应用多接收器电感耦合等离子体质谱法测定海洋碳酸盐中稳定铅同位素组成

研究了多接收器电感耦合等离子体质谱仪(MC-ICP MS)测定铅同位素比值时,影响测试结果准确度和精密度的主要因素及其优化过程。在优化条件下,10 h内连续30次测定4 ng/mL NIST SRM 981同位素标准溶液铅同位素比值,获得208Pb/206Pb、207Pb/206Pb和206Pb/204Pb相对标准偏差(RSDs)分别为0.005%、0.004%和0.054%。长期监测208Pb/206Pb、207Pb/206Pb和206Pb/204Pb,标准偏差(2SDs)分别为0.000 06、0.000 05和0.006 7。采用NEPTUNE MC-ICP MS法测定了低铅海洋碳酸盐样品中稳定铅的同位素比值,并对南海橙黄滨珊瑚(Porites lutea)和库氏砗磲(Tridacna gigas)进行了分析,得到全流程空白为8～10 pg,重复样误差优于0.1%。经0.50 mol/L HNO3洗脱之后,得到海南珊瑚样品中208Pb/206Pb、207Pb/206Pb的比值分别为2.086 2±0.001 5、0.849 90±0.001 47(n=16);海南砗磲样品中208Pb/206Pb、207Pb/206Pb的比值分别为2.116 9±0.004 2、0.864 81±0.001 62(n=9)。进一步考察了南海海洋碳酸盐中204Pb的同位素比值。分析结果表明,南海海洋碳酸盐中稳定铅同位素比值与中国气溶胶、珠江三角洲大气沉降、黄土及南海海底玄武岩等具有很好的相关性。方法适用于复杂基体高钙低铅的海洋碳酸盐样品中铅同位素比值的分析。     

电感耦合等离子体质谱法测定水泥样品中的铅同位素比值

研究和讨论了用电感耦合等离子体质谱仪(ICP—MS)测定铅的同位素比值测定时，影响测试结果的准确度和精密度的主要因素及其优化过程。在优化后的仪器分析条件下，测定5μg/L的NIST SRM981自然丰度铅同位素标准溶液的各对铅同位素比值，获得的^207Pb／^206Pb分析精度可优于0．1％。在该条件下测定了14个不同的水泥粉样品中的铅同位素比值，结果显示：铅的同位素比值分析技术可以用来示踪环境监测样品的铅污染源。     

激光烧蚀-多接收电感耦合等离子体质谱法测定铀颗粒物中铅杂质的同位素比值

为有效获取铀颗粒物中具有取证价值的铅杂质同位素信息,建立了激光烧蚀-多接收电感耦合等离子体质谱(LA-MC-ICP-MS)测定铀颗粒物中铅杂质同位素比值的方法.探究了诸多同位素分馏效应校正方法下铅本底对同位素测量的影响,选用的LA-MC-ICP-MS系统的本底对比值测量结果的影响小于0.001(208Pb的信号强度大于2.2× 103 cps),确定采用NIST SRM612为外标校正质量分馏,固定激光束斑直径30μm、脉冲重复率20 Hz、调节能量密度使LA-MC-ICP-MS分析NIST SRM612和铀颗粒物样品所得208Pb分别小于1.5×105 cps和3×104 cps,标准物质CRM124-4样品中206Pb/208Pb、206Pb/207Pb和207Pb/208Pb比值测量结果的相对实验标准不确定度小于0.48％、0.68％和0.40％.实际样品分析结果表明,本方法可有效区分铀颗粒物中的铅同位素比值差异,有助于鉴别其来源.     

土壤及其他背景样品中铅同位素比值的测定方法

为给铅同位素示踪技术在判别土壤、大气、水体和人体中铅与相关重金属污染来源,区别汽车尾气铅污染和工业铅污染等方面的应用提供科学依据。通过大量的对比条件实验,拟出了土壤、煤、汽车尾气和气溶胶样品中铅同位素比值的测定方法。利用这三个流程分别测定了采自杭州茶园的土壤及茶园附近的煤、汽车尾气和气溶胶样品的铅同位素比值,其中207Pb/206Pb的精度(2σ)均优于±0.03%。重复样误差优于±0.05%2。08Pb强度一般均在1V以上,有的高达8 V以上。监控分析流程的国际标准物质NBS981的207Pb/206Pb为0.91449±0.00004。全流程本底铅为10-8数量级。     

电感耦合等离子体质谱法分析大鼠血、毛发及脏器中铅浓度及同位素比值

建立了电感耦合等离子体质谱(ICP-MS)同时测定铅浓度及同位素比值的方法,并应用于染毒大鼠血、毛发及组织脏器测定,以考察大鼠体内铅浓度及同位素比值分布情况及染毒剂量对其的影响.标准物质牛全血铅浓度测定结果为(278±4) μg/L,在证书标准值(283±18)μg/L范围内;测定10 μg/L Pb标准溶液的RSD<...     

