Abundant Ions Research Articles

Groundwater Quality Assessment for Drinking and Irrigation Purposes at Al-Jouf Area in KSA Using Artificial Neural Network, GIS, and Multivariate Statistical Techniques

Groundwater is an essential resource for drinking and agricultural purposes in the Al-Jouf region, Saudi Arabia. The main objective of this study is to assess groundwater quality for drinking and irrigation purposes in the Al-Jouf region. Physicochemical characteristics of groundwater were determined, including total dissolved solids (TDS), pH, electric conductivity (EC), hardness, and various anions and cations. The groundwater quality index (WQI) was calculated to determine the suitability of groundwater for drinking purposes. The EC, sodium percentage (Na+ %), magnesium hazard (MH), sodium adsorption ratio (SAR), potential salinity (PS), and Kelley’s ratio (KR) were assessed to evaluate the suitability of groundwater for irrigation. Effective statistical tests and Feed-forward neural network (FFNN) modeling were applied to reveal the correlation between parameters and predict WQI. The results indicated that approximately all samples are appropriate for drinking and irrigation uses except samples of the Al Qaryat region. The ionic abundance ranking was Na+ > Ca2+ > Mg2+ > K+ for cations, and Cl− > SO42− > NO3− for anions. Moreover, the groundwater is dominated by alkali metals (K+ and Na+) and controlled by the rock–water interaction process. The indicators of groundwater quality for irrigation and drinking according to the following criteria (Na+ %, SAR, KR, MH, PS, WQI (WHO), and WQI (BIS)) can be predicted by the FFNN with root mean square errors (RMSE) of 0.136, 0.070, 0.022, 0.073, 2.45 × 10−3, 1.45 × 10−2, and 1.18 × 10−2, respectively, and R2 of 0.99, 1.00, 0.99, 0.99, 1.00, 1.00, and 1.00, respectively.

Formation of Highly Oxidized Organic Compounds and Secondary Organic Aerosol from α-Thujene Ozonolysis.

We conducted laboratory chamber experiments to probe the gas- and particle-phase composition of oxidized organics and secondary organic aerosol (SOA) formed from α-thujene ozonolysis under different chemical regimes. The formation of low-volatility compounds was observed using chemical ionization mass spectrometry with nitrate (NO3-) and iodide (I-) reagent ions. The contribution of measured low-volatility compounds to particle growth was predicted using a simple condensational growth model and found to underpredict the measured growth rates in our chamber (on the order of several nm min-1). The yields of low-volatility compounds and SOA mass were similar to those of other monoterpene ozonolysis systems. While semivolatile compounds C10H14-16O3-7 were measured most abundantly with I- reagent ion, a large fraction of products measured with NO3- were C5-7 fragments with predicted intermediate volatility. Additionally, particle composition was measured with ultrahigh-performance liquid chromatography with high-resolution mass spectrometry and compared to particle composition from α-pinene ozonolysis. Structural isomers were identified from tandem mass spectrometry analysis of two abundant product ions (C8H13O5-, C19H27O7-). Our results indicate that although this system efficiently generates low-volatility organics and SOA under the conditions studied, fragmentation pathways that produce more highly volatile products effectively compete with these processes.

Fog and rain water chemistry in a tea plantation of northern Taiwan.

