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.     

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.     

Precise isotope-ratio measurements of lead species by capillary gas chromatography hyphenated to hexapole Multicollector ICP-MS

The precision and accuracy of lead isotope-ratio determination on a short transient signal has been assessed by coupling capillary gas chromatography to the Isoprobe (Micromass, UK), a single-focusing inductively coupled plasma mass spectrometer with multicollector detection. A T-piece connecting the GC transfer line to the torch enabled continuous aspiration of thallium solution for mass-bias correction. The volatile lead species PbEt4 was derivatized from NIST isotopic certified lead standard SRM 981 and different amounts of PbEt4 dissolved in iso-octane were injected into the GC. Chromatograms were recorded in multicollection mode by use of Faraday cups; seven isotopes (204Pb, 206Pb, 207Pb, 208Pb,     

电感耦合等离子体质谱法同时测定食品中的铅、镉和总砷

建立了电感耦合等离子体质谱(ICP–MS)法同时测定食品中的铅、镉和总砷含量的分析方法。样品经消化后直接用ICP–MS分析,采用在线引入混合内标溶液校正基体干扰和仪器的信号漂移。铅、镉、总砷的质量浓度在0~50μg/L范围内与信号强度呈良好的线性,线性相关系数(r)均大于0.999 0。用该方法对标准物质进行测定,分别采用湿法、微波消解法对样品进行处理,两种前处理方式测定值无显著性差异,测定结果的相对标准偏差在0.45%~4.2%之间(n=6),检测结果均在参考值范围内。该方法可同时测定铅、镉和总砷含量,操作简便、重现性好、结果准确可靠,可以满足各种食品中铅、镉和总砷同时测定的要求。     

Determination of iodine, strontium and neodymium isotope ratios using a thermionic quadrupole mass spectrometer with an ion counting detector

Summary Isotope dilution mass spectrometry (IDMS) as a definitive method is a sensitive analytical technique for accurate trace analysis down to the sub-ppb level. The application of IDMS requires precise and accurate isotope ratio measurements. It has been demonstrated that these measurements can be carried out with a small, cost-efficient and easy-to-use quadrupole mass spectrometer equipped with both a Faraday detector and a secondary electron multiplier (SEM). Here we describe a new detector system for this instrument which allows pulse counting measurements of both positive and negative ions. The performance of the new detector system is shown for I, Sr and Nd isotope ratio measurements. A synthetic mixture of¹²⁷I and¹²⁹I was measured using negative thermal ionisation. The¹²⁷I/¹²⁹I isotope ratio was determined with a relative external precision of 0.6% using I loadings of 0.08 and 0.8 nmol. For Sr and Nd isotope ratios a relative external precision of 0.1%–0.2% and an accuracy of 0.06% were obtained for loadings of 0.01 to 0.05 nmol.

---

Bestimmung von Iod-, Strontium- und Neodym-Isotopenverhältnissen bei Verwendung eines Thermionen-Quadrupol-Massenspektrometers mit Einzelionenzähleinrichtung

     

Preconcentration of microamounts of elements in natural waters with 8-mercaptoquinoline and bis(8-quinolyl) disulphide for their atomic-absorption determination

A method has been developed for the group concentration of microamounts of metals (Fe, Co, Ni, Mn, Cu, Zn, Cd, Hg, Pb, Bi, Sb, Mo, W, V, Cr, Ga, In, Sn, Ag, Au, Pd, Pt) in the form of their 8-mercaptoquinolinates co-precipitated on bis(8-quinolyl) disulphide as collector, the latter being an oxidation product of 8-mercaptoquinoline. The collector is formed during the co-precipitation process, which is the reason for its high co-precipitating power. The elements thus concentrated are determined by atomic-absorption spectrometry after dissolution of the precipitate in dilute nitric acid.     

Precise determination of cadmium and lead isotopic compositions in river sediments

A method for the accurate determination of Cd and Pb isotope compositions in sediment samples is presented. Separation of Cd and Pb was designed by using an anionic exchange chromatographic procedure. Measurements of Cd isotopic compositions were carried out by multi-collector inductively coupled plasma mass spectrometer (MC-ICPMS), by using standard-sample bracketing technology for mass bias correction and Pb isotopic ratios were determined by thermal ionization mass spectrometry (TIMS). The factors that affect the accurate and precise Cd isotope compositions analysis, such as instrumental mass fractionation and isobaric interferences, were carefully evaluated and corrected. The Cd isotopic results were reported relative to an internal Cd solution and expressed as the δ^114/110Cd. Five Cd reference solutions and one Pb standard were repeatedly measured in order to assess the accuracy of the measurements. Uncertainties obtained were estimated to be lesser than 0.11‰ (2s) for the δ^114/110Cd value. Analytical uncertainties in 2s for Pb isotopic ratios were better than 0.5‰. The method has been successfully applied to the investigation of Cd and Pb isotope compositions in sediment samples collected from North River in south China.     

Investigation of the depth‐profiling capabilities of the Storing Matter technique

The so‐called Storing Matter technique allows the matrix effect observed in secondary ion mass spectrometry to be successfully circumvented. We therefore investigate in this work the depth‐profiling capabilities of the Storing Matter technique with a goal of developing protocols for quantitative depth profiles. The effect of the steps involved in the Storing Matter process on the main parameters such as the depth resolution and the dynamic range is studied experimentally and by simulations. A semi‐automated process consisting of the sputter‐deposition process on a rotating collector in the Storing Matter instrument followed by a complete analysis of the collector by secondary ion mass spectrometry is defined. This protocol is applied to depth profile a B implant in Si and a Sn/Zn multilayered sample, and the results are compared with those obtained with conventional secondary ion mass spectrometry. Copyright © 2015 John Wiley & Sons, Ltd.     

Studies on gaseous electrodeposition of recoiled nuclides from thorium series

A point source of²¹²Pb was prepared from²²⁸Th source by the gaseous electrodeposition method. A conical tube was placed between the electrodes and it served as a metallic shade to make lines of electric force converge to the collector cathode. The source was utilized to measure the rate of²⁰⁸Tl emission and the rate of electrodeposition in various gaseous matrices. The mechanism of the mass transfer of recoiled species from the source to the collector was also revealed predominantly to be migration of the recoiled ions.     

Röntgenspektrometrische bestimmung von blei in automatenstahl : Teil II. Sulfat-verfahren

A method is described for the x-ray spectrometric determination of 0.02–0.5% Pb in free-cutting steels. Lead in the sample solution is precipitated as sulphate with barium sulphate as collector, and the dried fixed precipitate is used for the X-ray Spectrometric measurement. The method shows a reproducibility (s) of ±0.002 % Pb. The time required is ca. 32 min for one determination and ca. 120 min for a series of 20 samples.