电喷雾飞行时间质谱与大气压化学电离质谱法分析烟叶中茄尼醇的比较

采用反相高效液相色谱(RP-HPLC-UV)和电喷雾飞行时间质谱(ESI-TOF/MS)、大气压化学电离质谱(APCI-MS),分析烟叶中的茄尼醇.使用反相G4色谱柱,以V(甲醇):V(水)=9:1为流动相,茄尼醇和烟草中的其它成分分离良好;茄尼醇在ESI正离子全范围扫描中主要形成[M-H2O H] 和[M NH4] 离子,只有微弱的[M H] 离子,同时会产生一些碎片离子;而在APCI正离子全范围扫描中主要形成[M-H2O H] 离子,检测不到[M H] 离子,碎片离子也很少;通过对茄尼醇的ESI-TOF/MS和APCI-MS的质谱分析特征比较可以发现,茄尼醇在ESI源分析中的信号强度远远小于在APCI源分析中的信号强度,说明APCI源更适于茄尼醇的定量分析.     

二烷氧基膦酰乙酸酯的电子轰击正离子和化学电离负离子质谱研究

本文报道一系列二烷氧基膦酰乙酸酯的电子轰击(EI)正离子和甲烷化学电离负离子(NCI)质谱.在EI谱上出现特征的[M+H]^+离子,进一步发生氢重排,然后失去烯烃,再失水和脱CH2CO.而在NCI谱中则生成[M-H]^-离子(基峰),易失去烷基,再失烷氧基和CH2CO,或氢重排后脱烯烃.正、负离子的断裂机理不同,但数据可以互相补充,以利于类似未知物的结构分析.     

固相萃取结合超高效液相色谱-串联质谱法及气相色谱-负化学源质谱法测定人血清中的四溴双酚A、六溴环十二烷和多溴联苯醚

建立了固相萃取同时提取、净化血清中四溴双酚A(TBBPA)、α, β, γ-六溴环十二烷(HBCD)和8种多溴联苯醚(PBDEs)同系物的样本前处理方法,并结合色谱-质谱分离分析技术检测人血清样本中该类化合物的含量。试样在加入各自的同位素内标物后以甲基叔丁基醚/正己烷(1:1, v/v)混合溶剂进行萃取,再经浓硫酸去除脂肪后,以LC-Si固相萃取柱分离HBCD/TBBPA和PBDEs。采用分步检测的方式,在50 mm长BEH C18反相色谱柱上以超高效液相色谱-串联质谱(UPLC-MS/MS)的多反应监测模式(MRM)检测HBCD和TBBPA,在15 m长的毛细管柱上以气相色谱-负化学源质谱(GC-NCI/MS)的选择离子监测模式(SIM)检测PBDEs。以胎牛血清为空白基质,当HBCD、TBBPA和BDE-209的加标水平为0.5 ng/g和5 ng/g、三溴至七溴联苯醚的加标水平为0.05 ng/g和0.5 ng/g时,它们的平均加标回收率为80.3%～108.8%,相对标准偏差为1.02%～11.42%(n=5);以信噪比(S/N)为3计算,方法的检出限(LOD)为1.81～42.16 pg/g。采用该方法对实际样品进行测定,结果表明,本方法快速、准确、灵敏度高,能够满足血清中HBCD、TBBPA和PBDEs残留的同时提取及测定的要求。     

取代螺环戊烷的电子轰击和化学电离正,负离子质谱

本文报道了苯取代螺环戊烷衍生物的电子轰击(EI)正离子和化学电离正、负离子(PNCI)质谱。通过亚稳离子测定,研究了该类化合物的裂解机理。在卤代螺环戊烷的EI质谱中,分子离子峰都很弱,甚至不出现M 离子。其特征离子为[M-X]~ 、[M-2X] 和[M-X-HX]~ 。CI正离子谱有较强的[M H]~ 、[M-2X]~ 和[M-x]~ ,CI负离子谱的特征离子为[M X]~-,它们在多数情况下为基峰离子,另外还出现HX_2~-或X~-离子。     