Tea plantations are expanding globally and many are in mountainous areas with frequent fog but few studies have examined fog chemistry in these areas. We examined chemical composition of fog and rain water at a tea plantation in northern Taiwan. Fog water was collected using a Kroneis passive cylindrical fog-water collector and rain water was collected using a 20-cm-diameter funnel. The most abundant ions were Cl- and Na+ in both fog and rain waters due to the proximity of the site to the coast. The order of abundance of other ions was NO3- > Mg2+ > SO42- > Ca2+ > NH4+ > K+ > H+ in fog water and SO42- > K+ > NO3- > NH4+ > Ca2+ > Mg2+ > H+ in rain water. The concentration enrichment ratio (fog to rain) ranged between 2.2 (K+) and 22 (Mg2+) lying between sites near major emission sources and sites in remote areas, possibly because the immediate surrounding landscape is covered with secondary forests although it is near large cities. Factor analysis highlights the influences of sea-salt aerosols on the variation of fog and rain water chemistry. Sea-salt corrections using Na+ as the sea salt tracer led to negative concentrations of Cl- and Mg2+ suggesting that assumptions involved in sea-salt corrections were not satisfied. Agriculture influence is identified as a unique factor for explaining variance of K+, NH4+, and dissolved organic nitrogen (DON) concentrations in fog water but not rain water. Ion concentrations in fog and rain water were generally higher in the weekly samples associated with air trajectories passing through the continental East Asia than those associated with oceanic trajectories pointing to the role of regional pollution sources in affecting local fog and rain water chemistry. Our study highlights greater effects of tea agriculture on fog than rain water chemistry.

Amyloid-β Tetramers and Divalent Cations at the Membrane/Water Interface: Simple Models Support a Functional Role.

Charge polarization at the membrane interface is a fundamental process in biology. Despite the lower concentration compared to the abundant monovalent ions, the relative abundance of divalent cations (Ca2+, Mg2+, Zn2+, Fe2+, Cu2+) in particular spaces, such as the neuron synapse, raised many questions on the possible effects of free multivalent ions and of the required protection of membranes by the eventual defects caused by the free forms of the cations. In this work, we first applied a recent realistic model of divalent cations to a well-investigated model of a polar lipid bilayer, di-myristoyl phosphatidyl choline (DMPC). The full atomistic model allows a fairly good description of changes in the hydration of charged and polar groups upon the association of cations to lipid atoms. The lipid-bound configurations were analyzed in detail. In parallel, amyloid-β 1-42 (Aβ42) peptides assembled into tetramers were modeled at the surface of the same bilayer. Two of the protein tetramers' models were loaded with four Cu2+ ions, the latter bound as in DMPC-free Aβ42 oligomers. The two Cu-bound models differ in the binding topology: one with each Cu ion binding each of the monomers in the tetramer; one with pairs of Cu ions linking two monomers into dimers, forming tetramers as dimers of dimers. The models here described provide hints on the possible role of Cu ions in synaptic plasticity and of Aβ42 oligomers in storing the same ions away from lipids. The release of structurally disordered peptides in the synapse can be a mechanism to recover ion homeostasis and lipid membranes from changes in the divalent cation concentration.

Application of in-source fragmentation to the identification of perfluoropentanoic acid and perfluorobutanoic acid in environmental matrices and human serum by isotope dilution liquid chromatography coupled with tandem mass spectrometry

Liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS) is the most common analytical technique for per- and polyfluoroalkyl substances (PFASs) research and monitoring. The PFAS identification requires a minimum of two multiple reaction monitoring (MRM) transition ions as quantifier transition ion and qualifier transition ion, respectively. The second transition ion abundance for perfluoropentanoic acid (PFPeA) and perfluobutanoic acid (PFBA) is too low for practical use. A method using the in-source fragment ions as the precursor ion for MRM or pseudo-MRM has been developed and evaluated for PFPeA and PFBA identification in various environmental abiotic and biotic samples including water, soil, sediment, WWTP sludge, fruits, vegetables, egg, macrophytes, fish, dolphin liver and human serum. The PFPeA qualifier MRM transition ion (m/z = 219 > 69) has been successfully applied in all the matrices with spike recoveries (90–125%), signal to noise ratios (>10) and transition ions ratio variation (80–120%). The PFBA qualifier pseudo-MRM transition ion (m/z = 169 > 169) works well in all the matrices except dolphin liver sample. The interpretation of pseudo-MRM results should be with cautions due to lower specificity compared to MRM. In addition, this project indicated under typical chromatographic conditions the MRM isobaric interference does happen frequently to PFPeA quantifier transition ion (m/z = 263 > 219) in serum and fish composite samples, and to PFBA quantifier transition ion (m/z = 213 > 169) in macrophytes, fish composite and dolphin liver samples.

