The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
Mitsutoshi Setou - One of the best experts on this subject based on the ideXlab platform.
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two step matrix application technique to improve Ionization Efficiency for matrix assisted laser desorption Ionization in imaging mass spectrometry
Analytical Chemistry, 2006Co-Authors: Yuki Sugiura, Shuichi Shimma, Mitsutoshi SetouAbstract:A novel matrix application protocol for direct tissue mass spectrometry is presented. Matrix-assisted laser desorption/Ionization is a popular Ionization procedure for direct tissue analysis and imaging mass spectrometry. Usually, matrixes are applied by dispensing droplets through either pipettes or automated dispensing machines, or by airbrushing. These techniques are very simple, but it was difficult to obtain uniform matrix crystals on the tissue surface, and nonuniform crystals degrade the spectrum qualities. Here we report a new matrix application protocol, which is a combination of spraying and dispensing droplets, and we have succeeded in overcoming these problems in conventional matrix applications on tissue surfaces. We call our new technique the “spray-droplet method”. In this technique, tiny matrix crystals formed by spraying act as seeds for crystal growth. Our technique leads to matrix spots that are filled homogeneously with minute crystals. Such matrix crystals dramatically improve peak in...
Anneli Kruve - One of the best experts on this subject based on the ideXlab platform.
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characterization of wines with liquid chromatography electrospray Ionization mass spectrometry quantification of amino acids via Ionization Efficiency values
Journal of Chromatography A, 2020Co-Authors: Artur Gornischeff, Anneli Kruve, Riin RebaneAbstract:Quantification of analysis results for the suspect and non-targeted screening is essential for obtaining meaningful insight from the measurements. Ionization Efficiency predictions is a possible approach to enable quantitation without standard substances. This is, however, especially challenging for the analysis carried out by combining the full scan mode either with fragmentation experiments in data-dependent or data-independent acquisition mode. Here we investigate the correlation of Ionization Efficiency values measured in full scan mode with the response factors measured in multiple reaction monitoring (MRM) mode for derivatized amino acids. We observe good correlation (R2 of 0.80) for 6-Aminoquinolyl-N-hydroxysuccinimidyl carbamate (AQC) derivatized amino acids. This encourages the use of the measured Ionization Efficiency values to estimate amino acid concentrations in different beverages. We apply the measured Ionization Efficiency values for estimating the concentration of amino acids for measurements done both in full scan as well as in MRM mode in wines and beers. We show that the calculated concentrations are in very good correlation with measured values (R2 of 0.71 to 1.00). The method possesses average trueness of 70.5% and shows an insignificant matrix effect.
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Ionization Efficiency ladders as tools for choosing Ionization mode and solvent in liquid chromatography mass spectrometry
Rapid Communications in Mass Spectrometry, 2019Co-Authors: Riin Rebane, Anneli Kruve, Jaanus Liigand, Piia Liigand, Artur Gornischeff, Ivo LeitoAbstract:Rationale The choice of mobile phase components and optimal ion source, mainly electrospray Ionization (ESI) or atmospheric pressure chemical Ionization (APCI), is a crucial part in liquid chromatography/mass spectrometry (LC/MS) method development to achieve higher sensitivity and lower detection limits. In this study we demonstrate how to rigorously solve these questions by using Ionization Efficiency scales. Methods Four Ionization Efficiency scales are used: recorded with both APCI and ESI sources and using both methanol- and acetonitrile-containing mobile phases. Each scale contains altogether more than 50 compounds. In addition, measurements with a chromatographic column were also performed. Results We observed a correlation between calibration graph slopes under LC conditions and logIE values in ESI (but not APCI) thereby validating the use of logIE values for choosing the ion source. Most of the studied compounds preferred ESI as an ion source and methanol as mobile organic phase. APCI remains the ion source of choice for polycyclic aromatic hydrocarbons. For APCI, both acetonitrile and methanol provide similar Ionization efficiencies with few exceptions. Conclusions Overall the results of this work give a concise guideline for practitioners in choosing an ion source for LC/MS analysis on the basis of the chemical nature of the analytes.
