| 1. |
- Önnerfjord, Patrik, et al.
(författare)
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Homogeneous sample preparation for automated high throughput analysis with matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry.
- 1999
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Ingår i: Rapid Communications in Mass Spectrometry. - 0951-4198 .- 1097-0231. ; 13:5, s. 315-22
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Tidskriftsartikel (refereegranskat)abstract
- This work presents a simple method for obtaining homogeneous sample surfaces in matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry (MALDI-TOFMS) for the automated analysis of peptides and proteins. The sample preparation method is based on applying the sample/matrix mixture onto a pre-deposited highly diluted matrix spot. The pre-deposited crystals act as seeds for the new sample containing crystals which become much smaller in size and more evenly distributed than with conventional methods. This 'seed-layer' method was developed, optimised and compared with the dried-droplet method using peptides and proteins in the 1000-20,000 Da range. The seed-layer method increases the surface homogeneity, spot to spot reproducibility and sample washability as compared with the commonly used dried-droplet method. This methodology is applicable to alpha-cyanohydroxycinnamic acid, sinapinic acid and ferulic acid, which all form homogeneous crystal surfaces. Within-spot variation and between-spot variation was investigated using statistics at a 95% confidence level (n = 36). The statistical values were generated from more than 5000 data points collected from 500 spectra. More than 90% of the sample locations results in high intensity spectra with relatively low standard deviations (RSDs). Typically obtained data showed an RSD of 19-35% within a sample spot as well as in-between spots for proteins, and an RSD of < or = 50% for peptides. Linear calibration curves were obtained within one order of magnitude using internal calibration with a point-RSD of 3% (n = 10). The sample homogeneity allows mass spectra (average of 16 laser shots) to be obtained on each individual sample within 15 sec, whereby a 100 spot target plate can be run in 25 min. High density target plates using the seed-layer method were prepared by spotting approximately 100 picoliter droplets onto the target, resulting in sample spots < or = 500 microns in diameter using a flow-through piezo-electric micro-dispenser. By using this automated sample preparation step lower standard deviations are obtained in comparison to manually prepared samples.
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| 2. |
- Palmblad, Magnus, et al.
(författare)
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Analysis of Enzymatically Digested Proteins and Protein Mixtures using a 9.4 Tesla Fourier Transform Ion Cyclotron Resonance Mass Spectrometer
- 2000
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Ingår i: Rapid Communications in Mass Spectrometry. - 0951-4198 .- 1097-0231. ; 14:12, s. 1029-1034
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Tidskriftsartikel (refereegranskat)abstract
- A commercially available 9.4 Tesla Fourier transform ion cyclotron resonance (FTICR) mass spectrometer was applied in the analysis of tryptic digests of protein mixtures without any separation. First, the method was demonstrated on a mixture of tryptic digests of equine cytochrome c, equine myoglobin and bovine serum albumin. The same method was then applied to human plasma from a healthy blood donor. Computer programs were employed to simplify analysis of the complex spectra. The 2745 peaks in the human plasma electrospray ionization FTICR spectrum could be reduced to 1165 isotopic clusters and 669 unique masses. Out of these, 82 masses matched tryptic fragments of serum albumin with mass measurement errors less than 10 ppm, covering 93% of the sequence. Another 16 masses were assigned to tryptic fragments of transferrin, covering 41% of the sequence on the 10 ppm mass measurement error level (14 within 2 ppm). The mass measurement errors were approximately normal distributed with a standard deviation of 1.7 ppm. This demonstrates the feasibility of combining the ultra-high mass resolving power and accuracy of FTICR mass spectrometry with automated computer analysis for investigating complex biological matrices.
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| 3. |
- Zubarev, Roman A., et al.
(författare)
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Delayed, gas-phase ion formation in plasma desorption mass spectrometry
- 1997
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Ingår i: Rapid Communications in Mass Spectrometry. - 0951-4198 .- 1097-0231. ; 11:9, s. 963-972
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Tidskriftsartikel (refereegranskat)abstract
- The formation mechanisms of secondary ions from organic targets under MeV ion bombardment were studied with a high-resolution time-of-flight (TOF) mass spectrometer. Promptly formed ions Hn+, Cn+ and CnH+ were used for calibrating the TOF scale. Theoretical flight times of other ions were calculated according to the calibration curve and compared to experimentally determined values. The TOF values of non-specific low mass fragments formed via rearrangement or breaking of several bonds and/or abstraction of several atoms, agree well with the theoretical values. On the other hand, target-specific organic ions, including molecular ions of peptides, have longer TOF values than predicted by the calibration curve. Time delays of a few hundred picoseconds were found for low-mass specific fragments, and a few nanoseconds for peptide molecular ions. For protonated species and non-covalent clusters, the delays are larger than for pre-formed and radical molecular ions. Metals contained in organic samples, as contamination, also give delayed ions. For inorganic targets of LiBF4, significant delays were found for the clusters (LiF)nLi+ with n >3. A strong correlation was observed between the delay of an ion and the tailing of its kinetic energy distribution. The conclusion was made that the majority of target-specific ions are formed in the gas phase, at a distance from the target surface of the order of 1 μm.
