基质辅助激光解吸附飞行时间质谱方法分析山竹果皮缩合单宁

在反射模式(Reflectron modes)下,去离子处理后, 引入Cs+(CsCl, 1.52 g/L) 作为阳离子化试剂,得到清晰的山竹果皮缩合单宁的MALDI-TOF质谱图.解析该质谱图能得到完整的山竹果皮缩合单宁的结构信息:山竹果皮缩合单宁是从三聚体(m/z 999)到十一聚体(m/z 3303)分布的多聚物,离子峰最强的为五聚体(m/z 1575);同时存在3种结构单元:(表)儿茶素(C/EC)、(表)棓儿茶素(GC/EGC)和(表)阿福豆素(AC/EAC),且C/EC、AC/EAC和 GC/EGC的离子峰强度依次降低,同时在四聚体(m/z 1440)到七聚体(m/z 2303)均存在棓酰基;从四聚体(m/z 1285)到八聚体(m/z 2436),不同的聚合物中普遍存在A型连接.本研究优化了获取植物缩合单宁结构信息的基质辅助激光解吸附飞行时间质谱方法.     

三元体系MCl-SbCl~3-HOAc (M=Li,Na; 25℃)的研究

测定了三元体系MCl-SbCl~3-HOAc(M=Li,Na;25℃)的溶度数据和饱和溶液的折光指数,并绘制了相应的溶度图及其折光指数曲线。M=Li时,体系的溶度曲线和折光指数曲线均由三支组成,分别与LiCl.0.5HOAc,LiCl,SbCl~3相对应。M=Na时,体系属于简单共饱型,无任何新相形成。研究结果表明,当M分别是Li,Na或K,NH~4,Rb,Cs时,体系的物理化学行为有着极为显著的不同,说明MCl-SbCl~3-HOAc(M=Li,Na,K,NH~4,Rb,Cs)体系可以作为区分碱金属系列阳离子性质差别的典型体系。     

改性Y分子筛的酸碱性能及吸附性能的研究

吡啶、吡咯、苯、甲苯、乙苯作为探针分子，在Li＋, Na＋, K＋, Cs＋改性的Y型分子筛上进行吸附，用TPD及IR方法系统地研究了不同碱金属离子改性的Y型分子筛的酸碱性能和吸附性能的变化. 结果表明，按Li、Na、K、Cs的顺序, 随着碱金属离子半径的增大, 其L酸酸强度依次减弱，L碱的强度逐渐增强.由于改性Y型分子筛所含碱金属离子的不同，其对芳烃的吸附的强弱及吸附量的大小亦不同.随着骨架外的阳离子的半径逐渐增大，碱的强度逐渐增强，与芳烃的作用愈强烈，导致TPD脱附峰温增高及芳烃和侧链上的C－H伸缩振动谱带向低波数位移愈多.由于位阻的原因，对含同一种碱金属离子的分子筛来说，随着芳烃侧链C数的增加，芳烃的吸附量逐渐减小.     

气相色谱-质谱法测定血浆中双氯芬酸钠的含量

提出了应用气相色谱-质谱法测定血浆中双氯芬酸钠含量。血浆样品中双氯芬酸钠经盐酸提取,并加入三甲基硅烷衍生化试剂进行衍生化,所得衍生化产物经萃取、净化后供气相色谱分离及质谱测定。采用选择离子质谱扫描方式,供试品双氯芬酸钠-三甲基硅烷衍生物定量选择离子检测质荷比为m/z367,内标物布洛芬-三甲基硅烷衍生物定量选择离子检测质荷比为m/z263。双氯芬酸钠的线性范围为0.005～5.0mg·mL-1,检出限(3S/N)为0.5μg.L-1。方法回收率在94.6%～97.4%之间,日内、日间相对标准偏差(n=6)均小于5%。     

