电子轰击型离子源中抑制H3+的几点思考

分析了在电子轰击型(EI)离子源中,磁场、进样量、阴极电流和阴极电压等4种主要仪器设备条件对产生H₃⁺的影响,在实验中得到较好的验证,并得到H₃⁺在4种条件下的基本影响趋势。本研究对使用低分辨率质谱计分析天然氢同位素时,EI离子源参数的调节和进样量的选取具有指导意义。     

Selected ion flow tube mass spectrometry (SIFT-MS) for on-line trace gas analysis

Selected ion flow tube mass spectrometry (SIFT-MS) is a new analytical technique for the real-time quantification of several trace gases simultaneously in air and breath. It relies on chemical ionization of the trace gas molecules in air/breath samples introduced into helium carrier gas using H(3)O(+), NO(+), and O(2) (+.) precursor ions. Reactions between the precursor ions and trace gas molecules proceed for an accurately defined time, the precursor and product ions being detected and counted by a downstream mass spectrometer, thus effecting quantification. Absolute concentrations of trace gases in single breath exhalation can be determined by SIFT-MS down to ppb levels, obviating sample collection and calibration. Illustrative examples of SIFT-MS studies include (i) analysis of gases from combustion engines, animals and their waste, and food; (ii) breath and urinary headspace studies of metabolites, ethanol metabolism, elevated acetone during ovulation, and exogenous compounds; and (iii) urinary infection and the presence of tumors, the influence of dialysis on breath ammonia, acetone, and isoprene, and acetaldehyde released by cancer cells in vitro. Flowing afterglow mass spectrometry (FA-MS) is briefly described, which allows on-line quantification of deuterium in breath water vapor.     

电子轰击源垂直加速式飞行时间质谱仪的研制

介绍了自制的电子轰击离子源（electron ionization, EI）垂直加速式飞行时间质谱仪（orthogonal acceleration time-of-flight mass spectrometer, Oa-TOF MS）的原理,结构以及初步的实验结果。搭建了电子轰击源垂直加速式飞行时间质谱仪,并得到室内空气成分谱图。结果表明,仪器分辨率优于2 000（full width at half maximum,FWHM）,质量精度优于4×10^-5,可以用于气体成分的快速定性分析。     

LC-MS/MS法测定大鼠血浆中MTP-131

MTP-131 is a tetrapeptide under development for treating diabetes. MTP-131 contains a lysine, an arginine, a phenylalanine and a modified tyrosine in its structure. The quantification of MTP-131 in rat plasma was developed and validated by liquid chromatography-tandem mass spectrometry(LC-MS/MS). MTP-131 was separated from plasma by Waters Oasis^® HLB cartridge solid phase extraction, then separated by C₁₈ column. The mobile phase consisted of V(acetonitrile):V(10 mmol L^－1 ammonium acetate):V(acetic acid)＝30:70:0.04. A mass spectrometer equipped with electrospray ionization source was used as a detector and operated in the positive ion mode. Selected reaction monitoring(SRM) using the double protonated molecules of [M＋2H]^2＋ for MTP-131, three main fragment ions of m/z 70, 84, 20 were used for the quantification. The d5-MTP-131 was used as the internal standard. The method exhibites a linear range of 1.0-10 000μg L^－1 for MTP-131 with a lower limit of quantification at 1.0 μg L^－1. The intra- and inter-assay precisions are below 9.9%, and relative errors within 6.0%. The mean extraction recovery of MTP-131 is above 80%. Under the selected chromatographic conditions and sample preparation conditions, there is no significant matrix effect of MTP-131 at low or high concentrations. The validated method proves to be sensitive, rapid, and is applied successfully for the pharmacokinetic study of MTP-131 in rat.     

联苯-取代哌嗪衍生物的质谱研究

合成了三类取代哌嗪修饰的新型联苯哌嗪化合物,并对这些化合物进行多级电喷雾 离子阱质谱裂解分析。在一级全扫描质谱中发现,三乙胺与4,4′-二甲氧基-5,6,5′,6′-二次甲二氧基联苯-2-甲酸酯-2′-甲酰基-4-取代哌嗪化合物形成[M+101+H]⁺。实验还发现,结构中有氟原子存在的联苯-2-甲酸酯-2′-甲酰基-4-取代哌嗪化合物更易与钠离子结合形成加钠的准分子离子[M+Na]⁺。二级质谱说明,4,4′-二甲氧基-5,6,5′,6′-二次甲二氧基联苯-2-甲酸酯-2′-甲酰基-4-取代哌嗪化合物的哌嗪上取代基的不同,对二级质谱的碎片离子形式有显著的影响。     