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| 4. |
- Axelsson, Jan, et al.
(författare)
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Electron Capture Dissociation of Substance-P using a Commercially Available Fourier Transform Ion Cyclotron Resonance Mass Spectrometer
- 1999
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Ingår i: Rapid Communications in Mass Spectrometry. - 0951-4198 .- 1097-0231. ; 13:6, s. 474-477
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Tidskriftsartikel (refereegranskat)abstract
- Electron capture dissociation of the peptide Substance P is reported for the first time, with an unmodified, commercially available Fourier transform ion cyclotron resonance (FTICR) mass spectrometer. The fragmentation pattern is compared with that obtained with collisionally induced dissociation of the ions in the electrospray ion source, and note that electron capture dissociation gives a more easily interpreted spectrum, showing mainly C-fragments. With the exception of the proline residues, which require cleavage of two chemical bonds, we observe all C-fragmental we find the bias voltage of the electron gun not to be very critical.
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| 5. |
- Bergquist, Jonas, et al.
(författare)
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Identification of catecholamines in the immune system by electrospray ionization mass spectrometry.
- 1998
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Ingår i: Rapid Communications in Mass Spectrometry. - 0951-4198 .- 1097-0231. ; 12:11, s. 683-8
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Tidskriftsartikel (refereegranskat)abstract
- The first evidence that catecholamines might be present in the immune system was provided by capillary electrophoresis combined with electrochemical detection. Here, we present the first structural characterization of the endogenous catecholamines isolated from human peripheral blood mononuclear cells. Dopamine, L-DOPA and norepinephrine were detected and were identified with electrospray ionization mass spectrometry by determination of the protonated molecular species of each catecholamine and their major fragments generated in the electrospray source with a nozzle-skimmer voltage method. This technique, in conjunction with accurate mass measurement, allowed us to identify in an unfractionated sample the content of catecholamines in extracted cells in a quantitative manner, with structure-specific methodology. The data unambiguously confirm our previous tentative findings, and also strengthen the importance of the regulatory function of catecholamines in the immune system and the existence of an autocrine loop, where lymphocytes may down-regulate their own activity.
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| 6. |
- Stolyarova, V.L, et al.
(författare)
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High-temperature Mass Spectrometric Study of the Vaporization of Dysprosium Trifluoride
- 1996
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Ingår i: Rapid Communications in Mass Spectrometry. - 0951-4198 .- 1097-0231. ; 10:5, s. 501-508
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Tidskriftsartikel (refereegranskat)abstract
- The high-temperature Knudsen effusion method was used to study the vaporization processes and thermodynamic properties of dysprosium trifluoride in the temperature range 1280-1440 K. Data on the partial vapour pressure of DyF3 as a function of temperature and the enthalpy of sublimation of DyF3 were obtained. Using the value of the enthalpy of formation of solid DyF3, available in the literature, the enthalpy of formation of the gaseous molecule of dysprosium trifluoride and its atomization energy were calculated. At 1382 K, the partial vapour pressure of Dy2F6 over dysprosium trifluoride was obtained and the Gibbs energy of the gaseous reaction (Dy2F6)=(2DyF3) was evaluated.
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| 7. |
- Zubarev, Roman A., et al.
(författare)
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Accurate monoisotopic mass measurements of peptides : Possibilities and limitations of high resolution time-of-flight particle desorption mass spectrometry
- 1996
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Ingår i: Rapid Communications in Mass Spectrometry. - 0951-4198 .- 1097-0231. ; 10:11, s. 1386-1392
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Tidskriftsartikel (refereegranskat)abstract
- The possibilities and limitations of time-of-flight particle-desorption mass spectrometry are analysed from the standpoint of accuracy of monoisotopic mass determination. For an instrument with mass reflector, typical mass accuracy was found to be ca. 20 ppm (standard deviation). The main limitation was found to be the mechanism of secondary ion production itself. A fraction of biological ions are formed in the gas phase and therefore exhibit both time delay and energy deficit. This leads to a limited resolving power and non-symmetric ion peaks. A peak shape model, taking into account gas-phase ion formation, is built and analysed, and a simple correction procedure proposed. The application of the correction has increased the mass accuracy to 12 ppm (standard deviation). It is shown that further progress cannot be achieved by a correction procedure without instrumental improvements.
