Sampling Cone Research Articles

Analysis of diluted honey samples from the province of Lower Silesia (Poland) by inductively coupled plasma mass spectrometry

The direct determination of 18 elements (B, Ba, Ca, Cd, Cs, Cu, Fe, K, Li, Mg, Mn, Na, Ni, Pb, Rb, Sr, Tl, and Zn) in 1% aqueous honey solutions (dilution factor = 100) by ICP MS was presented. The presence of sugar in sample solutions caused a decrease in analytical signals, the appearance of carbon-containing polyatomic ions, and the deposition of carbonaceous products on a sampler cone. On the flip side, these effects did not destabilize the ICP, while the internal standard calibration (9Be, 89Y, and 153Eu as standards) made it possible to correct matrix effects. Additionally, in the case of 11B, 23Na, 43Ca, and 57Fe isotopes, using a collision cell (He, 2 mL min−1) was required. Due to lower sample blanks, the analysis of water-diluted honey samples offered on average 3 times lower detection limits of elements than achieved for microwave-digested samples. The proposed method, characterized by high analytical throughput, was used for the analysis of 120 samples of honey from the apiaries in the Lower Silesia province. The average content of the major elements in the analyzed honey samples was: B 10.4 mg kg−1, Ca 61.0 mg kg−1, Fe 1.0 mg kg−1, K 1049 mg kg−1, Mg 27.8 mg kg−1, Mn 3.4 mg kg−1, Na 9.1 mg kg−1, Rb 1.4 mg kg−1, Zn 2.0 mg kg−1, and the average content of the trace elements: Ba 130 μg kg−1, Cd 3.2 μg kg−1, Cs 4.8 μg kg−1, Cu 315 μg kg−1, Li 3.8 μg kg−1, Ni 90 μg kg−1, Pb 8.0 μg kg−1, Sr 119 μg kg−1, Tl 1.2 μg kg−1. It was found that (1) the concentrations of all tested elements (except B and Tl) were higher in dark honey, (2) the content of Cs and Rb in honey from the mountain areas of the voivodeship was much higher than this in honey from the lowland areas, and (3) the best discriminators in terms of the color and the botanical origin of honey were the concentrations of Cu and Mn, and to a lesser extent also B, Ca, K, Mg, and Na; e.g., honeydew and buckwheat honey contained much higher amounts of Cu and Mn, sunflower honey was characterized by a significantly higher content of Ca, and rape honey showed an increased B content. Given that the proposed sample preparation procedure allows the simultaneous, reliable, and fast determination of major, trace, and ultra-trace elements, it seems to be a convenient method for the profiling of many honey samples in a very short time.

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).

A Novel Multi-ion Evaluation Scheme to Determine Stable Chlorine Isotope Ratios (37Cl/35Cl) of Chlordecone by LC-QTOF.

Organochlorinated pesticides are highly persistent organic pollutants having important adverse effects in the environment. To study their fate, compound-specific isotope analysis (CSIA) may be used to investigate their degradation pathways and mechanisms but is currently limited to 13C isotope ratios. The assessment of 37Cl isotope ratios from mass spectra is complicated by the large number of isotopologues of polychlorinated compounds. For method development, chlordecone (C10Cl10O2H2; hydrate form), an organochlorine insecticide that led to severe contamination of soils and aquatic ecosystems of the French West Indies, was taken as a model analyte. Chlorine isotope analysis of chlordecone hydrate was evaluated using high-resolution liquid chromatography quadrupole time-of-flight mass spectrometry (LC-QTOF-MS), enabling smooth ionization to detect the molecular ion. First, a new evaluation scheme is presented to correct for multiple isotope presence in polychlorinated compounds. The scheme is based on probability calculations of the most frequent isotopologues, distributions by binomial probability functions, and corrections for the presence of nonchlorine heavy isotopes. Second, mobile-phase modifiers, ionization energy (sampling cone tension) and scan time were optimized for accurate chlorine isotope ratios. Chlordecone standard samples were measured up to 10-fold and bracketed with a second chlordecone external standard. δ37Cl values were obtained after conversion to the SMOC scale by a two-point calibration. The robustness of the analysis method and evaluation scheme were tested and gave satisfactory results with standard errors (σm) of ±0.34‰ for precision and ±0.89‰ for long-term accuracy of chlorine isotope ratios of chlordecone hydrate. This work opens perspectives for applications of the C-Cl CSIA approach to investigate the fate of highly toxic and low reactive polychlorinated compounds in the environment.

