高效液相色谱-电喷雾离子阱质谱法分析6种氨基糖甙类抗生素

采用高效液相色谱-电喷雾离子阱质谱(HPLC-MSn)联用,分离和鉴定6种氨基糖甙类抗生素及其中的杂质,并探讨这6种结构相似的氨基糖甙类抗生素的质谱裂解规律。采用Agilent SB-C18(250 mm×4.6mm,5μm)色谱柱,流动相为0.05mol/L三氟乙酸溶液-甲醇(90∶10)和0.05 mol/L五氟丙酸溶液-甲醇(65∶35);在正离子检测方式下,用电喷雾离子阱质谱法对阿司米星、异帕米星、大观霉素、威替米星、奈替米星、西索米星及其杂质进行多级质谱分析。异帕米星、威替米星、奈替米星、西索米星及其杂质在二级质谱分析时,均可发生B环(脱氧链霉胺)与C环(氨基葡萄糖)之间的糖苷键断裂,生成脱去C环的碎片离子,并进一步发生A环(氨基葡萄糖)与B环之间的糖苷键断裂,生成A环或B环的碎片离子。鉴定了6种氨基糖甙类抗生素中7个杂质的结构。     

减肥产品中非法添加西布曲明类似物的ESI-MS/MS检测与确证

通过分析西布曲明和减肥类健康产品中未知化合物质谱图的质谱信息,由高分辨串联质谱获得裂解碎片离子的精密质量数,质谱软件给出碎片的可能组成,推测了西布曲明和未知化合物的质谱裂解途径,进而推测出该化合物的结构。并通过合成该结构的化合物,采用液相色谱-串联质谱法对样品作确证检验,证实样品中添加了新的西布曲明类似物。该实验提供了一种可用于检测和确证健康产品中非法添加合成药物未知类似物的方法。     

诊断离子技术在中药质谱分析中的应用

诊断离子是指在质谱碰撞过程中产生的能够代表某一类成分特征裂解行为的碎片离子。以诊断离子为基础,通过手动或自动过滤的方式对复杂中药样品中化学成分的结构类型进行快速判断、辅助化学成分的鉴定,是目前广泛采用的数据后处理方法。相比于质量亏损过滤、中性丢失过滤和分子网络等数据处理技术,诊断离子技术可以鉴定含有未知取代基的成分,且可在一定程度上消除大量杂质和共流出成分产生的干扰,在中药非靶向鉴定中具有独特的优势。该文对近十年来诊断离子技术在黄酮类、生物碱类、苯丙素类、酚酸类、萜类、甾体类等中药不同类型化学成分质谱鉴定中的应用进行总结,并对其后续发展进行了讨论和展望。     

天然产物的质谱智能解析研究

串联质谱在鉴定天然产物的分子结构方面起着重要的作用.每一类天然产物,在串联质谱中除有常规的质谱裂解方式外,通常还具有因特定骨架类型而产生的特征裂解.因此可以通过天然产物各类成分的特征质谱裂解所产生的特征碎片离子(diagnostic ions)来确认该类天然产物的结构类型,然后再由常规的裂解方式来推测其周边可能的取代基团.基于以上思路,我们设计并构建了一种天然产物质谱智能解析软件SmartMass.     

傅立叶变换离子回旋共振质谱法分析铝材封闭剂中的成分

该文采用傅立叶变换离子回旋共振质谱(FT-ICR-MS)技术,对一种铝材封闭剂(表面处理剂)中的未知成分进行了分析,发现了萘磺酸钠、醋酸镍、苯甲酸钠等成分。根据FT-ICR-MS测定得到的精确分子离子数据,以及同位素精细结构,推测出未知物离子分子式,再结合电感藕合等离子体质谱(ICP-MS)和气相色谱-质谱(GC-MS)分析,推断出未知成分的结构,确认其为萘磺酸钠等成分。文中还发现质谱图中有2组质量数相差62的簇离子:234.8、296.8、358.9和410.7、472.7、534.7,结合二级质谱分析,推断出这两组离子为醋酸镍与醋酸、苯甲酸加合产生的准分子离子,同时还产生二聚体、三聚体离子,合理地解析了质谱图中所出现的未知离子的归属。该研究对化工产品中未知物剖析及产品创新提供了一种新的思路和方法,并发现了镍金属离子与有机酸结合后在质谱中的离子化规律。     