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| 8. |
- Zubarev, Roman A., et al.
(författare)
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Kinetic energies of secondary ions in MeV and keV particle-induced desorption
- 1996
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Ingår i: Rapid Communications in Mass Spectrometry. - 0951-4198 .- 1097-0231. ; 10:15, s. 1966-1974
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Tidskriftsartikel (refereegranskat)abstract
- Kinetic energy distributions of secondary ions produced by MeV or keV primary-ion bombardment of molecularsolids were measured in a reflectron time-of-flight mass spectrometer. It was found that the energy distributionsof many ions exhibit tails extending towards energies lower than the accelerating potential. The degree of tailingdepends upon the nature of the desorbed ion and the conditions of the target surface. Some light ions (H' andC' ), ions from inorganic (alkali halide) samples, radical molecular ions (Cg) and pre-formed molecuiar ions (e.g.complexes of valinomycin with alkali metal ions) exhibit almost no tailing. For positive adduct-type molecularions, such as MH', more extensive tailing was observed for MeV compared with keV primary ions. The originof the energy tailing is attributed to gas-phase formation of a fraction of the secondary ions. For molecular ionsof peptides, the characteristic time of formation of that fraction of ions (*lo% of the whole molecular-ionpopulation) was estimated to be of the order of 10 ns, while the characteristic distance from the target surfacewas of the order of 10 pm.
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| 9. |
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| 10. |
- Adiels, Martin, 1976, et al.
(författare)
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Optimization of N-methyl-N-[tert-butyldimethylsilyl]trifluoroacetamide as a derivatization agent for determining isotopic enrichment of glycerol in very-low density lipoproteins.
- 2010
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Ingår i: Rapid communications in mass spectrometry : RCM. - : Wiley. - 1097-0231 .- 0951-4198. ; 24:5, s. 586-592
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Tidskriftsartikel (refereegranskat)abstract
- Stable isotope kinetic studies play an important role in the study of very-low density lipoprotein (VLDL) metabolism, including basic and clinical research. Today, [1,1,2,3,3-(2)H(5)]glycerol is the most cost-effective alternative to measure glycerol and triglyceride kinetics. Recycling of glycerol from glycolysis and gluconeogenesis may lead to incompletely labelled tracer molecules. Many existing methods for the measurement of glycerol isotopic enrichment involve the production of glycerol derivatives that result in fragmentation of the glycerol molecule after ionization. It would be favourable to measure the intact tracer molecule since incompletely labelled tracer molecules may be measured as fully labelled. The number of methods available to measure the intact tracer in biological samples is limited. The aim of this project was to develop a gas chromatography/mass spectrometry (GC/MS) method for glycerol enrichment that measures the intact glycerol backbone and is suitable for electron ionization (EI), which is widely available. A previously published method for N-methyl-N-[tert-butyldimethylsilyl]trifluoroacetamide (MTBSTFA) derivatization was significantly improved; we produced a stable derivative and increased recovery 27-fold in standards. We used the optimized MTBSTFA method in VLDL-triglyceride and found that further modification was required to take matrix effects into account. We now have a robust method to measure glycerol isotopic enrichment by GC/EI-MS that can be used to rule out the known problem of tracer recycling in studies of VLDL kinetics. Copyright (c) 2010 John Wiley & Sons, Ltd.
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| 11. |
- Allard, Erik, 1976-, et al.
(författare)
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Quantitative aspects of analyzing small molecules - monitoring singly or doubly charged ions? : A case study of ximelagatran.
- 2010
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Ingår i: Rapid Communications in Mass Spectrometry. - : Wiley. - 0951-4198 .- 1097-0231. ; 24:4, s. 429-435
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Tidskriftsartikel (refereegranskat)abstract
- Precision, reproducibility and lower limit of quantitation (LLOQ) are important characteristics of a quantitative method. We have investigated these properties for Ximelagatran (Xi), which has a high tendency to form doubly charged ions in electrospray ionization (ESI), by studying the percentage of doubly charged species formed when varying the formic acid (FA) concentration, analyte concentration, amount of organic modifier and flow rate. It was found that the percentage of [Xi + 2H]2+ can be controlled to be more than 90% or less than 10% by varying the amount of FA present, and that the change between these values is dramatic. Furthermore, the percentage of [Xi + 2H]2+ formed decreases with increased analyte concentration and increased flow rate. No apparent relationship with the amount of organic modifier was found. The results have the implication that, by carefully controlling the selected parameters, the LLOQ, precision and reproducibility can be improved. We have compared the fragmentation of the singly and doubly charged species and concluded that the [Xi + 2H]2+ ion is more inclined to undergo fragmentation than [Xi + H]+. As a consequence, unusual instrumental settings had to be used for the experiments. The fragmentation patterns are to a great extent similar, but the doubly charged species is more inclined to generate low-mass product ions.
