Peak splitting with a quadrupole mass filter operated in the second stability region

Peak splitting or structure has been studied for a quadrupole mass filter operated in the second stability region with Mathieu parameters (a,q) ≈ (0.02.7.55). Two sources of peak splitting are considered and modeled theoretically: nonlinear resonances caused by field imperfections and ion collection effects caused by the periodic properties of ion motion in the quadrupole field. The conditions for the appearance of the nonlinear resonances and ion collection effects are derived and presented in terms of the β variables which determine the frequencies of ion oscillation. Comparisons of calculated peak structure to experimental peak shapes show that ion collection effects dominate, at least for the experimental conditions reported here. It is also shown that neither nonlinear resonances nor ion collection effects can distort the peak at high resolution.     

电感耦合等离子体质谱分析

简要综述了我国学者近10年来在电感耦合等离子体质谱(ICP-MS)分析领域的研究工作.在ICP-MS新进样技术和ICP-MS生物分析方法学研究方面,我国科研人员开展了开拓性的研究工作,在元素形态分析和金属组学研究方面富有特色.ICP-MS仪器/部件的设计研制尚待加强;ICP-MS成像研究和在实际生命体系的应用有待进一步强化.     

Inductively coupled plasma mass spectrometer with axial field in a quadrupole reaction cell

A novel reaction cell for ICP-MS with an electric field provided inside the quadrupole along its axis is described. The field is implemented via a DC bias applied to additional auxiliary electrodes inserted between the rods of the quadrupole. The field reduces the settling time of the pressurized quadrupole when its mass bandpass is dynamically tuned. It also improves the transmission of analyte ions. It is shown that for the pressurized cell with the field activated, the recovery time for a change in quadrupole operating parameters is reduced to <4 ms, which allows fast tuning of the mass bandpass in concert with and at the speed of the analyzing quadrupole. When the cell is operated with ammonia, the field reduces ion-ammonia cluster formation, further enhancing the transmission of atomic ions that have a high cluster formation rate. Ni x (NH3)n+ cluster formation in a cell operated with a wide bandpass (i.e., Ni+ precursors are stable in the cell) is shown to be dependent on the axial field strength. Clusters at n = 2-4 can be suppressed by 9, 1200, and >610 times, respectively. The use of a retarding axial field for in-situ energy discrimination against cluster and polyatomic ions is shown. When the cell is pressurized with O2 for suppression of 129Xe+, the formation of 127IH2+ by reactions with gas impurities limits the detection of 129I to isotopic abundance of approximately 10(-6). In-cell energy discrimination against 127IH2+ utilizing a retarding axial field is shown to reduce the abundance of the background at m/z = 129 to ca. 3 x 10(-8) of the 127I+ signal. In-cell energy discrimination against 127IH2+ is shown to cause less I+ loss than a post-cell potential energy barrier for the same degree of 127IH2+ suppression.     

基于电感耦合等离子体质谱的生物分析

ESI/MALDI-MS在生物分子结构鉴定方面的优势是ICP-MS无法匹敌的;另一方面,针对生物分子的定量分析,ICP-MS因化学选择性和生物特异性元素标记策略的发展而极具优势。它们的联合使用必将为生物分析(特别是定量蛋白质组学和金属组学研究)提供解决问题的新途径,这时我们需要一个化学集成器(chemical hub)针对目标生物分子或细胞正交集成运用ESI/MALDI-MS和ICP-MS而不是简单地物理平行使用,使得ICP-MS知道定量的是何种生物分子或细胞,这对未知生物分子或细胞的发现和绝对定量十分重要。     

Inductively coupled plasma mass spectrometry for stable isotope tracer investigations

