纳升电喷雾串联质谱在阿托西班一级结构确证中的应用

利用电喷雾串联质谱对合成八肽阿托西班进行了二硫键还原前后的精确相对分子质量测定和一级结构的确证.首先通过全扫描模式测定了其还原前后的精确相对分子质量,然后通过串联质谱(MS/MS)得到母离子m/z 498.73(双电荷)的碎片离子,采用y离子的方法测定了阿托西班的序列并对其修饰位点进行了确证.该方法具有灵敏度高、速度快、样品无需纯化等特点,在多肽类药物一级结构分析方面具有独特的优势.     

基质辅助激光解析电离质谱和电喷雾质谱共同快速确证达托霉素结构

运用基质辅助激光解析电离-飞行时间串联质谱(MALDI-TOF/TOF MS)和电喷雾-四级杆-飞行时间质谱(ESI-Q-TOF MS)快速确证环脂肽达托霉素的结构。首先,ESI检测达托霉素相对分子量为1619.7107,与理论值偏差0.0007。选择其双电荷峰m/z 809.848作为母离子进行ESI串联质谱(MS/MS)测定,成功匹配了达托霉素环外氨基酸序列C9H19CO-Trp-Asn-Asp。其次,优化Li OH裂解达托霉素的实验条件,以MALDITOF/TOF MS监测开环效果,获得95%以上的开环样本后,分别运用MALDI和ESI进行MS/MS测定,达托霉素开环产物的b+和y+全部被匹配,达托霉素全部氨基酸序列得到确证。最后,对开环产物的ESI-MS/MS条件进一步优化,获得了丰富的低端碎片离子,解析了脂肪酸链结构,并绘制了脂肪酸链的裂解图。本方法快速、简便、准确,是确证环脂肽类化合物结构的可靠方法。     

反相高效液相色谱-电喷雾质谱法分析食源血管紧张素转换酶抑制肽

利用反相高效液相色谱/电喷雾离子阱质谱法,直接分析从牦牛乳酪蛋白中酶水解得到的血管紧张素转换酶抑制肽粗产物。RP-HPLC显示具有活性的多肽粗产物含有3个主要成分,质谱同步测定各组分的分子量(m/z)分别为815.2,1680.1,962.2,然后选择[M H] 离子通过串联质谱(MS/MS)得到碎片离子,利用b离子和y离子互补的方法鉴定了多肽序列。三条肽分别为Leu-Pro-Tyr-Tyr,Pro-Leu-Pro-Leu-Leu-Gln,Phe-Leu-Pro-Pro-Tyr-Tyr。结果显示,所获得的多肽序列与牛乳酪蛋白一级结构中相应肽段的序列一致。     

纳升电喷雾串联质谱鉴定重组人甲状旁腺素(1-34)

用先进的纳升电喷雾-四极杆-飞行时间串联质谱鉴定重组人PTH(1-34)。通过ESI-MS测定重组人PTH(1-34)分子量及MS/MS对其胰蛋白酶酶解后的肽段的序列和数据库查询进行结构鉴定。重组PTH(1-34)测定分子量为4115.21,与理论值相比测定相差0.06%。MS/MS测定出其中双电荷离子峰m/z728.4肽段序列为VSEIQLMHNLG,以及其他3个单电荷离子峰的序列。数据库检索后确定重组表达的PTH(1-34)一级结构完全正确,纳升电喷雾串联质谱以其灵敏、快速和准确为蛋白质鉴定提供了有效的手段。     

合成多肽的电喷雾质谱研究

利用电喷雾多极串联质谱对3种合成多肽进行了系统的鉴定和分析研究。首先通过全扫描模式测定了其分子量，然后选择[M H]^ 或[M 2H]^2 离子通过串联质谱(MS／MS)得到碎片离子，采用y离子和b离子互补的方法测定了多肽序列。利用文献数据对这种方法进行了验证，实验结果表明，该方法简便、快速、实用。     

基于GC/Q-TOF MS技术鉴定S-zorb汽油中噻吩类化合物

结合气相色谱分离技术和MS/MS串联质谱筛查技术,通过选定目标母离子进行碰撞诱导解离,获取精确质量子离子信息,实现汽油馏分中噻吩类化合物的痕量筛查分析.选取5种不同碳数取代噻吩类化合物作为标准物绘制定量标准曲线,建立了基于气相色谱-四极杆串联飞行时间质谱(GC/Q-TOF MS)直接测定汽油中噻吩类化合物的方法.利用该...     

