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Time-of-flight Mass Spectrometer (time-of-flight + mass_spectrometer)
Kinds of Time-of-flight Mass Spectrometer Selected AbstractsHigh-energy collision-induced dissociation of phosphopeptides using a multi-turn tandem time-of-flight mass spectrometer ,MULTUM-TOF/TOF'JOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 4 2008Shuichi Shimma [source] Exact mass measurement on an electrospray ionization time-of-flight mass spectrometer: error distribution and selective averagingJOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 10 2003Jiejun Wu Abstract An automated, accurate and reliable way of acquiring and processing flow injection data for exact mass measurement using a bench-top electrospray ionization time-of-flight (ESI-TOF) mass spectrometer is described. Using Visual Basic programs, individual scans were selected objectively with restrictions on ion counts per second for both the compound of interest and the mass reference peaks. The selected ,good scans' were then subjected to two different data-processing schemes (,combine-then-center' and ,center-then-average'), and the results were compared at various ion count limit settings. It was found that, in general, the average of mass values from individual scans is more accurate than the centroid mass value of the combined (same) scans. In order to acquire a large number of good scans in one injection (to increase the sampling size for statistically valid averaging), an on-line dilution chamber was added to slow down the typically rapid mass chromatographic peak decay in flow-injection analysis. This simple addition worked well in automation without the need for manual sample dilution. In addition, by dissolving the reference compound directly into the mobile phase, manual syringe filling can be eliminated. Twenty-seven samples were analyzed with the new acquisition and process routines in positive electrospray ionization mode. For the best method found, the percentage of samples with RMS error less than 5 ppm was 100% with repetitive injection data (6 injections per sample), and 95% with single injection data. Afterwards, 31 other test samples were run (with MW ranging from 310 to 3493 Da, 21 samples in ESI+ and 10 in ESI, mode) and processed with similar parameters and 100% of them were mass-calculated to RMS error less than 5 ppm also. Copyright © 2003 John Wiley & Sons, Ltd. [source] Formation and photodissociation of M+,C6H6 (M+ = V+ and Ta+) and Ta+,C6H4 complexes in a time-of-flight mass spectrometerJOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 5 2001Hsiu-Fang Lee Abstract A series of cyclic hydrocarbons were introduced to react with V+ and Ta+ using a pulsed beam expansion source in a time-of-flight mass spectrometer. The third-row metal Ta+ displayed high reactivity in dehydrogenation to form benzyne complexes, whereas benzene complexes were the terminal products for V+. M+,C6H6 (M+ = V+ and Ta+) and Ta+,C6H4 were selected to perform the photodissociation experiments. In contrast to the V+ fragment formation via simple cleavage of the V+,C6H6 bond, a photoinduced loss of C2H2 occurred in both the Ta+,C6H6 and Ta+,C6H4 complexes. Plausible explanations involved in the formation of Ta+,C6H6 and Ta+,C6H4 complexes are given for observing such photo-induced dissociation. The observed photodissociation in Ta+,C6H6 is analogous to the dissociative process previously investigated in metal ion,molecule reactions. The photodissociation spectrum of Ta+,C6H4 was obtained by recording the appearance of Ta+,C4H2 as a function of wavelength and yielded a dissociation energy of 91 ± 1 kcal mol,1. Copyright © 2001 John Wiley & Sons, Ltd. [source] Elucidation of fragmentation mechanisms involving transfer of three hydrogen atoms using a quadrupole time-of-flight mass spectrometerJOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 5 2001Cornelis E. C. A. Hop [source] On the high-resolution mass analysis of the product ions in tandem time-of-flight (TOF/TOF) mass spectrometers using a time-dependent re-acceleration techniqueRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 1 2010Sergey Kurnosenko The time-dependent reacceleration of product ions produced as a result of dissociation of a single precursor ion in a tandem time-of-flight mass spectrometer is considered for the first time. Analytical expressions for the shapes of electric pulses bringing all the kinetic energies of the product ions to the same value are derived for two cases: forward acceleration mode and deceleration, followed by re-acceleration in the reversed direction (reversed mode). Secondary time-of-flight focusing resulting from the re-acceleration in the reversed mode is shown to be mass-dependent and, when averaged over a wide mass range, the focusing is tight enough to provide mass resolution exceeding 10,000. After time-dependent re-acceleration, additional compression of the ion packet width leading to better mass resolution can be obtained