1，3-二甲基尿嘧啶二聚体的飞行时间质谱裂解规律研究

采用不同进样方式、不同电子轰击能量和不同反应气压力测定了1,3 二甲基尿嘧啶二聚体(DMUD) 的4个立体异构体A、B、C、D的化学电离(CI)和电子轰击电离(EI)飞行时间质谱.不同方式所测得的CI谱结 果一致,4个异构体出现了强度不同的准分子离子峰(m/z=281),由此推断它们结构之间的相对稳定性次序为: B(trans syn)>D(cis syn)>A(trans anti)>C(cis anti).这一结论被低能量(25eV)电子轰击的EI谱所证实, 并且与合成产物的比例相吻合.EI谱用任何方式测谱均不出现分子离子峰(m/z=280),而出现其单体离子(m/z =140)且为基峰。给出了DMUD的飞行时间质谱裂解途径,同时对CI谱的裂解碎片进行了细致的讨论.     

Comparison between a high-resolution single-stage Orbitrap and a triple quadrupole mass spectrometer for quantitative analyses of drugs

The capabilities of a high-resolution (HR), accurate mass spectrometer (Exactive-MS) operating in full scan MS mode was investigated for the quantitative LC/MS analysis of drugs in patients' plasma samples. A mass resolution of 50,000 (FWHM) at m/z 200 and a mass extracted window of 5?ppm around the theoretical m/z of each analyte were used to construct chromatograms for quantitation. The quantitative performance of the Exactive-MS was compared with that of a triple quadrupole mass spectrometer (TQ-MS), TSQ Quantum Discovery or Quantum Ultra, operating in the conventional selected reaction monitoring (SRM) mode. The study consisted of 17 therapeutic drugs including 8 antifungal agents (anidulafungin, caspofungin, fluconazole, itraconazole, hydroxyitraconazole posaconazole, voriconazole and voriconazole-N-oxide), 4 immunosuppressants (ciclosporine, everolimus, sirolimus and tacrolimus) and 5 protein kinase inhibitors (dasatinib, imatinib, nilotinib, sorafenib and sunitinib). The quantitative results obtained with HR-MS acquisition show comparable detection specificity, assay precision, accuracy, linearity and sensitivity to SRM acquisition. Importantly, HR-MS offers several benefits over TQ-MS technology: absence of SRM optimization, time saving when changing the analysis from one MS to another, more complete information of what is in the samples and easier troubleshooting. Our work demonstrates that U/HPLC coupled to Exactive HR-MS delivers comparable results to TQ-MS in routine quantitative drug analyses. Considering the advantages of HR-MS, these results suggest that, in the near future, there should be a shift in how routine quantitative analyses of small molecules, particularly for therapeutic drugs, are performed.     

Analysis of dammar resin with MALDI-FT-ICR-MS and APCI-FT-ICR-MS

Comprehensive analysis of high-resolution mass spectra of aged natural dammar resin obtained with Fourier transform ion cyclotron resonance mass spectrometer (FT-ICR-MS) using matrix-assisted laser desorption/ionization (MALDI) and atmospheric pressure chemical ionization (APCI) is presented. Dammar resin is one of the most important components of painting varnishes. Dammar resin is a terpenoid resin (dominated by triterpenoids) with intrinsically very complex composition. This complexity further increases with aging. Ten different solvents and two-component solvent mixtures were tested for sample preparation. The most suitable solvent mixtures for the MALDI-FT-ICR-MS analysis were dichloromethane-acetone and dichloromethane-ethanol. The obtained MALDI-FTMS mass spectrum contains nine clusters of peaks in the m/z range of 420-2200, and the obtained APCI-FTMS mass spectrum contains three clusters of peaks in the m/z range of 380-910. The peaks in the clusters correspond to the oxygenated derivatives of terpenoids differing by the number of C(15)H(24) units. The clusters, in turn, are composed of subclusters differing by the number of oxygen atoms in the molecules. Thorough analysis and identification of the components (or groups of components) by their accurate m/z ratios was carried out, and molecular formulas (elemental compositions) of all major peaks in the MALDI-FTMS and APCI-FTMS spectra were identified (and groups of possible isomeric compounds were proposed). In the MALDI-FTMS and APCI-FTMS mass spectrum, besides the oxidized C(30), triterpenoids also peaks corresponding to C(29) and C(31) derivatives of triterpenoids (demethylated and methylated, correspondingly) were detected. MALDI and APCI are complementary ionization sources for the analysis of natural dammar resin. In the MALDI source, preferably polar (extensively oxidized) components of the resin are ionized (mostly as Na(+) adducts), whereas in the APCI source, preferably nonpolar (hydrocarbon and slightly oxidized) compounds are ionized (by protonation). Either of the two ionization methods, when used alone, gives an incomplete picture of the dammar resin composition.     