多溴二苯醚取代特征对其芳香烃受体结合能力的效应分析

以已知18种多溴二苯醚（polybrominated diphenyl ethers,PBDEs）芳香烃受体结合能力实验值为因变量,构建基于取代基参数的PBDEs芳香烃受体结合能力定量构效关系模型以补足PBDEs芳香烃受体结合能力值,借助全析因实验的分析方法研究不同取代位置对PBDEs芳香烃受体结合能力的主效应及二阶交互效应,并分别从总取代基数、两苯环取代相似性、同一苯环取代基分布性综合研究PBDEs取代特征对芳香烃受体结合能力的影响规律.研究表明： PBDEs芳香烃受体结合能力受各取代位置主效应和二阶交互效应的显著影响,邻位取代基可显著降低PBDEs芳香烃受体结合能力,对位取代基则显著增强,间位取代基主效应较弱,主要通过与邻对位取代基间的二阶交互效应影响PBDEs芳香烃受体结合能力;总取代基数、两苯环取代相似性与PBDEs芳香烃受体结合能力无显著相关性,而同一苯环上取代基间分散性越大,同系物芳香烃受体结合能力越小.     

若干糖苷类化合物的负离子化学电离质谱研究

本文报道苦玄参苷类(picfeltarraenins)(1～5)、膜荚黄芪苷类(astramembrannins)(6～8)、雪胆素苷类(hemsamabilinins)(9,10)及其O-乙酰衍生物(11,12)和洋地黄毒苷(digitoxin)(13)的负离子化学电离质谱.用甲烷和二氯甲烷作为混合反应气,获得了满意的结果.谱中有特征的M~(?)或[M-1]~-,[M+Cl]~-和一系列脱糖基的碎片离子[M+Cl-nR]~-(R为不同类型的糖基)及糖基碎片离子[R+Cl]~-.乙酰化的糖苷还给出[M+Cl-nCH_2CO]~-或[M+Cl-nCH_3COOH]~-等碎片离子.     

反相高效液相色谱法测定对位酯工业品中的对位酯和对氯苯胺

建立了利用反相高效液相色谱测定工业对位酯中对位酯及其相关杂质对氯苯胺含量的方法。在C_(18)色谱柱(4.6×150 mm,5μm)上通过考察流动相种类、有机调节剂比例、p H等对保留的影响来优化色谱条件。分别建立了同时测定对位酯和对氯苯胺的反相离子对高效液相色谱法、快速测定对氯苯胺的反相高效液相色谱法,并建立了进一步分离对位酯中其他相关杂质的反相高效液相色谱法,可用于对位酯中相关杂质的液相色谱-质谱联用定性分析。在建立的同时测定对位酯和对氯苯胺的反相离子对高效液相色谱法中,对位酯和对氯苯胺分别在0.78~1000.0μg/m L(r=0.9997)和0.31~20.00μg/m L(r=0.9999)的浓度范围内成线性关系,平均回收率(n=3)分别为100.1%(RSD=0.62%)和100.8%(RSD=1.3%);在快速测定对氯苯胺的反相高效液相色谱法中,对氯苯胺在0.25~200.0μg/m L(r=0.9995)的浓度范围内成线性关系,平均回收率(n=3)为102.0%(RSD=0.43%)。     

多溴联苯醚与人血清白蛋白相互作用的表面等离子体共振及分子对接

采用表面等离子体共振(SPR)技术, 在模拟生理条件下实时动态研究了8种典型多溴联苯醚(PBDEs)与人血清白蛋白(HSA)相互作用的动力学和热力学行为. 通过分子对接模拟研究了PBDEs与HSA相互作用的分子机制, 探讨了不同PBDEs与蛋白的结合模式及作用力. 动力学实验结果表明, PBDEs中溴原子的个数和取代位置对相互作用有规律性的影响. 溴原子通过改变PBDEs分子与HSA作用过程中的解离速率来影响其亲和力, 溴原子个数越多, PBDEs与HSA作用的亲和力越强; 而取代基位置则影响PBDEs与HSA作用结合速率的快慢, 同分异构体中间位取代溴的亲和力大于邻位取代溴. 分子对接结果显示, 8种PBDEs主要结合于HSA的Site I位点, 但结合位点周边氨基酸残基类型的差异影响了结合力. 范德华力和氢键对结合能的贡献远大于静电力.     