天然维生素E制品中杂质的分离与鉴定

利用高效液相色谱、气相色谱-质谱联用与高分辨质谱对天然维生素E制品中的杂质进行了分离分析与结构鉴定。采用正相高效液相色谱法分离天然维生素E的4种异构体及2种杂质,并对杂质馏分进行富集纯化。将气相色谱-质谱联用与高分辨质谱检测相结合,用于获得杂质的结构信息。通过比较杂质精确相对分子质量和解析质谱碎片离子,推断杂质为芝麻素及其同分异构体表芝麻素。经与芝麻素对照品保留时间及碎片离子数据比对,确证了对杂质结构的推断。所建立的杂质鉴定方法快捷、有效,可应用于天然维生素E制品的食品安全控制。     

液相色谱能量相关二级质谱快速鉴定药物氧化降解产物

基于快速高分辨液相色谱(RRLC)的高分离能力和串联质谱技术的全扫描(TOF-MS)功能,开展了无需选择母离子可获得子离子的能量相关二级质谱(MSE)分析方法的研究.探讨了快速获取和挖掘复杂混合物中全面的组分信息,并将本方法应用于药物氧化降解产物的快速分析鉴定.对莫西沙星原料在30％H2O2中进行氧化降解,采用RRLC进行分离,分别设定高低碰撞能量的TOF-MS实验采集质谱数据,采用质量亏损过滤(MDF)进行数据处理,获取母离子与碎片离子等质谱信息,从而了解药物降解杂质的结构及相对含量.本方法为药物杂质分析和药品质量控制提供了新颖且高效的分析思路及手段.     

三唑仑苯二氮Chuo类药物的电喷雾质谱裂解特征

采用电喷雾/四极杆飞行时间质谱(ESI-QqTOF)联用技术，对3种三唑仑苯二氮Chuo类药物进行CID研究，并以质子化准分子离子[M H] 作为内标物，对碎片离子进行了准确质量测定，确认了这些碎片离子的元素组成，探讨了该类化合物的质谱裂解规律。研究发现，它们的ESI-MS2(源内)和ESI-MS3质谱分别生成脱去N2分子、HCN或CH3CN分子和C1原子的碎片离子，其中m/x 205为3种药物共有的碎片离子，这些特征可用于三唑仑苯二氮Chuo类药物的体内代谢转化和定量研究。     

手性酰氯探针对于盐酸兰地洛尔及其立体异构体识别的质谱研究

采用质谱技术,利用手性探针酰氯对盐酸兰地洛尔及其3个立体异构体进行了区分识别研究。本研究采用了两个手性酰氯探针N-对甲苯磺酰基-L-苯丙氨酰氯(TSPC)和(-)-莰烷酰氯与盐酸兰地洛尔反应产生共价结合产物,放大了盐酸兰地洛尔与其立体异构体的结构差异。在二级串联质谱实验中,与手性酰氯探针结合的产物容易丢失羟基产生碎片离子m/z 793和672,在不同构型的产物离子所产生的丢失水分子的碎片离子的丰度具有一定差异,(-)-莰烷酰氯衍生化产物的碎片离子m/z 603由于立体结构差异,导致稳定性不同,使得不同构型的碎片离子丰度产生差异,可通过比较药物和异构体杂质在二级质谱中特征碎片离子丰度的差异,实现盐酸兰地洛尔及其立体异构体的有效区分识别。所有碎片的元素组成都经过高分辨质谱进行确证。本研究通过质谱法对于盐酸兰地洛尔及其立体异构体进行快速、简单的区分识别,为盐酸兰地洛尔立体异构体杂质的质谱分析相关研究提供数据支持。     

三唑仑苯二氮(艹卓)类药物的电喷雾质谱裂解特征

采用电喷雾/四极杆飞行时间质谱(ESI-QqTOF)联用技术,对3种三唑仑苯二氮(艹卓)类药物进行CID研究,并以质子化准分子离子[M+H]+作为内标物,对碎片离子进行了准确质量测定,确认了这些碎片离子的元素组成,探讨了该类化合物的质谱裂解规律.研究发现,它们的ESI-MS2(源内)和ESI-MS3质谱分别生成脱去N2分子、HCN或CH3CN分子和Cl原子的碎片离子,其中m/z 205为3种药物共有的碎片离子,这些特征可用于三唑仑苯二氮(艹卓)类药物的体内代谢转化和定量研究.     

