2—羟基—4—邻苯二甲酰亚胺基丁酸的氢迁移反应

在甲烷为反应气的化学电离质谱条件下，质子化的２－羟基－４－邻苯二甲酰亚胺基丁酸的单分子质谱碎裂产生了ｍ／ｚ１４８的碎片离子，表明其碎裂过程发生了氢迁移反应，ＡＭ在分子轨道的理论计算结果为可能的质子化位置提供了理论依据；建立在氘代同位素标记和碰撞诱导解离实验的基础上，我们提出此离子的形成可能同时存在单氢迁移和双氢迁移，一些质谱图中的物征碎片中离子为可能的ＭｃＬａｆｆｅｒｔｙ重排和离子／中性（碎片）复     

2,5—双（4—羟基苯亚甲基）环戊酮中双电荷离子存在的串联质谱证据

应用串联质谱的碰撞诱导解离和联动扫描技术，研究了２，５－双（４－羟基苯亚甲基）环戊酮的质谱解离特征，提供了双电荷离子存在的实验证据。进一步对双电荷离子（ｍ／ｚ１４６）的碰撞诱导解离碎裂进行了讨论。     

两种氨基酸中[MH-CO2H2]+的特征质谱碎裂

运用低能碰撞诱导解离（ＣＩＤ）研究了电子轰击（ＥＩ）、快原子轰击（ＦＡＢ）电离条件下质子化亮氨酸与异亮氨酸解离产生亚稳离子「ＭＨ－ＣＯ２Ｈ２」的单分子质谱破裂，二种异构体呈现出了各自不同的解离特征，根据ＣＩＤ的特征碎片离子和氘代同位素标记实验，提出了其破裂过程的存在离子／中性（碎片）复合物中间体机理，并对有关的特征离子的形成进行了讨论。     

气相中甲苯离子-分子反应产物的串联质谱研究

应用碰撞诱导解离技术, 研究了甲苯自身化学电离条件下离子-分子反应产物离子m/z 182和184的碰撞诱导解离(CID)反应特性。m/z183和184离子碎裂反应具有多种过渡态结构, 如二苯基甲烷衍生物结构、卓翁离子与甲苯形成的共价键结构、甲苯自由基离子与甲苯分子形成的π-配合物结构和苄基离子与甲苯形成的π-配合物结构。     

丙硫咪唑的离子／中性碎片复合物中间体质谱破裂

报道了丙硫咪唑（５－丙硫基－苯并咪唑－２氨基甲酸酯）的电子轰击质谱。利用串联质谱的低能碰撞诱导解离（ＣＩＤ）技术研究了此化合物的单分子解离，并提出了可能的离子／中性碎片复合筘间体碎裂机理，用来解释在质谱碎裂过程中出现的氢迁移（尤其是远距离的氢迁移）现象。     

四卤合金属酸十八铵的X射线光电子能谱和质谱研究

利用Ｘ射线光电子能谱（ＸＰＳ）、质谱（ＭＳ）方法分别研究了１５种四卤合金属酸十八铵化合物。通过ＸＰＳ讨论了这些化合物的金属、卤素、氮原子的核心结合能的化学位移。根据Ｐａｕｌｉｎｇ电负性讨论了这些数据和计算电荷的关系。讨论了配位体Ｘ（Ｃｌ、Ｂｒ、Ｉ）、中心离子Ｍ（Ｚｎ、Ｃｏ、Ｃｕ、Ｍｎ、Ｃｄ）和质子化十八胺Ｃ１８Ｈ３７ＮＨ＋３的关系。通过ＭＳ讨论了在电子轰击、化学电离条件下，四碘合钴酸十八铵、四氯合钴酸十八铵加热分解产生的Ｃ１８Ｈ３７ＮＨ＋３（ｍ／ｚ２７０）离子碰撞诱导解离谱（ＣＩＤＭＳ）。通过低碰撞能量范围（０～１０ｅＶ），多次碰撞条件下观察到的远电荷碎裂反应，得出该离子比直接由正十八胺质子化得到的离子具有较高的内能     

