Robust and versatile assembly for emitter positioning, observation, and heating in atmospheric pressure field desorption mass spectrometry

Atmospheric pressure field desorption (APFD) mass spectrometry (MS) has recently been introduced as a new variant of field desorption (FD) mass spectrometry. The development aimed at providing the basic characteristics of FD-MS in combination with instruments equipped with an atmospheric pressure (AP) interface. Hitherto, APFD has been demonstrated to yield both positive and negative even electron ions of highly polar or ionic compounds as well as to enable the generation of positive molecular ions, M+•, of polycyclic aromatic compounds. The prototype setup for APFD was based on a nano-electrospray ionization (nanoESI) source slightly modified to allow for emitter positioning in front of the AP interface of a Fourier transform-ion cyclotron resonance (FT-ICR) mass spectrometer. The entrance electrode of the interface was set to negative or positive high voltage with respect to the emitter at ground potential, thereby permitting the formation of positive or negative ions, respectively. This work describes a custom-built device for quicker and more reproducible sample loading on and positioning of field emitters at the entrance electrode of the atmospheric pressure interface of a mass spectrometer. In addition, the device provides means for observation of the emitter during operation and for resistive emitter heating as employed in traditional FD-MS. Emitter heating both speeds up the desorption of the analytes and allows for the desorption/ionization of analytes of higher molecular weight than without emitter heating. In some cases, the signal-to-noise ratio of APFD mass spectra is improved due to higher ion currents effected by compressing the entire process into shorter periods of spectral acquisition. The new setup enables robust and reliable operation in APFD-MS. Moreover, it has been designed as to allow for use on a range of instruments as it can either be used on an FT-ICR mass spectrometer or in combination with a trapped ion mobility-quadrupole-time-of-flight (TIMS-Q-TOF) instrument.

Moderate Signal Enhancement in Electrospray Ionization Mass Spectrometry by Focusing Electrospray Plume with a Dielectric Layer around the Mass Spectrometer's Orifice

Electrospray ionization (ESI) is among the commonly used atmospheric pressure ionization techniques in mass spectrometry (MS). One of the drawbacks of ESI is the formation of divergent plumes composed of polydisperse microdroplets, which lead to low transmission efficiency. Here, we propose a new method to potentially improve the transmission efficiency of ESI, which does not require additional electrical components and complex interface modification. A dielectric plate-made of ceramic-was used in place of a regular metallic sampling cone. Due to the charge accumulation on the dielectric surface, the dielectric layer around the MS orifice distorts the electric field, focusing the charged electrospray cloud towards the MS inlet. The concept was first verified using charge measurement on the dielectric material surface and computational simulation; then, online experiments were carried out to demonstrate the potential of this method in MS applications. In the online experiment, signal enhancements were observed for dielectric plates with different geometries, distances of the electrospray needle axis from the MS inlet, and various compounds. For example, in the case of acetaminophen (15 μM), the signal enhancement was up to 1.82 times (plate B) using the default distance of the electrospray needle axis from the MS inlet (d = 1.5 mm) and 12.18 times (plate C) using a longer distance (d = 7 mm).

[Spatial Variation Characteristics, Influencing Factors, and Sources of Hydrogeochemical of Surface Water and Groundwater in Mountainous Area of Hutuo River]

Surface runoff has dropped sharply in the mountainous area of the Hutuo River, posing a huge challenge to the sustainable use of groundwater in the North China Plain (NCP). The Taihang Mountain area is the main recharge source area of groundwater in the NCP. An in-depth study of spatial variation characteristics, influencing factors, and sources of hydrogeochemical characteristics of surface water and groundwater in the mountainous area of the Hutuo River can facilitate a comprehensive understanding of regional water resource status and sustainable utilization of water resources. Based on isotopic, hydrogeochemical, and mathematical statistics methods, this study analyzed spatial variation of hydrochemical characteristics in surface water and groundwater and its sources and main controlling factors. The results showed that the river water, well water, and spring water were all recharged by atmospheric precipitation in the mountainous areas of the Hutuo River. Under the combined influence of natural factors and human factors, the hydrogeochemical characteristics of river, well, and spring water showed large spatial differences. On the whole, the hydrochemical types of mainstreams were relatively concentrated. In the upper and lower mining reach areas, the mainstream water chemical type was dominated by Ca·Mg-SO4·HCO3, whereas that in the natural vegetation area (middle reach:between Qingshui River and Longhua River) was dominated by Ca·Mg-HCO3·SO4. In the upper stream, the main hydrochemical type of the Yukou River and Ehe River tributaries was Ca·Mg-SO4·HCO3, which was consistent with that of the main stream. The main hydrochemical types of the Muma River and Qingshui River tributaries were Ca-HCO3, Ca·Mg-HCO3, and Ca·Mg-HCO3·SO4 in the midstream. The main hydrochemical types of the Mianhe River and Yehe River tributaries were Ca-SO4, Ca·Mg-SO4, and Ca·Mg-SO4·HCO3. Mineral dissolution was still the main controlling factor for the hydrochemical characteristics of surface water and groundwater in the mountainous area of the Hutuo River. The contribution rates were 69.86% and 18.84% for mineral dissolution and human activities, respectively. Therefore, in the future, water resource utilization in the upper reaches of the Hutuo River should not only consider the issue of water quantity but also a series of water environment problems such as nitrate pollution and mining pollution caused by human activities.