Inductively coupled plasma mass spectrometry (ICP-MS) has now been developed for application to stable isotope tracer investigations of several minerals/trace elements. Use of this method for such purposes requires an understanding of a number of fundamental issues: analytical chemistry performance of the method of isotopic analysis, relationship of the level of enriched isotope administered to the subject with background level of the isotope already present, the issues of cost, and finally the specific details of the biological issues to be explored.In this paper, a brief discussion of these issues is presented. As an example, the discussion is presented in relation to selected aspects of metabolism of selenium, employing the three stable isotopes⁷⁴Se,⁷⁷Se, and⁸²Se in the rat as the biological model.Analytical performance of hydride generation/ICP-MS is discussed for the required analyses of selenium isotopes. It is shown that for solutions containing 10 ng/ml Se of natural isotopic composition, optimized signal/background ratios greater than 40/1 can be obtained, resulting in worst-case detection limits (ng Se) of 2 (⁷⁴Se), and 0.6 (^77,82Se). The precision and accuracy of isotope ratio measurements for the method used routinely in biological studies is 1%. The accuracy of the method for quantitative isotopic analysis is compared with hydride generation/atomic absorption spectrophotometry (HG/AAS). The following results are given (g Se/g or ml; mean + 1 SD,n = 3–5; first HG/ICP-MS, second HG/AAS): SRM 1577a [bovine liver] 0.697 ± 0.002 versus 0.69 ± 0.01; human blood plasma 0.098 ± 0.001 versus 0.135 ± 0.008; human red cells 0.211 ± 0.002 versus 0.216 ± 0.012; and human urine 0.0473 ± 0.0003 versus 0.0489 ± 0.0003.An experiment is described with the rat to show the feasibility of the method for studies of selenium metabolism. Rats were placed on Se-free diet for eight weeks, given their Se requirements in the drinking water in the form of⁷⁶SeO ₃ ^2– and a single-day (day 3) replacement of their water with that containing highly enriched⁷⁴SeO ₃ ^2– . Isotopic analysis of carcass and selected organs revealed a high degree of isotopic enrichment with respect to⁷⁴Se during the entire eight weeks of the experiment, indicating the feasibility of this approach for detailed investigations of selenium metabolism in the rat.Presented in part at the 1989 European Winter Conference on Plasma Spectrochemistry, Reutte, Austria     

Matrix effects during phosphorus determination with quadrupole inductively coupled plasma mass spectrometry

A quadrupole inductively coupled plasma mass spectrometer was evaluated for use in the detection of phosphorus. The influences of nitric acid and methanol (simulating the composition of a sample solution after nitric acid digestion) on phosphorus determination were studied using two different measuring methods at different plasma conditions: detection of phosphorus ions at m/z 31 and detection of phosphorus oxide ions at m/z 47. The existence of polyatomic interferences at m/z 31 and 47 was explored. Nitric acid and methanol are shown to be the sources of polyatomic ions and therefore cause poorer detection limits. Better detection limits were achieved in such matrices when phosphorus was detected as ³¹P⁺. The presence of methanol improves the system sensitivity towards phosphorus sevenfold; however, this positive effect is hindered by the high background signal due to carbon-based polyatomic ions. For samples with an organic matrix an appropriate mineralization procedure should be applied (high excess of nitric acid and high temperature) to quantitatively oxidize organic compounds to carbon dioxide, which is easily removed from the sample, in order to achieve correct results.     

Inductively coupled plasma mass spectrometry (ICP MS): a versatile tool

Inductively coupled plasma (ICP) mass spectrometry (MS) is routinely used in many diverse research fields such as earth, environmental, life and forensic sciences and in food, material, chemical, semiconductor and nuclear industries. The high ion density and the high temperature in a plasma provide an ideal atomizer and element ionizer for all types of samples and matrices introduced by a variety of specialized devices. Outstanding properties such as high sensitivity (ppt-ppq), relative salt tolerance, compound-independent element response and highest quantitation accuracy lead to the unchallenged performance of ICP MS in efficiently detecting, identifying and reliably quantifying trace elements. The increasing availability of relevant reference compounds and high separation selectivity extend the molecular identification capability of ICP MS hyphenated to species-specific separation techniques. While molecular ion source MS is specialized in determining the structure of unknown molecules, ICP MS is an efficient and highly sensitive tool for target-element orientated discoveries of relevant and unknown compounds. This special-feature, tutorial article presents the principle and advantages of ICP MS, highlighting these using examples from recently published investigations.     