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pH Effects on Electrospray Ionization Efficiency
Journal of The American Society for Mass Spectrometry, 2017Co-Authors: Jaanus Liigand, Asko Laaniste, Anneli KruveAbstract:Electrospray Ionization Efficiency is known to be affected by mobile phase composition. In this paper, a detailed study of analyte Ionization Efficiency dependence on mobile phase pH is presented. The pH effect was studied on 28 compounds with different chemical properties. Neither p K _a nor solution phase Ionization degree by itself was observed to be sufficient at describing how aqueous phase pH affects the Ionization Efficiency of the analyte. Therefore, the analyte behavior was related to various physicochemical properties via linear discriminant analyses. Distinction between pH-dependent and pH-independent compounds was achieved using two parameters: number of potential charge centers and hydrogen bonding acceptor capacity (in the case of 80% acetonitrile) or polarity of neutral form of analyte and p K _a (in the case of 20% acetonitrile). It was also observed that decreasing pH may increase Ionization Efficiency of a compound by more than two orders of magnitude. Graphical Abstract ᅟ
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influence of mobile phase source parameters and source type on electrospray Ionization Efficiency in negative ion mode
Journal of Mass Spectrometry, 2016Co-Authors: Anneli KruveAbstract:Electrospray Ionization (ESI) Efficiency is known to be affected by the properties of the analytes, source design and source parameters. In this study, the Ionization Efficiency of 17 acidic compounds at various conditions in ESI negative ion mode was evaluated. Namely, the influence of organic solvent content in the mobile phase, Ionization source parameters, Ionization source geometry and functionality (conventional ESI, ESI with thermal focussing and with additional internal nebulizer gas) was studied. It was observed that the Ionization Efficiency in thermal focussing ESI is only marginally affected by the organic solvent composition, while for conventional ESI and ESI with internal nebulizer gas, the Ionization Efficiency increases significantly with increasing organic modifier content. For all Ionization sources and mobile phase compositions, the Ionization Efficiency values between different setups showed good correlation. Copyright © 2016 John Wiley & Sons, Ltd.
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establishing atmospheric pressure chemical Ionization Efficiency scale
Analytical Chemistry, 2016Co-Authors: Riin Rebane, Anneli Kruve, Jaanus Liigand, Piia Liigand, Koit Herodes, Ivo LeitoAbstract:Recent evidence has shown that the atmospheric pressure chemical Ionization (APCI) mechanism can be more complex than generally assumed. In order to better understand the processes in the APCI source, for the first time, an Ionization Efficiency scale for an APCI source has been created. The scale spans over 5 logIE (were IE is Ionization Efficiency) units and includes 40 compounds with a wide range of chemical and physical properties. The results of the experiments show that for most of the compounds the Ionization Efficiency order in the APCI source is surprisingly similar to that in the ESI source. Most of the compounds that are best ionized in the APCI source are not small volatile molecules. Large tetraalkylammonium cations are a prominent example. At the same time, low-polarity hydrocarbons pyrene and anthracene are ionized in the APCI source but not in the ESI source. These results strongly imply that in APCI several Ionization mechanisms operate in parallel and a mechanism not relying on evaporati...
Shuichi Shimma - One of the best experts on this subject based on the ideXlab platform.
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alternative two step matrix application method for imaging mass spectrometry to avoid tissue shrinkage and improve Ionization Efficiency
Journal of Mass Spectrometry, 2013Co-Authors: Shuichi Shimma, Yuki Takashima, Jun Hashimoto, Kan Yonemori, Kenji Tamura, Akinobu HamadaAbstract:Mass spectrometry (MS) was used to measure the concentrations of drug and biological compounds in plasma and tissues. Matrix-assisted laser desorption/Ionization (MALDI) imaging MS (IMS) has recently been applied to the analysis of localized drugs on biological tissue surfaces. In MALDI-IMS, matrix application process is crucial for successful results. However, it is difficult to obtain homogeneous matrix crystals on the tissue surface due to endogenous salts and tissue surface heterogeneity. Consequently, the non-uniform crystals degrade the quality of the spectrum and likely cause surface imaging artifacts. Furthermore, the direct application of matrix solution can cause tissue shrinkage due to the organic solvents. Here, we report an alternative two-step matrix application protocol which combines the vacuum deposition of matrix crystals and the spraying of matrix solution to produce a homogeneous matrix layer on the tissue surface. Our proposed technique can also prevent cracking or shrinking of the tissue samples and improve the Ionization Efficiency of the distributed exogenous material. Copyright © 2013 John Wiley & Sons, Ltd.
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two step matrix application technique to improve Ionization Efficiency for matrix assisted laser desorption Ionization in imaging mass spectrometry
Analytical Chemistry, 2006Co-Authors: Yuki Sugiura, Shuichi Shimma, Mitsutoshi SetouAbstract:A novel matrix application protocol for direct tissue mass spectrometry is presented. Matrix-assisted laser desorption/Ionization is a popular Ionization procedure for direct tissue analysis and imaging mass spectrometry. Usually, matrixes are applied by dispensing droplets through either pipettes or automated dispensing machines, or by airbrushing. These techniques are very simple, but it was difficult to obtain uniform matrix crystals on the tissue surface, and nonuniform crystals degrade the spectrum qualities. Here we report a new matrix application protocol, which is a combination of spraying and dispensing droplets, and we have succeeded in overcoming these problems in conventional matrix applications on tissue surfaces. We call our new technique the “spray-droplet method”. In this technique, tiny matrix crystals formed by spraying act as seeds for crystal growth. Our technique leads to matrix spots that are filled homogeneously with minute crystals. Such matrix crystals dramatically improve peak in...