锡苯和铅苯二聚反应的理论研究

采用密度泛函理论B3LYP方法,研究了锡苯和铅苯的[2+2],[4+2]及[4+4]二聚反应的微观机理和势能剖面,考察了Sn(Pb)原子上的2,4,6-三甲基苯基(Mes)取代基对反应势能剖面的影响.研究结果表明,所有反应均为协同过程,且大多数情况下,2个C—Sn(Pb)键同步形成.[2+2]和[4+2]反应在热力学和动力学上均比相应的[4+4]反应容易进行,而[4+2]反应在动力学上比相应的[2+2]反应有利.Sn(Pb)原子上的Mes取代基在热力学和动力学上均不利于反应的进行.铅苯的动力学稳定性与锡苯相当,但其热力学稳定性高于锡苯.     

增感效应悬浮液进样火焰原子吸收分光光度法测定汽油中的铅

铅是汽油的重要污染指标 ,传统的测定方法是将样品高温灰化后测定 ,由于组分浓度极低且存在由于样品易燃引起灰化时对铅的回收率较低 ,操作繁杂、耗时长等缺点。作者通过选用十二烷基磺酸钠 (ＳＤＳ)为增感剂[1 ] 并对其机理作了初步研究 ,选用正丁醇[2 ] 作悬浮液建立了直接测定样品中微量铅的新方法 ,其特征浓度为 0 .0 1 3μｇ/ｍＬ ,线性范围为 0～ 2 0 μｇ/ｍＬ ,且常见的离子不干扰测定。1　实验部分1 .1　仪器及工作参数ＷＦＸ 1Ｄ原子吸收分光光度计 (北京第二光学仪器厂 ) ;仪器条件为 :Ｐｂ空心阴极灯 ,波长 2 83.3ｎｍ ;灯电流 …     

激光剥蚀多接收杯电感耦合等离子体质谱仪原位分析硫化物铅同位素组成

采用193 nm准分子激光与MC-ICP-MS质谱仪探讨了原位微区分析过程中物质基体效应对铅同位素测定的影响,指出选择基体匹配标准物质对测定硫化物铅同位素具有重要意义.通过模拟计算发现准确测定Tl与Hg的分馏因子关系,可以在204Hg/204 Pb＜2的范围内有效校对204Hg对204 Pb的干扰.研究表明,束斑直径(24～160μm)和剥蚀频率(2～20 Hz)并不影响铅同位素组成测试.改变激光剥蚀参数可以解决MC-ICP-MS信号检测范围较窄的问题.针对目前硫化物固体标准物质缺乏的现状,采用压片法和快速熔融法制备硫化物标准物质.压片样品铅同位素组成表现出较好的均一性,而不同批次快速熔融法样品存在铅同位素分馏,仅单次制造的熔融样品内部铅同位素组成具有均匀性.结果表明,虽然快速熔融法还存在一定缺陷,但这两种方法都有望成为硫化物标准样品制作方法的备选方案.利用本方法对天然硫化物样品(黄铁矿和闪锌矿)及人工合成硫化物样品的铅同位素组成进行了准确测定,测定值与溶液值在误差范围内一致.     

湿法消解-原子吸收光谱法测定啤酒中痕量铅和锌

研究了用湿法消解啤酒样品、石墨炉原子吸收光谱(GFAAS)及火焰原子吸收光谱(FAAS)法分别测定啤酒中的痕量Pb2+和Zn2+。对仪器的工作参数进行了优化,探讨了混合酸消解体系、消解液用量,消解温度等因素的影响。结果表明,在200℃温度下,HNO3+HClO4(16+4)混酸能完全消解样品。Pb2+、Zn2+分别在0～80μg/L、0～1.50μg/mL范围内线性关系良好(线性相关系数r分别为0.9995和0.9997),其检出限分别为0.2μg/L、8.0μg/L。测定Pb2+、Zn2+的相对标准偏差(RSD)分别为1.8%和0.92%,加标回收率分别为96.5%和99.8%。该方法检出限低,精密度和准确度高,适用于啤酒样品中痕量铅、锌含量的测定。检测的9种啤酒样品中铅、锌含量范围分别为11.34～47.15μg/L、277～422μg/L,低于食品中的限量值。     