by decelerating the ions in a constant field. Copyright © 2009 John Wiley & Sons, Ltd. [source] Top-down proteomics with a quadrupole time-of-flight mass spectrometer and collision-induced dissociationRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 5 2009Andrea Armirotti With slight modifications of the instrumental parameters, we demonstrate that satisfactory top-down data can be obtained with collision-induced dissociation (CID) tandem mass spectrometry on a quadrupole time-of-flight (qTOF) instrument not originally designed for this purpose. Protein identification is achieved with both N- and C-terminal sequence tags and BLAST database searches. The accurate mass measurement of multiply charged fragment ions (mostly y and b-type) supplements the limited set of cleavage sites and provides a high degree of sequence coverage (90,100%). Post-translational modification issues can be addressed too. This approach might help those mass spectrometry (MS) core facilities that are not able to afford very high-resolution instruments, thus expanding the benefits of top-down protein analysis over the worldwide MS community. Copyright © 2009 John Wiley & Sons, Ltd. [source] Comparison of mass spectra of peptides in different matrices using matrix-assisted laser desorption/ionization and a multi-turn time-of-flight mass spectrometer, MULTUM-IMGRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 10 2008Hisanao Hazama The mass spectra of peptides obtained with different matrices were compared using a matrix-assisted laser desorption/ionization (MALDI) ion source and a multi-turn time-of-flight (TOF) mass spectrometer, MULTUM-IMG, which has been developed at Osaka University. Two types of solid matrices, , -cyano-4-hydroxycinnamic acid (CHCA) and 2,5-dihydroxybenzoic acid (DHB), and a liquid matrix made from a mixture of 3-aminoquinoline and CHCA were used. When measuring the peak signal intensity of human angiotensin II [M+H]+ from a fixed sample position, the liquid matrix produced a stable signal over 1000 laser shots, while the signal obtained with CHCA and DHB decayed after about 300 and 100 shots, respectively. Significant differences in the mass resolving power were not observed between the spectra obtained with the three matrices. Signal peak areas were measured as a function of the cycle number in a multi-turn ion trajectory, i.e., the total flight time over a millisecond time scale. For both [M+H]+ of human angiotensin II and bovine insulin, the decay of the signal peak area was the most significant with CHCA, while that measured with DHB was the smallest. The results of the mean initial ion velocity measurements suggested that the extent of metastable decomposition of the analyte ions increased in order of DHB, the liquid matrix, and CHCA, which is consistent with the difference in the decay of the signal peak area as the total flight time increased. Copyright © 2008 John Wiley & Sons, Ltd. [source] Liquid chromatography/mass spectrometry for metabonomics investigation of the biochemical effects induced by aristolochic acid in rats: the use of information-dependent acquisition for biomarker identificationRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 6 2008Wan Chan The toxic effects of oral administrations of nephrotoxic and carcinogenic aristolochic acid (AA) to male Sprague-Dawley rats were investigated by using high-performance liquid chromatography coupled with a quadrupole time-of-flight mass spectrometer. Analysis of the urine and plasma samples revealed distinct changes in the biochemical patterns in the AA-dosed rats. After peak finding and alignment, principal component analysis (PCA) and partial least-squares discriminant analysis (PLS-DA) were used for multivariate data analysis. Potential biomarkers were studied by high-resolution mass spectrometry (MS) and tandem mass spectrometry (MS/MS) analyses. The MS/MS spectra of all endogenous metabolites satisfying the pre-defined criteria were acquired in a single information-dependent acquisition (IDA) analysis, demonstrating that IDA was an efficient approach for structural elucidation in metabonomic studies. Citric acid and a glucuronide-containing metabolite were observed as potential biomarkers in rat urine. A significant increase in plasma creatinine concentration was also observed in the AA-dosed rats, which indicated that AA induced an adverse effect on the renal clearance function. Copyright © 2008 John Wiley & Sons, Ltd. [source] Molecular weight determination of ultra-high mass compounds on a standard matrix-assisted laser desorption/ionization time-of-flight mass spectrometer: PAMAM dendrimer generation 10 and immunoglobulin MRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 24 2006Roland Müller First page of article [source] Feasibility of different mass spectrometric techniques and programs for automated metabolite profiling of tramadol in human urineRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 14 2006Kati S. Hakala The purpose of the study