ESI-QqTOF-MS/MS and APCI-IT-MS/MS analysis of steroid saponins from the rhizomes of Dioscorea panthaica

Using high-resolution quadrupole time-of-flight mass spectrometry along with an electrospray ionization source (ESI-QqTOF-MS), accurate molecular weights of 13 steroid saponins extracted from the rhizomes of Dioscorea panthaica were acquired and the corresponding molecular formulae obtained. In order to elucidate the fragmentation pathways of steroid saponins in D. panthaica, 10 authentic samples were investigated using ESI-QqTOF-MS/MS. In addition, atmospheric pressure chemical ionization mass spectrometry combined with ion trap tandem mass spectrometry (APCI-IT-MS/MS) was used to analyze the structures of 13 steroid saponins in D. panthaica. Through the analysis of their tandem mass data, diagnostic fragment ions of the spirostanol and furostanol steroid saponins in D. panthaica were detected as m/z 271.2056 and 253.1951. In addition, four pairs of isomers were detected and the possible structures of four unknown steroid saponins in D. panthaica speculated. ESI-TOF and APCI-MS(n) have proved to be effective tools for research on fragmentation mechanism of steroid saponins and the rapid determination of native steroid saponins in extract mixture, thereby avoiding tedious derivation and separation steps.     

Fragmentation of organic ions bearing fixed multiple charges observed in MALDI MS

Matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry (MALDI TOF MS) was used to analyze a series of synthetic organic ions bearing fixed multiple charges. Despite the multiple intrinsic charges, only singly charged ions were recorded in each case. In addition to the pseudo‐molecular ions formed by counterion adduction, deprotonation and electron capture, a number of fragment ions were also observed. Charge splitting by fragmentation was found to be a viable route for charge reduction leading to the formation of the observed singly charged fragment ions. Unlike multivalent metal ions, organic ions can rearrange and/or fragment during charge reduction. This fragmentation process will evidently complicate the interpretation of the MALDI MS spectrum. Because MALDI MS is usually considered as a soft ionization technique, the fragment ion peaks can easily be erroneously interpreted as impurities. Therefore, the awareness and understanding of the underlying MALDI‐induced fragmentation pathways is essential for a proper interpretation of the corresponding mass spectra. Due to the fragment ions generated during charge reduction, special care should be taken in the MALDI MS analysis of multiply charged ions. In this work, the possible mechanisms by which the organic ions bearing fixed multiple charges fragment are investigated. With an improved understanding of the fragmentation mechanisms, MALDI TOF MS should still be a useful technique for the characterization of organic ions with fixed multiple charges.     

Structural characterization of trimethylsilyl methyl glycosides derivatives by high-resolution mass spectrometry,linked scans and MIKE experiments

Gas chromatography–mass spectrometry investigations have been carried out for the structural analysis of trimethylsilyl methyl derivatives of keto-deoxy sugars and sialic acids studied under electron ionization. Fragmentation patterns were determined. The three derivatives undergo some common fragmentation pathways. Formation of fragment ions possessing cyclic resonance-stabilized structures was demonstrated. As the sialic acid derivative contained a N-acetyl substituent, some additional fragmentations occurred and were also elucidated. Thus, the mechanism of fragmentation was revealed for these derivatives and new findings concerning some series of fragment ions are presented. Presented at the Annual French National Symposium on Mass Spectrometry, Electrophoresis and Proteomics, 20–23 September 2007 in Pau, France.     

Fragmentation of synthetic cannabinoids with an isopropyl group or a tert‐butyl group ionized by electron impact and electrospray

This study described a fragmentation pattern of 21 synthetic cannabinoids with an isopropyl group or a tert‐butyl group by electron impact ionization quadrupole mass spectrometry and electrospray ionization time‐of‐flight mass spectrometry in the positive mode. The compounds were categorized into four types according to substituted group such as a terminal amide and ester. The characteristic fragment ion in each group was obtained. The main common fragment ions for the two ionizations were formed by C–N cleavage of the amide group adjacent to the N‐hetero rings. Additionally, the fragment ions indicated the difference in the basic structure as well as substituted group, which are useful for estimating the chemical structures of unknown compounds. Copyright © 2015 John Wiley & Sons, Ltd.     