[Hydrochemical Evolution in the Yarlung Zangbo River Basin]

In order to explore the hydro-chemical evolution law of the Yarlung Zangbo River Basin from 1973 to 2020, the hydro-chemical characteristics and major ion sources were studied using a Piper diagram, Gibbs diagram, ion ratio, and correlation analysis, and the irrigation applicability of the Yarlung Zangbo River was evaluated using the sodium adsorption ratio (SAR), sodium percentage (Na⁺%), and permeability index (PI). The results showed that the mean value of TDS was (208.30±58.26) mg·L^-1, which increased with time. Ca²⁺ was the dominant cation, accounting for (65.49±7.67)% of the total cations. HCO^-₃ and SO^2-₄ were the dominant anions, accounting for (68.56±9.84)% and (26.85±9.82)% of the main anions, respectively. The annual growth rates of Ca²⁺, HCO^-₃, and SO^2-₄ were respectively 2.07, 3.19, and 4.70 mg·(L·10 a)^-1. The hydro-chemical type of the Yarlung Zangbo River was HCO₃-Ca type, and the main ionic chemistry was controlled by the chemical weathering of carbonate rocks. The weathering of carbonate rocks during the period of 1973 to 1990 was mainly controlled by carbonation, whereas from 2001 to 2020 it was mainly controlled by both carbonation and sulfuric acid. The main ion concentrations in the mainstream of Yarlung Zangbo River were within the range of drinking water standards, with SAR between 0.11-0.93, Na⁺% between 8.00-36.73, and PI values between 0.39-0.87, demonstrating that the waters were suitable for drinking and irrigation. The results were of great significance to the protection and sustainable development of water resources in the Yarlung Zangbo River Basin.

[Hydrochemical Characteristics and Control Factors of Pore-water in the Middle and Upper Reaches of Muwen River]

In order to study the hydrochemical characteristics and ion sources of pore water in the middle and upper reaches of the Mouwen River, 29 groups of pore-water samples were collected in the Laiwu Basin. The main ion characteristics and their controlling factors of pore-water in this area were analyzed by using correlation and principal component analysis, Piper trigram, and Gibbs diagram methods. The main material sources of pore water in this area were revealed. The results showed that HCO₃^-, NO₃^-, SO₄^2-, and Ca²⁺ were the main anions and cations in the pore water of the middle and upper reaches of the Mouwen River. With TDS >1000 mg·L^-1 as the standard, the normal water chemistry type was mainly HCO₃·NO₃·SO₄-Ca and HCO₃·SO₄-Ca·Mg, whereas the abnormal water chemistry type was mainly NO₃·Cl-Ca. The chemical evolution of groundwater was mainly influenced by rock weathering, cation alternation adsorption, and human activities. Na⁺+K⁺ mainly came from silicate weathering and dissolution, and HCO₃^-, Ca²⁺, and Mg²⁺ came from calcite weathering and dissolution involving carbonate and sulfuric acid. Alternation adsorption of cations and weathering of silicate rock provided a surplus of Ca²⁺ and Mg²⁺ for pore water. Industrial and mining activities such as domestic sewage mixing, agricultural planting activities, and iron and coal mining changed the chemical composition of pore water, especially NO₃^- exceeding the standard, which has become the main problem of the local groundwater chemical environment.

[Karst Hydrogeochemical Characteristics and Controlling Factors of Carlin-type Gold Mining Area Based on Hydrochemistry and Sulfur Isotope]

Mining activities change the groundwater level and flow conditions through pumping and drainage, which enhances the interaction between groundwater and aquifer rocks; mine drainage is discharged into the surface water system, which affects the whole karst water hydrogeochemical process. Based on hydrogeochemistry and the δ³⁴S isotope, the hydrogeochemical processes, characteristics, and main controlling factors for waste water, karst groundwater, and surface water in a typical Carlin gold mining area and its surrounding areas were revealed. The results showed that:chemical compositions of groundwater and surface water unaffected by gold mining activities were mainly controlled by the weathering of limestone and dolomitic limestone; Ca²⁺, Mg²⁺, and HCO₃^- were main ions; and the water chemical types were Ca-HCO₃. The mine wastewater and its downstream receiving water were affected by the dissolution of carbonate and silicate minerals, and cation exchange also played a role; the main ions were Ca²⁺, Mg²⁺, Na⁺, and SO₄^2-, and the hydrochemical type gradually evolved from Ca-HCO₃ to Ca-SO₄. SO₄^2- was the characteristic component in various water bodies affected by mining, and the concentration of SO₄^2- gradually decreased from top to bottom in the well. The values of δ³⁴S for unaffected groundwater and surface water were positive, and SO₄^2- was mainly derived from realgar oxidation. Conversely, mine wastewater and downstream water were negative, SO₄^2- was mainly influenced by the mixing action of realgar oxidation and meteoric precipitation, and pyrite also contributed to a certain extent. At the same time, NO₃^- came from agricultural fertilizer and rural domestic sewage discharge directly. Principal component analysis (PCA) further demonstrated:sulfide mineral oxidation and mining activities were the main controlling factors for the water chemical composition of mine wastewater and downstream water, whereas unaffected groundwater and surface water were mainly influenced by water-rock (carbonate rock) interactions. Agricultural fertilizer and rural sewage discharge also had a certain influence. Therefore, the study area should strengthen the interception of surface water, control-block-management of sulfide oxidation, rural domestic sewage treatment, and agricultural fertilizer.