气相色谱-质谱联用法同时测定乳及乳制品中的三聚氰胺及肌酐

建立了同时测定乳制品中三聚氰胺及肌酐的气相色谱-质谱联用方法。样品经1%三氯乙酸溶液萃取,混合型阳离子交换固相萃取净化,提取液用氮气吹干后加入N,O-双(三甲基硅基)三氟乙酰胺-三甲基氯硅烷(BSTFA-TMCS)硅烷化试剂,于75 ℃下衍生60 min,最后采用选择离子模式下的气相色谱-质谱测定。三聚氰胺和肌酐的定量限分别为0.10 mg/kg和0.20 mg/kg;在0.1～50 mg/L范围内的线性相关系数均大于0.99。实际样品中,肌酐在10～100 mg/kg和三聚氰胺在0.1～5.0 mg/kg添加范围内的回收率分别为80.7%～116.8%和77.6%～107.5%,相对标准偏差分别小于9.4%和8.5%。该方法能有效除去干扰,灵敏度高,回收率较好,可用于乳制品中三聚氰胺和肌酐的同时测定。     

高分辨质谱技术研究DART离子化条件下的背景离子及潜在应用

运用高分辨质谱技术对实时直接分析(DART)离子化条件下的多种背景离子进行研究和表征,追溯了这些信号可能的来源。研究表明:背景离子主要在阳离子条件下产生,且主要来自实验室环境中微量的增塑剂和聚二甲基硅氧烷,其中聚二甲基硅氧烷可能来自泵油挥发。了解和掌握这些背景离子有助于利用DART技术开展研究和测试方面的工作:(1)这些背景信号较弱,在DART的样品分析时不会产生显著干扰。可在不额外加入内标化合物的情况下,考察高分辨质谱质量轴的稳定性和准确度。(2)了解这些背景离子有助于DART质谱分析复杂体系时避免误判。     

电喷雾萃取电离质谱快速测定牙膏胶体中的二甘醇

将自行研制的电喷雾萃取电离源(EESI)和LTQ XL质谱仪耦合, 建立了选择性离子化快速测定牙膏胶状纳米级复杂基质样品中微量二甘醇的EESI-MS方法. 实验结果表明, 二甘醇与NH4+, Na+和K+离子在一级质谱中形成特征非共价配合物, 其它大量组分如纳米粒子及胶质等对测定无干扰. 该方法的样品消耗量约0.1 g, 灵敏度高, 单个样品的分析时间不到2 min, 可用于牙膏胶体中低含量二甘醇的选择性快速测定.     

κ-卡拉胶热可逆凝胶化行为研究

用固体小角激光散射方法研究κ 卡拉胶 (KC)的热可逆凝胶化行为 .以散色斑点的突停点温度为体系的凝胶化点Tgel,考察了溶液中加入Na+ ,K+ ,NH+4,Ca2 + ,Cu2 + ,Zn2 + 等抗衡离子对Tgel的影响 .结果是随抗衡离子浓度增大Tgel上升 ;Tgel与Na+ 的浓度呈线性关系 ,与K+ ,NH+4,Ca2 + ,Cu2 + ,Zn2 + 等离子浓度的平方根成线性关系 ;另外 ,还得到 30℃时KC在KCl盐溶液中的溶胶 凝胶相图 ,并对比了KC在NaCl溶液中透析前后Tgel的变化 .     

无机磷试剂辅助均环肽库的建立及其电喷雾质谱研究

在无机磷试剂辅助下建立了氨基酸自组装成均环肽的方法, 得到了相应的均环肽库. 均环肽库的建立增加了肽库的多样性, 为药物筛选提供了新的选择性. 采用电喷雾多级质谱技术, 对系列均环多肽 [M＋H]＋离子和[M＋Na]＋离子的质谱裂解规律进行了系统研究, 两种系列的离子具有不同的质谱裂解特征, 分别提出了其可能的质谱裂解机制. 该研究丰富了环多肽化合物的电喷雾多级质谱研究, 结果表明环肽化合物的加钠离子较加氢离子的质谱图可以更容易地用于环多肽的序列测定. 本研究为其它类似环肽化合物结构的分析鉴定及利用电喷雾质谱推测环肽序列提供了有效的质谱方法.     