Research on Sampling System for Abyssal Sediment Based on Image Recognition Technology

Abstract The pressure-holding sampling technology for deep-sea sediments has been identified as a prerequisite for studying the sedimentary environment with respect to the mechanical and biological characteristics of sediments. Thus, in this study, we designed a set of abyssal sediment sampling systems based on image recognition technology. First, a system camera was used to obtain the movement trajectory of the sampling cone in the laboratory simulation scene. After collecting the data of the image including the sampler, we preprocessed the data using an underwater image restoration method based on the dark channel prior. An image recognition unit was used to verify that the position of the sampling cone meets the requirement. The main control unit controlled the actuator of the sampling device to accurately control the position of the sampling cone. Furthermore, we used the Mask R-convolutional neural network architecture to build the network framework for controlling the expansion and braking of the sampler. The experimental results showed that the system achieved a very high detection accuracy for the position of the sampling cone.

Cationic structure of premixed near-stoichiometric CH4/O2/Ar flames at atmospheric pressure: New insights from mass spectrometry, quantum chemistry, and kinetic modeling

The spatial distributions of naturally occurring cations in near-stoichiometric (equivalence ratios ϕ = 0.8 and 1.2) burner-stabilized methane/oxygen/argon flames at atmospheric pressure are studied by molecular beam mass spectrometry (MBMS) and kinetic modeling. The disturbing effect of a nickel sampling cone used in the measurements on the flame was comprehensively modeled using a two-dimensional direct numerical simulation of reacting flow near the axially symmetric probe along with a reduced chemical kinetic mechanism. The use of one-dimensional numerical simulation for predicting the flame structure perturbed by the metallic probe was firmly justified. We also proposed and applied a procedure to correct the measured spatial profiles of cations on the contribution of signals from the hydrates formed slightly upstream the reaction zone due to the sampling probe effects. With all these methodological advantages, we validated the ion chemistry mechanisms proposed earlier in the literature against the novel experimental data on the spatial distributions of the following cations: HCO+, CH3+, H3O+, C2H3O+, CH5O+, C3H3+. The kinetic mechanism published recently by Chen et al. [Combust. Flame 202 (2019) 208] for the charged species formed in methane flames was revised in order to improve its predictive ability. To this end, the highly accurate W2-F12 quantum chemical calculations were used to obtain the reliable formation enthalpies of all cations considered in the mechanism. In the case of C2H3O+ and C3H3+ cations, the calculated values turned out to be profoundly lower than those reported before. Apart from this, the theory also predicted another exit channel for H3O+ + acetylene reaction yielding HCO+ + CH4 instead of C2H3O+ + H2 proposed earlier. The corrections significantly improved the predictive ability of the ion chemistry mechanism. We also considered the most important directions for the further refinement of the mechanism.

Effect of "Late Harvest" of Hops (Humulus lupulus L.) on the Contents of Volatile Thiols in Furano Beauty, Furano Magical, and Cascade Varieties.

In recent years, many hop varieties with unique aromas, so-called "flavor hops", have been bred and grown. Here, we investigated the effect of late-harvested hops using three flavor hop varieties; Furano Beauty, Furano Magical, and Cascade. The sample hops were harvested at different days after flowering (DAF): DAF 45 (normal harvest), DAF 65, DAF 75, and DAF 85. We measured the volatile thiols in sample cones. The results indicated that 4-methyl-4-sulfanylpentane-2-one contents showed almost no change or a slightly decrease with a delay in harvest, whereas 3-sulfanyl-4-methylpentan-1-ol (3S4MP) content in late-harvested samples increased several fold in comparison with normal-harvested samples. Additionally, 3S4MP contents in the beers brewed with DAF 65 samples were several times higher than those using DAF 45 ones. From these results, we propose a new method to control 3S4MP content in hop cones by changing its harvest date.