[Characteristics and Causes of Groundwater Salinization in the Plain Area of the Lower Kashgar River]

This study revealed the distribution characteristics and formation mechanism of groundwater salinization in the plain area of the lower Kashgar River in Xinjiang, which can provide scientific basis for a local sustainable groundwater exploitation plan and practical significance for local water supply security and social stability. Fifteen phreatic water samples, 38 shallow confined groundwater samples, and 16 deep confined groundwater samples were collected in September 2018. Mathematical statistics, a Duorv diagram, PCA-APCS-MLR model, ion ratios, and hydrogeochemical simulations were comprehensively used for sample analysis. The results showed that groundwater was weakly alkaline in general (pH ranged between 6.48 and 8.60 with an average of 7.57), with total dissolved solids (TDS) ranging from 573.0 to 16700.0 mg·L^-1. Groundwater was mainly composed of Cl^-, SO₄^2-, Na⁺, and Ca²⁺. The main groundwater hydrochemical types included were HCO₃·SO₄·Cl, SO₄, and SO₄·Cl. No brine was observed in the study area, phreatic water was mainly composed of brackish water and saline water, and confined groundwater was mainly composed of saline water. The salinization coefficient calculation results showed that the salinization degree gradually increased from phreatic water to deep confined groundwater. Evaporation concentration and lixiviation were the main factors leading to the salinization of groundwater. The dissolution and cation exchange of carbonate and silicate rocks gradually weakened from phreatic water to deep confined groundwater, whereas the dissolution of evaporite rock always dominated and was gradually strengthened, which was also the primary factor that caused the salinity of deep groundwater to be higher than that of shallow groundwater. Human activities such as agricultural fertilization, unreasonable use of surface water for irrigation, and improper treatment of domestic sewage had a certain impact on groundwater salinization. The leaking recharge of salt water from adjacent aquifers aggravated the groundwater salinization.

[Hydrochemical Characteristics and Controlling Factors of Surface Water and Groundwater in Wuding River Basin]

Taking Wuding River as the research object, the study explored the hydrochemical characteristics and discussed the source of solute and control factors of groundwater and surface water in the basin, in order to provide a reference for water quality management. Considering the seasonal differences, water samples were collected during the dry season and the flood season. By comprehensively using graphic methods, correlation analysis, and forward deduction models, we analyzed the temporal and spatial evolution characteristics of water chemistry, explored the formation mechanism of water chemistry, and quantified the contribution rates of different sources to solutes. The results showed that the overall water quality was weakly alkaline in Wuding River basin. HCO₃^- and Na⁺ were the main anions and cations in the water, respectively, and the main water chemistry type was HCO₃·SO₄-Na·Ca. The water quality gradually deteriorated along the river course from west to east, and the sampling points that exceeded the level Ⅲ water were mainly distributed in tributaries during the dry season and downstream during the flood season. The cation exchange effect increased the Na⁺ and K⁺ in the water, and NO₃^- and HCO₃^- differed significantly in different seasons, which may be affected by seasonal precipitation leaching soil and land use types. Evaporite weathering and silicate weathering were the main sources of solute contribution in the Wuding River basin, which were 35.0% and 46.5% in the dry season and 46.7% and 42.3% in the flood season,respectively.

[Hydrochemical Characteristic and Their Controlling Factors in the Yarkant River Basin of Xinjiang]

In this study, the hydrochemical characteristics of surface water in the Yarkant River Basin of Xinjiang and their controlling factors were analyzed using a Piper trilinear diagram, Gibbs diagram, saturation index, ion proportional relationship, and other methods. The study has significance to the surface water resources in the basin for development and utilization. The results indicated that the pH of the surface water ranged from 7.40 to 8.33, with a mean value of 7.92, which was weakly alkaline. The mean value of the total dissolved solids (TDS) of the river, canal, and reservoir water exhibited an increasing trend. The TDS mean of the river was 429.24 mg·L^-1, higher than the average value of rivers worldwide (115 mg·L^-1). The hydrochemical types of the river water were predominantly HCO₃·SO₄-Ca·Na and SO₄·HCO₃·Cl-Ca·Na·Mg types, of the canal water was mainly HCO₃·SO₄·Cl-Ca·Na type, and of the reservoir water was mostly the SO₄·Cl-Na·Ca type. The TDS of the river water along the Yarkant River and Tiznap River demonstrated a continuous increase and fluctuation trend, respectively, while the variation of the primary ions was relatively complex. The primary ions of surface water were mostly influenced by rock weathering, evaporation crystallization, and cation exchange, in which gypsum and rock salt were predominantly dissolved in the process of rock weathering. In addition, human activities had significant effects on the chemical composition of the surface water downstream.

