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Zhan-Fang Liu Bin Xu Zhen-Wen Sun Yu-You Sun Hong Zhou Jun Zhu 《Analytical letters》2017,50(14):2234-2245
Nitro compounds such as 2,4,6-trinitrotoluene, cyclotrimethylene trinitramine, and pentaerythritol tetranitrate are common ingredients of high explosives found in homeland security threats, minefields, and industrial materials. This study aims at developing a convenient surface analysis method for rapid identification of these compounds by direct analysis in real time coupled with time-of-flight mass spectrometry. The possible ionization mechanisms and fragmentation pathways using the direct analysis in real-time ionization source were developed for each compound based on the ions produced by in-source collision-induced dissociation and acquired by a time-of-flight mass spectrometer. These compounds release nitro groups and form nitroless characteristic fragments with other nitro adducts during in-source collision-induced dissociation processes. The characteristic ion [M?+?C2H4N3O2]? produced by cyclotrimethylene trinitramine was observed for the first time to our best knowledge. Direct analysis in real-time time-of-flight mass spectrometry has provided rapid identification of residues from various samples from explosion scenes and, therefore, is a potential powerful screening tool for criminal evidence. 相似文献
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Photodissociation Dynamics of 2-Iodotoluene Investigated by Femtosecond Time-Resolved Mass Spectrometry 下载免费PDF全文
The photodissociation dynamics of 2-iodotoluene following excitation at 266 nm have been investigated employing femtosecond time-resolved mass spectrometry. The photofragments are detected by multiphoton ionization using an intense laser field centered at 800 nm. A dissociation time of 38±50 fs was measured from the rising time of the co-fragments of toluene radical (C7H7) and iodine atom (I), which is attributed to the averaged time needed for the C-I bond breaking for the simultaneously excited nσ* and ππ* states by 266 nm pump light. In addition, a probe light centered at 298.23 nm corresponding to resonance wavelength of ground-state iodine atom is used to selectively ionize ground-state iodine atoms generated from the dissociation of initially populated nσ* and ππ* states. And a rise time of 40±50 fs is extracted from the fitting of time-dependent I+ transient, which is in agreement with the dissociation time obtained by multiphoton ionization with 800 nm, suggesting that the main dissociative products are ground-state iodine atoms. 相似文献
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Eileen Ryan Catherine Quynh Nhu Nguyen Christopher Shiea Gavin E. Reid 《Journal of the American Society for Mass Spectrometry》2017,28(7):1406-1419
Sphingolipids serve not only as components of cellular membranes but also as bioactive mediators of numerous cellular functions. As the biological activities of these lipids are dependent on their structures, and due to the limitations of conventional ion activation methods employed during tandem mass spectrometry (MS/MS), there is a recognized need for the development of improved structure-specific methods for their comprehensive identification and characterization. Here, positive-ionization mode 193 nm ultraviolet photodissociation (UVPD)-MS/MS has been implemented for the detailed structural characterization of lipid species from a range of sphingolipid classes introduced to the mass spectrometer via electrospray ionization as their lithiated or protonated adducts. These include sphingosine d18:1(4E), dihydrosphingosine (sphinganine) d18:0, sphingadiene d18:2(4E,11Z), the isomeric sphingolipids ceramide d18:1(4E)/18:0 and dihydroceramide d18:0/18:1(9Z), ceramide-1-phosphate d18:1(4Z)/16:0, sphingomyelin d18:1(4E)/18:1(9Z) the glycosphingolipids galactosyl ceramide d18:1(4E)/24:1(15Z) and lactosyl ceramide d18:1(4E)/24:0, and several endogenous lipids present within a porcine brain total lipid extract. In addition to the product ions formed by higher energy collision dissociation (HCD), UVPD is shown to yield a series of novel structurally diagnostic product ions resulting from cleavage of both sphingosine carbon–carbon and acyl chain carbon–carbon double bonds for direct localization of site(s) of unsaturation, as well as via diagnostic cleavages of the sphingosine backbone and N–C amide bond linkages. With activation timescales and dissociation efficiencies similar to those found in conventional MS/MS strategies, this approach is therefore a promising new tool in the arsenal of ion activation techniques toward providing complete structural elucidation in automated, high-throughput lipid analysis workflows. 相似文献
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Tyrosine phosphorylation and sulfation play many key roles in the cell. Isobaric phosphotyrosine and sulfotyrosine residues
in peptides were determined by mass spectrometry using phosphatase or sulfatase to remove the phosphate or the sulfate group.