Identification of isomeric 5-hydroxytryptophan- and oxindolylalanine-containing peptides by mass spectrometry

Cells continuously produce reactive oxidative species that can modify all cellular components. In proteins, for example, cysteine, methionine, tryptophan (Trp), and tyrosine residues are particularly prone to oxidation. Here, we report two new approaches to distinguish two isomeric oxidation products of Trp residues, i.e. 5-hydroxytryptophan (5-HTP) and oxindolylalanine (Oia) residues, in peptides. First, 2-nitrobenzenesulfenyl chloride, known to derivatize Trp residues in position 2 of the indole ring, was used to label 5-HTP residues. The mass shift of 152.98 m/z units allowed identifying 5-HTP- besides Trp-containing peptides by mass spectrometry, whereas Oia residues were not labeled. Second, fragmentation of the Oia- and 5-HTP-derived immonium ions at m/z 175.08 produced ions characteristic for each residue that allowed their identification even in the presence of y(1) ions at m/z 175.12 derived from peptides with C-terminal arginine residues. The pseudo MS(3) spectra acquired on a quadrupole time-of-flight hybrid mass spectrometer displayed two signals at m/z 130.05 and m/z 132.05 characteristic for Oia-containing peptides and a group of six signals (m/z 103.04, 120.04, 130.04, 133.03, 146.04, and 148.04) for 5-HTP-cointaining peptides. In both cases, the relative signal intensities appeared to be independent of the sequence providing a specific fingerprint of each oxidative modification.     

Analysis of cyclic boronated and trimethylsilylated phenolalkylamines by gas chromatography and electron impact mass spectrometry

The side chain of phenolalkylamines containing a bifunctional group was derivatized as the cyclic boronate, and then the residual phenolic group was trimethylsilylated. The resulting derivatives were single reaction products in each case, with good gas chromatographic properties and informative mass spectra to afford prominent molecular ions by gas chromatography with electron impact mass spectrometry (GC/EI-MS). The cyclic boronated-trimethylsilylated derivatives yielded the isotope pattern for boron ((10)B:(11)B =-1:4.2) and characteristic ions [M](+), [M - H](+), [M - CH(3)](+), [M - RBO](+), [M - TMSO](+), and [M - TMSO - C(6)H(5)](+) ions in the mass spectra. In order to distinguish between m- and p-phenolalkylamines, the mass spectra of the cyclic phenylboronated-trimethylsilylated (PBA-TMS) derivatives were compared with those of the trimethylsilylated (TMS) derivatives. The TMS derivatives of octopamine (p-) and norfenefrine (m-) showed identical mass spectra, while the PBA-TMS derivatives had mass spectra sufficiently different from one other to distinguish between the isomers. The most prominent ion of the PBA-TMS derivative is the [M - H](+) ion (m/z 310) for octopamine and the [M](+) ion (m/z 311) for norfenefrine. Copyright 1999 John Wiley & Sons, Ltd.     