Using matrix-assisted ionization method for mass spectral identification of fullerene-dye conjugates

Traditional soft ionization methods are not always suitable for mass spectral analysis of complex compounds. Factors such as laser radiation and heating resulting in fragmentations of sample molecules in the case of matrix-assisted laser desorption/ionization and difficulties in preparing suitable sample solutions in the case of electrospray ionization make it impossible to use these methods in some cases. Matrix-assisted ionization was used to analyze products of chemical synthesis involving pyropheophorbide and fullerene. Mass spectra were acquired using a simple effective modification of the Exactive Orbitrap mass spectrometer electrospray interface. Reliable identification of pyropheophorbide-fullerene dyad ions and its derivatives was carried out. An experimental comparison of a matrix-assisted ionization and an electrospray ionization technique demonstrated the significant advantage in sensitivity to the ions under study (approximately 20 times higher) of the matrix-assisted ionization method in this particular study.

[Hydrochemical Characteristics and Possible Controls of the Surface Water in Ranwu Lake Basin]

To study the chemistry of surface water and potential control measures in the Ranwu Lake basin, 19 samples were collected from Ranwu Lake in 2019. Conventional hydrochemical techniques and statistical analysis methods (descriptive statistics, the Gibbs figure, ion ratio, Piper triangular diagrams) were applied to better understand the solute geochemistry and surface water hydrochemistry in the Ranwu Lake catchment. Surface water in the Ranwu catchment is slightly alkaline (pH of the samples ranged from 7.54 to 8.48 with an average value of 8.06). The concentrations of total dissolved solids (TDS) in the water range from 59.89 to 96.75 mg ·L^-1 with an average of 79.98 mg ·L^-1, the total dissolved solids of all samples are less than 100 mg ·L^-1 and belong to fresh water. The TDS are dominated by Ca²⁺, Mg²⁺, HCO₃^-, and SO₄^2- in the Ranwu Lake. The ion concentrations in the lake water samples are in the order of Ca²⁺ > Mg²⁺ > Na⁺ > K⁺. The concentrations of Na⁺and K⁺are very low. Ranging from 0.5 to 1.21 mg ·L^-1, with an average value of 0.58 mg ·L^-1, the equivalent concentration of Ca²⁺ accounts for 63.3% to 76.2% of total cations with an average value of 67.2%. The equivalent concentration of Mg²⁺ accounts for 23.4% to 36.2% of total cations with an average value of 31.4%. Ca²⁺ and Mg²⁺ account for 98.5% of total cations. The main anions were HCO₃^- and SO₄^2-. The equivalent concentration of HCO₃^- accounts for 74.31% to 84.29% of total anions with an average value of 78.21%. The equivalent concentration of SO₄^2- accounts for 9.59% to 19.37% of total anions with an average value of 15.34%. HCO₃^- and SO₄^2- together account for 93.55% of total anions on average. All the water samples fall in the water-rock interaction field, which suggests that the weathering of rocks primarily controls the major ion chemistry of groundwater in this area. Solutes are mainly derived from carbonate weathering and silicate weathering. The role of cation exchange in the geochemical process of the lake and the influence of human activities on the lake are found to be weak.

Performance of a Low Energy Ion Source with Carbon Nanotube Electron Emitters under the Influence of Various Operating Gases

Low energy ion measurements in the vicinity of a comet have provided us with important information about the planet’s evolution. The calibration of instruments for thermal ions in the laboratory plays a crucial role when analysing data from in-situ measurements in space. A new low energy ion source based on carbon nanotube electron emitters was developed for calibrating the ion-mode of mass spectrometers or other ion detectors. The electron field emission (FE) properties of carbon nanotubes (CNTs) for H₂, He, Ar, O₂, and CO₂ gases were tested in the experiments. H₂, He, Ar, and CO₂ adsorbates could change the FE temporarily at pressures from10⁻⁶ Pa to10⁻⁴ Pa. The FE of CNT remains stable in Ar and increases in H₂, but degrades in He, O₂, and CO₂. All gas adsorbates lead to temporary degradation after working for prolonged periods. The ion current of the ion source is measured by using a Faraday cup and the sensitivity is derived from this measurement. The ion currents for the different gases were around 10 pA (corresponding to 200 ions/cm³ s) and an energy of ~28 eV could be observed.

[Analysis of Performance of the MINItrace Cyclotron before and after Upgrade]

OBJECTIVE

To compare the performance of the GE cyclotron MINItrace system before and after the upgrade.

