Analysis of small amounts of solid samples by spark-source mass spectrometry

Various elements were determined in solid samples weighing < 2 mg by spark-source mass spectrometry. The samples were fixed on the top of a cylindrical graphite electrode using a conductive silver paint. After baking, the samples were sparked against a tantalum or gold wire. The method was used for the determination of impurities in steel, iron, molybdenum and CdSe. For samples weighing ca. 1 mg, detection limits of the order of 1 μg g^?1 were obtained. A relationship between the relative sensitivity factor and physical properties is proposed.     

The analysis of geological samples for trace elements by direct-reading emission spectrometry

The experimental work is described that led to the development of a rapid and convenient method for the determination of a number of trace elements in geological samples by use of a direct-reading spectrometer. The technique involves the diluting of a sample in the ratio of 1 part of sample to 3 parts of a buffer consisting of graphite containing 20% lithium fluoride and 0.03% germanium oxide as a reference element. The mixture is loaded into a special electrode and is excited in a d.c. arc at 12 A for 80 ± 2 seconds. The excitation takes place in an inert atmosphere that is provided by a “double flow” gas-stabilizing jet. The resulting digital-voltmeter readings for the various elements are read against previously prepared calibration graphs, and the concentrations of the elements in the sample are derived. The elements determined in the direct-reader programme are Co, Cr, Cu, Mn, Mo, Ni, Pb, Sn, V, Zn and Zr. A photographic spectrographic variant of the method, developed at the same time, is also described. It permits the determination of a number of trace elements not in the direct-reader programme. The relative standard deviation for the method is 10–15%, and the accuracy is of the same order.     

Progress in multi-ion counting spark-source mass spectrometry (MIC-SSMS) for the analysis of geological samples

Spark source mass spectrometry (SSMS) has experienced important and significant improvements in nearly all analytical features by the use of a multiple ion counting (MIC) system. Two procedures have recently been developed to further increase the analytical capabilities of MIC-SSMS in geochemistry. These are a mathematical correction of interferences, which is often necessary for the ultra trace element analysis of Nb, Ta, Zr, Hf and Y, and the development of an autospark system to hold the total ion beam constant. New analytical data for geological samples, especially international reference materials, are presented using the improved MIC-SSMS technique. The data set consists of high precision and low abundance data for Zr, Nb and Y in depleted reference materials. The MIC-SSMS results are compared with those of conventional SSMS using photoplates for ion detection. The precision of the MIC-SSMS isotope ratio measurements (about 1%) is more than a factor of 3 better than that of conventional SSMS, as demonstrated by analyses of Hawaiian samples. Total uncertainties of MIC-SSMS concentration data including all sources of error are generally between 2 and 5% for concentrations higher than about 0.3 microg/g and about 10% for trace element abundances in the ng/g range.     

Progress in multi-ion counting spark-source mass spectrometry (MIC-SSMS) for the analysis of geological samples

Spark source mass spectrometry (SSMS) has experienced important and significant improvements in nearly all analytical features by the use of a multiple ion counting (MIC) system. Two procedures have recently been developed to further increase the analytical capabilities of MIC-SSMS in geochemistry. These are a mathematical correction of interferences, which is often necessary for the ultra trace element analysis of Nb, Ta, Zr, Hf and Y, and the development of an autospark system to hold the total ion beam constant. New analytical data for geological samples, especially international reference materials, are presented using the improved MIC-SSMS technique. The data set consists of high precision and low abundance data for Zr, Nb and Y in depleted reference materials. The MIC-SSMS results are compared with those of conventional SSMS using photoplates for ion detection. The precision of the MIC-SSMS isotope ratio measurements (about 1%) is more than a factor of 3 better than that of conventional SSMS, as demonstrated by analyses of Hawaiian samples. Total uncertainties of MIC-SSMS concentration data including all sources of error are generally between 2 and 5% for concentrations higher than about 0.3 μg/g and about 10% for trace element abundances in the ng/g range.     