Robust Potassium Isotopic Analysis of Geological and Biological Samples via Multicollector ICP-Mass Spectrometry Using the "Extra-High Resolution Mode".

Potassium isotopic analysis is arousing increasing interest, not only in geochemistry, but also in biomedicine. However, real-life applications are still hindered by the lack of robustness of the methods used. In this work, a novel and robust method for high-precision K isotopic analysis of geological and biological samples was developed, based on the use of a multicollector ICP-mass spectrometer providing a mass resolving power of 15,000 (extra-high resolution mode, XHR). After evaluation of different measurement conditions, i.e., hot vs cold plasma conditions, standard-type vs jet-type sampling cone, and high resolution (HR) vs XHR, a combination of hot plasma conditions, use of the high-transmission jet-type sampling cone, and the XHR mode allowed for high-precision and interference-free K isotopic analysis. Potassium signal monitoring was performed in the ArH+ interference-free 0.006-0.007 amu wide peak shoulder using the XHR mode. The within-run, short-term external, and long-term external precisions for the δ41K value were 0.02‰ (2se, N = 50), 0.03‰ (2SD, N = 7), and 0.06‰ (2SD, N = 163), respectively. A two-stage chromatographic procedure was developed for the isolation of K from both geological and biological samples, and potential matrix effects affecting the K isotope ratio were systematically evaluated. The method was first applied to geological reference materials (RMs) for validation purposes, and the K isotope ratio results were in good agreement with those previously reported. Subsequently, a series of biological RMs, including serum, whole blood, cerebrospinal fluid, bovine muscle, and lobster hepatopancreas, were characterized for their K isotopic composition.

Study on the enhancing water collection efficiency of cactus- and beetle-like biomimetic structure using UV-induced controllable diffusion method and 3D printing technology.

Collecting water from fog flow has emerged as a promising strategy for the relief of water shortage problems. Herein, using a UV-induced (ultraviolet light induced) controllable diffusion method combined with technology of three-dimensional (3D) printing, we fabricate biomimetic materials incorporating beetle-like hydrophobic–hydrophilic character and cactus-like cone arrays with various structure parameters, and then systematically study their fog-harvesting performance. The UV-induced controllable diffusion method can break away from the photomask to regulate the hybrid wettability. Moreover, employing 3D printing technology can flexibly control the structure parameters to improve the water collection efficiency. It is found that the water collection rate (WCR) can be optimized by controlling the hybrid wettability of the sample surface and cone distance and using substrates with printed holes, which lead to a 109% increase of WCR.

Increasing Collisional Activation of Protein Complexes Using Smaller Aperture Source Sampling Cones on a Synapt Q-IM-TOF Instrument with a Stepwave Source.

Quadrupole ion mobility time-of-flight (Q-IM-TOF) mass spectrometers have revolutionized investigation of native biomolecular complexes. High pressures in the sources of these instruments aid transmission of protein complexes through damping of kinetic energy by collisional cooling. As adducts are removed through collisional heating (declustering), excessive collisional cooling can prevent removal of nonspecific adducts from protein ions, leading to inaccurate mass measurements, broad mass spectral peaks, and obfuscation of ligand binding. We show that reducing the source pressure using smaller aperture source sampling cones (SC) in a Waters Synapt G2-Si instrument increases protein ion heating by decreasing collisional cooling, providing a simple way to enhance removal of adducted salts from soluble proteins (GroEL 14-mer) and detergents from a transmembrane protein complex (heptameric Staphylococcus aureus α-hemolysin, αHL). These experiments are supported by ion heating and cooling simulations which demonstrate reduced collisional cooling at lower source pressures. Using these easily swapped sample cones of different apertures is a facile approach to reproducibly extend the range of activation in Synapt-type instruments.

