小型高分辨电子轰击离子源反射式飞行时间质谱仪的研制

常用的气体分析质谱仪使用四极杆质谱作为分析器,分辨率一般低于300,无法解决同质量数离子带来的干扰问题.本实验自行研制了一种小型高分辨气体分析质谱仪,它采用电子轰击离子源反射式飞行时间质量分析器.仪器腔体总长45 cm,在m/z 28的位置,质量分辨率达到3000(Full width at half maximum,FWHM),实现了CO和N2的半峰谷分离;在m/z 69的位置,仪器分辨率达到5000(FWHM).在直接大气压进样条件下,可以检测到空气中136Xe(含量7.8 μ g/m3)和80Kr(含量2.8 μg/m3).使用ADC采集时,仪器的动态范围为1 06.该仪器将作为高端气体质谱仪,应用于过程监测在线分析、环境有机挥发物研究、热分析质谱及催化反应监测等领域.     

羊红膻中微量元素含量的测定

采用高分辨全谱直读电感耦合等离子体发射光谱仪测定了羊红膻(Pimpinella thellungianaWolff)药材地上与地下不同部位中含Cu、K、Na、Fe、Se、Mg、As、Ca、Cd、Cr、Mn、Ni、P、Pb和Zn等15种微量元素含量,并进行了比较。结果表明,重金属As和Pb几乎检测不到,K含量均高;同时也为羊红膻药理作用及临床用药提供科学依据。     

Probing the Effects of Reagent Gas Pressure and Ion Source Temperature for Dimethyl Ether Chemical Ionization of Tricyclic Antidepressants in an External Source Ion Trap Mass Spectrometer

This study examines the reagent gas pressure and ion source temperature dependence for dimethyl ether chemical ionization (DME CI) mass spectra recorded with an external source ion trap mass spectrometer (ITMS). Information for better controls of the reagent gas pressure in order to obtain fair CI spectra is provided. The origin of M^+? ions observed in DME CIMS is discussed in detail. Furthermore, the ion source temperature effect on the DME CI is also investigated.     

扫描式电感耦合等离子体光谱仪谱线峰位移的机理研究

通过对扫描式电感耦合等离子体原子发射光谱仪(ICP-AES)出射光谱线峰位移(Δλ)的机理研究,发现温度的变化、波长的变化以及光谱仪机械的系统误差是产生谱线峰位移的主要因素,首次测量了谱线峰位移与波长变化之间的非线性函数关系曲线Δλ-λ,以及谱线峰位移与温度变化之间的非线性函数关系曲线Δλ-T,并用多项式方程表达了这些函数关系。本研究还发现,不同的光栅单色仪有近似相同的Δλ-λ函数关系曲线,但是Δλ-T的函数关系曲线却很不相同。利用这些非线性函数方程式,设计开发了扫描式ICP-AES光谱仪的智能波长校正装置(IWC),用它取代传统的局部恒温系统及谱线描迹法进行样品分析的结果表明,智能波长校正的ICP光谱仪(ICP-IWC)谱线峰定位精度高,具有省时、安全、结构简单的特点,有广阔的应用前景。     

Multi-turn time-of-flight mass spectrometers with electrostatic sectors

The mass resolution of a time-of-flight (TOF) mass spectrometer is directly proportional to its total flight pathlength. Multi-turn or multi-passage ion optical geometries are necessary to obtain fight distances of sufficient length within reasonable size limitations. We have investigated ion optics for a multi-turn TOF mass spectrometer with electrostatic sectors. The concept of 'perfect' focusing conditions is introduced. Furthermore, a new type of multi-turn TOF mass spectrometer, the MULTUM Linear plus, was developed. It consists of four cylindrical electric sectors and 28 electric quadrupole lenses. It has a vacuum chamber 60 x 70 x 20 cm in size. Mass resolution is demonstrated to increase according to the number of ion cycles. A mass resolution of 350 000 (m/z = 28, FWHM) was achieved after 501.5 cycles. The MULTUM Linear plus analyzer is not simple, however; 28 electric quadrupole lenses are used. In order to reduce the number of ion optical parts, an improved multi-turn TOF mass spectrometer, the MULTUM II, consisting of only four toroidal electric sectors, was also developed. The possibility of tandem mass spectrometric applications using multi-turn TOF mass spectrometers is also discussed.     

Optimized precursor ion selection for labile ions in a linear ion trap mass spectrometer and its impact on quantification using selected reaction monitoring

The fragmentation of fragile ions during the application of an isolation waveform for precursor ion selection and the resulting loss of isolated ion intensity is well‐known in ion trap mass spectrometry (ITMS). To obtain adequate ion intensity in the selected reaction monitoring (SRM) of fragile precursor ions, a wider ion isolation width is required. However, the increased isolation width significantly diminishes the selectivity of the channels chosen for SRM, which is a serious problem for samples with complex matrices. The sensitive and selective quantification of many lipid molecules, including ceramides from real biological samples, using a linear ion trap mass spectrometer is also hindered by the same problem because of the ease of water loss from protonated ceramide ions. In this study, a method for the reliable quantification of ceramides using SRM with near unity precursor ion isolation has been developed for ITMS by utilizing alternative precursor ions generated by in‐source dissociation. The selected precursor ions allow the isolation of ions with unit mass width and the selective analysis of ceramides using SRM with negligible loss of sensitivity. The quantification of C18:0‐, C24:0‐ and C24:1‐ceramides using the present method shows excellent linearity over the concentration ranges from 6 to 100, 25 to 1000 and 25 to 1000 nM, respectively. The limits of detection of C18:0‐, C24:0‐ and C24:1‐ceramides were 0.25, 0.25 and 5 fmol, respectively. The developed method was successfully applied to quantify ceramides in fetal bovine serum. Copyright © 2014 John Wiley & Sons, Ltd.     