Detection and modelling of CH3NC in TMC-1

ABSTRACT Two closely related isomeric pairs of cyanides, CH3[CN/NC] and H2C[CN/NC], are studied in cold, dark interstellar cloud conditions. In contrast to the diverse detections of methyl cyanide (CH3CN) in space, methyl isocyanide (CH3NC) has previously only been observed in warm and hot star-forming regions. We report the detection of CH3NC in the cold pre-stellar core Taurus Molecular Cloud (TMC-1) using the Green Bank Telescope with a detection significance of 13.4σ. Hyperfine transitions in H2CCN and quadrupole interactions in CH3CN and CH3NC were matched to a spectral line survey from the Green Bank Telescope Observations of TMC-1: Hunting for Aromatic Molecules large project on the Green Bank Telescope, resulting in abundances with respect to hydrogen of $1.92^{+0.13}_{-0.07} \times 10^{-9}$ for the cyanomethyl radical (H2CCN), $5.02^{+3.08}_{-2.06} \times 10^{-10}$ for CH3CN, and $2.97^{+2.10}_{-1.37} \times 10^{-11}$ for CH3NC. Efforts to model these molecules with the three-phase gas-grain code nautilus in TMC-1 conditions overproduce both CH3CN and CH3NC, though the ratio of ∼5.9 per cent is consistent across observations and models of these species. This may point to missing destruction routes in the model. The models capture the larger abundance of H2CCN well. Dissociative recombination is found to be the primary production route for these molecules, and reactions with abundant ions are found to be the primary destruction routes. H + CH3NC is investigated with transition state theory as a potential destruction route, but found to be too slow in cold cloud conditions to account for the discrepancy in modelled and observed abundances of CH3NC.

S/N co-doped graphene porous skeleton loaded with Ni-Co active material for lithium storage

The flexible porous skeleton of S/N co-doped graphene aerogel (SNGA) can not only provide abundant ion transport channels but also improve the rate capability of graphene. Herein, taking the advantage of SNGA structure, NiCoO2 and NiCo2S4 were loaded onto the surface of SNGA (denoted as NiCoO2/SNGA-X and NiCo2S4/SNGA-X) via two-step hydrothermal and one-step hydrothermal method, respectively. The results show that NiCoO2 and NiCo2S4 particle agglomeration can be successfully mitigated since the Ni-Co binding process is influenced by the high specific surface area carbon source of SNGA. In addition, the NiCo2S4 prepared by one-step hydrothermal process plays the role of intercalation support during the formation of SNGA, which makes the porous structure of NiCo2S4/SNGA-X more compact and coherent. Benefiting from adequate active sites and porous structure, NiCoO2/SNGA-X and NiCo2S4/SNGA-X show high reversible capacity as anode materials for lithium energy storage. NiCoO2/SNGA-0.4 exhibits superior stability of 356.3 mA h g−1 at the current density of 1 A g−1 after 300 cycles, NiCo2S4/SNGA-0.3 exhibits excellent rate capability of 259.7 mA h g−1 at the current density of 5 A g−1. Lithium ion battery anode materials with high reversible specific capacity under high current density were successfully prepared. The research would provide a theoretical guidance for further application of SNGA skeletons.

Utilization of hydralazine as a reactive matrix for enhanced detection and on-MALDI-target derivatization of saccharides

Saccharides are a sort of ubiquitous and vital molecules within the whole life. However, the application of saccharides analysis with matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) is restricted by their low ionization efficiency and the instability of the sialic acid fraction. Derivatization strategy based on nonreductive amination provides a good solution, however, this is often time consuming and may result in sample loss due to removal of excessive derivatization reagents. Herein, hydralazine (HZN) was utilized as a reactive matrix for labeling reducing saccharides directly on MALDI target which eliminated tedious sample preparation and avoided sample loss. After optimization, effective and reproducible on-MALDI-target derivatization of neutral and acidic saccharides was achieved in both positive and negative modes. Compared with 2,5-dihydroxybenzoic acid (DHB) and 9-aminoacridine (9-AA), HZN improved the detection sensitivity of reducing saccharides and provided more abundant fragment ions in MS/MS analysis. Moreover, 26 kinds of neutral glycans and 5 kinds of sialic glycans were identified from ovalbumin (OVA) and bovine fetuin, respectively. Combined with the statistical models, this strategy could be used to distinguish and predict samples of 6 brands of beer, and discriminate 2 kinds of beer fermentation modes. In addition, HZN was applied for quantitative analysis of glucose in urine samples, and the obtained urine glucose concentrations of diabetic patients were consistent with the clinical test results, showing the potential of qualitative and quantitative analysis of reducing saccharides in complex samples.