Inductively coupled plasma with mass-spectrometry method development and validation for gadolinium in gadolinium-based contrast agents of pharmaceutical formulations

Gadolinium-based contrast agent interacts with the human body temporarily and improves the pictures of inside of the body produced by magnetic resonance imaging, computed tomography, X-rays and ultrasound and it also helps to distinguish the normal from abnormal conditions. In this study, the authors developed a simple, rapid, reliable and robust inductively coupled plasma mass-spectrometry method for estimation of gadolinium in gadolinium-based contrast agents to check the drug quality and ensure the patient safety. The samples were digested at 160°C using the microwave digestion system and the gadolinium was extracted in 0.4% (w/w) nitric acid. Interference of deposited gadolinium on sample cone and skimmer cone were investigated and evaluated. The developed method was validated as per ICH Q2 (R1) guideline and USP<730>. The precision was evaluated with six independent assays of gadolinium in each gadolinium-based contrast agent. The test method was found linear (r2 > 0.999) with five different levels covered from 25~200%, and accurate, mean recoveries were 92.5~107.5% at three different levels covered from 50~150%. The robustness was performed by changing the nitric acid concentration (0.4±0.04%, w/w) in diluent system. This method is suitable to quantitatively determine the amount of gadolinium in gadolinium-based contrast agent of drug products in presence of excipients used in formulation and also in drug substance.

UPLC-QTOF-MS Method for Identification of Mango Leaf Tea Metabolites

Abstract Objectives The study aim was to identify bioactive compounds in mango leaf tea using a new method - UPLC/Q-TOF-MS. Mango leaf tea is a natural product being investigated to manage type 2 diabetes due to its phytochemical properties. Methods Mango tea was extracted using 80% methanol overnight. The extract was analyzed with ultra-high-performance liquid chromatography-quadrupole time-of-flight (UPLC-Q-TOF) MS system (Waters Corp., Milford, MA) and injected into an Acquity UPLC BEH C18 column (2.1 mm × 100 mm, 1.7 µm, Waters Corp.). The column was equilibrated with distilled water containing 0.1% formic acid (FA) and eluted by a linear gradient of acetonitrile (ACN) containing 0.1% FA at a flow rate of 0.35 mL/min for 10 min and 40 °C of column temperature. Results The eluents were analyzed by A Vion IMS Q-TOF MS (Waters Corp.) with positive and negative electrospray ionization (ESI). The scan range of TOF MS data was 50–1500 m/z, the scan time was 0.2 sec, and the capillary and sampling cone voltages were 3 kV and 40 V, respectively. The desolvation flow rate and temperature were 800 L/h and 400 °C, respectively, and the source temperature was 100 °C. Leucine-enkephalin ([M + H] = 556.2771 Da; [M-H] = 554.2615 Da), used as a lack mass, was infused at a flow rate of 0.35 μL/min and a frequency of 10 s to ensure mass measurement accuracy of the metabolites analyzed by the instrument. Mass spectral data were collected from m/z 50 to 1500 with a scan time of 0.2 s. Collision energy was ramped from 10 to 40 eV for the collection of MS/MS data. The metabolites Mangiferin, quercetin/isoquercetin and iriflophenone 3-beta-glucoside were identified using ChemSpider in negative mode while only mangiferin and quercetin were defined in positive mode with different intensites: Mangiferin (421.07), quercetin/isoquercetin (303.05) and irrflophenone 3- beta- glucoside (407.097) that confirmed their molar mass. Conclusions The UPLC/Q-TOF-MS technique is a practical and novel method for identifying the fragmentation pattern of metabolites in mango leaf tea by measuring accurate mass with excellent resolution and sensitivity. Funding Sources N/A.