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| 12. |
- Alsberg, T., et al.
(författare)
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Determination of hydroxyalkyl derivatives of cobalamin (vitamin B12) using reversed phase high performance liquid chromatography with electrospray tandem mass spectrometry and ultraviolet diode array detection
- 2001
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Ingår i: Rapid Communications in Mass Spectrometry. - : Wiley. - 0951-4198 .- 1097-0231. ; 15:24, s. 2438-45
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Tidskriftsartikel (refereegranskat)abstract
- Electrospray ionization tandem mass spectrometry (ESI-MS/MS) and ultraviolet diode array detection (UV-DAD), coupled on-line to reversed phase high performance liquid chromatography (HPLC), was used for the characterization of hydroxyalkyl derivatives of cob(I)alamin. The reduced form of vitamin B12, cob(I)alamin, denoted a supernucleophile due to its high nucleophilic strength, has shown promise as an analytical tool in studies of electrophilically reactive compounds in vitro and in vivo. A method for analysis of DNA-phosphate adducts was developed earlier utilizing the supernucleophilicity of cob(I)alamin to transfer alkyl groups from the phosphotriester configuration in DNA, with the formation of a Co-substituted alkyl-cobalamin (alkyl-Cbl) complex. For the purpose of identification and quantification of alkyl-Cbls at high sensitivity, an MS/MS method has been developed with application to a number of 2-hydroxyalkyl-cobalamins (OHalkyl-Cbls). The precursor oxiranes were reacted with cob(I)alamin, followed by clean-up and mass spectrometric analysis of the resulting OHalkyl-Cbls. It was found that ionization was highly dependent on solvent composition. By using acetonitrile/water/trifluoroacetic acid (TFA) (eluent I), the base peak was the doubly protonated molecule [M + 2H](2+), whereas acetonitrile/water/1-methylpiperidine (eluent II) yielded the singly protonated molecule [M + H](+) as the base peak. Excellent separation was obtained with eluent II, with good separation between stereoisomers, thus enabling the characterization of these by means of UV spectra. Limits of quantitation for 2-hydroxypropyl-cobalamin (OHPr-Cbl) were 0.2 and 2 pg/microL (or 0.1 and 1 fmol/microL) using selected ion recording (SIR) with eluent I and II, respectively. The obtained detection level should be sufficient for analysis of alkyl-Cbls from a wide range of toxicological applications.
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| 13. |
- Andersson, Maria, et al.
(författare)
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Metabolic profiling of new synthetic cannabinoids AMB and 5F-AMB by human hepatocyte and liver microsome incubations and high-resolution mass spectrometry
- 2016
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Ingår i: Rapid Communications in Mass Spectrometry. - : WILEY-BLACKWELL. - 0951-4198 .- 1097-0231. ; 30:8, s. 1067-1078
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Tidskriftsartikel (refereegranskat)abstract
- RationaleAMB (methyl (1-pentyl-1H-indazole-3-carbonyl)-L-valinate)) and its fluoro analog 5F-AMB (methyl (1-(5-fluoropentyl)-1H-indazole-3-carbonyl)-L-valinate) are two new synthetic cannabinoids that are structural analogs of AB-PINACA and 5F-AB-PINACA, respectively. 5F-AMB is scheduled as an illicit drug in China, Germany, Singapore and Japan, and no metabolism data are currently available for either drug. The aim of the present work was to investigate the metabolism of AMB and 5F-AMB and propose appropriate markers to identify their intake in clinical or forensic cases. MethodsAMB and 5F-AMB were incubated in human hepatocytes (10 mol/L) to generate phase I and II metabolites, which were identified with a TripleTOF 5600(+) high-resolution mass spectrometer. AMB and 5F-AMB metabolic stability studies also were performed with human liver microsomes (HLM) to evaluate metabolic clearances, and to adequately design the human hepatocyte experiment. ResultsAMB and 5F-AMB were quickly metabolized in HLM with a 1.1 0.1 and 1.0 +/- 0.2min T-1/2, respectively. The predominant metabolic pathway for AMB and 5F-AMB in hepatocytes was ester hydrolysis, and further oxidation and/or glucuronidation. In total, 19 metabolites were identified for AMB and 17 for 5F-AMB. We describe metabolites to differentiate AMB from 5F-AMB, and metabolites that are common to both analytes due to oxidative defluorination of 5F-AMB. ConclusionsFor the first time, AMB and 5F-AMB metabolism profiles were characterized, providing valuable data for identifying these two novel psychoactive substances. The difficulties of differentiating AMB and 5F-AMB from AB-PINACA/5F-AB-PINACA metabolites also were examined. These data improve the interpretation of urinary markers after AMB and 5F-AMB intake. Published in 2016. This article is a U.S. Government work and is in the public domain in the USA
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| 14. |
- Andersson, M., et al.