Andre P De Leenheer - One of the best experts on this subject based on the ideXlab platform.
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influence of the eluent composition on the Ionization Efficiency for morphine of pneumatically assisted electrospray atmospheric pressure chemical Ionization and sonic spray
Rapid Communications in Mass Spectrometry, 2002Co-Authors: Riet Dams, Tom Benijts, Wolfgang Gunther, Willy E Lambert, Andre P De LeenheerAbstract:A comparative study of three atmospheric-pressure Ionization (API) sources for liquid chromatography/mass spectrometry (LC/MS), namely pneumatically assisted electrospray or ionspray (IS), atmospheric-pressure chemical Ionization (APCI), and sonic spray (SS), with respect to the influence of the eluent composition on the Ionization of morphine, is presented. The effect of organic modifiers, volatile acids, and buffer systems (with and without pH adjustment) in the LC mobile phase on the Ionization Efficiency of each interface is described. We conclude that for all three ion sources, the composition of the liquid phase had a serious impact on the Ionization of the target compound. For IS and SS, very similar behavior towards the LC eluent was observed. In both cases, an increase in organic modifier resulted in an increase in Ionization, while an increasing amount of volatile acid or buffer caused signal suppression. APCI, on the other hand, proved to respond completely differently towards the changes in the eluent. Again, an increased Ionization was observed with an increase in organic modifier content but this time also in the presence of mobile phase additives like acids or buffers. Finally, we concluded that APCI proved to be the preferred ion source for the test compound because of its robust character and its direct applicability in traditional LC analysis.
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sonic spray Ionization technology performance study and application to a lc ms analysis on a monolithic silica column for heroin impurity profiling
Analytical Chemistry, 2002Co-Authors: Riet Dams, Tom Benijts, Wolfgang Gunther, Willy E Lambert, Andre P De LeenheerAbstract:Sonic spray (SS) Ionization is a relatively novel atmospheric pressure Ionization technique for LC/MS, based on the principle of “spray Ionization”, which only recently became commercially available. In this paper, we evaluate the performance of this ion source as an interface for LC/MS in comparison with the more traditional and better studied pneumatically assisted electrospray or ion spray (IS). The effect of organic modifiers, volatile acids, and buffer systems in the LC eluent on the Ionization Efficiency of both interfaces is described and some possible explanations for the observed phenomena are highlighted. We could conclude that the presence of organic solvents gradually increased the Ionization Efficiency for IS and SS, while volatile acids or buffers gave a significant signal suppression. Furthermore, we present the application of the sonic spray interface to a fast LC/MS analysis, for the simultaneous determination of the seven prime opium alkaloids in heroin impurity profiling. Chromatographi...
Ivo Leito - One of the best experts on this subject based on the ideXlab platform.
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Ionization Efficiency ladders as tools for choosing Ionization mode and solvent in liquid chromatography mass spectrometry
Rapid Communications in Mass Spectrometry, 2019Co-Authors: Riin Rebane, Anneli Kruve, Jaanus Liigand, Piia Liigand, Artur Gornischeff, Ivo LeitoAbstract:Rationale The choice of mobile phase components and optimal ion source, mainly electrospray Ionization (ESI) or atmospheric pressure chemical Ionization (APCI), is a crucial part in liquid chromatography/mass spectrometry (LC/MS) method development to achieve higher sensitivity and lower detection limits. In this study we demonstrate how to rigorously solve these questions by using Ionization Efficiency scales. Methods Four Ionization Efficiency scales are used: recorded with both APCI and ESI sources and using both methanol- and acetonitrile-containing mobile phases. Each scale contains altogether more than 50 compounds. In addition, measurements with a chromatographic column were also performed. Results We observed a correlation between calibration graph slopes under LC conditions and logIE values in ESI (but not APCI) thereby validating the use of logIE values for choosing the ion source. Most of the studied compounds preferred ESI as an ion source and methanol as mobile organic phase. APCI remains the ion source of choice for polycyclic aromatic hydrocarbons. For APCI, both acetonitrile and methanol provide similar Ionization efficiencies with few exceptions. Conclusions Overall the results of this work give a concise guideline for practitioners in choosing an ion source for LC/MS analysis on the basis of the chemical nature of the analytes.