两种氨基酸中[MH-CO_2H_2]~ 的特征质谱碎裂

运用低能碰撞诱导解离（CID）研究了电子轰击（EI）、快原子轰击（FAB）电离条件下质子化亮氨酸与异亮氨酸解高产生亚稳离子［MH－CO2H2］＋的单分子质谱碎裂，二种异构体呈现出了各自不同的解离特征，根据CID的特征碎片离子和氘代同位素标记实验，提出了其碎裂过程存在离子／中性（碎片）复合物中间体碎裂机理，并对有关的特征离子的形成进行了讨论．     

气相中卤代苯离子-分子反应产物的串联质谱研究

应用碰撞诱导解离技术研究了氯代苯、溴代苯和碘代苯离子-分子反应产物的碎裂反应特性,与联苯的分子离子和质子化溴代联苯的碰撞诱导解离谱比较获得了产物离子的结构信息.     

氯代甲苯异构体双电荷离子电子捕获诱导解离谱研究

研究了４种Ｃ７Ｈ７Ｃｌ异构体在７０ｅＶ电子轰击下产生的［Ｃ７Ｈ７Ｃｌ］＾２＋、［Ｃ７Ｈ６Ｃｌ］＾２＋．和［Ｃ７Ｈ５Ｃｌ］＾２＋ ３种双电荷离子的电子捕获诱导解离（ＥＣＩＤ）反应。分子离子的ＥＣＩＤ反应明显的邻位效应，表明其结构仍保持中性分子的结构特征；而由各异构体产生的［Ｃ７Ｈ６Ｃｌ］＾２＋．和［Ｃ７Ｈ５Ｃｌ］＾２＋离子异构化成同一结构。３种双电荷离子ＥＣＩＤ反应的产物与离子所带电子的奇偶性有关，     

一些双官能团苯基醚化合物的离子／中性复合物中间体质谱碎裂

报道了３种含双官能团苯基醚化合物２－（２，６－二氯苯氧基）丙腈，Ｎ－羟基－４－丁基苯乙酰胺，２－（１－甲基乙氧基）苯酚甲氨基酸甲酸酯的电子轰击质谱破裂，用亚稳分析和低能碰撞诱导解离子研究了３种化合物的分子离子碎裂规律，除简单的直接键断裂外，还证实经历了离子／中性（碎片）复合物中间体的单分子解离反应同时存在的竞争机理，解释了观察到分子内单氢迁移，双氢迁移现象。     

An automatic reaction control chemical ionization technique in ion trap detector for quantitative plasma profding of arecoline in treated alzheimer patients

An automatic reaction control chemical ionization technique in an ion trap detector (lTD) was used to quantitate the levels of the cholinergic drug, arecoline, in plasma of treated patients with Alzheimer’s disease. The chemical ionization reaction was carried out with acetonitrile. The protonated molecules of arecoline (m I z 156) and the internal standard, homoarecoline (m / z 170), were monitored. Human plasma samples were extracted with a readily evaporable solvent mixture, the residues reconstituted and injected along with a tertiary amine-carrier into a capillary gas chromatograph interfaced with the ITD. Standard curves for plasma-extracted arecoline between 20-ng/mL and 156-pg/mL levels were linear (r> 0.9980). Satisfactory precision (relative standard deviation < 20%) and accuracy (relative error < 15%) at the limit of quantitation, 156 pg/mL arecoline, were achieved. Optimal conditions for handling of blood samples obtained by venipuncture were determined. The assay was successfully applied for the therapeutic monitoring of Alzheimer patients treated intravenously with arecoline.     

Analysis of triacetone triperoxide by gas chromatography/mass spectrometry and gas chromatography/tandem mass spectrometry by electron and chemical ionization