Confined intercalating sulfonated graphene quantum dots into GO laminates for fast alkali recovery

Graphene oxide (GO) membranes with uniform sub-nanometer interlayer channels have shown great promise in the ion sieving field. However, the lack of ion-transporting sites on the GO nanosheets usually leads to inferior ion permeation and selectivity. Although the intercalation of molecules with ionic groups into GO laminates is easily achieved to incorporate ion exchange sites, this approach inevitably enlarges the interlayer spacing, reducing the ionic sieving capacity. Thus, current methods are limited in breaking the permeation and selectivity “trade-off”. Herein, we report a confined intercalation strategy to inject ample sulfonic acid groups into GO laminates using sulfonated graphene quantum dots (SGQD) as intercalators. SGQD with abundant ion exchange sites assembles on the sp2 domains of GO via π-π interactions and confers the GO membranes with continuous ion conduction pathways. Meanwhile, benefiting from the ultra-small size SGQD as well as its sheet morphology, it can well accommodate in the GO laminates. This strategy fulfills the incorporation of ionic sites without expanding channel width and destructing the two-dimensional (2D) regularity for GO laminates, resulting in simultaneous improvements in ion permeability and selectivity. Correspondingly, the resulting membranes show synergistically improving OH- dialysis coefficients of 3.5 × 10−3-8.2 × 10−3 m h−1 and OH-/WO42- separation factors of 56–116 compared with the GO membrane (0.9 × 10−3 m h−1 and 8.4) for separating simulated NaOH/Na2WO4 alkaline effluents. We believe the confined intercalating regulation can act as a versatile and fine way to modify 2D membranes for intensifying ion separation.

Analysis of Transferrin in the Urine of Patients with Bladder Cancer Using Nanobodies.

It is known that the saturation ratio of transferrin (Tf) with iron in human blood is an important clinical parameter. Specific antibodies can be used to analyze subtle changes in the relative abundance of different forms of transferrin potentially associated with a pathological process. Recently, the authors of this study were able to obtain and characterize highly specific single-domain antibodies (nanobodies) that predominantly recognize the iron-saturated (holo-Tf) or iron-unsaturated (apo-Tf) form of transferrin. In this work, under conditions closer to physiological than in the previous experiments, we further demonstrated that these unique nanobodies have extremely high differential binding specificity for different forms of Tf in different human biological fluids. Using these nanobodies, we were able to analyze for the first time relative abundance of the transferrin forms in urine samples from the patients with bladder cancer (BC). We have shown that increase in the concentration of total Tf in the urine samples normalized for creatinine is associated with the degree of progress and growth of malignancy of BC. In the samples of healthy donors and in the early stages of BC (G1), Tf is detected in much smaller amounts (compared to the later stages) and only with additional concentration of the studied samples. For most of the studied urine samples from the BC patients, it is expected (as previously shown in the case of Tf in the blood of terminal ovarian cancer patients) that the concentration of apo-Tf is clearly higher than holo-Tf, especially in the case of the most advanced muscle-invasive BC. It was a surprise for us that approximately equal amounts of apo-Tf and holo-Tf were found in the urine samples of some patients with BC. We hypothesized that the holo-Tf fraction in this case could be largely represented by the "secondary complexes" formed by apo-Tf in combination with ions other than Fe3+, which accumulate in the urine of some cancer patients and are able to bind to apo-Tf, changing its conformation towards holo-Tf. By using inductively coupled plasma mass spectroscopy (ICP-MS), we obtained first results confirming our hypothesis. Preparation of the holo-Tf in these urine samples was found to be highly enriched in zinc and nickel. Also, relative enrichment in cadmium has been observed in this preparation, but at much lower concentrations. The obtained data indicate that the used nanobody, while recognizing predominantly the iron-saturated form of transferrin (holo-Tf), is also capable of binding transferrin in association with other metal ions that are different from iron. This ability could potentially open up new possibilities for investigation of relative abundance of various metal ions in association with transferrin in human biological fluids in normal and pathological conditions.