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establishing atmospheric pressure chemical Ionization Efficiency scale
Analytical Chemistry, 2016Co-Authors: Riin Rebane, Anneli Kruve, Jaanus Liigand, Piia Liigand, Koit Herodes, Ivo LeitoAbstract:Recent evidence has shown that the atmospheric pressure chemical Ionization (APCI) mechanism can be more complex than generally assumed. In order to better understand the processes in the APCI source, for the first time, an Ionization Efficiency scale for an APCI source has been created. The scale spans over 5 logIE (were IE is Ionization Efficiency) units and includes 40 compounds with a wide range of chemical and physical properties. The results of the experiments show that for most of the compounds the Ionization Efficiency order in the APCI source is surprisingly similar to that in the ESI source. Most of the compounds that are best ionized in the APCI source are not small volatile molecules. Large tetraalkylammonium cations are a prominent example. At the same time, low-polarity hydrocarbons pyrene and anthracene are ionized in the APCI source but not in the ESI source. These results strongly imply that in APCI several Ionization mechanisms operate in parallel and a mechanism not relying on evaporati...
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transferability of the electrospray Ionization Efficiency scale between different instruments
Journal of the American Society for Mass Spectrometry, 2015Co-Authors: Jaanus Liigand, Anneli Kruve, Asko Laaniste, Piia Liigand, Marion Girod, Rodolphe Antoine, Ivo LeitoAbstract:For the first time, quantitative electrospray (ESI) Ionization efficiencies (IE), expressed as logIE values, obtained on different mass-spectrometric setups (four mass analyzers and four ESI sources) are compared for 15 compounds of diverse properties. The general trends of change of IE with molecular structure are the same with all experimental setups. The obtained IE scales could be applied on different setups: there were no statistically significant changes in the order of Ionization Efficiency and the root mean of squared differences of the logIE values of compounds between the scales compiled on different instruments were found to be between 0.21 and 0.55 log units. The results show that orthogonal ESI source geometry gives better differentiating power and additional pneumatic assistance improves it even more. It is also shown that the Ionization Efficiency values are transferable between different mass-spectrometric setups by three anchoring points and a linear model. The root mean square error of logIE prediction ranged from 0.24 to 0.72 depending on the instrument. This work demonstrates for the first time the inter-instrument transferability of quantitative electrospray Ionization Efficiency data.
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Effect of Mobile Phase on Electrospray Ionization Efficiency
Journal of The American Society for Mass Spectrometry, 2014Co-Authors: Jaanus Liigand, Anneli Kruve, Ivo Leito, Marion Girod, Rodolphe AntoineAbstract:Electrospray (ESI) Ionization efficiencies (IE) of a set of 10 compounds differing by chemical nature, extent of Ionization in solution (basicity), and by hydrophobicity (tetrapropylammonium and tetraethylammonium ion, triethylamine, 1-naphthylamine, N,N -dimethylaniline, diphenylphthalate, dimethylphtahalate, piperidine, pyrrolidine, pyridine) have been measured in seven mobile phases (three acetonitrile percentages 20%, 50%, and 80%, and three different pH-adjusting additives, 0.1% formic acid, 1 mM ammonia, pH 5.0 buffer combination) using the relative measurement method. MS parameters were optimized separately for each ion. The resulting relative IE data were converted into comparable log IE values by anchoring them to the log IE of tetrapropylammonium ion taking into account the differences of Ionization in different solvents and thereby making the log IE values of the compounds comparable across solvents. The following conclusions were made from analysis of the data. The compounds with p K _a values in the range of the solution pH values displayed higher IE at lower pH. The sensitivity of IE towards pH depends on hydrophobicity being very strong with pyridine, weaker with N,N -dimethylaniline, and weakest with 1-naphthylamine. IEs of tetraalkylammonium ions and triethylamine were expectedly insensitive towards solution pH. Surprisingly high IEs of phthalate esters were observed. The differences in solutions with different acetonitrile content and similar pH were smaller compared with the pH effects. These results highlight the importance of hydrophobicity in electrospray and demonstrate that high hydrophobicity can sometimes successfully compensate for low basicity. Graphical Abstract ᅟ
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Negative electrospray Ionization via deprotonation: predicting the Ionization Efficiency.
Analytical chemistry, 2014Co-Authors: Anneli Kruve, Karl Kaupmees, Jaanus Liigand, Ivo LeitoAbstract:Electrospray Ionization (ESI) in the negative ion mode has received less attention in fundamental studies than the positive ion electrospray Ionization. In this paper, we study the Efficiency of negative ion formation in the ESI source via deprotonation of substituted phenols and benzoic acids and explore correlations of the obtained Ionization Efficiency values (logIE) with different molecular properties. It is observed that stronger acids (i.e., fully deprotonated in the droplets) yielding anions with highly delocalized charge [quantified by the weighted average positive sigma (WAPS) parameter rooted in the COSMO theory] have higher Ionization Efficiency and give higher signals in the negative-ion ESI/MS. A linear model was obtained, which equally well describes the logIE of both phenols and benzoic acids (R2 = 0.83, S = 0.40 log units) and contains only an Ionization degree in solution (α) and WAPS as molecular parameters. Both parameters can easily be calculated with the COSMO-RS method. The model was...