The explosive triacetone triperoxide (TATP) has been analyzed by gas chromatography/mass spectrometry (GC/MS) and sub-nanogram detection limits are reported by ammonia positive ion chemical ionization (PICI), electron ionization (EI) and methane negative ion chemical ionization (NICI). Analysis by methane PICI and ammonia NICI gave detection limits in the low nanogram range. Analyses were carried out on (linear) quadrupole and ion trap instruments. Analysis of TATP by PICI using ammonia reagent gas is the preferred analytical method, producing low limits of detection as well as an abundant (greater than 60% of base peak) diagnostic adduct ion at m/z 240 corresponding to [TATP + NH4]+. Isolation of the [TATP + NH4]+ ion with subsequent collision-induced dissociation (CID) produces extremely low abundance product ions at m/z values greater than 60, and the m/z 223 ion corresponding to [TATP + H]+ was not observed. Density functional theory (DFT) calculations at the B88LYP/DVZP level indicate that dissociation of the complex to form NH4+ and TATP occurs at energies lower than peroxide bond dissociation, while protonation of TATP leads to cleavage of the ring structure. These results provide a method for pico-gram detection levels of TATP using commercial instrumentation commonly available in forensic laboratories. As a point of comparison, a detection limit of 15 ng was obtained by flame ionization detection.     

Fast determination of the total free resveratrol content in wine by direct-exposure-probe, positive-ion chemical ionization and collision-induced-dissociation mass spectrometry

In the present work, a fast method has been developed for the determination of total free resveratrol in wine extracts by positive-ion chemical ionization using methane as reagent gas and direct introduction of the sample into the mass spectrometer. Quantitative analysis is performed using 4',5,7-trihydroxyflavone as internal standard, by recording the product ions at m/z 135 for resveratrol and m/z 153 for the internal standard, both generated by collision-induced dissociation experiments on the related [M+H](+) ions. The method showed sufficient repeatability and satisfactory linearity in the range of concentration studied. Alternatively, because of the marked effect of matrices on the compounds released in the vaporization step, quantitative analysis was performed by addition of standard resveratrol to the sample, and the total free resveratrol content extrapolated from the calibration curve. Calibration curves for three different wine extracts had correlation coefficients between 0.91 and 0.99, and total free resveratrol contents between 11.8 and 17.2 mg/L were found. This method enabled us to determine the resveratrol-potential of wine within a few minutes, thereby overcoming the time- and solvent-consuming procedures needed for chromatographic methods.     

Electron-impact and chemical ionization detection of nicotine and cotinine by gas chromatography-mass spectrometry in rat plasma and brain.

Nicotine and its metabolite, cotinine, were measured in rat plasma and brain by gas chromatography-mass spectrometry. Both agents were extracted from plasma and brain, separated on a capillary column, and quantified by single-ion monitoring. The major fragment ions of nicotine and cotinine at m/z 84 and m/z 98, respectively, were monitored by electron-impact ionization detection and the protonated molecular ions at m/z 163 and m/z 177, respectively, were monitored by chemical ionization detection. Both compounds were quantified using deuterium-labeled nicotine and cotinine, respectively, as internal standards.     

Determination of calcium acetylhomotaurinate in human plasma and urine by combined gas chromatography-negative-ion chemical ionization mass spectrometry

A highly sensitive and specific assay has been developed for the determination of calcium acetylhomotaurinate and the internal standard (LM 3041) at the picomole level in human plasma and urine by gas chromatography-mass spectrometry with methane as the reagent gas. After a multiple-step extraction process, the cleaned-up organic extract was derivatized with pentafluorobenzoyl chloride at ambient temperature. Subsequently, chlorination followed by amidation of the sulphonic acid group led to the N-pentafluorobenzoyl di-n-butylamide derivatives. The mass spectrometer was set to monitor the abundant [M - HF]- ions (m/z 424 and 438), which were generated in the ion source switched in the negative-ion chemical ionization mode. This assay required 1 ml of plasma or 50 microliters of urine, and the detection limit was 1 ng/ml. The accuracy of the assay was tested day by day with quality control specimens spiked blind to the analyst. The mean difference between the theoretical and actual values was less than 8%.     

Mass spectrometric study of persistent acid metabolites of nonylphenol ethoxylate surfactants