Computational approach to structural identification of phospholipids using raw mass spectra from nanoflow liquid chromatography-electrospray ionization-tandem mass spectrometry

A qualitative analysis tool (LiPilot) for identifying phospholipids (PLs), including lysophospholipids (LPLs), from biological mixtures is introduced. The developed algorithm utilizes raw data obtained from nanoflow liquid chromatography-electrospray ionization-tandem mass spectrometry experiments of lipid mixture samples including retention time and m/z values of precursor and fragment ions from data-dependent, collision-induced dissociation. Library files based on typical fragmentation patterns of PLs generated with an LTQ-Velos ion trap mass spectrometer are used to identify PL or LPL species by comparing experimental fragment ions with typical fragment ions in the library file. Identification is aided by calculating a confidence score developed in our laboratory to maximize identification efficiency. Analysis includes the influence of total ion intensities of matched and unmatched fragment ions, the difference in m/z values between observed and theoretical fragment ions, and a weighting factor used to differentiate regioisomers through data filtration. The present study focused on targeted identification of particular PL classes. The identification software was evaluated using a mixture of 24 PL and LPL standards. The software was further tested with a human urinary PL mixture sample, with 93 PLs and 22 LPLs identified. Copyright ? 2012 John Wiley & Sons, Ltd.     

Evidence of simple intramolecular rearrangement at polymer end groups in secondary ion mass spectrometry

Polystyrenes with various end groups were analyzed by time-of-flight secondary ion mass spectrometry (TOF-SIMS). These end groups were obtained by termination of the active anionic group by sulfonate or chlorosilane derivatives. Characteristic end group fragments for each sulfonate derivative were observed. On the one hand, for PS capped by methyl sulfonate, or -(CH(2))(4)-O-SO(2)-CH(3), almost complete end group fragment is observed at m/z 95 and a [O-SO(2)-CH(3)](-) molecular structure. On the other hand, when PS is terminated by silyl methyl sulfonate, or -Si(CH(3))(2)-(CH(2))(3)-O-SO(2)-CH(3), the most characteristic fragment in the fingerprint secondary ion mass spectrum is located at m/z 153 with [Si(CH(3))(2)-O-SO(2)-CH(3)](+) and the complete end group peak, [Si(CH(3))(2)-(CH(2))(3)-O-SO(2)-CH(3)](+), at m/z 201, is absent. According to the molecular structure, characteristic end group secondary ions can be emitted as complete or rearranged fragments. Various silylalkyl alcohol or sulfonate functionalities are analyzed and fragmentation pathways are discussed. To our knowledge, this is the first time that such rearrangement at silyl functions has been observed and demonstrated in fingerprint secondary ion mass spectra. Copyright 1999 John Wiley & Sons, Ltd.     

Static secondary ion mass spectrometry (S-SIMS) in advanced textile research: Study of additives in polypropylene (PP) films

The development of novel PP textiles requires materials of which the surface has well defined hydrophilic properties, for instance, by the use of additives before extrusion and drawing. The feasibility of static secondary ion mass spectrometry (S-SIMS) to provide detailed information on the molecular surface composition of materials in the form of 30 μm thick films has been explored. Extensive charge build-up during S-SIMS analysis prevents direct characterisation of such materials. Several methods have been used to circumvent the problem. Specifically, deposition of gold over the entire surface and pressing a slot grid into the material allow the commercial hydrophilic additive in PP to be detected. While the slot grid preserves the pristine surface composition, mass spectra from gold-coated samples reflect the occurrence of redistribution artefacts.     

