进样量和信号强度对气相色谱-燃烧-同位素比值质谱测定δ13C和δ15N的影响

采用气相色谱-燃烧-同位素比值质谱（GC-C-IRMS）法对咖啡因化合物和混合体系中特定氨基酸的δ13C和δ15N进行测定,在保证高测定精度和准确度的前提下,探讨GC C IRMS对进样量和信号强度变化的响应特征。分析结果表明,当C质量≥ 1 ng或m/z 44信号≥ 100 mV时,以及N质量≥5 ng或m/z 28信号≥ 100 mV时,咖啡因δ13C和δ15N测定结果的精度（<03‰）和准确度（<02‰）均能够满足实验室测试要求。针对混合体系中氨基酸δ13C和δ15N的测定,GC C IRMS可以在极少的进样量下实现对特定氨基酸色谱峰的有效分离。12种氨基酸δ13C测定结果未表现出对m/z 44信号强度的依赖性（斜率接近0）,其δ13C平均测定精度为056‰;而δ15N测定结果表现出良好的时间稳定性（4天）,与元素分析 稳定同位素比值质谱（EA IRMS）单独测定结果的平均偏差为077‰。     

气相色谱-燃烧-同位素比值质谱法测定发酵液中尿素δ~(13)C和δ~(15)N

在酸性环境下,尿素与丙二醛-二甲基乙缩醛反应生成2-羟基嘧啶,随后由重氮甲烷甲基化形成2-甲氧基嘧啶。本研究以酵母发酵液为例,建立了气相色谱-燃烧-同位素比值质谱(GC-C-IRMS)法测定发酵液中尿素δ~(13)C和δ~(15)N,并对前处理方法和GC条件进行了优化。结果表明:尿素在不同13 C(0~5%)和15 N(0~10%)标记丰度下,标记量与GC-C-IRMS测定结果的相关性良好,线性相关系数R2分别为0.998和0.999,说明可在极低标记浓度下对尿素中δ~(13)C和δ~(15)N进行准确测定。采用该方法测定了酵母发酵液尿素中δ~(13)C和δ~(15)N,其重复性相对标准偏差分别为0.21‰和0.30‰,再现性相对标准偏差分别为0.23‰和0.29‰。该方法精度高、准确性好,可为低稳定同位素标记尿素示踪实验以及尿素循环代谢研究提供方法基础。     

多接收双聚焦等离子体质谱法测定高精度同位素比

采用 VG Axiom型多接收双聚焦等离子质谱仪 ( MC-ICPMS)测定 Nd、Pb、U同位素比值 ,应用指数公式对测定的结果进行质量歧视校正。结果表明 :测定参考物质 Ames Nd获得的钕同位素比值为 14 3 Nd/14 4 Nd=0 .5 1 2 1 44± 0 .0 0 0 0 1 5 (确认值为 0 .5 1 2 1 3 5 )、14 5Nd/14 4 Nd=0 .3 4841 7± 0 .0 0 0 0 1 9(确认值为 0 .3 4841 8) ;测定参考物质 NIST SRM981获得的铅同位素比值为 2 0 8Pb/2 0 4Pb=3 6.71 1 4± 0 .0 0 81、2 0 7Pb/2 0 4Pb=1 5 .4886± 0 .0 0 3 8、2 0 7Pb/2 0 6Pb=0 .91 44 5 6± 0 .0 0 0 0 3 9、2 0 6Pb/2 0 4Pb=1 6.93 82± 0 .0 0 3 1、2 0 8Pb/2 0 6Pb=2 .1 660 1± 0 .0 0 0 1 6;测定参考物质 NIST SRM 0 1 0获得的铀同位素比值为 2 3 4 U/2 3 8U =0 .0 0 0 0 5 46±0 .0 0 0 0 0 0 3 (确认值为 0 .0 0 0 0 5 46)     

ZTQ-201型~(13)C检测仪的研制

研制成功ZTQ 2 0 1型13C检测仪 ,该仪器采用色谱分离和质谱测量原理 ,测定人体呼出气中CO2 的13C/ 12 C比值 ,测量精度 (δ)优于 0 5‰。本文介绍仪器的工作原理、组成和性能。     

不同城市居民头发中碳、氮稳定同位素比值特征研究

头发中蕴含了个体的饮食情况等信息,不同地区居民饮食习惯不同,其头发中碳（C）、氮（N）稳定同位素比值也具有一定的差异性。本研究采集了华中、华东、华南、西南和西北地区8个城市常住居民的头发样本,利用元素分析仪 稳定同位素比质谱（EA-IRMS）进行C、N稳定同位素比值检测。结果表明：部分城市间居民头发中C、N稳定同位素比值存在显著差异。居民头发δ¹³C与人均蔬菜消费量呈显著负相关,居民头发δ¹⁵N与人均肉类消费量呈显著正相关,鱼类的大量摄入可能会提高居民头发δ¹⁵N值。男性和女性居民头发中C、N稳定同位素比值没有显著性差异,女性居民头发δ¹³C与年龄呈较弱负相关。中国与其他国家居民头发中C、N稳定同位素比值存在差异,这主要是由不同国家居民的饮食习惯不同导致的。     