大鼠体内铅镉分布的稳定同位素示踪ICP-MS研究

采用稳定同位素示踪技术研究重金属元素铅、镉在大鼠体内的分布,通过对大鼠进行浓缩同位素206Pb、112Cd灌喂,解剖取其肝、肾、睾丸和心脏等脏器,通过相应的化学处理,用电感耦合等离子体质谱(ICP-MS)测量铅、镉元素在各个脏器中的含量及其同位素组成变化.根据同位素比值的变化研究Pb、Cd在各脏器中的分布、蓄积规律和各脏器对引入的浓缩同位素利用率.结果发现:重金属Pb和Cd蓄积的最主要场所是肝和肾,其次是睾丸和心脏,而在脑中的积累最少.在肝和肾中Cd的同位素利用率为0.048 8%、0.015 4%,Pb的同位素利用率为0.010 1%、0.007 8%,远高于其它脏器.与传统的方法相比较,该法具有更接近慢性中毒、危害性小,能将重金属来源分为天然来源和人为引入等特点.     

ICP-MS测定土壤中铅同位素比值及地域差异性比较

建立用HNO_3-H_2O_2-HF体系微波消解前处理样品,利用电感耦合等离子体质谱测定土壤中铅同住素比值的方法,探讨并优化了影响测试结果的两种干扰因素.该方法中~(207)Pb/~(206)Pb和~(208)Pb/~(206)Pb的短期测量稳定性RSD分别达到0.12%和0.13%,长期测量的偏差分别在0.002和0.01以内,样品测量的最佳范围是10～40μg/L.采用标样-样品交叉法测定了湖南、湖北、云南、贵州、河南、福建、辽宁7个省的48个地区土壤中的铅同位素比值,结合聚类分析和主成分分析比较了各省土壤中同位素分布的差异,初步探讨了利用~(207)Pb/~(206)Pb和~(208)Pb/~(206)Pb比较烟叶产区的可能性.     

Isotopic precision for a lead species (PbEt4) using capillary gas chromatography coupled to inductively coupled plasma-multicollector mass spectrometry

Precision and accuracy of lead isotope ratios of a volatile lead species (PbEt₄) were determined by coupling a capillary GC to a magnetic sector multicollector ICP-MS. PbEt₄ was prepared by ethylation of a certified lead isotope solution (NIST SRM 981). Coupling was achieved by a transfer line, which allowed simultaneous introduction of a thallium standard solution to correct for mass discrimination. Seven isotopes (²⁰²Hg, ²⁰³Tl, ²⁰⁴Pb, ²⁰⁵Tl, ²⁰⁶Pb, ²⁰⁷Pb, ²⁰⁸Pb) were monitored simultaneously with a transient resolution of 50 ms. Pb isotope ratios for the PbEt₄ peaks were calculated using transient peak integrals of each isotope signal. Absolute detection limits were 20 (²⁰⁴Pb), 0.7 (²⁰⁶Pb), 1 (²⁰⁷Pb) and 0.3 pg (²⁰⁸Pb). Precision was assessed for five replicate injections of PbEt₄ in iso-octane, corresponding to a total amount of 300 pg of Pb. Precision of isotope ratios for ²⁰⁶Pb, ²⁰⁷Pb and ²⁰⁸Pb were better than 0.07% (RSD), with ratios including ²⁰⁴Pb being one order of magnitude worse. Accuracy using mass bias correction via ²⁰³Tl/²⁰⁵Tl ranged from 0.18% for ²⁰⁸Pb/²⁰⁶Pb to 0.9% for ²⁰⁸Pb/²⁰⁴Pb.     

Lead isotopic compositions of environmental certified reference materials for an inter-laboratory comparison of lead isotope analysis.