Unique Br signature was introduced to the resulting tyrosine residues by incubation with 32% HBr at −20 °C for 20 min. MS/MS
analysis of the brominated peptide enabled unambiguous determination of the phosphotyrosine and the sulfotyrosine sites. When
phosphotyrosine and sulfotyrosine as well as free tyrosine were present in the same peptide, they could be determined simultaneously
using either phosphatase or sulfatase following acetylation of the free tyrosine. 相似文献
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近年来,以RDX为代表的痕量爆炸物检测已经是反恐斗争和国土安全领域的重要课题[1]。本实验将醋酸作为辅助试剂直接添加到待分析水样中,采用电喷雾电离直接进样,在正离子检测模式下,建立了直接快速测定水样中衡量RDX的电喷雾质谱分析方法。在样品流量为10.0μL/m in,喷雾电压为5.0 kV,毛细管温度为200℃条件下获得的RDX的检出限为0.001μg/L,线性范围为0.005~100μg/L。对天然湖水、矿泉水和自来水中添加的衡量RDX的回收率分别在92%~108%之间。单个样品分析(含串联质谱分析)所需时间不超过2 m in。 相似文献
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Dr. Javier Sastre Toraño Dr. Oier Aizpurua-Olaizola Na Wei Dr. Tiehai Li Dr. Luca Unione Dr. Gonzalo Jiménez-Osés Dr. Francisco Corzana Dr. Victor J. Somovilla Dr. Juan M. Falcon-Perez Prof. Dr. Geert-Jan Boons 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(6):2149-2154
Glycans possess unparalleled structural complexity arising from chemically similar monosaccharide building blocks, configurations of anomeric linkages and different branching patterns, potentially giving rise to many isomers. This level of complexity is one of the main reasons that identification of exact glycan structures in biological samples still lags behind that of other biomolecules. Here, we introduce a methodology to identify isomeric N-glycans by determining gas phase conformer distributions (CDs) by measuring arrival time distributions (ATDs) using drift-tube ion mobility spectrometry-mass spectrometry. Key to the approach is the use of a range of well-defined synthetic glycans that made it possible to investigate conformer distributions in the gas phase of isomeric glycans in a systematic manner. In addition, we have computed CD fingerprints by molecular dynamics (MD) simulation, which compared well with experimentally determined CDs. It supports that ATDs resemble conformational populations in the gas phase and offer the prospect that such an approach can contribute to generating a library of CCS distributions (CCSDs) for structure identification. 相似文献
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建立了实时直接分析-四极杆飞行时间质谱(DART-QTOF-MS)技术结合化学计量学分析快速鉴别油茶籽油的方法。4种食用油(油茶籽油、菜籽油、花生油和大豆油)用甲醇-异丙醇(50∶50,含5 mmol/L乙酸铵)稀释后经实时直接分析离子源解吸电离,在正离子模式下以TOF MS和信息依赖采集模式获得质谱数据,对4种食用油的质谱图进行了初步鉴定,并采用化学计量学建立主成分分析(PCA)和正交偏最小二乘法-判别分析(OPLS-DA)模型,以实现数据可视化和油茶籽油的快速鉴别。结果表明,4种食用油的质谱图存在明显差异,主要为甘油三酯(TAG)氨加合离子[TAG+NH4]+(m/z 850~1 100)、甘油二酯(DAG)氨加合离子[DAG+NH4]+(m/z 600~700)和DART源内碎片离子,共检出20种甘油三酯和6种甘油二酯。进一步采用化学计量学对4种植物油指纹图谱进行分析,发现该方法可准确鉴别和预测油茶籽油、菜籽油、花生油和大豆油,具有前处理简单、分析速度快、操作方便和准确可靠等优点,可用于油茶籽油的鉴别研究。 相似文献
