谱图检索结合二级质谱定性分析烟草中挥发性成分

采用同时蒸馏萃取法提取烟叶中的挥发性成分,利用气相色谱-质谱联用仪(GC-MS)分离测定,通过谱库检索和匹配度定性结合色谱保留指数方法鉴定烟叶中挥发性成分,并引入离子阱二级质谱对谱库检索匹配度差距小、含量低,背景干扰大的物质准确定性.采用谱图检索结合二级质谱定性共鉴定144个化合物,其中104个化合物在烟草挥发性成分的文献中已有报道,报道中有9个化合物是通过二级质谱定性,其余40个化合物还未见报道.结果表明,离子阱二级质谱定性的引入提高了对未知化合物定性的准确性和可靠性,适合于烟叶这类复杂植物体系的化学组分研究.     

新型含氟液晶类化合物的质谱研究

本文报道66个新型含氟液晶类化合物的电子轰击电离质谱(EIMS). 66个化合物分为三个类型, 即炔醚类, 炔酯类和炔类. 并利用MS/MS联用技术和高分辨质谱(HRMS)数据研究了三种不同类型化合物的裂解机理, 并总结其规律性, 结果将有助于未知的类似化合物的结构鉴定 .     

芍药苷的电喷雾串联质谱研究

采用电喷雾串联质谱(ESI-MSn)技术, 结合H/D交换方法, 在正、负离子检测模式下对白芍药材中主要成分芍药苷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较好的质谱信息, 且在正离子模式下, 电喷雾质谱分析的灵敏度更高. 同时获得了其质谱裂解规律, 为白芍中其它化合物的分析鉴定提供了有效的质谱方法.     

N-苯乙烯基糖精的质谱研究

本文对N-苯乙烯基糖精在70eV电子束轰击下质谱的裂解规律进行了研究.这类化合物都有较强的分子离子峰,大部分是基锋,[M-HSO~2]^+是它们的特征碎片.实验证明,糖精母体的SO~2有可能和苯环邻位H或取代基苯环上的H络合而消去HSO~2.当苯乙烯基邻位取代基为NO~2时,由于硝基氧的迁移,使质谱上的m/z119成为基峰.     

刺五加叶中黄酮类化合物的结构鉴定

利用电喷雾质谱发现刺五加叶中存在4种黄酮类化合物,进一步分离得到其中的两种,经核磁质谱鉴定,一种为槲皮甙(槲皮素－3－O－α－L－鼠李糖),另一种为金丝桃甙(槲皮素－3－O－β-D－半乳糖).其余两种难以分离的黄酮甙经电喷雾多级串联质谱分析,初步推断为槲皮素和芦丁(槲皮素－3-O－芦丁糖).以上4种均为黄酮醇类化合物,除金丝桃甙外,其它3种为刺五加叶中尚未见报道的黄酮类成分.     

有机锡化合物的电喷雾电离质谱

报道了一系列有机锡ＲＲＰ（Ｓ）ＳＳｎ（Ｃｙ）３化合物的电喷雾电离质谱（ＥＳＩ－ＭＳ）及碰撞诱导解离质谱（ＣＩＤ－ＭＳ）,总结了其谱图特征,讨论了其碎裂机理,为该类化合物的鉴定提供了依据。     

反应质谱及其在有机立体化学中的应用

从手性检测、差向异构体的区分、赤式、苏式异构体的区分、取代苯的鉴定、绝对构型的测定、确定甾体化合物3位羟基的键型和取代烯的立体化学分析七个方面介绍了反应质谱在立体化学中的应用,列出了若干种化合物的RMS相对丰度值。     

中国雪参挥发油成分的色谱—质谱分析

本文测定了中国雪参根中人参挥发油的含量，并用色谱－质谱联用仪分析了化学成分及百分含量。从中分离出１３２种化合物，初步鉴定出４９种，占挥发油总量的８７．７３％，有２８种化合物尚未见报道。     