气相色谱-质谱联用法分析~(15)N标记精氨酸发酵液中的氨基酸组分及其同位素丰度

建立了精氨酸、赖氨酸、丝氨酸、缬氨酸、亮氨酸等15种氨基酸的气相色谱-质谱联用(GC-MS)检测方法。以硅烷化试剂N-甲基-N-(三甲基硅烷)三氟乙酰胺(MSTFA)为衍生化试剂对氨基酸进行衍生化,在优化的色谱-质谱条件下,15种氨基酸均达到基线分离。结合混合阳离子(MCX)固相萃取柱对氨基酸发酵液实际样品进行净化,将所建立的方法用于~(15)N标记精氨酸发酵液中的氨基酸组成(包括亮氨酸-~(15)N、脯氨酸-~(15)N、精氨酸-~(15)N_4、谷氨酰胺-~(15)N和赖氨酸-~(15)N_2)分析,并根据EI图谱的离子碎片信息对~(15)N标记精氨酸发酵液中的氨基酸同位素丰度进行计算。     

Characterization of Acacia mangium polyflavonoid tannins by MALDI-TOF mass spectrometry and CP-MAS C NMR

The MALDI-TOF mass spectrometry (MS) and solid state CP-MAS ¹³C Nuclear Magnetic Resonance (NMR) spectroscopic technique were introduced to characterize Acacia mangium tannin (condensed tannins). The MALDI-TOF MS illustrated a series of peaks corresponding to oligomers of condensed tannins of up to 11 flavonoid units (3200 Da). A. mangium condensed tannins were found to consist predominantly of prorobinetinidin combined with profisetinidin and prodelphinidin. Both the MALDI-TOF mass spectra and the solid state CP-MAS ¹³C NMR indicated that the A. mangium tannins obtained from Kudat, had an almost completely linear structure; In addition, Lembah Beringin, consist of “angular” polymer structure; and Tawau, has included “twice-angular” polymer structures present in oligomers type of up to 7 flavonoid units. The high degree of polymerization of linear, angular type, twice-angular structures and longer oligomer (3200 Da) chains have not been observed in previous studies of condensed tannins. The spectra also indicated that A. mangium tannins are more heavily branched and have higher degree of polymerization (>7.0) compared to commercial mimosa (A. mearnsii) tannin (4.9). Because tannins are phenolic, it was expected that they can be used to replace phenol-formaldehyde (PF) adhesives.     

不同助剂的硫化MoO3／ZrO2催化剂上CO加氢合成低碳混合醇的反应性能

研究了碱金属离子（Li^ 、Na^ 、K^ 、Cs^ ）和碱土金属离子（Ca^2 、Sr^2 、Ba^2 ）为助剂的硫化MoO3/ZrO2催化剂上CO加氢合成低碳混合醇的反应性。碱金属离子（Li^ ,K^ )、特别是钾离子为助剂的催化剂比之碱土金属离子助剂具有 更好的合成低碳醇的活性和选择性。从一系列的实验和分析发现，硫化K－MoO3/ZrO2的合 成低碳醇的活性和选择性强烈依赖于钾助剂的含量和反应条件。合理 选择 最佳K／Mo比（－0.5原子比）、反应压力、温度和空速可以获得较好的合成醇活性和选择性。     

水及有机溶剂中离子溶剂化焓的理论计算

In the light of the interactions between particles, this paper is a calculation of the standard solvation enthalpies for ions Li~+, Na~+, K~+, Rb~+, Cs~+, Ag~+, Cl~-, Br~- and I~- in solvents as H_2O, MeOH, FA, DMF, DMSO, MeCN, PC and SL. The contributions from the cavity formation process, electrostatic attraction, electrostatic repulsion and those from nonelectrostatic interactions are considered. The accordance between the calculated values and those from literature is good except Li~+.     