Matrix-assisted ionisation in vacuum mass spectrometry and imaging on a modified quadrupole-quadrupole-time-of-flight mass spectrometer

Matrix-Assisted Ionisation in Vacuum (MAIV) is a new ionisation technique which ionises non-volatile compounds producing electrospray ionisation-like spectra. Its simple, matrix-assisted laser desorption/ionisation-like sample preparation allows for rapid analysis, with no requirement for external energy in the form of a laser or high voltage to produce ions. Ionisation occurs when the matrix (often 3-nitrobenzonitrile) is exposed to sub-ambient pressure. Here, the first use of this revolutionary new ionisation technique to image biological samples is reported. A commercial quadrupole-quadrupole-time-of-flight mass spectrometer was modified to incorporate control of the ion source pressure and a reduced sampling cone orifice diameter. In initial experiments, optimisation of source pressure and matrix composition was carried out to increase the longevity of ion formation. It was noted during these experiments that ion production was only observed when the sample was directly under the sampling cone. Optimisation of sample extraction into the MAIV matrix by the addition of 5% chloroform enabled MAIV mass spectrometry imaging of lipids in rat brain sections to be carried out in raster imaging mode. Modification of the size and position of the sampling cone improved the selectivity obtainable in these images. Although the quality of these initial images is relatively poor, work is underway to improve the spatial resolution by further modification of the ion source and progress is reported.

Effects of cone combinations on accurate and precise Mg-isotopic determination using multi-collector inductively coupled plasma mass spectrometry.

High-precision determination of magnesium (Mg) isotopes can now be routinely achieved by multi-collector inductively coupled plasma mass spectrometry (MC-ICP-MS). The analytical sensitivity and instrumental mass discrimination behavior of this method are, however, sensitive to the types of sample and skimmer cones used in these measurements, so it is important that these parameters should be investigated. Using the sample-standard-bracketing method in the wet-plasma mode, four available combinations of sample and skimmer cones [Jet sample cone + H skimmer cone (Jet + H), standard sample cone + H skimmer cone (Standard + H), standard sample cone + X skimmer cone (Standard + X), and Jet sample cone + X skimmer cone (Jet + X)] were systematically investigated for peak shape, sensitivity, mass discrimination, accuracy, and precision in Mg-isotopic ratio determination using a Neptune plus MC-ICP mass spectrometer. The results showed that different cone combinations do not affect peak shapes but would significantly change the sensitivities for Mg-isotopic determinations. Compared with using the Standard + H, the sensitivities of Mg-isotopic determinations were enhanced by approximately a factor of 1.3, 1.4, and 1.9 by using the Standard + X, the Jet + H, and the Jet + X combinations, with the most stable mass discrimination behaviors obtained by the Jet + H. The instrumental mass fractionation slope for any combination of a modified cone geometry (i.e. Standard + X, Jet + X, and Jet + H) is 0.500, while it is 0.510 for the Standard + H. In addition, the mass discrimination behavior is related to Mg concentrations once the combination is set, indicating the necessity of concentration match during Mg-isotopic determination. The precision and accuracy of the Jet + H combination are better than those of the other combinations, and this is further supported by the validation of the Mg-isotope data for four international reference materials: Cambridge-1, NASS-6, AGV-2, and BHVO-2. As the Jet + H combination also provides a high signal, this combination gives the most robust strategy for the highly precise and accurate determination of Mg isotopes.

High-Throughput/High-Precision Sampling of Single Cells into ICP-MS for Elucidating Cellular Nanoparticles.