婴幼儿奶瓶中迁移双酚A的高效液相色谱-电喷雾串联质谱检测方法研究

建立了婴幼儿奶瓶中双酚A(BPA)迁移量的高效液相色谱-电喷雾串联质谱(HPLC-ESI-MS/MS)测定方法。奶瓶食品模拟浸泡液经过弗罗里硅土玻璃层析柱净化,高效液相色谱分离,采用选择反应性监测模式(SRM)检测。以一级质谱得到的准分子离子m/z 227作为母离子,进行二级质谱(MS2)分析。选择MS2的碎片离子m/z 212、133、93定性确证,m/z 212作为定量离子定量。实验优化了质谱条件,并对二级质谱碎裂机理和特征离子进行了研究。测定结果的相对标准偏差不大于8.2%(n=7),回收率在87.7%～105%之间;检出限为2μg/L,能够满足欧盟、美国等对奶瓶中双酚A的限制要求。该法已成功应用于婴幼儿奶瓶中BPA迁移量的测定。     

DART-Q-Exactive快速分析案件可疑物中新精神活性物质

使用实时直接分析离子源串联四极杆和轨道阱杂交高分辨质谱仪,对来源于实际案件中的可疑植物碎末进行分析。分析取样量小于2 mg,可疑植物碎末的一级质谱主峰质荷比范围为m/z 384.1695~384.1699,全离子裂解后得到质荷比m/z 324.15,253.08和m/z 109.04的3个主要碎片离子。通过精确分子量检索与模拟碎裂实验,推断可疑植物碎末中含有AMBFUBINACA成分,并经气相色谱-质谱联用技术确证。通过模拟添加样品考察方法灵敏度及重现性,方法检出限为0.1μg/mg。     

阿莫西林的傅立叶变换-离子回旋共振质谱研究

阿莫西林为β-内酰胺类广谱抗菌药物,由于疗效好、安全可靠且不良反应少,成为临床上广泛应用的一线抗生素.阿莫西林颗粒U服给药,具有服用方便、患者依从性好等优点,尤其适用于儿童使用.近年部分厂家阿莫西林颗粒市售产品抽验不合格,为控制相应经营品种质量,本研究首次应用傅立叶变换离子回旋共振质谱(FT-ICR-MS)和傅立叶变换离子回旋共振串联质谱(FT-ICR-MSn,n=2)对阿莫西林产品进行分析研究,给出了阿莫西林的精确相对分子质量和串联质谱碎片的精确质量,以确证其结构.     

高效液相色谱-串联质谱法测定纺织品中的致癌芳香胺

建立了高效液相色谱-串联质谱法(LC/MS/MS)测定纺织品中致癌芳香胺的检测方法.纺织品中的偶氮染料在柠檬酸缓冲液中用连二亚硫酸钠还原为芳香胺,用硅藻土提取还原液中的芳香胺,用乙醚洗脱,浓缩至近干后用甲醇定容.使用液相色谱-串联质谱进行测定,色谱柱为XTerra MS C18柱,流动相为甲醇和0.025 mol/L乙...     

蛋白质分子量测定过程中的酸效应

在基质辅助激光解吸电离飞行时间质谱（MALDI-TOF-MS）和电喷雾质谱（ESI-MS）测定蛋白质分子分子量的过程中,适当提高样品的酸度,可提高分析测试的灵敏度。在选定最佳样品分子浓度的基础上,通过适当加入三氟乙酸（TFA）来调整测试样品的酸度,准确测定了标准蛋白质-溶菌酶（lysozyme）的分子量,并且对蛋白质分子在“软电离”质谱中,受酸效应的影响进行了初步探讨。     