(författare)
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Size and structure characterization of ethylhydroxyethyl cellulose by the combination of field-flow fractionation with other techniques. Investigation of ultralarge components
- 2004
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Ingår i: Biomacromolecules. - : Wiley. - 1525-7797 .- 1526-4602. ; 5:1, s. 97-105
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Tidskriftsartikel (refereegranskat)abstract
- Ethylhydroxyethyl cellulose (EHEC) of three different viscosity classes (EHEC I, II, and III) was analyzed by programmed cross-flow asymmetrical flow field-flow fractionation coupled to multiangle light scattering and refractive index detectors to determine their size and molar mass distribution. Two size populations were detected in the two lower viscosity classes, EHEC I and II, one high molar mass and one ultrahigh molar mass (UHM). The two covered molar masses from 10(4) up to 10(9) g.mol(-1). The highest viscosity class EHEC III was less size-dispersed covering molar masses from 5x10(5) to 5x10(7) g.mol(-1). Filtering of the EHEC II solution removed small amounts of compact UHM material. Enzyme treatments were performed on EHEC II to further characterize it. Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry and anion ion-exchange chromatography coupled to pulsed amperometric detection showed that the UHM component contained EHEC.
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| 15. |
- Axén, Jakob, et al.
(författare)
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Efforts to improve detection sensitivity for capillary electrophoresis coupled to atmospheric pressure photoionization mass spectrometry.
- 2010
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Ingår i: Rapid Communications in Mass Spectrometry. - : John Wiley & Sons Ltd. - 0951-4198 .- 1097-0231. ; 24:9, s. 1260-1264
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Tidskriftsartikel (refereegranskat)abstract
- Electrospray ionization performs best with volatile buffers. However, generally the best separation performance for capillary electrophoresis (CE) is achieved with non-volatile buffers. Hyphenation of CE with mass spectrometry (MS) utilizing atmospheric pressure photoionization (APPI) enables use of a wider range of separation buffers without compromising detection sensitivity. As APPI is considered to be mass flow sensitive, the use of a larger inner diameter separation capillary (75 microm) allows larger volumes to be injected, without decreased separation performance, thus providing improved sensitivity (approx. a factor of 10), compared to the use of a 25 microm capillary. However, nebulizing gas flow and position of capillary tip in the sprayer have to be carefully optimized to prevent excessive band broadening. Further improvement in sensitivity (approx. a factor of 2) was obtained by decreasing the distance between the sprayer and ionization region, indicating that a specially designed CE/APPI-MS interface for low flow rates will be favourable.
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| 16. |
- Badea, Silviu‐Laurentiu, et al.
(författare)
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Development of an enantiomer-specific stable carbon isotope analysis (ESIA) method for assessing the fate of α‐hexachlorocyclohexane in the environment
- 2011
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Ingår i: Rapid Communications in Mass Spectrometry. - : John Wiley & Sons, Ltd. - 0951-4198 .- 1097-0231. ; 25:10, s. 1363-1372
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Tidskriftsartikel (refereegranskat)abstract
- α‐Hexachlorocyclohexane (α‐HCH) is the only chiral isomer of the eight 1,2,3,4,5,6‐HCHs and we have developed an enantiomer‐specific stable carbon isotope analysis (ESIA) method for the evaluation of its fate in the environment.The carbon isotope ratios of the α‐HCH enantiomers were determined for a commercially available α‐HCH sample using a gas chromatography‐combustion‐isotope ratio mass spectrometry (GC‐C‐IRMS) system equipped with a chiral column. The GC‐C‐IRMS measurements revealed δ‐values of −32.5 ± 0.8‰ and −32.3 ± 0.5‰ for (−) α‐HCH and (+) α‐HCH, respectively. The isotope ratio of bulk α‐HCH was estimated to be −32.4 ± 0.6‰ which was in accordance with the δ‐values obtained by GC‐C‐IRMS (−32.7 ± 0.2‰) and elemental analyzer‐isotope ratio mass spectrometry (EA‐IRMS) of the bulk α‐HCH (−32.1 ± 0.1‰). The similarity of the isotope ratio measurements of bulk α‐HCH by EA‐IRMS and GC‐C‐IRMS indicates the accuracy of the chiral GC‐C‐IRMS method. The linearity of theα‐HCH ESIA method shows that carbon isotope ratios can be obtained for a signal size above 100mV. The ESIA measurements exhibited standard deviations (2σ) that were mostly < ± 0.5‰. In order to test the chiral GC‐C‐IRMS method, the isotope compositions of individual enantiomers in biodegradation experiments of α‐HCH withClostridium pasteurianum and samples from a contaminated field site were determined. The isotopic compositions of theα‐HCHenantiomers show a range of enantiomeric and isotope patterns, suggesting that enantiomeric and isotopefractionation can serve as an indicator for biodegradation and source characterization of α‐HCH in the environment.