双取代环戊二烯基卤化钼（Ⅳ）及钨（Ⅳ）化合物质谱

报道了一系列双环戊二烯基二卤化钼（Ⅳ）及钨（Ⅳ）化合物在７０ｅＶ电离能量下的电子轰击质谱（ＥＩ）及以甘油作底物的快原子轰击质谱（ＦＡＢ），分别总结了其谱图特征，讨论了其碎裂机理，为这类化合物结构鉴定提供了依据。     

海绵Rhaphisisa pallida Ridley中甾类成分的质谱分析

介绍了南沙海域采集的ＲｈａｐｈｉｓｉａｐａｌｌｉｄａＲｉｄｌｅｙ海绵样品中分离得到的混合甾类样品，采用气相色谱－质谱法鉴定其组分，应用质谱裂解规律结合计算机检索确定了十一种甾体化合物的结构，其中两个是首次在海绵生物中发现的甾体激素化合物。     

Simultaneous determination of ginsenoside Rb1, ginsenoside Rg1, paeoniflorin,albiflorin and oxypaeoniflorin in rat plasma by liquid chromatography–tandem mass spectrometry: Application to a pharmacokinetic study of wen‐Yang‐Huo‐Xue soft capsule

A simple and sensitive HPLC–MS/MS method was developed and fully validated for simultaneous determination of ginsenoside Rb1, ginsenoside Rg1, paeoniflorin, albiflorin and oxypaeoniflorin in rat plasma. Plasma samples were pretreated with protein precipitation using acetonitrile. The chromatographic separation was carried out on a C₁₈ column with a gradient mobile phase consisting of acetonitrile and water (containing 0.1% formic acid). All analytes and digoxin (internal stand, IS) were quantitated through electrospray ionization in negative ion multiple reaction monitoring mode. All calibration curves exhibited good linearity (r > 0.9960) over a wide concentration range for all components. The intra‐day and inter‐day precisions (RSD) at three different levels were all <12.0% and the accuracies (RE) ranging from −6.1 to 6.2%. The extraction recoveries of the five compounds ranged from 89.2 to 97.1%. The validated method was successfully applied in a comparative pharmacokinetic study of Wen‐Yang‐Huo‐Xue soft capsule (WYHXSC) in rats. Compared with single pure component, the exposure of the investigated components, except for oxypaeoniflorin, increased after oral administration of WYHXSC in rats, which suggested a synergistic effects between the herbs in the WYHXSC preparations.     

药物泰瑞沙的质谱分析及其未知杂质的结构解析

利用气相色谱-质谱法在电子电离源下对用于治疗肺癌的药物泰瑞沙(Tagrisso)进行分析,对主成分奥斯替尼(Osimertinib)在质谱中产生的主要的碎片离子进行归属,推测其可能的质谱裂解途径。参考主成分奥斯替尼的质谱裂解方式,由质谱裂解机理的角度出发对该药物中的4个未知的关键杂质的结构进行有效解析。此外,发现奥斯替尼及其个别杂质在质谱裂解过程中出现了显著的违背偶电子规则的碎片离子。通过对药物泰瑞沙的质谱分析期望能够提供一些分析、解析药物中未知杂质的思路和方法。     

Determination of three bioactive constituents in moutan cortex by capillary electrophoresis with electrochemical detection.

Capillary electrophoresis with electrochemical detection has been employed for the separation and determination of the three active constituents (paeonol, benzoyloxypaeoniflorin, and oxypaeoniflorin) in traditional Chinese medicine, Moutan Cortex (root cortex of Paeonia suffruticosa Andrews). The effects of several important factors, such as the concentration of running buffer, the separation voltage, the injection time, and the detection potential, were investigated to determine the optimum conditions. The detection electrode was a 300 microm diameter carbon-disc electrode at a working potential of +0.90 V (versus SCE). The three analytes could be well separated within 7 min in a 40 cm length fused-silica capillary at a separation voltage of 12 kV in a 50 mM borate buffer (pH 9.2). The relation between the peak current and the analyte concentration was linear over 3 orders of magnitude with detection limits (S/N = 3) ranging from 0.4 to 0.7 microM for all analytes. The proposed method has been successfully applied to the determination of paeonol, benzoyloxypaeoniflorin, and oxypaeoniflorin in real plant samples with satisfactory assay results.     