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The determination of rosiglitazone in dietary supplements by direct analysis in real-time mass spectrometry normally provides low repeatability. The [M+H]+ signal sharply decreased in the presence of strong-base and weak-acid ionic compounds because rosiglitazone decomposition occurred due to the hydrolysis of strong-base and weak-acid anions. The repeatability was improved and the influence of ionic compounds was minimized by the use of pioglitazone as an internal standard. Orbitrap mass spectrometry was used to provide high resolution in which isotopic interferences from M?+?1 of pioglitazone upon M of rosiglitazone were eliminated. This approach was used to determine rosiglitazone in tablet and dietary supplements in 1?min per sample. 相似文献
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采用激光解吸电离飞行时间质谱对富勒醇样品进行研究,并与富勒烯标准品的质谱特征比较,以正负离子模式联合检测方法考察其特征结构。结果显示,正离子模式下,富勒醇碳笼易为规律性的碎裂峰,负离子模式下,则保留碳笼主体结构的特征峰,而富勒烯的碳笼结构在两种模式下不发生变化。表明该方法可以方便、快速地鉴别富勒醇的结构。采用该方法对富勒醇在二甲基亚砜(DMSO)中的稳定性进行分析,结果发现富勒醇可稳定存在于DMSO溶剂中,用于碱式反应条件下合成富勒醇的鉴别与条件筛选,选择反应碱的最佳浓度为1.0 g/mL。 相似文献
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The fragmentation behavior of nitrated and S-nitrosylated peptides were studied using collision induced dissociation (CID)
and metastable atom-activated dissociation mass spectrometry (MAD-MS). Various charge states, such as 1+, 2+, 3+, 2–, of modified
and unmodified peptides were exposed to a beam of high kinetic energy helium (He) metastable atoms resulting in extensive
backbone fragmentation with significant retention of the post-translation modifications (PTMs). Whereas the high electron
affinity of the nitrotyrosine moiety quenches radical chemistry and fragmentation in electron capture dissociation (ECD) and
electron transfer dissociation (ETD), MAD does produce numerous backbone cleavages in the vicinity of the modification. Fragment
ions of nitrosylated cysteine modifications typically exhibit more abundant neutral losses than nitrated tyrosine modifications
because of the extremely labile nature of the nitrosylated cysteine residues. However, compared with CID, MAD produced between
66% and 86% more fragment ions, which preserved the labile –NO modification. MAD was also able to differentiate I/L residues
in the modified peptides. MAD is able to induce radical ion chemistry even in the presence of strong radical traps and therefore
offers unique advantages to ECD, ETD, and CID for determination of PTMs such as nitrated and S-nitrosylated peptides. 相似文献