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| 17. |
- Bengtsson, Jörgen, et al.
(författare)
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On-line desalting and determination of morphine, morphine-3-glucuronide and morphine-6-glucuronide in microdialysis and plasma samples using column switching and liquid chromatography/tandem mass spectrometry
- 2005
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Ingår i: Rapid Communications in Mass Spectrometry. - : John Wiley & Sons. - 0951-4198 .- 1097-0231. ; 19:15, s. 2116-2122
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Tidskriftsartikel (refereegranskat)abstract
- A sensitive and reproducible method for the determination of morphine and the metabolites morphine-3-glucuronide (M3G) and morphine-6-glucuronide (M6G) was developed. The method was validated for perfusion fluid used in microdialysis as well as for sheep and human plasma. A C18 guard column was used to desalt the samples before analytical separation on a ZIC HILIC (hydrophilic interaction chromatography) column and detection with tandem mass spectrometry (MS/MS). The mobile phases were 0.05% trifluoroacetic acid (TFA) for desalting and acetonitrile/5 mM ammonium acetate (70:30) for separation. Microdialysis samples (5 microL) were directly injected onto the system. The lower limits of quantification (LLOQ) for morphine, M3G and M6G were 0.50, 0.22 and 0.55 ng/mL, respectively, and the method was linear from LLOQ to 200 ng/mL. For plasma, a volume of 100 microL was precipitated with acetonitrile containing internal standards (deuterated morphine and metabolites). The supernatant was evaporated and reconstituted in 0.05% TFA before the desalting process. The LLOQs for sheep plasma were 2.0 and 3.1 ng/mL and the ranges were 2.0-2000 and 3.1-3100 ng/mL for morphine and M3G, respectively. For human plasma, the LLOQs were 0.78, 1.49 and 0.53 ng/mL and the ranges were 0.78-500, 1.49-1000 and 0.53-500 ng/mL for morphine, M3G and M6G, respectively.
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| 18. |
- Benkestock, Kurt, et al.
(författare)
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Electrospray ionization mass spectrometry as a tool for determination of drug binding sites to human serum albumin by noncovalent interaction
- 2005
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Ingår i: Rapid Communications in Mass Spectrometry. - : Wiley. - 0951-4198 .- 1097-0231. ; 19:12, s. 1637-1643
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Tidskriftsartikel (refereegranskat)abstract
- Most proteins in blood plasma bind ligands. Human serum albumin (HSA) is the main transport protein with a very high capacity for binding of endogenous and exogenous compounds in plasma. Many pharmacokinetic properties of a drug depend on the level of binding to plasma proteins. This work reports studies of noncovalent interactions by means of nanoelectrospray ionization mass spectrometry (nanoESI-MS) for determination of the specific binding of selected drug candidates to HSA. Warfarin, iopanoic acid and digitoxin were chosen as site-specific probes that bind to the main sites of HSA. Two drug candidates and two known binders to HSA were analyzed using a competitive approach. The drugs were incubated with the target protein followed by addition of site-specific probes, one at a time. The drug candidates showed predominant affinity to site I (warfarin site). Naproxen and glyburide showed affinity to both sites I and II. The advantages of nanoE-SI-MS for these studies are the sensitivity, the absence of labeled molecules and the short method development time.
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| 19. |
- Benkestock, Kurt, et al.