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.     

全乙酰化低聚木糖的质谱研究

本文报道了全乙酰化木糖(1)～木六糖(6)的电子轰击质谱(70eV,20eV)及化学电离(反应气体CH_4,i-C_4H_(10),NH_3)质谱的研究结果.根据亚稳峰及高分辨测定资料,阐述了木糖全乙酰化物的碎裂途径,讨论了木二糖～木六糖全乙酰化物的碎裂机理,指出了低聚木糖质谱的特征碎片离子.在所研究的电子轰击质谱中均未观察到分子离子,只有以NH_3为反应气体的化学电离质谱才获得准分子离子,其中全乙酰化木糖(1)～木三糖(3)的[M+NH_4]~+为基峰,而全乙酰化木四糖(4)～木六糖(6)的[M+NH_4]~+离子强度较弱。     

Applications of HPLC-MS in compound Ilex pubescens extract study

In this paper, high performance liquid chromatography (HPLC) along with mass spectrometry (MS) and HPLC along with a diode array detector (DAD) was used to study the compound Ilex pubescens extract. Two ionization techniques: electro spray ionization (ESI) and atmospheric pressure chemical ionization (APCI) were used in this work. The liquid chromatograms obtained by DAD, total ion chromatograms (TIC) from positive-and negative-ion ESI-MS and the positive-and negative-ion APCI-MS were compared. The liquid chromatograms obtained by TIC from ESI-MS provided more information on chromatographic peaks than those obtained by DAD or TIC from APCI-MS. It is suggested that the fingerprints of the compound Ilex pubescens extract should be provided by the liquid chromatograms obtained by DAD together with TIC from the negative-ion ESI-MS. The molecular weights of the nine main components in an HPLC-DAD chromatogram were determined by the corresponding positive-and negative-ion ESI and the positive-and negative-ion APCI mass spectra information. In the liquid chromatogram obtained by TIC from the negative-ion ESI-MS, the molecular weights of 23 main components were determined based on the corresponding positive-and negative-ion ESI mass spectra information.     

Mass spectrometric characteristics of decabromodiphenyl ether and the application of isotopic dilution in the electron capture negative ionization mode for the analysis of polybrominated diphenyl ethers

The mass spectrometric properties of (12)C-and (13)C-labeled decabromodiphenyl ether (BDE-209) in the low-resolution mass spectrometry electron capture negative ionization mode (ECNI-MS) is described in detail and are compared with those of polybrominated diphenyl ethers (PBDEs) with a lower degree of bromination. The mass spectrometric properties of BDE-209 make it possible to apply (13)C-labeled BDE-209 as an internal surrogate standard for the determination of BDE-209 by isotopic dilution. A combination of the [Br](-) and [C(6)Br(5)O](-) fragment ions is proposed for the detection with ECNI-MS in the selected ion monitoring mode to increase selectivity, sensitivity and accuracy in the determination of decabromodiphenyl ether together with other polybrominated diphenyl ethers. The importance of optimizing the instrument parameters to obtain optimal response from the mass spectrometer in the analysis of PBDEs is discussed in detail.     

New perspective on the determination of flame retardants in sewage sludge by using ultrahigh pressure liquid chromatography–tandem mass spectrometry with different ion sources