5-乙氧羰基-4-取代-6-甲基-3,4-二氢嘧啶-2（1H）-酮的电子轰击飞行时间质谱表征

研究了一系列5-乙氧羰基-4-取代-6-甲基-3,4-二氢嘧啶-2(1H)-酮的电子轰击飞行时间质谱,建立了此类化合物的裂解方式和分子离子峰的强度规律.利用飞行时间质谱的中分辨能力,测得了各碎片离子的精确质量,这些数据经OpenLynx软件导出所有分子离子和碎片离子的元素组成.根据质谱裂解规律,主要质谱离子得到了归属.两类主要裂解途径为:对所有标题化合物,通过失去4位上的R1,酯基上的C2H4(麦氏重排)和H2O(通过环状六员过渡态)形成三种阳离子;对4-芳基化合物,通过失去EtCO2形成另一类阳离子.此外,还提出了个别化合物的一些重要裂解行为.     

Static secondary ion mass spectrometry (S-SIMS) analysis of atmospheric plasma treated polypropylene films

Time-of-Flight (TOF) static secondary ion mass spectrometry (S-SIMS) was used to gain molecular information on the surface modifications introduced by plasma treatment of polypropylene (PP) films. A procedure using slotted electron microscopy grids was developed to deal with the charge build-up of samples with a thickness of about 30 μm. The surface composition was studied as a function of the plasma treatment time. A comparison of the mass spectra from untreated and treated PP showed significant differences of signal intensities of ions that could be specifically related to the presence of oxygen-containing species.     

Analysis of t-butylphenol acetylene condensed resin with methyl-methine linkages in vulcanized rubber by pyrolysis-gas chromatography/mass spectrometry

Methyl-methine linkages of Novolac, a commercially available t-butylphenol acetylene condensed (TBPA) resin, have been identified by recognition of pyrolysis pathways using pyrolysis-gas chromatography/mass spectrometry (Py-GC/mS) in vulcanized rubber. The diagnostic mass spectrum of t-butylphenol with methyl-methine linkages between phenolic rings was observed at m/z 192, corresponding to 4-t-butyl-2-ethyl-6-methylphenol. Other molecular ions were observed at m/z 178, 164, and 150 in the characteristic pyrolyzates. The ion at m/z 192 in the TBPA resin was observed to be characteristic for methyl-methine linkages between the phenolic groups, and the analytical pyrolysis-GC/mS method was thus able to identify the resin at low levels in vulcanized rubber. Copyright 1999 John Wiley & Sons, Ltd.     

5-乙酰(苯甲酰)基-4-芳基-3,4-二氢嘧啶-2(1H)-酮的质谱裂解规律

利用飞行时间质谱仪的高分辨本领和离子阱串联质谱技术研究了5乙酰(苯甲酰)基4芳基3,4二氢嘧啶2(1H)酮(1-5)的电子轰击质谱的裂解规律.将所有质谱离子的精确质量数据经OpenLynx软件导出其分子离子和碎片离子的元素组成.根据质谱裂解规律,主要质谱离子得到了归属,并经离子阱串联质谱技术加以证实.化合物1-3的质谱出现了丰度很强的分子离子峰,其中1和3的分子离子为基峰,证明此类化合物的结构相当稳定.但4和5的分子离子峰却很弱(相对丰度在4%以下),这是由于嘧啶环4位上的苯环分别含有强吸电子基团-NO2(在苯环的间位才有此效应)和-Cl(苯环的2和4位均含有氯)所致.化合物1-5的主要裂解包括:分子离子失去芳基形成丰度很高的阳离子(M-Ar)+;分子离子失去羰基形成中等强度的阳离子(M-RCO)+;分子离子失去氢原子所产生的(M-H)+峰,以及消除中性分子NH=C=X的嘧啶环破裂裂解.此外,所有化合物在低质量区都发现明显的苯基阳离子Ph+(m/z77).并且还提出个别化合物的几个额外裂解过程为:化合物4(分子中苯环的3位上含有硝基)出现的基峰(M-OH)+;化合物5(分子中苯环的2和4位上都含有氯原子)出现了的基峰(M-Cl)+;化合物3和5分别出现了m/z238(16%)和m/z241(29%)的特征离子峰,它们由相应的离子消除中性分子四员内酰胺生成查耳酮离子,该离子具有共轭大Π键而稳定存在.     