Structural elucidation of disinfection by-products in treated drinking water

Two unusual disinfection by-products have been detected periodically in the gas chromatography/mass spectrometry (GC/MS) characterization analyses of semi-volatile organics in treated drinking water. The electron ionization (EI) mass spectra contained mono-chlorinated and mono-brominated ions at m/z 107/109 and 151/153, respectively. Library searching techniques suggested mono-halogenated butanol structures but no matches could be found. Positive ion chemical ionization (CI) spectra contained mono-chlorinated and mono-brominated ions at m/z 105/107 and 149/151, respectively. No [M + H]+ ions were initially observed. Accurate mass measurements confirmed the empirical formulae for the significant ions in the EI spectra and the mono-halogenated butanol structures. Further CI experiments with other reagent gases and instruments revealed possible molecular weights of 139 and 183 Da, respectively. Tandem mass spectrometry (MS/MS) experiments in EI and CI were used to elucidate the fragmentation schemes. The two compounds have been tentatively identified as 1-aminoxy-1-chlorobutan-2-ol and 1-aminoxy-1-bromobutan-2-ol, respectively.     

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.     

Electrospray ionization mass spectrometry for analysis of low-molecular-weight anticancer drugs and their analogues

In this study, several anticancer drugs and their analogues consisting of organic and organometallic compounds were analyzed by electrospray ionization mass spectrometry (ESI/MS) using a quadrupole mass spectrometer. Protonated molecular ions [M+H]⁺ were observed for all of the compounds studied, and in the case of the two steroid sulfates, deprotonated molecular ions [M-H]^? were obtained. Tandem mass spectrometry was performed on these quasimolecular ions, and the product ions formed provided useful fragmentation patterns that were characteristic for the compounds. This study provides evidence that ESI/MS is a sensitive technique for structure confirmation and identification of small organic and organometallic molecules.     

Multiply charged ions in ionspray tandem mass spectrometry

Multiply charged anions of some 30 species containing multiple carboxylic, sulphonic and/or phosphoric groups generated by ionspray were studied by using tandem mass spectrometry (MS/MS). Two trends emerged: (1) lower-charged ions are preferentially evaporated, and (2) for more highly charged ions, evaporability is a function of ion size. Triply and quadruply charged ions were observed for azo dyes with molecular masses in the 700-900 Dalton range. Daughter-ion mass spectra of selected multiply charged ions are presented.     

Determination of polychlorodibenzo-p-dioxins and polychlorodibenzofurans by gas chromatography/tandem mass spectrometry and gas chromatography/triple mass spectrometry in a quadrupole ion trap

The determination of tetra- to octachlorodibenzo-p-dioxins and tetra- to octachlorodibenzofurans (PCCD/Fs) by high-resolution gas chromatography/tandem mass spectrometry (HRGC/MS/MS) and high-resolution gas chromatography/triple mass spectrometry (HRGC/MS(3)) in a quadrupole ion trap, equipped with an external ion source, is presented. MS/MS involves a typical four-step process, namely ionization, parent ion isolation, collision-induced dissociation (CID) and mass analysis of the daughter ions. For the MS(3) experiment, the MS/MS scan function is used with the addition of selected daughter ion isolation, their CID and the mass analysis of second-generation product ions called 'grand-daughter ions.' For both methods, the energies necessary for the CID of the 17 PCDD/Fs were determined and optimized using multiple scan functions with different CID amplitudes. The CID efficiency, defined as the signal ratio of fragment ions detected from the major dissociation channels to molecular ions isolated, was 1.15-2.40 V for parent ion dissociation (MS/MS) and 1.05-1.50 V for daughter ion dissociation (MS(3)) and for all the chloro congeners. The same sensitivity (1 pg microl(-1)) can be reached with both the MS/MS and MS(3) methods and linear responses were obtained between 1 and 100 pg microl(-1) injected.     