In single-cell analysis with ICP-MS it is highly important to ensure precise single-cell sampling into ICP. For this purpose, a simple configured pressure-resistant MicroCross interface is developed for high-throughput/high-precision microdroplet generation and single-cell encapsulation. Aqueous cell suspension is ejected and sheared into droplets by tangent-flowing hexanol-continuous phases in the flow-focusing geometry of MicroCross, wherein to precisely trap a single cell into a droplet, with an extremely low probability of <0.005% for a single droplet encapsulating two cells. MicroCross interface is coupled with time-resolved ICP-MS (TRA-ICP-MS) for quantifying nanoparticles in single MCF-7 cells. At the optimal conditions, sufficient temporal-spatial resolution of the microdroplets is achieved facilitating high-throughput sampling of single cells into ICP. For solving the serious carbon deposition on the sampling cone and the unstable plasma torch caused by incomplete oxidation of hexanol phase in ICP, dimethyl carbonate (DMC) is for the first time used as a superb oxygen compensation reagent, which ensures adequate oxidation of hexanol, effectively eliminates the carbon deposition, and maintains a stable plasma. The single-cell analysis results indicated a remarkable discrepancy of the number of nanoparticles among the individual cells, falling into a range of 130-584 per MCF-7 cell in the case of AuNPs.

Optimizing MC-ICP-MS with SEM protocols for determination of U and Th isotope ratios and 230Th ages in carbonates

Abstract We have optimized techniques to measure uranium and thorium isotopic compositions using secondary electron multiplier (SEM) and peak-jumping protocols on a multi-collector inductively coupled plasma mass spectrometer (MC-ICP-MS, Thermo Scientific Neptune Plus). This instrument is equipped with an advanced interface pump, X-skimmer cone, Jet sample cone, and desolvating nebulizer system (CETAC Aridus II) that enables overall ionization and transmission efficiency up to 3% for both U and Th. Approximately 50 fg 234U or 230Th can routinely yield a precision of 1–2‰ (2σ) for abundance and isotopic measurements. Non-linear behavior was not observed in the MasCom SEM with a retarding potential quadrupole in our MC-ICP-MS system when the beam intensity was limited to

Effects of different cone combinations on accurate and precise determination of Li isotopic composition by MC-ICP-MS

The multiple collector inductively coupled plasma mass spectrometer (MC-ICP-MS) is booming to be a high-precision, fast, and accurate instrument in measuring lithium (Li) isotopes. Modified highly sensitive Jet sample and X skimmer cones have largely upgraded analytical sensitivity and reduced sample consumption with distinct instrumental mass bias behaviors. Herein, four available combinations of the sample and skimmer cones [Jet sample cone + X skimmer cone (Jet + X), Standard sample cone + X skimmer cone (Standard + X), Standard sample cone + H skimmer cone (Standard + H), and Jet sample cone + H skimmer cone (Jet + H)] were tested for their effects on peak shape, sensitivity, mass bias behavior, and accuracy and precision of Li isotopic measurements in solution mode. The results showed that all four combinations were able to attain an ideal peak shape by adjusting the associated parameters, with a positively linear relation between 7Li (and 6Li) signals and Li concentrations. For a given Li concentration, the sensitivities were enhanced 3–7 times using the Standard + X, the Jet + H, and the Jet +X combinations compared to that of using the Standard + H. The enhanced sensitivity is attributable to more plasma ions introduced into the mass spectrometer through the Jet and X cones. Mass bias is distinct for different cone combinations, with a slight difference with various Li concentrations, indicating the neccesity of concentration match during measurement. Among the four cone combinations, the best reproducibility can be obtained by using the Standard + X cones to determine precise and accurate Li isotopes for samples. Furthermore, a pretreatment by 5% HNO3 and 0.1% HF, and then 2% HNO3 prior to analyses can minimize the memory effect of Li.

Determination of Sm‐Nd Isotopic Compositions in Fifteen Geological Materials Using Laser Ablation MC‐ICP‐MS and Application to Monazite Geochronology of Metasedimentary Rock in the North China Craton