Analysis of 11 polybrominated diphenyl ethers (PBDEs), tetrabromobisphenol A bis 2,3-dibromopropylether (TBBPA-bis), tetrachlorobisphenol A (TCBPA), tetrabromobisphenol A (TBBPA) and hexabromocyclododecanes (HBCDs) was optimized by ultrahigh pressure liquid chromatography/tandem mass spectrometry (UPLC–MS/MS) operating in negative ion (NI) mode. Electrospray ionization (ESI), atmospheric pressure photoionization (APPI) and atmospheric pressure chemical ionization (APCI) sources were tested and for PBDEs APCI gave higher sensitivity than APPI while for TBBPA-bis APCI and APPI showed similar performance. ESI was the best option for TCBPA, TBBPA and HBCDs. Detection limits were between 20 and 59 fg for the compounds analyzed by ESI, 0.10 and 0.72 pg for PBDEs and 6 pg for TBBPA-bis. The matrix effect of sewage sludge extract was also tested showing negligible ion suppression for APCI and an increase of the background level of all investigated pollutants leading to a worsening of the limits of quantification by a factor between 1.2 and 3.3. The UPLC-APCI/MS/MS method for PBDEs, after pressurized liquid extraction (PLE), was validated by comparison with the concentration values from the NIST 1944 standard reference material. The advantages of the methods include low detection limits, PBDE congeners specificity using selected multiple reaction monitoring (MRM) transitions, and the absence of thermal degradation of higher PBDE congeners, especially BDE-209. The methods were applied for the determination of the above reported flame retardants in sewage sludge in order to get more information about the degradation on PBDEs (in particular BDE-209) during municipal wastewater treatments.     

Effect of eluent on the ionization process in liquid chromatography-mass spectrometry

The most widely used ionization techniques in liquid chromatography-mass spectrometry (LC-MS) are electrospray ionization (ESI), atmospheric pressure chemical ionization (APCI) and atmospheric pressure photoionization (APPI). All three provide user friendly coupling of LC to MS. Achieving optimal LC-MS conditions is not always easy, however, owing to the complexity of ionization processes and the many parameters affecting mass spectrometric sensitivity and chromatographic performance. The selection of eluent composition requires particular attention since a solvent that is optimal for analyte ionization often does not provide acceptable retention and resolution in LC. Compromises must then be made between ionization and chromatographic separation efficiencies. The review presents an overview of studies concerning the effect of eluent composition on the ionization efficiency of ESI, APCI and APPI in LC-MS. Solvent characteristics are discussed in the light of ionization theories, and selected analytical applications are described. The aim is to provide practical background information for the development and optimization of LC-MS methods.     

Targeted lipidomics using electron capture atmospheric pressure chemical ionization mass spectrometry

There is an increasing need to be able to conduct quantitative lipidomics analyses as a complement to proteomics studies. The highest specificity for proteomics analysis can be obtained using methodology based on electrospray ionization (ESI) or atmospheric pressure chemical ionization (APCI) coupled with liquid chromatography/tandem mass spectrometry (LC/MS/MS). For lipidomics analysis it is often necessary to be able to separate enantiomers and regioisomers. This can be very challenging when using methodology based on conventional reversed-phase chromatography. Normal-phase chromatography using chiral columns can provide dramatic improvements in the resolution of enantiomers and regioisomers. However, conventional ESI- and APCI-MS/MS has limited sensitivity, which makes it difficult to conduct studies in cell culture systems where only trace amounts of non-esterified bioactive lipids are present. The use of electron capture APCI-MS/MS overcomes this problem. Enantiomers and regioisomers of diverse bioactive lipids can be quantified using stable isotope dilution methodology coupled with normal-phase chiral chromatography and electron capture APCI-MS/MS. This methodology has allowed a lipidomics profile from rat epithelial cells maintained in culture to be delineated and allowed the effect of a non-selective lipoxygenase inhibitor to be assessed.     

Comparison of universal detectors for high-temperature micro liquid chromatography

This study compares, through micro high-temperature liquid chromatography (microHTLC), three commercial universal detectors that allow a direct detection of lipids. The detectors are: the charged aerosol detector (CAD), the evaporative light-scattering detector (ELSD) and the ion trap mass spectrometer with atmospheric pressure chemical ionization (APCI) and electrospray ionization (ESI) sources (APCI-MS and ESI-MS). This study shows the feasibility to use the high temperature with these detectors and hybrid behavior between concentration and mass flow rate detector in microHTLC. The detectors were compared in terms of response intensity, linearity and limit of detection for different high temperatures. The charged aerosol detector shows a linear response from 5 to 500 microg/mL and the correlation coefficients (r(2)) obtained for squalene, cholesterol and ceramide IIIB exceed 0.99.     