三过氧化三丙酮的稳定同位素比值特征研究

本研究采用稳定同位素质谱(IRMS)探讨了不同原料、不同工艺合成的三过氧化三丙酮(TATP)的稳定同位素比值特征,所合成TATP的δ¹³C、δ²H、δ¹⁸O值分别为-31.62‰～-27.50‰、-144.09‰～-107.85‰、30.61‰～38.02‰。结果表明,依据稳定同位素特征可区分不同原料、工艺合成的TATP。所合成的TATP碳、氢稳定同位素比值主要受丙酮影响,氧稳定同位素比值主要与过氧化氢有关,酸作为催化剂并未对TATP的稳定同位素比值产生显著影响。随着反应时间的增加,TATP的δ¹³C值呈增加趋势。本研究结果对调查TATP的来源有重要意义。     

MC-ICP-MS测定铀系定年标样的~(230)Th年龄

本研究利用Neptune Plus型多接收电感耦合等离子体质谱仪(MC-ICP-MS)测定了U和Th标准溶液的同位素比值及U系定年标样的~(230)Th年龄。结果显示:CRM 112A和Harwell Uraninite-1(HU-1)的234 U/238 U原子比值分别为(52.860±0.042)×10~(-6)(δ234 U=(-38.36±0.77)‰,n=17)和(54.911±0.007)×10-6(δ234 U=(-1.04±0.13)‰,n=27),实验数据在2σ不确定范围内与国际同类实验室一致;NBS Th标准,0.6pg ~(230)Th测试精度优于3‰;5个碳酸盐标准样品76001、GBW04412、RKM-6、RKM-5和RKM-4的230 Th年龄分别为(47 520±220)y、(86 880±340)y、(130 830±550)y、(129 380±480)y和(197 970±1 590)y,与美国明尼苏达大学、西安交通大学同类实验室测定的数据具有良好的重复性。上述数据表明,本实验建立的MC-ICP-MS法230 Th定年技术可应用于中晚更新世以来碳酸盐的U-Th定年与示踪研究。     

具有动态稀释功能的EA-IRMS联机系统在δ13C和δ15N测定中的应用

自然界的样品中C、N元素含量或C/N变化极大,以往的元素分析 稳定同位素比值质谱仪（EA-IRMS）大多采用固定比例稀释样品气,不仅需要预先了解样品中元素含量及C/N等信息,还需要精确控制取样量。为了提高样品分析效率,本实验初步建立了具有动态稀释功能的EA-IRMS联机系统,快速分析有机碳、总氮稳定同位素比值（δ¹³C和δ¹⁵N）。结果表明,该联机系统与传统的固定比例稀释方法的δ¹³C和δ¹⁵N测定结果一致性较好（p>0.05）。对于C/N差异较大或难以精确称重的9种样品,该联机系统的δ¹³C和δ¹⁵N测定结果具有良好的重复性。通过动态稀释,δ¹³C和δ¹⁵N的测定精度分别为0.07‰~0.32‰和0.05‰~0.27‰。该联机系统在不同时间（间隔45天）的测定结果再现性良好（p>0.05）,δ¹³C和δ¹⁵N的测定偏差分别小于0.2‰和0.3‰。结合动态稀释功能的EA-IRMS,无需精确控制样品质量,省时、省力,具有一定的应用前景。     

电感耦合等离子体质谱测定铅同位素比值的准确度和精密度研究

通过对电感耦合等离子体质谱 (ICPMS)的工作条件和参数进行了最优化 ,有效降低由于进样系统、ICPMS瞬间不稳定和电子元件噪音等因素造成的测量同位素比值波动的影响。通过对质谱死时间、系统漂移和质量歧视效应的校正 ,可获得准确度高的同位素比值。茶叶、人发和灌木枝叶标准样品中铅的含量分别为 4.44、9.0 6和 46.80 ng/g,标准偏差 (s)分别为± 0 .0 7、± 0 .2 4和± 1 .2 4,与其确认值一致。     

四川盆地西部天然气碳同位素组成分析及应用

测定了 1 4种四川盆地西部南段平落坝气田和中段新场气田天然气样品的甲、乙烷碳同位素组成。这些样品的 δ13C1>-3 .92 % ,C2 +/Σ Cn>0 .8% ,结果表明这两处气田的烃类气体是由沉积物有机质经热解作用生成的。由此两处气田的δ13C1、δ13C2 相对分馏值 ,计算出气田的烃源岩生烃温度分别为 5 1～ 81℃、1 0 0～1 1 8℃ ;并从两处气田各气藏的 δ13C1、δ13C2 值同气藏深度的良好函数关系及其同位素分馏机理 ,认识到平落坝气田和新场气田的烃类是从下伏烃源岩垂直向上迁移而聚集成藏的     

Liquid chromatography combined with mass spectrometry for 13C isotopic analysis in life science research