Mass spectral studies of native and mass-labeled perfluorooctanesulfonamides

This work examines the mass spectra of several environmentally relevant amides, perfluorooctanesulfonamide (FOSA), NMeFOSA, NEtFOSA, and NMe(2)FOSA, under electron ionization conditions. A previous mass spectral study of FOSA and NEtFOSA led the authors to propose possible structures for some of the fragment ions and fragmentation pathways that might explain their formation. In the present communication, further fragment ions are identified for these two compounds and alternative fragmentation pathways proposed. Mass spectral analyses of NMeFOSA and NMe(2)FOSA and of mass-labeled NMeFOSA and NEtFOSA reinforce our conclusions about potential fragmentation pathways for these amides and the fragment ions expected. The mass spectral data presented here will help chemists to identify signals found in a gas chromatographic/mass spectrometric (GC/MS) analysis that stem from these perfluoroalkylsulfonamides.     

Mass spectrometric study of six cyclic esters

A series of cyclic esters, which are optically active as a consequence of their helical structures, were synthesized to investigate the relationships between their structures and their optical activities. This paper reports the electron impact fragmentation mechanisms of these six cyclic esters. Accurate mass measurements and mass analyzed ion kinetic energy spectrometry confirmed fragmentation patterns. The stability of the fragment ions has a great influence on the fragmentation pathways, but no correlation with the optical activity was found.     

Electrospray tandem mass spectrometry of lexitropsins

Several compounds, representative of the class of lexitropsins, were analyzed by electrospray tandem mass spectrometry. The study of the fragmentations of the protonated molecular species ([M + H](+)) and of selected fragment ions allowed proposals for the main fragmentation pathways of compounds of this type. The interpretation of the fragmentation pathways of these compounds was complicated because of intramolecular hydrogen migration. In order to better understand the fragmentation pathways, the MS/MS/MS spectra of several compounds, and the MS/MS and MS/MS/MS spectra of the deuterated compounds, were obtained. Accurate mass measurements helped elucidate the structures of smaller fragment ions. Low-energy collision-induced decomposition (CID) tandem mass spectrometry of lexitropsins with electrospray ionization has proven to be a good method for the structural characterization and identification of this class of compounds. Main fragmentation pathways occur by cleavage of the peptide bond followed by the elimination of the substituted pyrrole ring, and their elucidation will facilitate structural characterization of new lexitropsins.     

Study of collision-induced decomposition of phenothiazine by ion trap mass spectrometry

The collision-induced decomposition pathways of phenothiazine were studied in detail by ion trap mass spectrometry. With this approach, different amounts of energy can be deposited into the fragment ions, thus favouring particular structures. Different relative abundances in the fragmentation patterns of selected ions are observed, depending on whether they are produced by electron impact or multiple mass spectrometry [(MS)ⁿ] methods.     

Electrospray Ionization Mass Spectra of Amino Acid Methyl Ester 5′-Phosphoramidates of 2′,3′-Isopropylideneuridine

Amino acid methyl ester phosphates were synthesized and determined by using positive-ion mode electrospray ionization mass spectrometry(ESIMS) in combination with multistage tandem mass spectrometry. The fragmentation pathways were investigated, and it was observed that most fragment ions contained the phosphoryl group. It was interesting to observe that the fragmentation pathways of the protonated molecule show some differences when compared with those of the sodium ion adduct. The methoxy group of amino acid methyl ester can migrate from the carbonyl group to the phosphoryl group in the sodium ion adduct.     

Electrospray Ionization Mass Spectra of Amino Acid Methyl Ester 5 ＇-Phosphoramidates of 2＇, 3＇-Isopropylideneuridine

Amino acid methyl ester phosphates were synthesized and determined by using positive-ion mode dectrospmy ionization mass spectrometry（ESIMS） in combination with multistage tandem mass spectrometry. The fragmentation pathways were investigated, and it was observed that most fragment ions contained the phosphoryl group. It was interesting to observe that the fragmentation pathways of the protonated molecule show some differences when compared with those of the sodium ion adduct. The methoxy group of amino acid methyl ester can migrate from the carbonyl group to the phosphoryl group in the sodium ion adduct.