermodynamic calculations was employed to measure vanadium-containing samples. Evolutions of four characteristic vanadium species, H2VO4- (0-1%), V2 species (0-1%), V4 species (1-20%), and V10 species (60-95%), were comprehensively studied from acidic to neutral conditions, based on which thermodynamic model and vanadium phase diagram were established to visualize transformation pathways. More than 30 types of aqueous vanadium species could be semi-quantitatively detected by employing this method with less than 5% relative error, and the corresponding existing forms and concentration of these vanadium species could be well predicted. The vanadium species identified in MS results were confirmed by NMR. This method can be widely used for the understanding of vanadium speciation in practical examples, especially involving V(V), Cr(VI) ions or organic complexes.

Recovery of High-Purity Vanadium from Aqueous Solutions by Reusable Primary Amines N1923 Associated with Semiquantitative Understanding of Vanadium Species

The recovery of high-purity vanadium has attracted significant attention regarding both sustainability and environmental protection necessities. However, insufficient understanding of vanadium species in aqueous solution constrains further optimization of the vanadium recovery process. Here, a closed-loop technical route (extraction and stripping) was realized to recover high-purity vanadium products by in situ monitoring/controlling vanadium species. The evolution of vanadium species in the extraction reaction was semiquantitatively visualized by the system combined with annular centrifugal contactors (ACCs) and electrospray ionization time-of-flight mass spectrometry (ESI-TOF-MS), while the active (V4 and V10 species) and nonactive (H2VO4–) vanadium species were identified. In the stripping process, the behaviors of vanadium species have been described, which affected the morphology of recycled NH4VO3 products. As a result, the transformation pathway of vanadium species in the whole recovery process was...