电感耦合等离子体质谱测定钼矿石中的铼

以三酸消解钼矿石中的铼, 不经分离富集, 用电感耦合等离子体质谱法直接测定钼矿石样品中的铼。方法检出限可达0.012μg/g , 通过对国家岩石一级标准样品的测试, 测定结果一致;对GBW07285标准样品11 次测定的相对标准偏差(RSD) 为1.13%。     

Inductively coupled plasma mass spectrometry and electrospray mass spectrometry for speciation analysis: applications and instrumentation

To gain an understanding of the function, toxicity and distribution of trace elements, it is necessary to determine not only the presence and concentration of the elements of interest, but also their speciation, by identifying and characterizing the compounds within which each is present. For sensitive detection of compounds containing elements of interest, inductively coupled plasma mass spectrometry (ICP-MS) is a popular method, and for identification of compounds via determination of molecular weight, electrospray ionization mass spectrometry (ESI-MS) is gaining increasing use. ICP-MS and ESI-MS, usually coupled to a separation technique such as chromatography or capillary electrophoresis, have already been applied to a large number of research problems in such diverse fields as environmental chemistry, nutritional science, and bioinorganic chemistry, but a great deal of work remains to be completed. Current areas of research to which ICP-MS and ESI-MS have been applied are discussed, and the existing instrumentation used to solve speciation problems is described.     

Inductively coupled plasma mass spectrometry: Application to the determination of arsenic species

The application of ion-pair reversed phase chromatography (HPLC) and inductively coupled plasma mass spectrometry to the determination of six species of arsenic is described: arsenious acid (As^III), arsenic acid (As^V), monomethylarsinic acid (MMA), dimethylarsinic acid (DMA), arsenocholine (AsC) and arsenobetaine (AsB) in marine biota and in natural fresh water. The coupling conditions of HPLC-ICP-MS are given and also the evaluation of the extraction procedure applied to determine these species in marine organisms. The limits of detection are between 6 and 25 g.l^–1.     

Inductively coupled plasma mass spectrometry: a versatile tool for a variety of different tasks

In a laboratory that is working in many different fields, a systematic approach is needed to decide ¶efficiently how a given analytical task should be handled. Four typical examples are presented to show how ICP-MS may be used to solve client’s problems. The examples are: the identification of lead projectiles, the determination of total and leachable fractions of impurities in a polymer (PVDF), used for manufacturing components of ultra-pure water distribution systems, the authentication of ¶antique silver alloys, and the determination of rare earth elements in geological materials. These examples demonstrate not only typical challenges for the instruments and the analysts handling them, but also ways to reach ¶a satisfactory solution within a reasonable amount of time.     

Inductively coupled plasma mass spectrometry: a versatile tool for a variety of different tasks

In a laboratory that is working in many different fields, a systematic approach is needed to decide efficiently how a given analytical task should be handled. Four typical examples are presented to show how ICP-MS may be used to solve client's problems. The examples are: the identification of lead projectiles, the determination of total and leachable fractions of impurities in a polymer (PVDF), used for manufacturing components of ultrapure water distribution systems, the authentication of antique silver alloys, and the determination of rare earth elements in geological materials. These examples demonstrate not only typical challenges for the instruments and the analysts handling them, but also ways to reach a satisfactory solution within a reasonable amount of time.     