Comparison of atmospheric pressure chemical ionization and electrospray ionization mass spectrometry for the detection of lignans from sesame seeds

In sesame seeds, high concentrations of lignans are present. When these lignans are fermented in the human colon, a range of structurally different lignans is formed. A good liquid chromatography/mass spectrometry (LC/MS) protocol for the analysis of lignans in complex mixtures is lacking. In order to develop such a protocol, electrospray ionization (ESI)-MS and atmospheric pressure chemical ionization (APCI)-MS, both in the positive and negative ionization mode, were compared. An extract from defatted sesame meal was analyzed by APCI-MS and ESI-MS, before and after deglucosylation. APCI-MS was found to be a more generic method than ESI-MS because lignans, especially sesamolin, sesamin and pinoresinol, were better detected by APCI-MS than by ESI-MS. Positive and negative ionization modes had to be combined in order to detect all lignans in a bacterial culture grown on aglyconic, acid-treated lignans from sesame oil and defatted sesame meal. Lignans with methylenedioxy-bridged furanofuran structures mostly lack phenolic hydroxyl groups and were, therefore, optimally detected in positive ionization mode. Dibenzylbutadiene lignans, which were formed during fermentation, carry hydroxyl groups and were better detected in negative ionization mode.     

食品中多溴联苯醚残留的气相色谱-串联质谱分析方法研究

建立了食品中8种多溴联苯醚(PBDEs) 残留的气相色谱-串联质谱分析方法,初步解析了PBDEs的电子轰击串联质谱(EI MS/MS)图,为各种目标物的准确定性分析提供依据.以BDE-28、BDE-47、BDE-66、BDE-85、BDE-99、BDE-100、BDE-153、BDE-154为研究对象,对EI MS/MS各分析参数进行了优化.用超声提取-酸性硅胶层析柱净化的前处理方法制备样品,当空白样品的加标水平为10.0、25.0 μg/kg时,8种PBDEs的平均加标回收率为82% ～112%,相对标准偏差为3.1% ～15%,方法检出限均低于1.5 μg/kg;8种PBDEs的线性范围为10.0 ～500 μg/kg,相关系数均大于0.994 7.     

Use of porous graphitic carbon for the analysis of nitrate ester, nitramine and nitroaromatic explosives and by-products by liquid chromatography-atmospheric pressure chemical ionisation-mass spectrometry

A new LC/MS method was developed for the analysis of sixteen different analytes including the most common organic explosives encountered in forensic investigations. The separation was achieved using a porous graphitic carbon (PGC) column with a binary gradient elution. Molecular modeling suggested a possible interpretation for the elution order of explosive compounds on PGC. The introduction of ammonium formate in the mobile phase resulted in the formation of characteristic adduct ions thus enhancing the mass spectrometric detection of nitrate ester and nitramine compounds. Atmospheric pressure chemical ionization (APCI) and electrospray ionization (ESI) were compared in terms of sensitivity. The final LC/APCI-MS method allowed easy identification of investigated compounds with limits of detection ranging from 0.04 to 1.06 ng/microl. The analysis of simulated forensic samples confirmed the performance of the method.     

Analysis of native amino acid and peptide enantiomers by high-performance liquid chromatography/atmospheric pressure chemical ionization mass spectrometry

High-performance liquid chromatography (HPLC) coupled to atmospheric pressure chemical ionization (APCI) mass spectrometry was used for the separation and detection of amino acid and peptide enantiomers. With detection limits as low as 250 pg, 25 amino acids enantiomers were baseline resolved on a Chirobiotic T chiral stationary phase. APCI demonstrated an order of magnitude better sensitivity over electrospray ionization (ESI) for free amino acids and low molecular mass peptides at the high LC flow-rates necessary for rapid analysis. As the peptide chain length increased (peptides with M(r) > or = 300 Da), however, ESI proved to be the more ideal atmospheric pressure ionization source. A mobile phase consisting of 1% (w/w) ammonium trifluoroacetate in methanol and 0.1% (w/w) formic acid in water increased the sensitivity of the APCI method significantly. A step gradient was then used to separate simultaneously all 19 native protein amino acid enantiomers in less than 20 min using extracted ion chromatograms.