Shotgun lipidomics on a LTQ Orbitrap mass spectrometer by successive switching between acquisition polarity modes

Top-down shotgun lipidomics relies on direct infusion of total lipid extracts into a high-resolution tandem mass spectrometer and implies that individual lipids are recognized by their accurately determined m/z. Lipid ionization efficiency and detection specificity strongly depend on the acquisition polarity, and therefore it is beneficial to analyze lipid mixtures in both positive and negative modes. Hybrid LTQ Orbitrap mass spectrometers are widely applied in top-down lipidomics; however, rapid polarity switching was previously unfeasible because of the severe and immediate degradation of mass accuracy. Here, we report on a method to rapidly acquire high-resolution spectra in both polarity modes with sub-ppm mass accuracy and demonstrate that it not only simplifies and accelerates shotgun lipidomics analyses but also improves the lipidome coverage because more lipid classes and more individual species within each class are recognized. In this way, shotgun analysis of total lipid extracts of human blood plasma enabled to quantify 222 species from 15 major lipid classes within 7?min acquisition cycle.     

高分辨质谱用于分析和检测α-硫羰基硫代甲酰胺类化合物

苯乙酮及其衍生物与氯化亚砜反应所得中间产物再与仲胺反应得α－羰基硫代甲酰胺（1a-1f),经硫代得目标物α－硫羰基硫代甲酰胺（2a-2f)。化合物2a-2f含有二个硫羰基,为深红或深绿色晶体,可用作远红外吸收染料、激光Q开关及有机导体等。本文利用英国Micromass公司的OA－TOF高分辨质谱仪对α－硫羰基硫代甲酰胺类化合物的裂解行为进行了详细的研究。结果表明该类化合物容易失去S2分子形成特征的碎片离子M－S2（基峰）,为分析和检测这类化合物提供了一种有效的分析方法。OA－TOF高分辨质谱仪体积小、操作简单、快速,适合于分析纯的α－硫羰基硫代甲酰胺类化合物、检测混合物中及作为反应中间体的这类化合物。     

Remote detection of similar biological materials using femtosecond filament-induced breakdown spectroscopy

We demonstrated the feasibility of remote detection and differentiation of some very similar agricultural-activity related bioaerosols, namely barley, corn, and wheat grain dusts, through nonlinear fluorescence of fragments induced by the high-intensity inside filaments of femtosecond laser pulses in air. The signals were detected in Lidar configuration with targets located at 4.7 m away from the detection system. All the species showed identical spectra, namely those from molecular C₂ and CN bands, as well as atomic Si, C, Mg, Al, Na, Ca, Mn, Fe, Sr and K lines. These identical spectral bands and lines reveal similar chemical compositions; however, the relative intensities of the spectra are different showing different element abundances from these three bio-targets. The intensity ratios of different elemental lines were used to distinguish these three samples. Good reproducibility was obtained. We expect that this technique could be used at long distance and thus played as a sensor of similar biological hazards for public and defense security. PACS 42.68.Wt; 95.75.Fg     

The use of mass defect in modern mass spectrometry

Mass defect is defined as the difference between a compound's exact mass and its nominal mass. This concept has been increasingly used in mass spectrometry over the years, mainly due to the growing use of high resolution mass spectrometers capable of exact mass measurements in many application areas in analytical and bioanalytical chemistry. This article is meant as an introduction to the different uses of mass defect in applications using modern MS instrumentation. Visualizing complex mass spectra may be simplified with the concept of Kendrick mass by plotting nominal mass as a function of Kendrick mass defect, based on hydrocarbons subunits, as well as slight variations on this theme. Mass defect filtering of complex MS data has been used for selectively detecting compounds of interest, including drugs and their metabolites or endogenous compounds such as peptides and small molecule metabolites. Several strategies have been applied for labeling analytes with reagents containing unique mass defect features, thus shifting molecules into a less noisy area in the mass spectrum, thus increasing their detectability, especially in the area of proteomics. All these concepts will be covered to introduce the interested reader to the plethora of possibilities of mass defect analysis of high resolution mass spectra.     