Monoterpene Glycosides from the Roots of Paeonia lactiflora

The roots of Paeonia lactiflora Pall. is one of the most important traditional Chinese medicines, which has been used for the treatment of dizziness, spasm, menstrual disorder, spontaneous and night sweating, and as a general analgesic1. Chemical constitu…     

High resolution end group determination of low molecular weight polymers by matrix-assisted laser desorption ionization on an external ion source fourier transform ion cyclotron resonance mass spectrometer

Matrix-assisted laser desorption ionization was performed on an external ion source Fourier transform ion cyclotron resonance mass spectrometer equipped with a 7-T superconducting magnet to analyze end groups of synthetic polymers in the mass range from 500 to 5000 u. Native, perdeutero methylated, propylated, and acetylated polyethylene glycol and polyvinyl pyrrolidone with unknown end-group elemental composition were investigated in the mass range up to 5000 u by using a 2,5-dihydroxybenzoic acid matrix. A small electrospray setup was used for the deposition of the samples. Two methods to process data were evaluated for the determination of end groups from the measured masses of the component molecules in the molecular weight ranges: a regression method and an averaging method. The averaging method is demonstrated to allow end-group mass determinations with an accuracy within 3 mu for the molecular weight range from 500 to 1400 and within 20 mu for the molecular weight range from 3400 to 5000. This is sufficient to identify the elemental composition of end groups in unknown polymer samples.     

A simple radioisotope X-ray fluorescence method for provenance studies of archaeological ceramics employing principal component analysis

A simple radioisotope X-ray fluorescence method of 1000 s irradiation of the samples by a ¹⁰⁹Cd source combined with principal component analysis is described for determining the relative mass fractions of trace elements in majolica ceramics for provenance classification. Six provenances from Europe using 29 samples as standards and 12 unknown samples were investigated and characterized using selected trace elements as the variables. The unknown samples were previously assigned, but not definitively, by stylistic analysis and/or thermoluminescence measurements to the provenances of Teruel (Spain) and Holland. Because of a moderate fluorescence time, only the four net peak intensities of Pb, Rb, Sr and Zr could be used as variables. We have also studied the effect of not including the Pb variable, since the clay matrixes could have been contaminated in the glazing process or when the Pb-Sn enamel was removed. It is shown in both cases that the results were more consistent with the stylistic analysis and thermoluminescence measurements when the Pb concentration variable was not considered. A comparison of principal component analysis employing the three elements was similar to plotting of the relative mass fractions on a triangle graph.     

Sequence Elucidation of an Unknown Cyclic Peptide of High Doping Potential by ETD and CID Tandem Mass Spectrometry

Identification of an unknown substance without any information remains a daunting challenge despite advances in chemistry and mass spectrometry. However, an unknown cyclic peptide in a sample with very limited volume seized at a Pennsylvania racetrack has been successfully identified. The unknown sample was determined by accurate mass measurements to contain a small unknown peptide as the major component. Collision-induced dissociation (CID) of the unknown peptide revealed the presence of Lys (not Gln, by accurate mass), Phe, and Arg residues, and absence of any y-type product ion. The latter, together with the tryptic digestion results of the unusual deamidation and absence of any tryptic cleavage, suggests a cyclic structure for the peptide. Electron-transfer dissociation (ETD) of the unknown peptide indicated the presence of Gln (not Lys, by the unusual deamidation), Phe, and Arg residues and their connectivity. After all the results were pieced together, a cyclic tetrapeptide, cyclo[Arg-Lys-N(C₆H₉)Gln-Phe], is proposed for the unknown peptide. Observations of different amino acid residues from CID and ETD experiments for the peptide were interpreted by a fragmentation pathway proposed, as was preferential CID loss of a Lys residue from the peptide. ETD was used for the first time in sequencing of a cyclic peptide; product ions resulting from ETD of the peptide identified were categorized into two types and named pseudo-b and pseudo-z ions that are important for sequencing of cyclic peptides. The ETD product ions were interpreted by fragmentation pathways proposed. Additionally, multi-stage CID mass spectrometry cannot provide complete sequence information for cyclic peptides containing adjacent Arg and Lys residues. The identified cyclic peptide has not been documented in the literature, its pharmacological effects are unknown, but it might be a “designer” drug with athletic performance-enhancing effects.     