was to determine the advantages of different mass spectrometric instruments and commercially available metabolite identification programs for metabolite profiling. Metabolism of tramadol hydrochloride and the excretion of it and its metabolites into human urine were used as a test case because the metabolism of tramadol is extensive and well known. Accurate mass measurements were carried out with a quadrupole time-of-flight mass spectrometer (Q-TOF) equipped with a LockSpray dual-electrospray ionization source. A triple quadrupole mass spectrometer (QqQ) was applied for full scan, product ion scan, precursor ion scan and neutral loss scan measurements and an ion trap instrument for full scan and product ion measurements. The performance of two metabolite identification programs was tested. The results showed that metabolite programs are time-saving tools but not yet capable of fully automated metabolite profiling. Detection of non-expected metabolites, especially at low concentrations in a complex matrix, is still almost impossible. With low-resolution instruments urine samples proved to be challenging even in a search for expected metabolites. Many false-positive hits were obtained with the automated searching and manual evaluation of the resulting data was required. False positives were avoided by using the higher mass accuracy Q-TOF. Automated programs were useful for constructing product ion methods, but the time-consuming interpretation of mass spectra was done manually. High-quality MS/MS spectra acquired on the QqQ instrument were used for confirmation of the tramadol metabolites. Although the ion trap instrument is of undisputable benefit in MSn, the low mass cutoff of the ion trap made the identification of tramadol metabolites difficult. Some previously unreported metabolites of tramadol were found in the tramadol urine sample, and their identification was based solely on LC/MS and LC/MS/MS measurements. Copyright © 2006 John Wiley & Sons, Ltd. [source] Reactions of platinum cluster ions with benzeneRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 12 2006Hongtao Liu In this work, the cation and anion products of the reactions between platinum clusters produced by laser ablation and the benzene molecules seeded in argon have been studied using a high-resolution reflectron time-of-flight mass spectrometer (RTOFMS). The dominant cation products are [C6nH6n,,,k]+ and [Ptm(C6H6)n]+ complexes, while the dominant anion products are dehydrogenated species, [C6H5PtH],, [PtC12Hk], and [PtmC6H4,·,·,·,(C6H6)n],, etc. Some important intermediate structures ([PtC6H6]+, [Pt(C6H6)2]+, [Pt2(C6H6)3]+, [C6H5PtH],, [Pt2C6H4],, [Pt3C6H4], and [Pt4C6H4],) have been analyzed using density functional theory (DFT) calculations. Different reaction mechanisms are proposed for platinum cluster cations and anions with benzene, respectively. Copyright © 2006 John Wiley & Sons, Ltd. [source] Increasing throughput and information content for in vitro drug metabolism experiments using ultra-performance liquid chromatography coupled to a quadrupole time-of-flight mass spectrometerRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 6 2005Jose Castro-Perez The field of drug metabolism has been revolutionized by liquid chromatography/mass spectrometry (LC/MS) applications with new technologies such as triple quadrupoles, ion traps and time-of-flight (ToF) instrumentation. Over the years, these developments have often relied on the improvements to the mass spectrometer hardware and software, which has allowed users to benefit from lower levels of detection and ease-of-use. One area in which the development pace has been slower is in high-performance liquid chromatography (HPLC). In the case of metabolite identification, where there are many challenges due to the complex nature of the biological matrices and the diversity of the metabolites produced, there is a need to obtain the most accurate data possible. Reactive or toxic metabolites need to be detected and identified as early as possible in the drug discovery process, in order to reduce the very costly attrition of compounds in late-phase development. High-resolution, exact mass measurement plays a very important role in metabolite identification because it allows the elimination of false positives and the determination of non-trivial metabolites in a much faster throughput environment than any other standard current methodology available to this field. By improving the chromatographic resolution, increased peak capacity can be achieved with a reduction in the number of co-eluting species leading to superior separations. The overall enhancement in the chromatographic resolution and peak capacity is transferred into a net reduction in ion suppression leading to an improvement in the MS sensitivity. To investigate this, a number of in vitro samples were analyzed using an ultra-performance liquid chromatography (UPLC) system, with columns packed with porous 1.7,,m particles, coupled to a hybrid quadrupole