(författare)
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On-line microdialysis for enhanced resolution and sensitivity during electrospray mass spectrometry of non-covalent complexes and competitive binding studies
- 2002
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Ingår i: Rapid Communications in Mass Spectrometry. - : Wiley. - 0951-4198 .- 1097-0231. ; 16:21, s. 2054-2059
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Tidskriftsartikel (refereegranskat)abstract
- Many proteins and macromolecules easily form metal adduct ions which impairs their analysis by mass spectrometry. The present study describes how the formation of undesired adducts can be minimized by on-line microdialysis for non-covalent binding studies of macromolecules with low molecular mass ligands with electrospray ionization mass spectrometry (ESI-MS). The technique was indispensable for protein-ligand studies due to reduction of unwanted adduct ions, and thus gave excellent resolution and a sensitivity improvement of at least 5 times. The core of the analytical system was a modified microdialysis device, which was operated in countercurrent mode. A novel technique based on microdialysis for competitive binding studies is also presented. The noncovalent complex between a protein and a ligand was formed in the sample vial prior to analysis. The complex was injected into an on-line microdialysis system where a competitive ligand was administered in the dialysis buffer outside of the fiber. The second ligand competitively displaced the first ligand through transport via the wall of the dialysis fiber, and the intact complexes were detected by ESI-MS.
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| 20. |
- Bergh, Caroline, et al.
(författare)
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Simultaneous selective detection of organophosphate and phthalate esters using gas chromatography with positive ion chemical ionization tandem mass spectrometry and its application to indoor air and dust
- 2010
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Ingår i: Rapid Communications in Mass Spectrometry. - : Wiley. - 0951-4198 .- 1097-0231. ; 24:19, s. 2859-2867
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Tidskriftsartikel (refereegranskat)abstract
- A selective and sensitive method for the simultaneous determination of 14 organophosphate and six phthalate esters using gas chromatography (GC) and mass spectrometry (MS) is presented. Both of these compound classes are frequently found in the indoor environment due to their use as bulk additives in numerous polymers, consumer products and building materials. GC/MS utilizing positive ion chemical ionisation (PICI) in selected reaction monitoring (SRM) mode with isobutane as the reagent gas was found to be the best of the tested methods; it proved superior to electron ionisation (EI) in selected ion monitoring (SIM) mode and to PICI using methane as the reagent gas. The method was applied to indoor air samples collected by active air sampling using solid-phase extraction (SPE) cartridges. Organophosphates and phthalates were simultaneously determined with method detection limits (MDLs) in the range of 0.1-47 ng m(-3). For most compounds the MDLs were <= 0.2 ng m(-3), but due to the presence of some of these ubiquitous indoor air pollutants in the blanks, significantly higher MDLs were observed for a few compounds. Finally, the method was also applied in the screening of a much more complex sample matrix, indoor dust.
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| 21. |
- Björklund, Jonas, et al.
(författare)
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Selective determination of organophosphate flame-retardants and plasticizers in indoor air by gas chromatography, positive-ion chemical ionization and collision-induced dissosiation mass spectrometry
- 2004
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Ingår i: Rapid Communications in Mass Spectrometry. - : Wiley. - 0951-4198 .- 1097-0231. ; 18:24, s. 3079-3083
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Tidskriftsartikel (refereegranskat)abstract
- Gas chromatography/ion trap mass spectrometry with in-source ionization and dissociation was used in positive-ion chemical ionization (PICI) mode for the determination of organophosphate triesters in indoor air. These compounds are widely used as additive flame retardants and plasticizers in different types of materials and have become ubiquitous pollutants in indoor environments. When using collision-induced dissociation in PICI mode the fragmentation of the organophosphate triesters can be performed in a more controllable way than in electron ionization (EI) mode. The developed selected-reaction monitoring method provided high selectivity for the investigated compounds. For 8-h air measurements (corresponding to 1.5 m3 of sampled air) the limit of detection of the method was determined to be in the range 0.1–1.4 ng m−3, which is comparable with nitrogen-phosphorus detection and about 50-fold lower than when using EI in selected-ion monitoring mode. The presented method was applied to samples from three common indoor environments, in which a number of organophosphate triesters were identified and quantified. The dominating compound was found to be tris(2-chloropropyl) phosphate, which occurred at levels up to 0.8 μg m−3.
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| 22. |
- Bohlin, Madeleine, et al.