Weighted two-band target entropy minimization for the reconstruction of pure component mass spectra: Simulation studies and the application to real systems

A method is proposed, on the basis of a recently developed algorithm--Band Target Entropy Minimization (BTEM)--to reconstruct mass spectra of pure components from mixture spectra. This method is particular useful in dealing with spectral data with discrete features (like mass spectra). Compared to the original BTEM, which has been applied to differentiable spectroscopies such as Fourier-transfer infrared spectroscopy (FTIR), ultraviolet (UV), Raman, and nuclear magnetic resonance (NMR), the latest modifications were obtained through: (1) Reformulating the objective function using the peak heights instead of their derivatives; (2) weighting the abstract vector VT to reduce the effect of noise; (3) using a two-peak targeting strategy (tBTEM) to deal with strongly overlapping peaks; and (4) using exhaustive search to locate all the component spectra. A set of 50 multi-component mass spectra was generated from ten reference experimental pure component spectra. Many of the compounds chosen have common MS fragments and therefore, many of the pure component spectra have considerable intensity in same data channels. In addition, a set of MS spectra from a real system with four components was used to examine the newly developed algorithm. Successful reconstruction of the ten component spectra of the simulated system and the four component spectra of the real system was rapidly achieved using the new tBTEM algorithm. The advantages of the new algorithm and its implication for rapid system identification of unknown mixtures are readily apparent.     

Quality evaluation of cortex moutan by high performance liquid chromatography coupled with diode array detector and electrospary ionization tandem mass spectrometry

An high performance liquid chromatography (HPLC) coupled with diode array detector (DAD) and electrospray ionization tandem mass spectrometry (ESI/MS(n)) method was developed for quality evaluation of Cortex Moutan through identification of common constituents based on chromatographic fingerprints and determination of key pharmacological compounds. The representative chromatographic fingerprints of Cortex Moutan were obtained by analyzing 10 batches of samples under the optimized HPLC conditions and the results showed that the chromatographic profiles of the analyzed samples were very similar. Total of nineteen common peaks were detected and seventeen of them were identified rapidly by their characteristic UV profile and the information of molecular structure provided by ESI/MS(n) experiments. Simultaneously, five key pharmacological compounds, namely gallic acid, oxypaeoniflorin, paeoniflorin, benzoylpaeoniflorin and paeonol, were determined by the validated HPLC-DAD method. The linear calibration curves were acquired with correlation coefficients higher than 0.999. The precisions of intra-day and inter-day were not exceeding 3.1%, and the recoveries of five analytes were from 92.86 to 99.35%. This developed method that combined the chromatographic fingerprints and quantification assay ensured the phytoequivalence and pharmacological effects of Cortex Moutan and was successfully applied to the quality control of Cortex Moutan.     

A correlation method in library search

The identification of unknown pure compounds or mixtures by means of mass spectral library search can be improved by partly resolving the spectra of the individual components within the spectrum of the measured unknown. This is accomplished by investigating sequential spectra in series of spectra; masses with highly correlating sequential intensities are clustered into individual groups. On the assumption that correlated masses belong to the same component spectrum, a filtering algorithm is developed to exclude spectra of non-identical compounds. The basic ideas, methods, examples and experiences gained with applications are reported.