time-of-flight (ToF) mass spectrometer. This technique showed very clear examples for fundamental gains in sensitivity, chromatographic resolution and speed of analysis, which are all important factors for the demands of today's HTS in discovery. Copyright © 2005 John Wiley & Sons, Ltd. [source] Accurate mass measurement in nano-electrospray ionization mass spectrometry by alternate switching of high voltage between sample and reference sprayersRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 4 2005Yoshinori Satomi An electrospray dual sprayer, which generates separate sample and reference sprays by alternately switching the high voltage between the two sprayers, is described. The technique permits accurate mass measurements in nano-electrospray ionization mass spectrometry (ESI-MS) to be obtained using a quadrupole/orthogonal acceleration time-of-flight mass spectrometer (Q-TOF). Similar to the method employed with a dual ESI source (Wolff JC et al., Anal. Chem. 2001; 73: 2605), the two sprays are orthogonal with respect to each other, but can be independently sampled without any baffle between these sprays. The reference sprayer is used in the original configuration of the ESI source and was optimized for a 1,2,,L/min flow, whereas the sample sprayer can be either a conventional glass capillary or a borosilicate tip of the type used for nano-ESI. Both sprayers can be positioned close to the cone so as to give maximum ion currents. The sample and reference sprays are independently generated by raising the potentials on the sample and reference sprayers to 1.4 and 3.0,kV, respectively; the high voltages can be rapidly turned on and off in ca. 1,ms. A nano-ESI-MS or nano-flow LC/ESI-MS experiment using a Q-TOF coupled with the above system gave mass accuracies within 3,ppm for measurements of ions up to m/z 1000 using subpicomole samples. Copyright © 2005 John Wiley & Sons, Ltd. [source] Sequence- and site-specific photodissociation at 266,nm of protonated synthetic polypeptides containing a tryptophanyl residueRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 22 2004Joo Yeon Oh Photodissociation at 266,nm of protonated synthetic polypeptides containing a tryptophanyl residue was investigated using a homebuilt tandem time-of-flight mass spectrometer equipped with a matrix-assisted laser desorption/ionization source. Efficient photodissociation of the protonated peptides was demonstrated. Most of the intense peaks in the laser-induced tandem mass spectra were sequence ions. Furthermore, sequence ions due to cleavages at all the peptide bonds were observed; this is a feature of the technique that is particularly useful for peptide sequencing. Fragmentations at both ends of the tryptophanyl residue were especially prevalent, which can be useful for location of the tryptophanyl chromophore in a peptide. Copyright © 2004 John Wiley & Sons, Ltd. [source] Application of single-particle laser desorption/ionization time-of-flight mass spectrometry for detection of polycyclic aromatic hydrocarbons from soot particles originating from an industrial combustion processRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 8 2003R. Zimmermann Combustion-related soot particles were sampled in situ from the stoker system of a 0.5,MW incineration pilot plant (feeding material was wood) at two different heights over the feed bed in the third air supply zone. The collected particles were re-aerosolized by a powder-dispersing unit and analyzed by a single-particle laser desorption/ionization (LDI) time-of-flight mass spectrometer (aerosol-time-of-flight mass spectrometry, ATOFMS). The ATOFMS instrument characterizes particles according to their aerodynamic size (laser velocimetry) and chemical composition (LDI mass spectrometry). Chemical species from the particles are laser desorbed/ionized by 266,nm Nd:YAG laser pulses. ATOFMS results on individual ,real world' particles in general give information on the bulk inorganic composition. Organic compounds, which are of much lower concentrations, commonly are not detectable. However, recent off-line laser microprobe mass spectrometric (LMMS) experiments on bulk soot aerosol samples have emphasized that organic compounds can be desorbed and ionized without fragmentation in LDI experiments from black carbonaceous matrices. This paper reports the successful transfer of the off-line results to on-line analysis of airborne soot particles by ATOFMS. The detection of polycyclic aromatic hydrocarbons from soot particles is addressed in detail. The results are interpreted in the context of the recent LMMS results. Furthermore, their relevance with respect to possible applications in on-line monitoring of combustion processes is discussed. Copyright © 2003 John Wiley & Sons, Ltd. [source] Electrospray ionization with ambient pressure ion mobility separation and mass analysis by orthogonal time-of-flight mass spectrometryRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 23 2001Wes E. Steiner Rapid screening