In this study, we report both 143Nd/144Nd and 147Sm/144Nd values in twelve minerals (apatite, titanite, monazite and eudialyte) based on analyses over 4 years using LA‐MC‐ICP‐MS. The positive correlation between the measured βSm and βNd (r2 = 0.9981) over this time in our laboratory demonstrates the excellent long‐term stability of the method. Compared with the normal method, Sm and Nd signal intensities were improved by a factor of 2.9 with the use of X skimmer and Jet sample cones in combination with the addition of nitrogen at 3–6 ml min−1 to the central gas flow. The enhancement of signal intensity benefits the accurate in situ determination of the Sm‐Nd isotopes of samples poor in these elements. 143Nd/144Nd values were also determined in two manganese nodules and GSMC Co‐rich crust with low mass fractions of Nd (94–293 μg g−1). Generally, most of the obtained Sm‐Nd isotopic compositions in these geological materials are consistent with published values. ‘External reproducibility’ (2s) of 143Nd/144Nd and 147Sm/144Nd was typically better than 0.06‰ and 2.5‰, respectively, demonstrating that the Durango, Otter Lake, NW‐1 and MAD apatites, the Khan, and OLT‐1 titanites, MGMH#117531 monazite and LV01 eudialyte are promising candidate reference materials for in situ Sm‐Nd isotopic determinations. The Trebilcock, Mae Klang and 44069 monazites are only suitable for in situ Nd isotopic determinations because of their heterogeneous Sm/Nd compositions. The heterogeneous Sm‐Nd composition of titanite BLR‐1 demonstrates that it is not a suitable reference material for in situ Sm‐Nd isotopic determinations. Deep‐sea samples (NOD‐A‐1 and NOD‐P‐1 manganese nodule, GSMC Co‐rich crust) with low mass fractions of Nd also show homogenous Nd isotopic compositions. Sm‐Nd isotopic ratios of a monazite (MQG‐22) from the North China Craton were measured as a case study and gave a 147Sm‐143Nd isochron age of 1792 ± 35 Ma (MSWD = 3.2) consistent with the published metamorphic age of the host metasedimentary rocks. The results for both candidate reference materials and geological samples demonstrate that the in situ LA‐MC‐ICP‐MS analytical protocol described is feasible and robust for research in geological evolution.

Multielement analysis of Zanthoxylum bungeanum Maxim. essential oil using ICP-MS/MS.

The concentrations of trace elements (Cr, Ni, As, Cd, Hg, and Pb) in Zanthoxylum bungeanum Maxim. essential oil (ZBMEO) were determined by inductively coupled plasma tandem mass spectrometry. The ZBMEO sample was directly analyzed after simple dilution with n-hexane. Aiming for a relatively high vapor pressure of n-hexane and its resultant loading on plasma, we used a narrow injector torch and optimized plasma radio frequency power and carrier gas flow to ensure stable operation of the plasma. An optional gas flow of 20% O2 in Ar was added to the carrier gas to prevent the incomplete combustion of highly concentrated organic carbon in plasma and the deposition of carbon on the sampling and skimmer cone orifices. In tandem mass spectrometry mode, O2 was added to the collision/reaction cell to eliminate the interferences. The limits of detection for Cr, Ni, As, Cd, Hg, and Pb were 2.26, 1.64, 2.02, 1.35, 1.76, and 0.97 ng L-1, respectively. After determination of 23 ZBMEO samples from different regions in China, we found that the average concentration ranges of trace elements in the 23 ZBMEO samples were 0.72-6.02 ng g-1, 0.09-2.87 ng g-1, 0.21-5.84 ng g-1, 0.16-2.15 ng g-1, 0.13-0.92 ng g-1, and 0.17-0.73 ng g-1 for Cr, Ni, As, Cd, Hg, and Pb, respectively. The trace elements in ZBMEO differed significantly when different extraction technologies were used. The study revealed that the contents of the toxic elements As, Cd, Hg, and Pb were extremely low, and hence they are unlikely to pose a health risk following ZBMEO ingestion. Graphical abstract The working mechanism of sample analysis by ICP-MS/MS.

Mass spectrometry in untargeted liquid chromatography/mass spectrometry metabolomics: Electrospray ionisation parameters and global coverage of the metabolome.