Among the different disciplines covered by mass spectrometry, measurement of (13)C/(12)C isotopic ratio crosses a large section of disciplines from a tool revealing the origin of compounds to more recent approaches such as metabolomics and proteomics. Isotope ratio mass spectrometry (IRMS) and molecular mass spectrometry (MS) are the two most mature techniques for (13)C isotopic analysis of compounds, respectively, for high and low-isotopic precision. For the sample introduction, the coupling of gas chromatography (GC) to either IRMS or MS is state of the art technique for targeted isotopic analysis of volatile analytes. However, liquid chromatography (LC) also needs to be considered as a tool for the sample introduction into IRMS or MS for (13)C isotopic analyses of non-volatile analytes at natural abundance as well as for (13)C-labeled compounds. This review presents the past and the current processes used to perform (13)C isotopic analysis in combination with LC. It gives particular attention to the combination of LC with IRMS which started in the 1990's with the moving wire transport, then subsequently moved to the chemical reaction interface (CRI) and was made commercially available in 2004 with the wet chemical oxidation interface (LC-IRMS). The LC-IRMS method development is also discussed in this review, including the possible approaches for increasing selectivity and efficiency, for example, using a 100% aqueous mobile phase for the LC separation. In addition, applications for measuring (13)C isotopic enrichments using atmospheric pressure LC-MS instruments with a quadrupole, a time-of-flight, and an ion trap analyzer are also discussed as well as a LC-ICPMS using a prototype instrument with two quadrupoles.     

植物样品中稳定碳同位素的EA-IRMS系统分析方法

通过多组实验对比,分析并讨论了利用元素分析仪-稳定同位素比率质谱仪（EA-IRMS）联用技术测定植物样品中碳同位素比值的实验条件。初步建立了植物样品中稳定碳同位素组成的分析方法,同时对系统分析的稳定性和精密度等进行了检验分析。结果表明：当IRMS真空度为7×10^-8kPa,高压3.0 kV,EA系统Carrier-He载气流量在90～100 mL•min-1,Conflo-He载气压力为80 kPa,氧喷条件为110 mL•min^-1时,使用Cr₂O₃/Co₃O₄作为EA氧化柱氧化剂填料,在严格控制样品残余和本底空白的条件下,植物样品的测定精密度为±0.20‰,测定值与给定值值偏离0.01‰。     

上海-南极中山站沿途表层海水悬浮颗粒物中的天然15N

The suspended particle material (SPM) samples of surface seawater were collected on the board at 45 stations along the shipping line of Xuelong Ship. The natural abundances of 15N in SPM were measured and the distributions of δ15N along the shipping line were studied. The δ15N values varied from 0.57‰ to 9.87‰ with the mean of 4.12‰. The δ15N distribution showed trans-sea area characteristics and it increased or decreased sharply on sailing from one into the other sea area. The lowest δ15N values with the average of 1.65‰ were observed in Southern Indian Ocean.     

SIMS分析含铀微粒同位素比测量条件的初步研究

The isotope ratios of uranium in particles were closely related to the activities performed in nuclear facilities where the particles were collected, so that the determination of ratio is very important in environmental sample analysis for nuclear safeguards. The method based on the use of secondary ion mass spectrometry (SIMS) was presented for the determination of uranium isotopic composition. The parameters of SIMS were studied in the paper, such as contrast aperture(CA)、lence4(L4)、image field(IF)、the accelerated voltage of primary ions and the secondary ions and so on. These parameters are optimized by measuring the standard reference uranium materials (CRM005 CRM200) for improving the measurement accuracy and the precision of uranium isotopic ratio.     

Quantitative APT analysis of Ti(C,N)

A specially produced Ti(C,N) standard material, with a known nominal composition, was investigated with laser assisted atom probe tomography. The occurrence of molecular ions and single/multiple events was found to be influenced by the laser pulse energy, and especially C related events were affected. Primarily two issues were considered when the composition of Ti(C,N) was determined. The first one is connected to detector efficiency, due to the detector dead-time. The second one is connected to peak overlap in the mass spectrum. A method is proposed for quantification of the C content in order to establish the C/N ratio. A correction was made to the major C peaks, C at 6 and 12 Da, with the ¹³C isotopes, at 6.5 and 13 Da, according to the known natural abundance. In addition, a correction of the peak at 24 Da, where C and Ti overlap, is proposed based on the occurrence of single/multiple events for respective element. The results were compared to the results from other techniques such as electron energy loss spectroscopy, chemical analysis and X-ray diffraction. After applying the corrections, atom probe tomography results were satisfactory. Furthermore, the content of dissolved O in Ti(C,N) was successfully quantified.     

天然气单体烃氢同位素组成质谱分析

用色谱 -热转换 -质谱 ( GC/ TC/ MS)对天然气单体烃氢同位素组成进行了测定。实验表明 :热转换温度、进样量和分流比等条件的改变对氢同位素组成的测量结果有影响。以文 3 1井甲烷氢同位素组成 ( -1 5 4‰ )为参考 ,对天然气中甲烷、乙烷和丙烷氢同位素组成的测量不确定度进行了分析。结果表明 :甲烷和乙烷的测量精度都较高 ,但由于参考标准的不确定度较大 ,所以测量结果的不确定度较大