and identification of drug and other mixtures are possible using a novel ambient pressure high-resolution ion mobility (APIMS) orthogonal reflector time-of-flight mass spectrometer (TOFMS). Departing ions from the APIMS drift tube traversed a pressure interface between the APIMS and TOFMS where they were subjected to numerous gas collisions that could produce selective fragmentation. By increasing the accelerating field in the pressure interface region, the ions generated using water-cooled electrospray ionization (ESI) underwent collision-induced dissociation (CID). Mixtures of ESI ions were separated by APIMS based on their respective size-to-charge (s/z) ratios while CID and analysis of mass-to-charge (m/z) ratios occurred in the pressure interface and TOFMS. Product ions that were formed in this pressure interface region could be readily assigned to precursor ions by matching the mobility drift times. This process was demonstrated by the examination of a mixture of amphetamines and the resulting fragmentation patterns of the mobility-separated precursor ion species [M,+,H]+. Copyright © 2001 John Wiley & Sons, Ltd. [source] The nature of collision-induced dissociation processes of doubly protonated peptides: comparative study for the future use of matrix-assisted laser desorption/ionization on a hybrid quadrupole time-of-flight mass spectrometer in proteomicsRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 22 2001R. Cramer Comparative MS/MS studies of singly and doubly charged electrospray ionization (ESI) and matrix-assisted laser desorption/ionization (MALDI) precursor peptide ions are described. The spectra from these experiments have been evaluated with particular emphasis on the data quality for subsequent data processing and protein/amino acid sequence identification. It is shown that, once peptide ions are formed by ESI or MALDI, their charge state, as well as the collision energy, is the main parameter determining the quality of collision-induced dissociation (CID) MS/MS fragmentation spectra of a given peptide. CID-MS/MS spectra of singly charged peptides obtained on a hybrid quadrupole orthogonal time-of-flight mass spectrometer resemble very closely spectra obtained by matrix-assisted laser desorption/ionization post-source decay time-of-flight mass spectrometry (MALDI-PSD-TOFMS). On the other hand, comparison of CID-MS/MS spectra of either singly or doubly charged ion species shows no dependence on whether ions have been formed by ESI or MALDI. This observation confirms that, at the time of precursor ion selection, further mass analysis is effectively decoupled from the desorption/ionization event. Since MALDI ions are predominantly formed as singly charged species and ESI ions as doubly charged, the associated difference in the spectral quality of MS/MS spectra as described here imposes direct consequences on data processing, database searching using ion fragmentation data, and de novo sequencing when ionization techniques are changed. Copyright © 2001 John Wiley & Sons, Ltd. [source] A simple and robust conductive graphite coating for sheathless electrospray emitters used in capillary electrophoresis/mass spectrometryRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 21 2001Stefan Nilsson A graphite-polyimide mixture was used as a conductive coating for sheathless electrospray emitters. The coating procedure described is simple and inexpensive compared to previously described methods. An investigation of the stability of the conductive coating carried out by electrochemical methods revealed good performances during oxidative stress. In addition, no decrease in emitter performance was seen during continuous electrospray in the positive electrospray mode for two weeks. Fast capillary electrophoresis with attomole sensitivity demonstrated the excellent performance of the described sheathless interface when used in conjunction with an orthogonal time-of-flight mass spectrometer. The overall simplicity, stability and low cost of this type of sheathless emitter make the described approach highly suitable for any on-column coupling of low flow rate separation techniques to a mass spectrometer. Copyright © 2001 John Wiley & Sons, Ltd. [source] Liquid chromatography,mass spectrometry for analysis of a novel ,2 -adrenoceptor agonist trantinterol and its metabolites in beagle dog urineBIOMEDICAL CHROMATOGRAPHY, Issue 3 2010Yanjuan Wang Abstract A liquid chromatography,tandem mass spectrometry method was developed for the identification of metabolites of trantinterol, a novel ,2 -adrenoceptor agonist, in beagle dog urine. The separation of metabolites was performed on a reversed-phase C8 column using 0.1% formic acid in water and methanol (70 : 30, v/v) as the mobile phase. The structural information and elemental information of metabolites were acquired by an electrospray ionization tandem mass spectrometer and a quadrupole time-of-flight mass spectrometer, respectively. A total of 13 metabolites were detected and