A mass spectrometric study was carried out on two nonylphenoxycarboxylic acids, NP1EC and NP2EC (where 1 and 2 indicate the number of ethoxylate units attached to the nonylphenoxy moiety), that are persistent metabolites of widely used nonionic surfactant nonylphenol ethoxylates. In a gas chromatographic/mass spectrometric (GC/MS) study of the methyl esters of NP1EC and NP2EC, two series of fragment ions were observed in electron ionization (EI) mass spectra; m/z (179 + 14n, n = 0-7) and m/z (105 + 14n, n = 0-4) for NP1ECMe and m/z (223 + 14n, n = 0-7) and m/z (107 + 14n, n = 0-5) for NP2ECMe. Similarity indices were used to compare quantitatively the mass spectra of isomers. The mass spectra of two isomers were found to be similar whereas those of the remaining isomers were readily distinguishable from each other. The abundant fragment ions of the two NPECMes were investigated further by GC/MS/MS; product ions resulting from cleavage in the alkyl moiety, cleavage in the ECMe moiety and cleavage in both moieties were detected. Possible structures of the nonyl groups in the two esters were inferred. GC/chemical ionization (CI) mass spectra of the NPECMes with isobutane as reagent gas showed characteristic hydride ion-abstracted fragment ions shifted by 1 Da from those in the corresponding EI mass spectra. The sensitivity of a selected ion monitoring quantitation method for the NPECMes is enhanced under CI conditions compared with that under EI conditions. With electrospray ionization MS/MS, [M - H](-) ions of NP1EC (m/z 277) and NP2EC (m/z 321) were observed and, upon collision-induced dissociation of [M - H](-) of each of the two acids, fragment ions of m/z 219 corresponding to deprotonated nonylphenol, were observed in each case. Based on this observation, a rapid, simple and reliable selected product ion quantitation method is proposed for NP1EC and NP2EC.     

Ion trap mass spectrometry of trimethylsilylamides following gas chromatography

Fatty acid amides are a class of compounds with newly discovered biological activity. The ion trap mass spectrometric characteristics of silylated fatty acid amides were examined. Silylation of primary fatty acid amides is required prior to gas chromatography owing to thermal instability of the underivatized compound. The trimethylsilylated amides do not yield a molecular ion under normal electron ionization conditions (70 eV). With methane as a chemical ionization gas, the [M+H]+ ion appears. The [M+H]+ ion also appears when the helium buffer gas pressure is increased in the ion trap. There are three fragments other than the [M+H]+ peak that are predominant in the ion trap mass spectra of these compounds. Two of the fragments have been reported previously, namely the m/z 59 and the [M-71]+ fragments. The fragment of m/z 72 was identified and is the result of a rearrangement. Isotopic labeling was used to confirm fragment identity and the composition of the rearrangement products. Fragmentation patterns were affected by the amide chain length and concentration.     

甲基羟基铀酰离子与水的复分解反应

以醋酸铀酰为主要试剂, 在负离子检测模式下, 采用电喷雾串联质谱法制备了甲基羟基铀酰负离子. 实验发现, 气相中的甲基羟基铀酰离子与水分子发生分子离子复分解反应, 并用串联质谱法对反应产生的离子性产物进行了结构确认, 提出了反应的可能机理. 热力学计算结果表明, 该反应的ΔGReaction为-473.0 kJ/mol, ΔHReaction为-236.5 kJ/mol, ΔSSystem为0.792 kJ·mol-1·K-1. 该反应的速率常数为2.26 s-1.     

Electrospray and chemical ionization mass spectrometry of di-n-butyl sulfate. Unimolecular chemistry of its protonated form and quantification method by liquid chromatography/electrospray ionization tandem mass spectrometry

Di-n-butyl sulfate (DNBS) has been studied by electrospray (ESI) and chemical (CI) ionization mass spectrometry. The use of methanol as solvent in electrospray ionization allows observation of relatively abundant [DNBS + CH(3)OH + H](+) ions (m/z 243) which upon collision dissociate to [DNBS + H](+) ions (m/z 211). In both ESI and CI experiments, it is found that [DNBS + H](+) ions lead to m/z 113 daughter ions. The composition of this m/z 113 fragment ion and its mechanism of formation have been established by high resolution measurements and CID-MIKE experiments. An 'internal substitution' reaction involving an ion-neutral intermediate is proposed to explain the formation of a [C(8)H(17)](+) ion (m/z 113) by loss of a H(2)SO(4) molecule. Finally, a LC/ESI-MS/MS quantification method is proposed in which a detection limit of di-n-butyl sulfate in the ppm range is obtained. It is suggested that the quantification method might be extended to higher dialkyl sulfates. Copyright 2000 John Wiley & Sons, Ltd.