Liquid chromatography coupled to mass spectrometry (LC/MS) is a dominant analytical platform in metabolomics, because of the high sensitivity and resolution, thus enabling large-scale coverage of metabolomes. Correspondingly, electrospray ionisation (ESI) is the favoured ionisation method in untargeted LC/MS metabolomics given the ability to produce large numbers of ions. In the workflow of LC/ESI-MS metabolomics, maximising the ionisation efficiency over a wide mass range is inevitably an essential and determining step, subsequently defining the extent of coverage of the metabolome under investigation. Thus in this study, electronic factors related to the functioning of the ESI source, namely the capillary and sample cone voltages, were explored to investigate the influence on the data acquired in metabolomic investigations. Hydromethanolic samples from an untargeted study (sorghum plants responding dynamically to fungal infection) were analysed on a high-resolution/definition LC/ESI-MS system. Here the capillary and sample cone voltages of the ZSpray™ ESI source were varied between 1.5-3.0kV and 10.0-40.0V, respectively. The acquired data were processed with MarkerLynx™ software and analysed using central composite design response surface methodology and chemometric approaches (principal component analysis and orthogonal projection latent structures-discriminant analysis). The results evidently demonstrate that both capillary and sampling cone voltages not only significantly influence the recorded MS signals with regard to the number and abundance of features, but also the overall structure of the collected data. This consequently impacts on the information extracted from the data and thus affects coverage of the metabolome. The observations postulate in that, untargeted LC/MS metabolomics, 'what you see is what you ionise'. Although there is convergence of collected data under different ESI conditions, the nuances observed indicate that the exploration of different ion source settings could be the best trade-off in expanding and maximising the metabolome coverage in untargeted metabolomic experiments.

New High Resolution Ion Mobility Mass Spectrometer Capable of Measurements of Collision Cross Sections from 150 to 520 K.

We present a new variable temperature (VT), high resolution ion mobility (IM) drift tube coupled to a commercial mass spectrometer (MS). Ions are generated in an electrospray ion source with a sampling cone interface and two stacked ring RF guides which transfer ions into the mobility analyzer located prior to a quadrupole time-of-flight mass spectrometer. The drift cell can be operated over a pressure range of 0.5-3 Torr and a temperature range of 150-520 K with applied fields typically between 3 and 14 V cm-1. This makes the instrument suitable for rotationally averaged collision cross section (CCS) measurements at low E/N ratios where ions are near thermal equilibrium with the buffer gas. Fundamental studies of the effective ion temperatures can be performed at high E/N ratios. An RF ion trap/buncher is located at the beginning of the drift region, which modulates the continuous ion beam into spatially narrow packets. Packets of ions then drift in a linear electric field, which is 50.5 cm long, and are separated according to their mobility in an inert buffer gas. Post-drift, an ion funnel focuses the radially spread pulses of ions into the inlet of a commercial MS platform (Micromass QToF2). We present the novel features of this instrument and results from VT-IM-MS experiments on a range of model systems-IMS CCS standards (Agilent ESI Tune Mix), the monomeric protein Ubiquitin (8.6 kDa), and the tetrameric protein complex Concanavalin A (103 kDa). We evaluate the performance of the instrument by comparing ambient DTCCSHe values of model compounds with those found in the literature. Several effects of temperature on collision cross sections and resolution are observed. For small rigid molecules, changes in resolution are consistent with anticipated thermal diffusion effects. Changes in measured DTCCSHe for these rigid systems at different temperatures are attributed primarily to the effect of temperature on the long-range attractive interaction. Similar effects are seen for protein ions at low temperatures, although there is also some evidence for structural transitions. By heating the protein ions, their conformational profiles are significantly altered. Very high temperatures narrow the conformational space presented by both Ubiquitin and Concanavalin; it appears that diverse conformational families are "melted" into more homogeneous populations. Because of this conformational heterogeneity, the apparent IMS resolution obtained for proteins at ambient and reduced temperatures is an order of magnitude lower than the expected diffusion limited resolution (Rmax). This supports a hypothesis that the broad DTCCSHe features frequently observed for proteins do not correspond to interconverting conformers, but rather to high numbers of intrinsically stable structures.