Understanding the desalination mechanism of a two-dimensional graphene-like membrane using data-driven design

Global freshwater resources are not inexhaustible, and the deterioration in water quality and the shortage of drinkable water are serious challenges for human beings. To date, the development of two-dimensional (2D) nanomaterials provides an essential guarantee for seawater desalination technology. However, 2D nanomaterials are still lacking in desalination efficiency. Herein, we used a data-driven design to analyze the desalination mechanism of a 2D graphene-like membrane. A 2D graphene-like desalination membrane (Desa-C) with a multiporous structure has been screened first through machine learning (ML). Then, the desalination efficiency and other comprehensive properties of mechanics, adsorption, diffusion, and electron are analyzed based on molecular dynamics simulations and first-principles density functional theory. The results indicate that the low free energy barrier of water molecules, abundant salt ions adsorption sites, and periodically distributed 0.53 nm nanopores endow Desa-C with ideal permeability and selectivity; In particular, the salt ions rejection efficiency could constantly be ensured at 100 % within 125 MPa pressure, and this value holds 97 % even if the pressure increases to 145 MPa. Moreover, the Desa-C membrane featuring metallicity could achieve a self-cleaning effect with reverse voltage conditions, which prolongs the lifetime of the desalination membrane. These findings have potential application values in desalination technology and provide a positive theoretical contribution to the innovation of desalination membranes.

Methanol Formation through Reaction of Low-energy CH3 + Ions with an Amorphous Solid Water Surface at Low Temperature

We have performed experimental investigations of methanol formation via the reactions of low-energy CH3 + ions with an amorphous solid water (ASW) surface at ∼10 K. A newly developed experimental apparatus enabled irradiation of the ASW surface by several eV ions and detection of trace amounts of reaction products on the surface. It was found that methanol molecules were produced by low-energy CH3 + irradiation of the ASW surface and that hydroxy groups in the produced methanol originated from water molecules in the ASW, as predicted in a previous theoretical study. Little temperature dependence of the observed methanol intensity is apparent in the temperature range 12–60 K. Ab initio molecular dynamics simulations under constant-temperature conditions of 10 K suggested that this reaction spontaneously produced a methanol molecule and an H3O+ ion, regardless of the contact point of CH3 + on the ASW surface. We have performed a simulation with an astrochemical model under molecular-cloud conditions, where the reaction between CH3 + and H2O ice, leading to methanol formation, was included. We found that the impact of the reaction on methanol abundance was limited only at the edge of the molecular cloud (<1 mag) because of the low abundance of CH3 + in the gas phase, whereas the reaction between the abundant molecular ion (HCO+) and H2O ice, which has not yet been confirmed experimentally, can considerably affect the abundance of a complex organic molecule. This work sheds light on a new type of reaction between molecular ions and ice surfaces that should be included in astrochemical models.

Significant changes in size distribution of aerosols in Beijing after clean air actions