METHODS

The upgrade of the MINItrace system included replacing the silver target with the Nb syetem and adopting the latest RF control and management system and lastest ion source system.The failrue rate and production efficiency were retrospectively analyzed before and after the upgrade.

RESULTS

After the upgrade, the cyclotron failure rate decreased by 86.2%, the average capacity increased by 45%.

CONCLUSIONS

After the upgrade of MINItrace cyclotron, the failure rate is sharply reduced, and the production efficiency is grately improved.

Design, Fabrication and Mass-spectrometric Studies of a Micro Ion Source for High-Field Asymmetric Waveform Ion Mobility Spectrometry

A needle-to-cylinder electrode, adopted as an ion source for high-field asymmetric ion mobility spectrometry (FAIMS), is designed and fabricated by lithographie, galvanoformung and abformung (LIGA) technology. The needle, with a tip diameter of 20 μm and thickness of 20 μm, and a cylinder, with a diameter of 400 μm, were connected to the negative high voltage and ground, respectively. A negative corona and glow discharge were realized. For acetone with a density of 99.7 ppm, ethanol with a density of 300 ppm, and acetic ether with a density of 99.3 ppm, the sample gas was ionized by the needle-to-cylinder chip and the ions were detected by an LTQ XL™ (Thermo Scientific Corp.) mass spectrometer. The mass spectra show that the ions are mainly the protonated monomer, the proton bound dimer, and an ion-H₂O molecule cluster. In tandem with a FAIMS system, the FAIMS spectra show that the resolving power increases with an increase in the RF voltage. The obtained experimental results showed that the micro needle-to-cylinder chip may serve as a miniature, low cost and non-radioactive ion source for FAIMS.

[Hydrochemical Characteristics and Possible Controls of Groundwater in the Xialatuo Basin Section of the Xianshui River]

In order to study the characteristics of groundwater chemistry and groundwater flow system in the Xianshui River fault zone, samples of precipitation, surface water, groundwater, and hot spring samples in the Xialatuo Basin were collected and tested. Through the test data, the main ions and the sources of recharge were analyzed by means of ionic relations, correlation analysis, Gibbs plot, Piper triangular diagrams, and saturation index. The groundwater recharge sources in the basin were studied using combined hydrogen and oxygen isotope information. Results show that all the water samples in the study area were weakly alkaline. The predominant cations were Ca²⁺, Mg²⁺, and Na⁺. Among these, Ca²⁺ accounted for 2.6%-53.6%, with an average value of 28.84%, Mg²⁺ accounted for 2.7%-57%, with an average value of 40.6%, and Na⁺ accounted for 6.2%-93.1%, with an average value of 28.6%. The anions were mainly HCO₃^-, accounting for 82.4%-98% of the total anions and with an average value of 89.6%. HCO₃^- and Na⁺ accounted for most of the ions with 93.1% and 98%, respectively, in the Zhanggu hot spring. The total dissolved solids (TDS) of the groundwater ranged from 116.11 to 372.75 mg·L^-1, and with an average value of 281.91 mg·L^-1. The hydrogeochemical type of groundwater was HCO₃-Mg·Ca and HCO₃-Ca·Mg. It is controlled by carbonatite dissolution with a circulatory depth range in dozens of meters. The hot springs are controlled by the fault zone and are mainly distributed along the main stem of the Xianshui River fault. Their water is of the HCO₃-Na type. The hydrogeochemical process is controlled by silicate dissolution with a circulatory depth range in thousands of meters.

Compositional elucidation of heavy petroleum base oil by GC × GC-EI/PI/CI/FI-TOFMS

Comprehensive two-dimensional gas chromatography (GC × GC) coupled to time-of-flight mass spectrometry is a powerful separation tool for complex petroleum product analysis. However, the most commonly used electron ionization (EI) technique often makes the identification of the majority of hydrocarbons impossible due to the exhaustive fragmentation and lack of molecular ion preservation, prompting the need of soft-ionization energies. In this study, three different soft-ionization techniques including photo ionization (PI), chemical ionization (CI), and field ionization (FI) were compared against EI to elucidate their relative capabilities to reveal different base oil hydrocarbon classes. Compared with EI (70 eV), PI (10.8 eV) retained significant molecular ion (M^+· ) information for a large number of isomeric species including branched-alkanes and saturated monocyclic hydrocarbons along with unique fragmentation patterns. However, for bicyclic/polycyclic naphthenic and aromatic compounds, EI played upper hand by retaining molecular as well as fragment ions to identify the species, whereas PI exhibited mainly molecular ion signals. On the other hand, CI revealed selectivity towards different base oil groups, particularly for steranes, sulfur-containing thiophenes, and esters, yielding protonated molecular ions (M + H)⁺ for unsaturated and hydride abstracted ions (M-H⁺ ) for saturated hydrocarbons. FI, as expected, generated intact molecular ions (M^+· ) irrespective to the base oil chemical classes. It allowed elemental composition by TOFMS with a mass resolving power up to 8000 (FWHM) and a mass accuracy of 1 mDa, leading to the calculation of heteroatomic content, double bond equivalency, and carbon number of the compounds. The qualitative and quantitative results presented herein offer a unique perspective into the detailed comparison of different ionization techniques corresponding to several hydrocarbon classes.