(författare)
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High-precision determination of lithium and magnesium isotopes utilising single column separation and multi-collector inductively coupled plasma mass spectrometry
- 2018
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Ingår i: Rapid Communications in Mass Spectrometry. - : Wiley. - 0951-4198 .- 1097-0231. ; 32:2, s. 93-104
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Tidskriftsartikel (refereegranskat)abstract
- Rationale Li and Mg isotopes are increasingly used as a combined tool within the geosciences. However, established methods require separate sample purification protocols utilising several column separation procedures. This study presents a single-step cation-exchange method for quantitative separation of trace levels of Li and Mg from multiple sample matrices.Methods The column method utilises the macro-porous AGMP-50 resin and a high-aspect ratio column, allowing quantitative separation of Li and Mg from natural waters, sediments, rocks and carbonate matrices following the same elution protocol. High-precision isotope determination was conducted by multi-collector inductively coupled plasma mass spectrometry (MC-ICPMS) on the Thermo Scientific NEPTUNE Plus fitted with 1013Ω amplifiers which allow accurate and precise measurements at ion beams <0.51 V.Results Sub-nanogram Li samples (0.3-0.5 ng) were regularly separated (yielding Mg masses of 1-70 μg) using the presented column method. The total sample consumption during isotopic analysis is <0.5 ng Li and <115 ng Mg with long-term external 2σ precisions of ±0.39‰ for δ7Li and ±0.07‰ for δ26Mg. The results for geological reference standards and seawater analysed by our method are in excellent agreement with published values despite the order of magnitude lower sample consumption. Conclusions The possibility of eluting small sample masses and the low analytical sample consumption make this method ideal for samples of limited mass or low Li concentration, such as foraminifera, mineral separates or dilute river waters.
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| 23. |
- Boström, Emma, et al.
(författare)
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The Use of Liquid Chromatography/Mass Spectrometry for Quantitative Analysis of Oxycodone, Oxymorphone and Noroxycodone in Ringer Solution, Rat Plasma and Rat Brain Tissue
- 2004
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Ingår i: Rapid Communications in Mass Spectrometry. - : Wiley. - 0951-4198 .- 1097-0231. ; 18:21, s. 2565-2576
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Tidskriftsartikel (refereegranskat)abstract
- Sensitive and reproducible methods for the determination of oxycodone, oxymorphone and noroxycodone in Ringer solution, rat plasma and rat brain tissue by liquid chromatography/mass spectrometry are described. Deuterated analogs of the substances were used as internal standards. Samples in Ringer solution were analyzed by direct injection of 10 microL Ringer solution diluted by an equal volume of water. The limit of quantification was 0.5 ng/mL and the method was linear in the range of 0.5-150 ng/mL for all substances. To analyze oxycodone and oxymorphone in rat plasma, 50 microL of plasma were precipitated with acetonitrile, and the supernatant was directly injected onto the column. To analyze oxycodone, oxymorphone and noroxycodone in rat plasma, 100 microL of rat plasma were subjected to a C18 solid-phase extraction (SPE) procedure, before reconstituting in mobile phase and injection onto the column. For both methods the limit of quantification in rat plasma was 0.5 ng/mL and the methods were linear in the range of 0.5-250 ng/mL for all substances. To analyze the content of oxycodone, oxymorphone and noroxycodone in rat brain tissue, 100 microL of the brain homogenate supernatant were subjected to a C18 SPE procedure. The limit of quantification of oxycodone was 20 ng/g brain, and for oxymorphone and noroxycodone 4 ng/g brain, and the method was linear in the range of 20-1000 ng/g brain for oxycodone and 4-1000 ng/g brain for oxymorphone and noroxycodone. All methods utilized a mobile phase of 5 mM ammonium acetate in 45% acetonitrile, and a SB-CN column was used for separation. The total run time of all methods was 9 min. The intra-day precision and accuracy were <11.3% and <+/-14.9%, respectively, and the inter-day precision and accuracy were <14.9% and <+/-6.5%, respectively, for all the concentrations and matrices described.
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| 24. |
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| 25. |
- Burman, Johan, 1966, et al.
(författare)
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A simplified method of preparing phosphoric acid for stable isotope analyses of carbonates
- 2005
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Ingår i: Rapid Communications in Mass Spectrometry. - : Wiley. - 0951-4198 .- 1097-0231. ; 19:21, s. 3086-3088
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Tidskriftsartikel (refereegranskat)abstract
- In order to produce CO2 for stable isotope analyses (delta(18)O and delta(13)C), carbonate samples are commonly digested in phosphoric acid. The acid recipe here presented is based on phase shifting crystalline orthophosphoric acid of pro-analysis quality to a liquid state through heating, followed by pre-vacuum treatment during a start-up procedure before mass analyses for common acid bath preparation, or adding a small amount of phosphoric pentoxide for single drop equipments, respectively. This methodology results in a final acid concentration of 104%. Copyright (C) 2005 John Wiley & Sons, Ltd.
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