Over the past few years, the physicochemical characteristics and sources of aerosols have changed following the implementation of strict clean air policies in Beijing. In this study, size-segregated particulate matters (PM) were collected using a micro-orifice uniform deposit impactor (MOUDI) in Beijing from July 2021 to June 2022 to understand the responses of particle size distribution and chemical composition to the implemented emission reduction measures. The results showed that although particulate pollution greatly improved, it is still severe in Beijing, especially in autumn and winter, with the annual average PM1.8 (aerosol particle with aerodynamic diameter less than 1.8 μm) concentration reaching 46.7 ± 37.4 μg/m3. NO3− was the most abundant ion in the particles throughout all seasons, and its proportion to water-soluble inorganic ions increased significantly with the aggravation of pollution. This highlights the importance and urgency of controlling mobile sources in future control measures. The highest concentration of SO42− occurring during summer demonstrates the effectiveness of fossil fuel combustion control in winter. The measured size distributions of PM and secondary inorganic ions were trimodal, which significantly differed from the observations conducted in Beijing using MOUDI before 2017, in which the measured size distributions of PM and secondary inorganic ions were bimodal. The enhancement of atmospheric oxidation and reduction of gaseous precursors can affect the formation path of aerosols, and thus, their particle size distribution. Aerosol aqueous-phase reactions play a vital role in pollution development, with the droplet mode further growing hygroscopically into a coarse mode during pollution maintenance.

Wintertime characteristics of water-soluble organic carbon in PM2.5 during haze and non-haze days in Jinan in the North China Plain

Water-soluble organic carbon (WSOC) makes up a substantial proportion of organic carbon (OC) in fine particles that can disrupt aerosol hygroscopicity, influence global climate change, and harm human health. In the winter of 2014, carbonaceous species and water-soluble inorganic ions (WSII) were analyzed in PM2.5 samples collected from Jinan in the North China Plain. According to the results, the primary components of PM2.5 include SO42−, NO3−, NH4+ (SNA) and organic carbonaceous aerosol. Except for Ca2+, the average concentration of each chemical component was higher on hazy days than on clear days. Secondary aerosol generation probably played a vital role in haze production, as the relative abundance of secondary inorganic ions and secondary organic carbon was higher on haze days compared to non-haze days. The average WSOC concentration during the sampling period was 10.89 ± 4.66 μg m−3, accounting for 0.47 ± 0.14 of OC. The level of WSOC increased from 9.60 ± 3.32 μg m−3 on days without haze to 16.94 ± 5.43 μg m−3 on haze days. Analyses of linear regression and quantitative calculations demonstrated that burning of biomass and the generation of secondary aerosols were essential contributors to WSOC. WSOC increased with relative humidity/aqueous water content, suggesting that secondary WSOC (WSOCsec) may originate from reactions in the aqueous phase, particularly on haze days. The absorption Ångstrom exponents (AAE) were 6.55 ± 1.79 on non-haze days and 6.59 ± 0.90 on haze days. The average mass absorption efficiency (MAE) at 365 nm on haze days (1.07 ± 0.21 m2 g−1) was higher than on non-haze days (0.88 ± 0.33 m2 g−1), indicating the slightly stronger WSOC's light absorption ability during haze times. Four quantitative sources of WSOC were identified using positive matrix factorization modeling: (i) a mixed primary source (21.78%), (ii) biomass burning (22.14%), (iii) a process comparable to NO3− formation (33.17%) and (iv) a process similar to SO42− formation (22.91%). Comparatively, secondary sources (factors 3 and 4) contributed more to WSOC (56.08%) than primary sources (43.92%, factors 1 and 2). Secondary formation contributed more to WSOC during haze conditions.

Minerals with a palmierite-type structure. Part II. Nomenclature and classification of the palmierite supergroup.

AbstractThe palmierite supergroup, approved by the IMA-CNMNC, includes five mineral species characterised by the general crystal-chemical formula XIIM1XM22(IVTO4)2 (Z = 3). On the basis of the crystal-chemical arguments and heterovalent isomorphic substitution scheme M++T6+ ↔ M2++T5+, the palmierite supergroup can be formally divided into two groups: the palmierite group M12+M22+(T6+O4)2, and the tuite group M12+M222+(T5+O4)2. Currently, the palmierite group includes palmierite K2Pb(SO4)2, and kalistrontite K2Sr(SO4)2, whereas the tuite group combines tuite Ca3(PO4)2, mazorite Ba3(PO4)2, and gurimite Ba3(VO4)2. The isostructural supergroup members crystallise in space group R$\bar{3}$m (no. 166). The palmierite-type crystal structure is characterised by a sheet arrangement composed of layers formed by M1O12 and M2O10 polyhedra separated by TO4 tetrahedra perpendicular to the c axis. The abundance of distinct ions, which may be hosted at the M and T sites (M = K, Na, Ca, Sr, Ba, Sr, Pb, Rb, Zn, Tl, Cs, Bi, NH4 and REE; T = Si, P, V, As, S, Se, Mo, Cr and W) implies many possible combinations, resulting in potentially new mineral species. Minerals belonging to the palmierite supergroup are relatively rare and usually form under specific conditions, and their synthetic counterparts play a significant role in various industrial applications.