Cathode Design Optimization toward the Wide-Pressure-Range Miniature Discharge Ion Source for a Vacuum Micropump

It is difficult to generate and maintain the vacuum level in vacuum MEMS (Micro-Electro-Mechanical Systems) devices. Currently, there is still no single method or device capable of generating and maintaining the desired vacuum level in a vacuum device for a long time. This paper proposed a new wide-pressure-range miniature ion source, which can be applied to a vacuum micropump. The miniature ion source consists only of silicon electrodes and a glass substrate. Its operating pressure range covers seven orders of magnitude, starting from atmospheric pressure, a promising solution to the difficulty. Based on the principle of gas discharge, the ion source features a simple two-electrode structure with a two-stage electrode spacing, operating under DC voltage excitation. The first-stage electrode spacing of the ion source is small enough to ensure that it starts working at atmospheric pressure down to a certain reduced pressure when it automatically switches to discharge at the larger second-stage electrode spacing and operates from that pressure down to a high vacuum. Two configurations of the ion source have been tested: without-magnet, operating from atmospheric pressure down to 1 mbar; and with-magnet, operating from atmospheric pressure to 10^-4 mbar, which covers seven orders of magnitude of pressure. The ion source can be applied not only to a MEMS ion pump to meet demands of a variety of vacuum MEMS devices, but can also be applied to other devices, such as vacuum microgauges and mass spectrometers.

[Major Ionic Features and Possible Controls in the Groundwater in the Hamatong River Basin]

In order to study the major ion chemistry and controls of groundwater, 59 groundwater samples were collected and their major ions measured in the Hamatong River Basin. The hydrogeochemical characteristics of groundwater in this basin were analyzed by means of mathematical statistics, Piper triangular diagrams, Gibbs figures, and ionic relations, and the water chemical evolution and ion sources of the Hamatong River Basin were determined. The results showed that Ca²⁺ was the main cation in the groundwater, accounting for 22.1% to 72.4% of the total cations, with an average value of 48.7%. HCO₃^- was the main anion, accounting for 35.3% to 97.5% of the total anions, and with an average value of 80%. Total dissolved solids concentration ranged from 93.3 mg·L^-1 to 521.1 mg·L^-1 with a median value of 219.1 mg·L^-1. The hydrochemical types of groundwater are HCO₃-Ca, HCO₃-Ca·Mg, and HCO₃-Ca·Na. Chemical weathering rates of carbonates and silicates were estimated, and the chemical composition of groundwater samples located in the middle of Gibbs model indicated that the major chemical process of groundwater was controlled by rock weathering. Silicate weathering is believed to significantly contribute to dissolved solute compositions, and carbonate weathering played an important role as the source of dissolved ions.

[Fate and Origin of Major Ions in River Water in the Lhasa River Basin, Tibet]

In order to understand the temporal and spatial variations of major ions in water and their sources in the Lhasa River Basin, water samples were collected monthly at the hydrological station in the Lhasa River from August 2014 to July. The results show that HCO₃^- is the dominant anion in the water of the Lhasa River, which accounts for 68.73% of the anions, followed by SO₄^2-. Ca²⁺ is the dominant cation, which accounts for 67.75% of the cations, followed by Mg²⁺. The pH values of the river water range between 8.31 and 8.90, with a mean of 8.59 throughout the year, generally showing alkaline water. The highest pH values occur in summer, which is probably due to the photosynthesis of aquatic plants and the growth of phytoplankton. Electrical conductivity (EC) varies between 155.0 and 257.0 μS·cm^-1, with a mean of 210.5 μS·cm^-1. Because of the frequent uplift of the Tibetan Plateau that enhanced the mechanical weathering of rocks and mineral dissolution, the total dissolved solid (TDS) concentration, at an average of 181.35 mg·L^-1, is significantly higher than the average value of rivers around the world. The Lhasa River is recharged by surface runoff, so the concentrations of major ions in water are higher during winter, but lower in summer. An ion source analysis indicates that Ca²⁺, Mg²⁺, and HCO₃^- are mainly derived from chemical weathering of carbonate minerals, Cl^-, SO₄^2-, and NO₃^- are mainly affected by precipitation and rock weathering. Furthermore, the concentrations of major ions in the water have a negative correlation with the river discharge rate, which suggests there might be a dilution effect occurring during the rainy season.