Experimental validation of an effective carbon number-based approach for the gas chromatography–mass spectrometry quantification of ‘compounds lacking authentic standards or surrogates’

For the quantitative analysis of ‘compounds lacking authentic standards or surrogates’ (CLASS) in environmental media, we previously introduced an effective carbon number (ECN) approach to develop an empirical equation for the prediction of their response factor (RF). In this research, a series of laboratory experiments were carried out to benchmark the reliability of an ECN approach for sorbent tube/thermal desorption/gas chromatography (GC)/mass spectrometry (MS) applications. First, the ECN values were determined using external calibration data from 25 reference volatile organic compounds (VOCs) using two MS dectectors (quadrupole (Q) and time-of-flight (TOF)). Then, a certified standard mixture of 54 VOCs was analyzed by each system as a simulated unknown sample. The analytical bias, assessed in terms of percentage difference (PD) between the certified and ECN-predicted mass values, averaged 19.2 ± 16.1% (TOF-MS) and 28.2 ± 27.6% (Q-MS). The bias using a more simplified carbon number (CN)-based prediction increased considerably, yielding 53.4 ± 53.3% (TOF-MS) and 61.7 ± 81.3% (Q-MS). However, the bias obtained using the ECN-based prediction decreased significantly to yield average PD values of 9.84 ± 7.28% (TOF-MS) and 16.8 ± 8.35% (Q-MS), if the comparison was limited to 26 (out of 54) VOCs with CN ≥ 4 (i.e., 25 aromatics and hexachlorobutadiene).     

超高效液相色谱-线性离子阱/静电场轨道阱高分辨质谱鉴别纺织品中禁用芳香胺及其异构体

针对目前纺织品中禁用偶氮染料检测中的假阳性问题,建立了一套应用超高效液相色谱-线性离子阱/静电场轨道阱高分辨质谱（UPLC-LTQ/Orbitrap）同时筛选24种禁用芳香胺及其常见的14种异构体的方法。样品经连二亚硫酸钠还原,叔丁基甲醚提取后,以水/甲醇（9/1,v/v）稀释定容,用ZORBAX SB-C₁₈色谱柱（150 mm×2.1 mm,5 μm）分离,以0.1%甲酸水溶液和甲醇为流动相,电喷雾正离子（ESI⁺）模式电离。以准分子离子峰的精确质量数和保留时间定性,以提取的色谱图峰面积定量。38种芳香胺的线性相关系数大于0.99,方法检出限为0.5~5 μg/kg。该方法可通过一次实验同时对24种禁用芳香胺及其常见的14种异构体准确定性定量,大大缩短检测周期,实际样品检测也进一步验证了其灵敏性和准确性。     

Development of an automated dual‐mode supercritical fluid chromatography and reversed‐phase liquid chromatography mass‐directed purification system for small‐molecule drug discovery

We report the development of a dual‐mode mass‐directed supercritical fluid chromatography and reversed‐phase liquid chromatography purification system. The addition of a third pump allows for flexible mobile phase control between the two techniques, and enables operation of either chromatography mode within minutes by activation of a set of switching valves on a single system. Software control, fluidic pathways, interface to the mass spectrometer, and fraction collection have been modified for compatibility between both separation methods. The conditioning solvent and tuning parameters for the mass spectrometer were adjusted to achieve an ideal signal trace in either mode with good linearity (r² > 0.970) over a range of concentrations and minimal noise for accurate peak detection and isolation. The registration success rate is 90% and overall sample recovery for either technique is 80?90%. Combining two orthogonal separation and purification modes in one single system has improved the purification throughput of complex mixtures and has been a valuable, cost‐saving tool in our laboratory.     

Liquid chromatography–high-resolution mass spectrometry for identifying aqueous chlordecone hydrate dechlorinated transformation products formed by reaction with zero-valent iron

Chlordecone (CLD) is a persistent toxic chlorinated pesticide which contaminates different ecosystems in French West Indies. A soil remediation process including zero-valent iron (ZVI) has produced promising results but failed to completely degrade CLD, and the analytical procedures used yielded little information on the transformation products. To fill these gaps, dechlorination of aqueous CLD by micrometric particles of ZVI has been investigated. Aliquots of water with 25% (v/v) of acetone spiked with 100 ppm CLD were taken at different times during a 30-day ZVI treatment and directly analysed by ultra-high-performance liquid chromatography in negative electrospray ionisation mode. CLD has been totally transformed after 14 days into 14 dechlorinated degradation products, including 9 isomeric compounds. The maximum chloride concentrations appearing in the medium represent 44% of that which would result from total dechlorination of CLD. The CLD transformation products identified by accurate mass measurements on an ultra-high-resolution Q-TOF mass spectrometer (Q-TOF-MS) were C₁₀H₃Cl₉O₂, C₁₀H₄Cl₈O₂, C₁₀H₅Cl₇O₂, C₁₀H₆Cl₆O₂ and C₁₀H₇Cl₅O₂. The results show the interest of LC-Q-TOF-MS for identifying transformation products of organic contaminants, and the effectiveness of micrometric ZVI particles to totally transform CLD into less chlorinated products.