Fragment Ion Abundance Reveals Information about Structure and Charge Localization in Highly Charged Proteins.

Top-down mass spectrometry (MS) is a versatile tool that has been employed to investigate both protein sequence and structure. Although a variety of different fragmentation methods are available in top-down MS that can potentially yield structural information, quantifying differences between spectra remains challenging. Herein, we show that subtle differences in spectra produced by a variety of fragmentation methods are surprisingly sensitive to protein structure and/or charge localization, even in highly unfolded proteins observed in high charge states. In addition to exposing information about the protein structure, differences in fragmentation also reveal insight into the mechanisms underlying the dissociation methods themselves. The results further reveal that small changes in experimental parameters (such as the addition of methanol instead of acetonitrile) lead to changes in structure that are reflected in statistically reproducible differences in dissociation. Collisional annealing of structurally dissimilar ions in the gas phase eventually leads to dissociation spectra that are indistinguishable, suggesting that structural differences can be erased by sufficient thermal activation. Additional experiments illustrate that identical charge states of the same protein can be distinguished if those produced directly by electrospray are compared to ions manipulated by in vacuo proton-transfer charge reduction. Overall, the results show that subtle differences in both three-dimensional structure and charge-site localization can influence the abundance of fragment ions produced by top-down MS, including dissociation methods not typically thought to be structurally sensitive.

Differentiation of Aspartic and Isoaspartic Acid Using 193 nm Ultraviolet Photodissociation Mass Spectrometry.

Spontaneous conversion of aspartic acid (Asp) to isoaspartic acid (isoAsp) is a ubiquitous modification that influences the structure and function of proteins. This modification of Asp impacts the stability of biotherapeutics and has been linked to the development of neurodegenerative diseases. We explored the use of 193 nm ultraviolet photodissociation (UVPD) to distinguish Asp and isoAsp in the protonated and deprotonated peptides. The differences in the relative abundances of several fragment ions uniquely generated by UVPD were used to differentiate isomeric peptide standards containing Asp or isoAsp. These fragment ions result from the cleavage of bonds N-terminal to Asp/isoAsp residues in addition to the side-chain losses from Asp/isoAsp or the losses of COOH, CO2, CO, or H2O from y-ions. Fragmentation of Asp-containing tryptic peptides using UVPD resulted in more enhanced w/w + 1/y - 1/x ions, while isoAsp-containing peptides yielded more enhanced y - 18/y - 45/y - 46 ions. UVPD was also used to identify an isomerized peptide from a tryptic digest of a monoclonal antibody. Moreover, UVPD of a protonated nontryptic peptide resulted in more enhanced y ions N- and C-terminal to isoAsp and differences in b/y ion ratios that were used to identify the isoAsp peptide.

Quantitative Distributions of Product Ions and Reaction Times with a Binary Mixture of VOCs in Ambient Pressure Chemical Ionization.