Lead isotope ratios, viz. 207Pb/206Pb and 208Pb/206Pb, of the commercially available certified reference materials (CRMs) issued in Japan are presented with an objective to provide a data set, which will be useful for the quality assurance of analytical procedures, instrumental performance and method validation of the laboratories involved in environmental lead isotope ratio analysis. The analytical method used in the present study was inductively coupled plasma quadrupole mass spectrometry (ICPQMS) preceded by acid digestion and with/without chemical separation of lead from the matrix. The precision of the measurements in terms of the relative standard deviation (RSD) of triplicated analyses was 0.19% and 0.14%, for 207Pb/20Pb and 208Pb/206Pb, respectively. The trueness of lead isotope ratio measurements of the present study was tested with a few CRMs, which have been analyzed by other analytical methods and reported in various literature. The lead isotopic ratios of 18 environmental matrix CRMs (including 6 CRMs analyzed for our method validation) are presented and the distribution of their ratios is briefly discussed.     

A rapid and reliable method for Pb isotopic analysis of peat and lichens by laser ablation-quadrupole-inductively coupled plasma-mass spectrometry for biomonitoring and sample screening

An analytical protocol for rapid and reliable laser ablation-quadrupole (LA-Q)- and multi-collector (MC-) inductively coupled plasma-mass spectrometry (ICP-MS) analysis of Pb isotope ratios (²⁰⁷Pb/²⁰⁶Pb and ²⁰⁸Pb/²⁰⁶Pb) in peats and lichens is developed. This technique is applicable to source tracing atmospheric Pb deposition in biomonitoring studies and sample screening. Reference materials and environmental samples were dry ashed and pressed into pellets for introduction by laser ablation. No binder was used to reduce contamination. LA-MC-ICP-MS internal and external precisions were <1.1% and <0.3%, respectively, on both ²⁰⁷Pb/²⁰⁶Pb and ²⁰⁸Pb/²⁰⁶Pb ratios. LA-Q-ICP-MS internal precisions on ²⁰⁷Pb/²⁰⁶Pb and ²⁰⁸Pb/²⁰⁶Pb ratios were lower with values for the different sample sets <14.3% while external precisions were <2.9%. The level of external precision acquired in this study is high enough to distinguish between most modern Pb sources. LA-MC-ICP-MS measurements differed from thermal ionisation mass spectrometry (TIMS) values by 1% or less while the accuracy obtained using LA-Q-ICP-MS compared to solution MC-ICP-MS was 3.1% or better using a run bracketing (RB) mass bias correction method. Sample heterogeneity and detector switching when measuring ²⁰⁸Pb by Q-ICP-MS are identified as sources of reduced analytical performance.     

Isotope-ratio measurements of lead in NIST standard reference materials by multiple-collector inductively coupled plasma mass spectrometry

The capability of a second-generation Nu Instruments multiple collector inductively coupled plasma mass spectrometer (MC-ICP-MS) has been evaluated for precise and accurate isotope-ratio determinations of lead. Essentially the mass spectrometer is a double-focusing instrument of Nier-Johnson analyzer geometry equipped with a newly designed variable-dispersion ion optical device, enabling the measured ion beams to be focused into a fixed array of Faraday collectors and an ion-counting assembly. NIST SRM Pb 981, 982, and 983 isotopic standards were used. Addition of thallium to the lead standards and subsequent simultaneous measurement of the thallium and lead isotopes enabled correction for mass discrimination, by use of the exponential correction law and 205Tl/203Tl = 2.3875. Six measurements of SRM Pb-982 furnished the results 206Pb/204Pb = 36.7326(68), 207Pb/204Pb = 17.1543(30), 208Pb/204Pb = 36.7249(69), 207Pb/206Pb = 0.46700(1), and 208Pb/206Pb = 0.99979(2); the NIST-certified values were 36.738(37), 17.159(25), 36.744(50), 0.46707(20), and 1.00016(36), respectively. Direct isotope lead analysis in silicates can be performed without any chemical separation. NIST SRM 610 glass was dissolved and introduced into the MC-ICP-MS by means of a micro concentric nebulizer. The ratios observed were in excellent agreement with previously reported data obtained by TIMS and laser ablation MC-ICP-MS, despite the high Ca/Pb concentration ratio (200/1) and the presence of many other elements at levels comparable with that of lead. Approximately 0.2 microg lead are sufficient for isotope analysis with ratio uncertainties between 240 and 530 ppm.     