Inductively coupled plasma mass spectrometry in separation techniques: recent trends in phosphorus speciation

Inductively coupled plasma-MS (ICP-MS) and its combined use with molecular mass spectrometric techniques have become the most promising detection techniques in speciation studies. High sensitivity and element specificity of ICP-MS has the advantage of detecting trace amounts of the species of interest in complex matrices. This review is divided into two parts. In the first part, suitable use of ICP-MS either online or offline with currently used separation techniques such as HPLC, CE, and gel electrophoresis in speciation analysis is briefly discussed. In the second part, recent applications (1999-2005) of phosphorus speciation is presented to elucidate the importance of ICP-MS in separation methods and to illustrate its importance in nonmetal detection.     

Inductively coupled plasma mass spectrometry based platforms for studies involving nanoparticle effects in biological samples

The widespread application of nanoparticles (NPs) in recent times has caused concern because of their effects in biological systems. Although NPs can be produced naturally, industrially synthesized NPs affect the metabolism of a given organism because of their high reactivity. The biotransformation of NPs involves different processes, including aggregation/agglomeration, and reactions with biomolecules that will be reflected in their toxicity. Several analytical techniques, including inductively coupled plasma mass spectrometry (ICP‐MS), have been used for characterizing and quantifying NPs in biological samples. In fact, in addition to providing information regarding the morphology and concentration of NPs, ICP‐MS‐based platforms, such as liquid chromatography/ICP‐MS, single‐particle ICP‐MS, field‐flow fractionation (asymmetrical flow field‐flow fractionation)‐ICP‐MS, and laser ablation‐ICP‐MS, yield elemental information about molecules. Furthermore, such information together with speciation analysis enlarges our understanding of the interaction between NPs and biological organisms. This study reports the contribution of ICP‐MS‐based platforms as a tool for evaluating NPs in distinct biological samples by providing an additional understanding of the behavior of NPs and their toxicity in these organisms.     

Ion source emittance influence on the transmission of a quadrupole operated in the second stability region

The variation of transmission (T) with resolution (R) has been calculated for a quadrupole mass filter operated in the second stability region with Mathieu parameters q=7.547 and a=0 to 0.02995. The fringing fields at the entrance to the quadrupole, which can be strongly defocusing, and which can dramatically reduce the acceptance, have been included in the calculation. Even in the absence of fringing fields, at a resolution of 10,000 the acceptance in the x and y directions is less than 2 × 10^?4 πr ₀ ⁴ f ², which is about 10^?3 of the acceptance in the first stability region at low resolution. Because the source emittance can strongly effect the T(R) behavior, the calculation of ion transmission has been done for two source emittances that correspond to different degrees of focusing of ions into the quadrupole. The T(R) characteristics for two realistic source emittances give behavior markedly different from the decrease in acceptance with increasing resolution which previously has been used as a measure of the quadrupole transmission. Comparisons of the calculated transmission losses with increasing resolution to earlier experimental results obtained with an inductively coupled plasma source show good agreement provided an emittance which corresponds to ions being tightly focused into the quadrupole is used. The calculation demonstrates that up to a resolution at half height of 7000 in the experiment, the transmission losses were a result of the decreasing quadrupole acceptance. At higher resolution the experimental transmission was limited by either the residence time of the ions in the quadrupole or the rod quality. It is also shown that the strong defocusing effects of the fringing fields at the entrance of the quadrupole can be largely overcome by accelerating the ions through these fields and then decelerating the ions in the quadrupole.     

Properties and performance of a quadrupole mass filter used for resonance ionization mass spectrometry

The performance of commercial quadrupole mass spectrometers (QMS) with a number of imperfections, as compared to the ideal hyperbolic geometry, has been characterized using the computer simulation program version 6.0. The analysis of simulated QMS geometries focuses primarily on modeling of the internal potential, the study of field deviations, and the influence of finite length on performance of the QMS. The computer simulation of ion trajectories in the QMS field yields predictions for optimum working conditions and provides estimates for the resolving power and the maximum isotopic abundance sensitivity. Experimental measurements that confirm these expectations are presented. Optimization of the geometry and various operational parameters of the QMS is an important step in the development of a system for highly selective ultratrace determination using laser-based resonance ionization mass spectrometry.