First direct mass measurement of the two-neutron halo nucleus 6He and improved mass for the four-neutron halo 8He

The first direct mass measurement of {6}He has been performed with the TITAN Penning trap mass spectrometer at the ISAC facility. In addition, the mass of {8}He was determined with improved precision over our previous measurement. The obtained masses are m({6}He)=6.018?885?883(57) u and m({8}He)=8.033?934?44(11) u. The {6}He value shows a deviation from the literature of 4σ. With these new mass values and the previously measured atomic isotope shifts we obtain charge radii of 2.060(8) and 1.959(16) fm for {6}He and {8}He, respectively. We present a detailed comparison to nuclear theory for {6}He, including new hyperspherical harmonics results. A correlation plot of the point-proton radius with the two-neutron separation energy demonstrates clearly the importance of three-nucleon forces.     

13-乙酰基-9-甲基-11-羰基-8-氧代-10,12-二氮杂三环[7.3.1.02,7]十三碳-2,4,6-三烯的一锅煮合成和结构表征

描述了一种有效的环境友好的“一锅煮”法合成13-乙酰基-9-甲基-11-羰基-8-氧代-10,12-二氮杂三环[7．3．1．0~(2,7)]十三碳-2,4,6-三烯。该法用廉价易得的溴化镁作催化剂,在无溶剂存在下,由起始原料水杨酸,乙酰丙酮和脲通过Biginelli缩合反应伴随着分子内的Michael加成反应一步完成。用核磁共振氢谱、碳谱、飞行时间质谱以及红外光谱数据表征了产物的结构为一氧桥多环化合物,而不是带有自由羟基的二氢嘧啶酮。最后由质谱给出的精确质量及其所代表的元素组成推出了该化合物的质谱裂解途径。     

Identification of overlapping optical lines in molecular spectra by means of the coherent population trapping of quantum levels

A new method of molecular beam spectroscopy with the ultrahigh resolution is theoretically suggested. This method is based on the phenomenon of the coherent population trapping of molecular levels and allows the identification of the overlapping optical lines in complex spectra (typical for polyatomic molecules), even when frequency intervals between the centers of given lines are less than their natural line widths. The theoretical analysis is carried out on the basis of the Schrödinger equation for the three-level molecular A-system interacting with the two-frequency laser radiation. The conditions of the practical realization and possible applications of the suggested spectroscopy method are discussed.     

Effect of nitro groups and alkyl chain length on the negative ion tandem mass spectra of alkyl 3-hydroxy-5-(4'-nitrophenoxy) and alkyl 3-hydroxy-5-(2', 4'-dinitrophenoxy) benzoates

Tandem mass spectrometric behaviour was studied for a small combinatorial library of alkyl 3-hydroxy-5-(4'-nitrophenoxy) benzoates (A1-A5) and alkyl 3-hydroxy-5-(2', 4'-dinitrophenoxy) benzoates (B1-B5). The spectra were recorded by negative ion electrospray low-energy collision induced dissociation (CID) tandem mass spectrometry. The product ion spectra of [M - H](-) of the benzoates A1-A5 are similar, as are those of benzoates B1-B5. However, the spectra of the B series compounds differ significantly from those of the A series owing to the second electron-withdrawing nitro substituent in the B compounds. In addition, the length of the alkyl chain has an effect on the fragmentation. However, both series of compounds exhibit an abundant nitrophenoxy ion formed by the loss of 3-hydroxybenzoate. This is at m/z 138 in A1-A5 and at m/z 183 in B1-B5. A precursor ion scan of the nitrophenoxy ion provides a rapid method to identify the synthesised compounds in this type of combinatorial mixture. Copyright 1999 John Wiley & Sons, Ltd.