characterized on the basis of their tandem MS/MS fragmentation patterns. The accurate masses of nine metabolites were determined and two metabolites were further confirmed by comparing with reference standards. The metabolic pathways of trantinterol in beagle dog are proposed. Copyright © 2009 John Wiley & Sons, Ltd. [source] Identification and human pharmacokinetics of dihydroergotoxine metabolites in man: preliminary resultsBIOPHARMACEUTICS AND DRUG DISPOSITION, Issue 1 2008Beatriz Bicalho Abstract Dihydroergotoxine is a mixture of semi-synthetic ergot alkaloids mainly used for age-related cognitive impairment. In this study, dihydroergotoxine (30,µM) was added to incubates of rat and bovine liver microsomes, and the resulting major metabolites were identified as hydroxy-dihydroergocornine, hydroxy-dihydroergocryptine and hydroxy-dihydroergocristine on the basis of molecular mass measurements, determined with a time-of-flight mass spectrometer. The relevance of these to humans was then investigated by simultaneously monitoring dihydroergotoxine and its hydroxy-metabolites in human plasma by LC-MS/MS after oral dosing of dihydroergotoxine mesylate (27,mg) to a healthy volunteer (male, age 45, height 1.93,m, weight 103,kg). In this preliminary approach, the peaks (Cmax) of dihydroergocornine, dihydroergocryptine and dihydroergocristine were about 0.04,µg/l. The peaks (Cmax) of their hydroxy-metabolites were 0.98, 0.53 and 0.30,µg/l, respectively. In conclusion, in this preliminary approach it was found that hydroxy-dihydroergocornine, hydroxy-dihydroergocryptine and hydroxy-dihydroergocristine were one order of magnitude higher in concentration than their parents in human plasma. Copyright © 2007 John Wiley & Sons, Ltd. [source] C20 Carbon Clusters: Fullerene,Boat,Sheet Generation, Mass Selection, Photoelectron CharacterizationCHEMISTRY - A EUROPEAN JOURNAL, Issue 24 2006Horst Prinzbach Prof. Dr. Abstract Electron-impact ionization in a time-of-flight mass spectrometer of C20H0,3Br14,12 probes,secured from C20H20 dodecahedrane by a "brute-force" bromination protocol,provided bromine-free C20H0,2(3) anions in amounts that allowed the clean mass-separation of the hydrogen-free C20, ions and the photoelectron (PE) spectroscopic characterization as C20 fullerene (electron affinity (EA)=2.25±0.03 eV, vibrational progressions of 730±70). The extremely strained C20 fullerene ions surfaced as kinetically rather stable entities (lifetime of at least the total flight time of 0.4 ms); they only very sluggishly expel a C2 unit. The HOMO and LUMO are suggested to be almost degenerate (,E=0.27 eV). The assignment as a fullerene was corroborated by the PE characterization of the C20 bowl (EA=2.17±0.03 eV, vibrational progression of 2060±50 cm,1) analogously generated from C20H10 corannulene (C20H1,3Br9,8 samples) and comparably stable. Highly resolved low-temperature PE spectra of the known C20 ring (EA=2.49±0.03 eV, vibrational progressions 2022±45 and 455±30 cm,1), obtained from graphite, display an admixture of, most probably, a bicyclic isomer (EA=3.40±0.03 eV, vibrational progression 455±30 cm,1). The C20+(,) and C20H2+(,) cluster ions generated from polybrominated perylene (C20H0,2Br12,10) have (most probably) retained the planar perylene-type skeleton (sheet, EA=2.47±0.03 eV, vibrational progressions of 2089±30 and 492±30 cm,1 and EA=2.18±0.03 eV, vibrational progressions of 2105±30 and 468±30 cm,1). [source] LC-MS: a powerful tool in workplace drug testingDRUG TESTING AND ANALYSIS, Issue 3 2009E. Gallardo Abstract Workplace drug testing is a well-established application of forensic toxicology and it aims to reduce workplace accidents caused by affected workers. Several classes of abused substances may be involved, such as alcohol, amphetamines, cannabis, cocaine, opiates and also prescription drugs, such as benzodiazepines. The use of alternative biological specimens such as hair, oral fluid or sweat in workplace drug testing presents several advantages over urinalysis,mainly the fact that sample collection can be performed easily without infringing on the examinee's privacy, so the subject is more likely to perform the test. However, drugs are usually present in these alternative specimens at low concentrations and the amount of sample available for analysis is small. The use of highly sensitive techniques is therefore necessary. In fact, the successful interface of liquid chromatography with mass spectrometry (LC-MS) has brought a new light into bioanalytical and forensic sciences as it allows the detection of drugs and metabolites at concentrations that are difficult to analyse using the more commonly adopted GC-MS based techniques. This paper will discuss the importance of LC-MS in supporting workplace drug-testing programmes. The combination of LC-MS with innovative instrumentation such as triple quadrupoles, ion traps and time-of-flight mass spectrometers will also be focused. Copyright © 2009 John Wiley & Sons, Ltd. [source] | ||||||||||