[Major Ionic Features and Their Possible Controls in the Water of the Niyang River Basin]

In order to study the hydrochemical characteristics and their possible controls for the chemical composition of the water from the Niyang River Basin, 30 samples were collected from wells, springs, and the river in 2014 and major ion concentrations were measured. Descriptive statistics, the Gibbs figure, an ion ratio, and Piper triangular diagrams were used to investigate the hydrochemical characteristics, influencing factors, and hydrochemical evolution of the water in the basin. The results showed that the major cations in this water were Ca²⁺ and Mg²⁺, accounting for more than 84% of cations and the main anions were HCO₃^- and SO₄^2-, accounting for more than 97% of anions The hydrochemical typology of the water is HCO₃·SO₄(SO₄·HCO₃)-Ca·Mg (Mg·Ca). The total dissolved solids (TDS) in the water ranges from 79.11 to 290.48 mg·L^-1 with an average of 165.21 mg·L^-1. The chemical composition of water samples is located to the left of the Gibbs model, which indicates that the chemical process of Niyang River Basin are controlled by rock weathering. According to the principal component analysis and correlation analysis, the hydrochemical composition is controlled by silicate weathering, however, carbonate weathering also plays an important role.

High-brightness Cs focused ion beam from a cold-atomic-beam ion source

We present measurements of focal spot size and brightness in a focused ion beam system utilizing a laser-cooled atomic beam source of Cs ions. Spot sizes as small as (2.1 ± 0.2) nm (one standard deviation) and reduced brightness values as high as (2.4 ± 0.1) × 10⁷ A m^-2 Sr^-1 eV^-1 are observed with a 10 keV beam. This measured brightness is over 24 times higher than the highest brightness observed in a Ga liquid metal ion source. The behavior of brightness as a function of beam current and the dependence of effective source temperature on ionization energy are examined. The performance is seen to be consistent with earlier predictions. Demonstration of this source with very high brightness, producing a heavy ionic species such as Cs⁺, promises to allow significant improvements in resolution and throughput for such applications as next-generation circuit edit and nanoscale secondary ion mass spectrometry.

Electrospray Modifications for Advancing Mass Spectrometric Analysis

Generation of analyte ions in gas phase is a primary requirement for mass spectrometric analysis. One of the ionization techniques that can be used to generate gas phase ions is electrospray ionization (ESI). ESI is a soft ionization method that can be used to analyze analytes ranging from small organics to large biomolecules. Numerous ionization techniques derived from ESI have been reported in the past two decades. These ion sources are aimed to achieve simplicity and ease of operation. Many of these ionization methods allow the flexibility for elimination or minimization of sample preparation steps prior to mass spectrometric analysis. Such ion sources have opened up new possibilities for taking scientific challenges, which might be limited by the conventional ESI technique. Thus, the number of ESI variants continues to increase. This review provides an overview of ionization techniques based on the use of electrospray reported in recent years. Also, a brief discussion on the instrumentation, underlying processes, and selected applications is also presented.

An Integrated Microfabricated Chip with Double Functions as an Ion Source and Air Pump Based on LIGA Technology

The injection and ionization of volatile organic compounds (VOA) by an integrated chip is experimentally analyzed in this paper. The integrated chip consists of a needle-to-cylinder electrode mounting on the Polymethyl Methacrylate (PMMA) substrate. The needle-to-cylinder electrode is designed and fabricated by Lithographie, Galvanoformung and Abformung (LIGA) technology. In this paper, the needle is connected to a negative power supply of -5 kV and used as the cathode; the cylinder electrodes are composed of two arrays of cylinders and serve as the anode. The ionic wind is produced based on corona and glow discharges of needle-to-cylinder electrodes. The experimental setup is designed to observe the properties of the needle-to-cylinder discharge and prove its functions as an ion source and air pump. In summary, the main results are as follows: (1) the ionic wind velocity produced by the chip is about 0.79 m/s at an applied voltage of -3300 V; (2) acetic acid and ammonia water can be injected through the chip, which is proved by pH test paper; and (3) the current measured by a Faraday cup is about 10 pA for acetic acid and ammonia with an applied voltage of -3185 V. The integrated chip is promising for portable analytical instruments, such as ion mobility spectrometry (IMS), field asymmetric ion mobility spectrometry (FAIMS), and mass spectrometry (MS).

Charge state distribution studies of pure and oxygen mixed krypton ECR plasma - signature of isotope anomaly and gas mixing effect

We report the charge state distributions of the pure, 25% and 50% oxygen mixed krypton plasma to shed more light on the understanding of the gas mixing and the isotope anomaly [A. G. Drentje, Rev. Sci. Instrum. 63 (1992) 2875 and Y Kawai, D Meyer, A Nadzeyka, U Wolters and K Wiesemann, Plasma Sources Sci. Technol. 10 (2001) 451] in the electron cyclotron resonance (ECR) plasmas. The krypton plasma was produced using a 10 GHz all-permanent-magnet ECR ion source. The intensities of the highly abundant four isotopes, viz. ⁸² Kr (~11.58%), ⁸³ Kr (~11.49%), ⁸⁴ Kr (~57%) and ⁸⁶ Kr (17.3%) up to ~ +14 charge state have been measured by extracting the ions from the plasma and analysing them in the mass and the energy using a large acceptance analyzer-cum-switching dipole magnet. The influence of the oxygen gas mixing on the isotopic krypton ion intensities is clearly evidenced beyond +9 charge state. With and without oxygen mixing, the charge state distribution of the krypton ECR plasma shows the isotope anomaly with unusual trends. The anomaly in the intensities of the isotopes having quite closer natural abundance, viz. ⁸² Kr, ⁸⁶ Kr and ⁸³ Kr, ⁸⁶ Kr is prominent, whereas the intensity ratio of ⁸⁶ Kr to ⁸⁴ Kr shows a weak signature of it. The isotope anomaly tends to disappear with increasing oxygen mixing in the plasma. The observed trends in the intensities of the krypton isotopes do not follow the prediction of linear Landau wave damping in the plasma. Copyright © 2016 John Wiley & Sons, Ltd.