A model to quantitatively predict ion abundances from atmospheric pressure chemical ionization (APCI) between hydrated protons and a volatile organic compound (VOC) was extended to binary mixtures of VOCs. The model includes differences in vapor concentrations, rate coefficients, and reaction times and is enhanced with cross reactions between neutral vapors and protonated monomers. In this model, two specific VOCs were considered, a ketone, 6-methyl-5-hepten-2-one (M, and an amine, 2,6-di-tert-butyl-pyridine (N), with measured "conditional rate coefficients" (in cm3·s-1) of kM = 1.11 × 10-9 and kN = 9.17 × 10-10, respectively. The cross reaction of MH+(H2O)x to NH+(H2O)y was measured as kcr = 1.31 × 10-12 at 60 °C. Cross reactions showed an impact on ion abundances at t > 30 ms for equal vapor concentrations of 100 ppb for M and N. In contrast, this impact was negligible for vapor concentrations of 1 ppb and did not exceed 5% change in product ion abundance up to 1000 ms reaction times. The model was validated with laboratory measurements to within ∼10% using an ion mobility spectrometer and effective reaction time obtained from computational fitting of experimental findings. This was necessitated by complex flow patterns in the ion source volume and was determined as ∼10.5 ms. The model has interpretative and predictive value for quantitative analysis of responses with ambient pressure ion sources for mass spectrometry and ion mobility spectrometry.

Evaluating dynamic traveling wave profiles for the enhancement of separation and sensitivity in traveling wave structures for lossless ion manipulations

The amenability of traveling wave ion mobility spectrometry (TWIMS) to extended separation pathlengths has prompted a recent surge of interest concerning the technique. While promising, the optimization of ion transmission, particularly when analyzing increasingly disparate species, remains an obstacle in TWIMS. To address this issue, we evaluated a suite of dynamic TW profiles using an original TW structures for lossless ion manipulations (TW-SLIM) platform developed at Washington State University. Inspired by the range of gradient elution profiles used in traditional chromatography, three distinct square TW profiles were evaluated: a static approach which represents a traditional waveform, a dual approach which consists of two distinct TW profiles within a given separation event; and a ramp approach which varies TW speed and amplitude at a fixed rate during separation. The three waveform profiles were evaluated in terms of their impact on separation (quantified as resolution) and sensitivity (quantified using signal-to-noise ratio (SNR), and ion abundance). Concerning separation, the highest resolution (R) was observed when operating with the static waveform (R = 7.92); however, the ramp waveform performed comparably (R = 7.70) under similar conditions. Regarding SNR, optimum waveform profiles were species dependent. Bradykinin2+ displayed the largest gains in SNR (36.6% increase) when ramping TW speed, while the gains were greatest (33.5% increase) for tetraoctylammonium when modulating TW amplitude with the static waveform. Lastly, significant (>10%) increases in the abundance of tetraoctylammonium ions were observed exclusively when utilizing a ramped waveform. The present set of experiments outline the results and challenges related to optimizing separations using alternative TW profiles and provides insight concerning TW-SLIM method development which may be tailored to enhance select analytical metrics.

Hydrogeochemical characterization of ground and surface water in the eastern part of the Adamawa-Yade domain, Bertoua-Cameroon

Groundwater and surface water are major sources of water supply to the inhabitants of Bertoua. Hydrogeochemical study conducted in the study area aimed at identifying the processes that control the chemistry of groundwater sources and to examine the quality of the water sources for domestic and agricultural purposes. Fifty water samples were collected from boreholes, open wells, springs, and rivers within the study area in January 2022 (the dry season). The samples were analyzed for physicochemical characteristics including pH, electrical conductivity (EC), total dissolved solids (TDS) and major ions. The water samples were acidic with 94% of pH values less than 6.5. The EC varied from 21 to 776 µS/cm and TDS (8.5–388 mg/l). The low EC and TDS indicate low mineralization and fresh water. The relative abundance of major ions (meg/l) was Ca2+> Mg2+> K+>Na+ for cations and {text{H}text{C}text{O}}_{3}^{-}>Cl−>NO3−>SO42− for anions. These major ions concentrations were low and within the WHO guideline values for drinking water. From Piper diagram three water facies were observed; Ca-SO4, Ca-HCO3 and mixed Ca-Mg-Cl. Rock-water interaction, ion exchange, silicate weathering and anthropogenic activities were the processes responsible for the groundwater chemistry with some minor evaporative effects. Based on Sodium Adsorption Ratio and Residual Sodium Bicarbonate all samples fall in the excellent category for agriculture.