在线质谱仪与在线气相色谱仪的比较及应用

本文介绍了在线质谱仪和在线气相色谱仪的原理及结构,并根据各自的特点对其应用进行简单总结和比较。由于两者工作原理的差异,在线质谱仪具有更快的分析速度和定性能力,而在线气相色谱仪对成分复杂的气体可达到更好的分离效果,在日常维护中,两者也存在较大的差别。因此,在实际应用中,要考虑现场监测的需要来选择合适的仪器。     

一种在线监测快速过程质谱仪的设计与测试

工业生产过程中,如何实现准确、连续、可靠地检测目标组分是产物及排放物在线监测的重点。本工作研制了一种在线监测快速过程质谱仪,采用高增益的复合跨导线性放大技术代替传统的过程质谱仪所采用的对数放大技术,该技术可实现质谱仪在高增益条件下仍然具有超高速的特点,结合16位高速AD转换器,可以实现更快的扫描速度和更高的数据输出频率,能够更准确地捕捉快速反应（如热解）过程的气体生成物随时间的变化信息,进而实现反应特性的精准分析和量化,为反应动力学研究提供无失真的在线分析数据。本实验对该仪器的质量分辨率、灵敏度、质量轴稳定性、长时稳定性等关键技术指标进行了测试,同时结合煤热解反应过程监控需求进行了实际应用测试。结果表明,该仪器各项指标已基本达到市场主流过程质谱仪器的水平。     

Mass spectrometric studies of elusive molecules that contain an N(+)-X- bond

This review will be concerned with the gas phase chemistry of 1,2- and 1,3-dipolar systems that contain a carbon-nitrogen bond. Although most of these compounds are stable molecules under normal conditions, certain congeners are reactive species that cannot be prepared using conventional procedures. The isolation and observation of these elusive compounds therefore require appropriate experimental conditions such as those provided by the gas phase of a mass spectrometer. In these experiments, the radical cations, corresponding to the molecule under study, must be prepared via indirect procedures, including dissociative electron ionization, on-line flash-vacuum pyrolysis-mass spectrometry, or ion-molecule reactions. Their characterization is mainly based on collisional activation and ion-molecule reactions. The formation of the corresponding highly reactive neutrals is attempted by neutralization-reionization mass spectrometry. This review presents more than one hundred different molecules together with their methods of preparation and the experiment used to identify them.     

HPLC-MS/MS法测花旗松素在Beagle犬血浆中的浓度及其药代动力学研究

A rapid, sensitive and selective method for the determination of taxifolin in Beagle dog plasma was described by high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS). Resveratrol was used as internal standard (I.S.). MS detection and quantitation were done by mass spectrometer using selected reaction monitoring at m/z 303 and 285 [M－H]^－ for taxifolin, and m/z 227 and 185 [M－H]^－ for resveratrol. The calibration curve is linear (r＞0.998) from 2 to 1 000 μg L^－1, and the lower limit of quantification(LLOQ) is 2 μg L^－1.     

人参、红参皂苷类成分指纹图谱研究

为了建立一种快速鉴定人参和红参的方法,应用超高效液相色谱-串联质谱研究人参和红参中的皂苷类成分指纹图谱。室温下用甲醇提取人参粉末,提取液离心,并用0.22 μm滤膜过滤。色谱柱是BEH Shield RP₁₈ 柱( 1.7 μm×2.1×50 mm, Waters ,USA)和BEH保护柱;流动相：乙腈（A）,水（B）;0~5 min A从25%到50%,5~8 min,A从50%变化到90%,8~10 min,A从90%变到100%,10~12 min,A保持在100%;进样体积10 μL,检测波长195 nm。质谱喷雾电压-4.5 kV,金属毛细管电压-45 V,温度250 ℃,壳气（氮气）流速27 L/h,辅助气（He）流速180 L/h,质量扫描范围m/z 200~1 500,碰撞气为氦气,质谱碎裂信息用来鉴定皂苷。液质联用数据显示在人参炮制过程中化学成分发生了变化,结果表明不同批次的人参与红参能够清晰分组。该方法快速,简单,特征性和重现性良好。