[Hydrochemical Characteristics and Sources of Ions in Precipitation at the East Qilian Mountains]

Precipitation of the northwest China is different from that in other regions of China. The vapor reaches this region after long distance transportation with little precipitation, and the ratio of precipitation variation is large. Wushaoling at the east Qilian Mountains is an important divided line of climate in China. The east region of it is affected by South Asia and East Asia monsoon, while the west region of it is influenced by Westerly circulation. So ion combinations in precipitation are complex for the trajectories of water vapor transportation, the natural environments and the development levels of social and economy in different regions. Precipitation samples were collected at Heisongyi located at the east Qilian Mountains. Hydrochemical characteristics and sources of ions were analyzed by factor analysis, Enrichment factor analysis and back trajectory analysis. EC values in precipitation ranged from 29.20 to 892.00 μS·cm^-1, which were controlled by alkaline element. The precipitation was weak alkaline with pH values ranging from 7.02 to 8.89. EC values in precipitation were higher in autumn and winter than in spring and summer, opposite to pH values. The type of precipitation was SO₄^2--Ca²⁺ for the cation concentrations following the order of Ca²⁺ >Mg²⁺ >Na⁺ >NH₄⁺ >K⁺ and the anion concentrations following the order of SO₄^2- >Cl^- >NO₃^-. The concentrations of K⁺, Mg²⁺, Ca²⁺, NH₄⁺, Cl^-, NO₃^- and SO₄^2- were the highest in autumn, but the peak value of Na⁺ concentration appeared in winter. As a whole, ion concentrations were higher in autumn and winter than in spring and summer. Enrichment factor indicated that Na⁺and Cl^- mainly came from marine source but Na⁺ partly originated from crust source in winter and Cl^- partly originated from anthropogenic source in winter, and that K⁺, Mg²⁺ and Ca²⁺ mainly came from crust source except that Mg²⁺ partly originated from anthropogenic source in winter, and that NO₃^- and SO₄^2- mainly came from anthropogenic source. The trajectories of water vapor transportation from directions of northwest, north, north with southeast, northwest with southeast, northwest with southwest, northwest with north and southeast were ion original sources in precipitation, and the major trajectory came from northwest direction. Among these trajectories of water vapor transportation, that from northwest, north and north with southeast appeared in each season, but that from northwest with southeast appeared in spring and summer, that from northwest with southwest and northwest and north with southeast appeared in summer. Though ions originated from marine transport by Westerly and monsoon, from crust provided by desert and Gobi in central Asia, Xingjiang and Mongolian plateau, and from humanity activity related to cities pollution and industrial and agriculture production of oasis at all trajectories, the concentrations of ions in precipitation were effected by the strong and weak variations of different weather systems.

What Is the Opposite of Pandora's Box? Direct Analysis, Ambient Ionization, and a New Generation of Atmospheric Pressure Ion Sources

The introduction of DART and DESI sources approximately seven years ago led to the development of a new series of atmospheric pressure ion sources referred to as "ambient ionization" sources. These fall into two major categories: spray techniques like DESI or plasma techniques like DART. The selectivity of "direct ionization," meaning analysis without chromatography and with little or no sample preparation, depends on the mass spectrometer selectivity. Although high resolution and tandem mass spectrometry are valuable tools, rapid and simple sample preparation methods can improve the utility of ambient ionization methods. The concept of ambient ionization has led to the realization that there are many more ways to form ions than might be expected. An interesting example is the use of a flint-and-steel spark source to generate ions from compounds such as phenolphthalein and Gramicidin S.

Improving liquid chromatography-mass spectrometry sensitivity using a subambient pressure ionization with nanoelectrospray (SPIN) interface

In this work, the subambient pressure ionization with nanoelectrospray (SPIN) ion source and interface, which operates at ~15-30 Torr, is demonstrated to be compatible with gradient reversed-phase liquid chromatography-MS applications, exemplified here with the analysis of complex samples (a protein tryptic digest and a whole cell lysate). A low liquid chromatographic flow rate (100-400 nL/min) allowed stable electrospray to be established while avoiding electrical breakdown. Efforts to increase the operating pressure of the SPIN source relative to previously reported designs prevented solvent freezing and enhanced charged cluster/droplet desolvation. A 5- to 12-fold improvement in sensitivity relative to a conventional atmospheric pressure nanoelectrospray ionization (ESI) source was obtained for detected peptides.