不同赋存形态土壤铅同位素比值用于判别地域性差异的研究

由于各地区地质结构不同,造成了铅同位素组成具有地域特征。本研究利用电感耦合等离子体质谱测定了福建不同茶园土壤的铅同位素比值,比较了土壤全消解和残渣态两种赋存形态的铅同位素比值的差异,发现残渣态的铅的地域性特征较强,可用来作为地区土壤的判别依据。     

Accuracy and long-term reproducibility of lead isotopic measurements by multiple-collector inductively coupled plasma mass spectrometry using an external method for correction of mass discrimination

The precision of isotopic measurements of Pb by thermal ionization mass spectrometry (TIMS) is limited by the fact that this element does not possess an invariant isotope ratio that can be used for the correction of mass fractionation by internal normalization. Multiple-collector inductively coupled plasma mass spectrometry (MC-ICPMS) can overcome this limitation, because with plasma ionization, elements with overlapping mass ranges are thought to display identical mass discrimination. With respect to Pb, this can be exploited by the addition of Tl to the sample solutions; the mass discrimination factor obtained for Tl can then be used for the correction of the measured Pb isotope ratios. In this article we present the results of a detailed study that investigates the accuracy and precision of such an external correction technique for mass discrimination based upon the results of multiple analyses of a mixed standard solution of NIST SRM-981 Pb and SRM-997 Tl. Our data indicate that normalization of the Pb isotope ratios to the certified isotopic composition of SRM-997 Tl produces Pb isotopic results that are significantly lower than recently published reference values by TIMS. This systematic offset can be eliminated by renormalization of the Pb data to a different Tl isotopic composition to obtain an empirically determined mass discrimination factor for Pb that generates accurate results. It is furthermore shown that a linear law is least suited for the correction of mass discrimination, whereas a power or exponential law function provide significantly more accurate and precise results. In detail, it appears that a power law may provide the most appropriate correction procedure, because the corrected Pb isotope ratios display less residual correlations with mass discrimination compared to the exponentially corrected data. Using an exponential or power law correction our results, obtained over a period of over seven months, display a precision (2σ) of better than 60 parts per million (ppm) for ²⁰⁸Pb/²⁰⁶Pb and ²⁰⁷Pb/²⁰⁶Pb and of better than 350 ppm for ²⁰⁶Pb/²⁰⁴Pb, ²⁰⁷Pb/²⁰⁴Pb/²⁰⁴Pb, and ²⁰⁸Pb/²⁰⁴Pb. This represents a significant improvement compared to conventional TIMS techniques and demonstrates the potential of MC-ICPMS for routine, high-precision measurements of Pb isotopic compositions.     

A simple method for rapid calibration of faraday and ion‐counting detectors on movable multicollector mass spectrometers

Methods are presented for rapid determination of relative efficiencies of Faraday cups in a multicollector array with movable cups and of Daly or electron multiplier detector dead time and gain values. The Faraday calibration approach is based on measuring the same isotopic ratio in two sequences with different collector configurations having one collector in common. Changes in thermal fractionation during the two measurement sequences are monitored using the same two collectors. Since the relative efficiencies are determined by measuring the same ratio in different cups corrected for time‐dependent changes in fractionation, it is unnecessary to use a standard of known composition and calculations are simple, not requiring the solution of multiple equations. Determination of dead time and gain values for a Daly detector are shown based on multidynamic measurements of masses 207, 206, and 208 from Pb standard SRM982 in two sequences consisting of L1‐Daly‐H1 and Daly‐H1‐H2. This provides two equations that can be solved for Daly dead time and gain. This method uses static measurements and is therefore insensitive to signal instability. It also does not require use of a standard of known isotopic composition. The potential of using known cup efficiencies to help determine absolute isotopic abundances is discussed.     

Determination of sources of lead in tap water by inductively coupled plasma mass spectrometry (ICP-MS)

We measured the concentrations of Pb and its isotope ratios in coconmittantly obtained tap water and plumbing materials by inductively coupled mass spectrometry (ICP-MS). The Pb concentrations were determined by external calibration with²⁰⁹Bi as an internal standard. Isotope ratios were measured and mass discrimination corrected by normalization to NIST SRM-981 (common lead isotopic standard). Student/s t-test was used to compare the isotopic ratios of²⁰⁶Pb/²⁰⁷Pb,²⁰⁶Pb/²⁰⁸Pb, and²⁰⁷Pb/²⁰⁸Pb in the tap water with those in various plumbing materials. The comparisons revealed that the source of Pb in most of the tap water samples was derived from copper pipe or solder.