Analysis of catechins and condensed tannins by thermally assisted hydrolysis/methylation-GC/MS and by a novel two step methylation

The objective of this study is to observe high molecular weight markers of catechins and condensed tannins by thermally assisted hydrolysis/methylation (THM)-GC/MS. Techniques for formation of intact methylated flavanols of catechins using THM in the presence of trimethylsulfonium hydroxide (TMSH), and, of a dimer marker of condensed tannins using a novel two step methylation technique, are presented. The two step methylation procedure involves pre-methylation of the sample with trimethylsilyl diazomethane (TMS-diazomethane) followed by THM. The dimer marker, a methylated product containing the C–C linkage between adjacent flavanol units, has a molecular weight of 540. Intact methylated flavanols of catechins were also successfully observed as high molecular weight compounds including partially methylated catechin and epicatechin (3-flavanol, 3′,4′,5,7-tetramethoxy, cis/trans; m/z = 346), epigallocatechin and gallocatechin (3-flavanol, 3′,4′,5,5′,7-pentamethoxy, cis/trans; m/z = 376). These techniques were successfully applied to the analysis of series of condensed tannins isolated from plants, and catechins and other phenolics present in (hot water) extracts of tea leaves. In green tea the major catechins were identified as epicatechin and epigallocatechin along with flavonols and tannin dimers.     

水及有机溶剂中离子溶剂化焓的理论计算

离子溶剂化热力学的理论研究是一项令人感兴趣的工作.在Born理论的基础上人们先后提出了多种较详细的计算离子溶剂化热力学量的模型或公式,并对离子在不同溶剂中的溶剂化自由能进行了理论计算.本文从离子-溶剂间的相互作用力出发,分别考虑了离子溶剂化过程中造腔作用、静电吸引、静电排斥及非静电相互作用对离子溶剂化焓的贡献,得到了一个具有一定意义的、计算离子溶剂化焓的理论公式。     

Solid sampling technique for direct detection of condensed tannins in bark by matrix-assisted laser desorption/ionization mass spectrometry

A novel method for the direct analysis of condensed tannin components in bark was developed on the basis of matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) combined with a simple solid sampling technique. The MALDI mass spectra obtained from the wood (bark) powder sample clearly showed a series of peaks corresponding to the sodium ion adducts of condensed tannin oligomers up to around m/z 3000. The results indicate that the condensed tannins in the bark sample used in this work mostly consist of combinations of flavan-3-ol units such as profisetinidin (PF), prorobinetinidin (PR) and prodelphinidin (PD), at least up to 10-mers (m/z approximately 3000).     

Isolation and Purification of Condensed Tannins from Flamboyant Tree and Their Antioxidant and Antityrosinase Activities

Flamboyant tree, a kind of medicinal plant, was studied as a source of condensed tannins. The antioxidant activities of the condensed tannins from the leaf, fruit, and stem bark of flamboyant tree were screened by ABTS radical and hydroxyl radical scavenging activity methods. The results indicated that these compounds possessed potent antioxidant activity. Their structures were then characterized by high-performance liquid chromatography-electrospray ionization mass spectrometry (HPLC-ESI-MS) after thiolytic degradation. The results showed that the leaf condensed tannins were composed of afzelechin/epiafzelechin, catechin/epicatechin, and gallocatechin/epigallocatechin, while the fruit and stem bark condensed tannins had afzelechin/epiafzelechin and catechin/epicatechin. In addition, the condensed tannins were evaluated for their antityrosinase ability. They were found to have significant antityrosinase activity. The IC₅₀ values were 35 ± 2.0 and 40 ± 0.5 μg/ml for the condensed tannins of fruit and stem bark, respectively. Further, fluorescence quenching and copper interacting techniques were utilized to unravel the molecular mechanisms of the inhibition. The results showed that the hydroxyl group of the condensed tannins could chelate the dicopper center of the enzyme and interact with tryptophan residues. Our studies revealed that condensed tannins might be suitable for use in food, agriculture, cosmetic, nutraceutical, and pharmaceutical applications.     