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建立了液相色谱-串联质谱联用法(LC-MS/MS)同时检测辐照蛋白类功能食品中邻酪氨酸(o-Tyrosine)和间酪氨酸(m-Tyrosine)的分析方法。样品在氮气环境下经6 mol/L盐酸酸解过夜,酸解液再经氮气吹干,1 mL水复溶后,用Phenomenex Kinetex PFP色谱柱分离,以5 mmol/L乙酸铵溶液和甲醇为流动相进行梯度洗脱。质谱采用电喷雾负离子(ESI-)模式电离,多反应监测(MRM)模式检测,基质匹配标准溶液外标法定量。酪氨酸同分异构体与基质干扰峰得到良好的分离,在0.005~1.0 mg/L浓度范围内,其峰面积与浓度呈良好的线性关系,线性系数(r2)不低于0.999。在乳清粉和乳清蛋白粉中添加3种浓度水平的酪氨酸同分异构体,平均加标回收率为81.8%~98.2%,相对标准偏差(n=6)低于8.0%,方法定量下限(LOQ)和检出限(LOD)分别为5.0,8.0μg/kg和1.5,2.4μg/kg。将该方法应用于实际样品分析,表明辐照剂量与辐照蛋白类功能食品中o-Tyrosine和m-Tyrosine含量存在相关性,符合拟合多项式(r20.98)。该方法可对蛋白类功能食品是否经过辐照给予定性鉴定,从而为辐照蛋白类功能食品中辐照标志物的检测方法研究提供理论依据。 相似文献
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Vacuum Ultraviolet Free-Electron Laser Photoionization Mass Spectrometry of Alpha-pinene Ozonolysis 下载免费PDF全文
Xiangyu Zang Zhaoyan Zhang Chong Wang Tiantong Wang Huijun Zheng Hua Xie Jiayue Yang Dongxu Dai Guorong Wu Weiqing Zhang Gang Li Xueming Yang Ling Jiang 《化学物理学报(中文版)》2022,35(2):281-288
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The characterization of polymers by pyrolysis directly in the ion source of a double focusing magnetic sector mass spectrometer, operating in the chemical ionization mode, is described. Pyrolysis is achieved by two different probe techniques. A low temperature, slow heating rate direct insertion probe (DIP) is used at 400°C, and a specifically constructed high temperature, fast heating rate, high temperature pyrolysis (HTP) probe is used at 1000°C. This probe is capable of achieving pyrolysis temperatures of 1200°C at controlled heating rates up to 20,000°C/s. The mass spectrometric analysis of the pyrolysis products was achieved under chemical ionization (CI) conditions utilizing methane, isobutane, and ammonia as reagent gases. Under CI conditions the molecular ions formed in the mass spectrometer show little tendency to fragment. The CI mass pyrograms are very simple, with each peak in the spectra ascribable to a particular component in the pyrolysis product mixture. The results of the two probe pyrolysis techniques are compared and the utility of each technique for the characterization of polymers is demonstrated using the vinyl polymers polymethyl methacrylate, polyvinyl chloride, and polystyrene. 相似文献
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采用电喷雾-离子阱-飞行时间串联质谱(ESI-IT-TOF)技术, 在正/负离子检测模式下对芒柄花素及其同分异构体7-甲氧基异黄酮的质谱裂解规律进行了系统研究. 实验结果表明, 该化合物在正、负离子模式下均得到了5级高分辨质谱. 结果显示, 二者在负离子模式下的碎片相同, 而在正离子模式下的碎片裂解不同. 根据正负离子模式的5级高分辨质谱推导了两者的可能裂解规律, 丰富了异黄酮的ESI-MSn数据, 为其它异黄酮类化合物的分析鉴定提供了有效的质谱方法. 相似文献
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利用同步辐射真空紫外光电离结合飞行时间质谱对五氟乙烷(CHF2CF3)进行了光电离光解离的研究,测定了CHF2CF3的电离势及该分子主要碎片离子的出现势. 结果表明: CHF2CF3的绝热电离势为(12.25±0.10) eV, 主要碎片离子有CF2CF3+、CHFCF3+、CF2CF2+、CF3+、CHF2+、CHF+和CF+,其出现势分别为 (13.93±0.10) eV, (15.25±0.10) eV, (15.12±0.10) eV, (13.30±0.05) eV, (13.05±0.08) eV, (19.17±0.10) eV和 (19.56±0.15) eV. 另外,用从头算分子轨道理论计算了解离电离过程中所有碎片的总能量,并给出了电子态及对称性. 根据实验结果和理论计算,分析了可能的解离通道,并得到了分子及母体离子的键解离能等重要的热力学数据. 相似文献