Structural analysis of platycosides in Platycodi Radix by liquid chromatography/electrospray ionization-tandem mass spectrometry

Platycosides extracted from Platycodi Radix were analyzed by HPLC coupled with electrospray ionization multistage tandem mass spectrometry (HPLC/ESI-MS(n)). Predominant [M+Na](+) ions in positive mode and [M-H](-) ions in negative mode in the direct ESI-MS spectra of extract provided information on molecular weights, but minor components and isomers could not be discriminated. However, combining HPLC and ESI-MS(n), allowed eleven platycosides, including four acetylated platycodin isomers and two prosapogenines to be analyzed. During MS(2) analysis conducted to elucidate the structures of platycosides, fragment ions provided information on sugar moieties attached at C-28 of triterpene structure of the platycosides. Glycosidic bond cleavages at C-3 were revealed by fragment ions in MS(3) spectra. Some characteristic fragment ions not related to sugar bond cleavage revealed that an esterified triterpene is linked to sugars at C-28. The only sugar ring-cross cleavage corresponding to 90 Da in the negative MS(2) spectrum took place at an arabinosyl sugar moiety. By using HPLC/ESI-MS(n), three acetylated platycosides in Platycodi Radix extract were newly identified.     

Analysis of polypropyleneglycols using electrospray ionization mass spectrometry. Effects of cationizing agents on the mass spectra

In electrospray ionization mass spectrometry (ESI-MS) of polypropyleneglycol (PPG), effects of cationizing agents were examined. When NaI was used as a cationizing agent, the distribution of multiply-charged ions in the spectra was greatly affected by the ratio of cationizing agent and PPG. However, the distribution was not affected by the use of CH(3)COONH(4). With an increase of cone voltage, fragmentation occurred by in-source collision-induced dissociation (CID) when CH(3)COONH(4) was used. On the contrary, no decomposition of the PPG backbone was observed with NaI. Instead, the intensity of the lower-charged ions, whose mass-to-charge (m/z) ratios are larger, increased because of the elimination of Na(+) with increase of cone voltage. Under optimum conditions for ESI-MS analysis, PPGs that have different molecular weights, different initiators or end groups were easily and accurately characterized. A tandem mass spectrometry (MS/MS) study of NH(4)(+) adduct ions of PPG indicated that a vinyl-terminated linear structure is formed at the end group during the fragmentation.     

Dual parallel electrospray ionization and atmospheric pressure chemical ionization mass spectrometry (MS), MS/MS and MS/MS/MS for the analysis of triacylglycerols and triacylglycerol oxidation products

Two mass spectrometers, in parallel, were employed simultaneously for analysis of triacylglycerols in canola oil, for analysis of triolein oxidation products, and for analysis of triacylglycerol positional isomers separated using reversed-phase high-performance liquid chromatography. A triple quadrupole mass spectrometer was interfaced via an atmospheric pressure chemical ionization (APCI) interface to two reversed-phase liquid chromatographic columns in series. An ion trap mass spectrometer was coupled to the same two columns using an electrospray ionization (ESI) interface, with ammonium formate added as electrolyte. Electrospray ionization mass spectrometry (ESI-MS) under these conditions produced abundant ammonium adduct ions from triacylglycerols, which were then fragmented to produce MS/MS spectra and then fragmented further to produce MS/MS/MS spectra. ESI-MS/MS of the ammoniated adduct ions gave product ion mass spectra which were similar to mass spectra obtained by APCI-MS. ESI-MS/MS produced diacylglycerol fragment ions, and additional fragmentation (MS/MS/MS) produced [RCO](+) (acylium) ions, [RCOO+58](+) ions, and other related ions which allowed assignment of individual acyl chain identities. APCI-MS of triacylglycerol oxidation products produced spectra like those reported previously using APCI-MS. APCI-MS/MS produced ions related to individual fatty acid chains. ESI-MS of triacylglycerol oxidation products produced abundant ammonium adduct ions, even for those molecules which previously produced little or no intact molecular ions under APCI-MS conditions. Fragmentation (MS/MS) of the [M+NH(4)](+) ions produced results similar to those obtained by APCI-MS. Further fragmentation (MS/MS/MS) of the diacylglycerol fragments of oxidation products provided information on the oxidized individual fatty acyl chains. ESI-MS and APCI-MS were found to be complementary techniques, which together contributed to a better understanding of the identities of the products formed by oxidation of triacylglycerols.