阳离子交换色谱中色谱柱温度对碱金属与碱土金属离子保留的影响

研究了非抑制型阳离子交换色谱中色谱柱温度(25~50℃)对碱金属离子(Li+、Na+、K+、Rb+)和碱土金属离子(Mg2+、Ca2+、Sr2+)以及NH4+保留的影响。在Shim-pack IC-C1磺酸型阳离子交换柱上,以硝酸为流动相分离碱金属离子,以乙二胺或乙二胺-草酸(柠檬酸)为流动相分离碱土金属离子,随着色谱柱温度的升高,碱金属和碱土金属离子的保留时间均增长,其范特霍夫曲线具有良好的线性关系,斜率为负值,表明在此条件下碱金属和碱土金属离子的保留为吸热过程。在Shim-pack IC-SC1羧酸型阳离子交换柱上,以硫酸为流动相同时分离碱金属和碱土金属离子,随着色谱柱温度的升高,Mg2+、Ca2+的保留时间增长,而K+、Rb+的保留时间缩短,Li+、Na+、NH4+的保留时间基本不变。在此条件下,Mg2+、Ca2+、K+和Rb+的范特霍夫曲线具有良好的线性关系,其中Mg2+和Ca2+的曲线斜率为负值,K+和Rb+的曲线斜率为正值,表明Mg2+和Ca2+的保留表现为吸热过程,K+和Rb+的保留表现为放热过程。研究表明在不同固定相和流动相条件下,色谱柱温度对碱金属和碱土金属离子保留行为的影响不同。     

Solvent selection for matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometric analysis of synthetic polymers employing solubility parameters

The principle relating to the selection of a proper matrix, cationization reagent, and solvent for matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry (MALDI‐TOF MS) of synthetic polymers is still a topic of research. In this work we focused on the selection of a suitable MALDI solvent. Polystyrene PS7600 and poly(ethylene glycol) PEG4820 were analyzed by MALDI‐TOF MS using various solvents which were selected based on the Hansen solubility parameter system. For polystyrene (PS), dithranol was used as the matrix and silver trifluoroacetate as the cationization reagent whereas, for poly(ethylene glycol) (PEG), the combination of 2,5‐dihydroxybenzoic acid and sodium trifluoroacetate was used for all experiments. When employing solvents which dissolve PS and PEG, reliable MALDI mass spectra were obtained while samples in non‐solvents (solvents which are not able to dissolve the polymer) failed to provide spectra. It seems that the solubility of the matrix and the cationization reagent are less important than the polymer solubility. Copyright © 2010 John Wiley & Sons, Ltd.     

Molecular mass determination of saturated hydrocarbons: reactivity of eta5-cyclopentadienylcobalt ion (CpCo*+) and linear alkanes up to C-30

The present study demonstrates the feasibility of the eta5-cyclopentadienylcobalt ion (CpCo*+) as a suitable cationization reagent for saturated hydrocarbon analysis by mass spectrometry. Ion/molecule reactions of CpCo*+ and three medium chain-length n-alkanes were examined using Fourier-transform ion cyclotron resonance mass spectrometry. Second-order rate constants and reaction efficiencies were determined for the reactions studied. Loss of two hydrogen molecules from the CpCo-alkane ion complex was found to dominate all reactions ( > or = 80%). Furthermore, this dehydrogenation reaction efficiency increases with increasing chain length. These preliminary results suggest that the CpCo*+ ion may be a promising cationization reagent of longer chain saturated hydrocarbons and polyolefins.