Application of slurry nebulization to trace elemental analysis of some biological samples by inductively coupled plasma mass spectrometry

Summary The application of slurry nebulization/inductively coupled plasma mass spectrometry (ICP-MS) to trace elemental analysis of biological samples has been investigated. Three standard samples of the National Institute of Standards and Technology (NIST) were dispersed in 1% aqueous Triton X-100 solution by grinding with a planetary micronizing mill. The resulting slurries were nebulized into an ICP without any additional treatments. The 1% (m/v) slurry of the NIST bovine liver showed no significant influence on cone blockage and signal suppression/enhancement. Detection limit, precision and accuracy were discussed for the determination of 24 elements of interest in bovine liver, rice flour and pine needles. Detection limits ranged from 0.0001 g g^–1 for U to 0.52 g g^–1 for Zn at the effective integrating time of 10 s. For high mass elements, low blank values were obtained, yielding excellent limits (<0.01 g g^–1). Acceptable accuracy and precision were obtained for most of the elements in the NIST bovine liver and rice flour, even for the volatile elements, such as As, Se and Br. However, relatively poor accuracy was obtained for the analysis of pine needles.     

Inorganic trace analysis by mass spectrometry

Mass spectrometric methods for the trace analysis of inorganic materials with their ability to provide a very sensitive multielemental analysis have been established for the determination of trace and ultratrace elements in high-purity materials (metals, semiconductors and insulators), in different technical samples (e.g. alloys, pure chemicals, ceramics, thin films, ion-implanted semiconductors), in environmental samples (waters, soils, biological and medical materials) and geological samples. Whereas such techniques as spark source mass spectrometry (SSMS), laser ionization mass spectrometry (LIMS), laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS), glow discharge mass spectrometry (GDMS), secondary ion mass spectrometry (SIMS) and inductively coupled plasma mass spectrometry (ICP-MS) have multielemental capability, other methods such as thermal ionization mass spectrometry (TIMS), accelerator mass spectrometry (AMS) and resonance ionization mass spectrometry (RIMS) have been used for sensitive mono- or oligoelemental ultratrace analysis (and precise determination of isotopic ratios) in solid samples. The limits of detection for chemical elements using these mass spectrometric techniques are in the low ng g⁻¹ concentration range. The quantification of the analytical results of mass spectrometric methods is sometimes difficult due to a lack of matrix-fitted multielement standard reference materials (SRMs) for many solid samples. Therefore, owing to the simple quantification procedure of the aqueous solution, inductively coupled plasma mass spectrometry (ICP-MS) is being increasingly used for the characterization of solid samples after sample dissolution. ICP-MS is often combined with special sample introduction equipment (e.g. flow injection, hydride generation, high performance liquid chromatography (HPLC) or electrothermal vaporization) or an off-line matrix separation and enrichment of trace impurities (especially for characterization of high-purity materials and environmental samples) is used in order to improve the detection limits of trace elements. Furthermore, the determination of chemical elements in the trace and ultratrace concentration range is often difficult and can be disturbed through mass interferences of analyte ions by molecular ions at the same nominal mass. By applying double-focusing sector field mass spectrometry at the required mass resolution—by the mass spectrometric separation of molecular ions from the analyte ions—it is often possible to overcome these interference problems. Commercial instrumental equipment, the capability (detection limits, accuracy, precision) and the analytical application fields of mass spectrometric methods for the determination of trace and ultratrace elements and for surface analysis are discussed.     

Simultaneous multi-element analysis of trace elements in soil samples by means of high-resolution inductively coupled plasma sector field mass spectrometry (SF-ICP-MS)

The potential of SF-ICP-MS for trace element analysis in complex environmental matrices such as soil solutions was investigated. Spectral interferences found in mass spectra of soil matrices are presented in detail. Furthermore, the influences of single components of the soil matrix on the signal intensity of selected elements were studied. Detection limits of different elements are presented with respect to the composition of the matrix. A fast and accurate method for quasi-simultaneous determination of Al, Si, P, V, Cr, Mn, Fe, Ni, Co, Cu, Zn, As, Se, Sr, Mo, Cd, Sn, Hg and Pb in aqueous soil extracts was established.     

Simultaneous multi-element analysis of trace elements in soil samples by means of high-resolution inductively coupled plasma sector field mass spectrometry (SF-ICP-MS)

The potential of SF-ICP-MS for trace element analysis in complex environmental matrices such as soil solutions was investigated. Spectral interferences found in mass spectra of soil matrices are presented in detail. Furthermore, the influences of single components of the soil matrix on the signal intensity of selected elements were studied. Detection limits of different elements are presented with respect to the composition of the matrix. A fast and accurate method for quasi-simultaneous determination of Al, Si, P, V, Cr, Mn, Fe, Ni, Co, Cu, Zn, As, Se, Sr, Mo, Cd, Sn, Hg and Pb in aqueous soil extracts was established. Received: 3 January 2000 / Revised: 28 March 2000 / Accepted: 31 March 2000     

Analysis of high purity arsenic by spark-source mass spectrometry

Very low (μg kg^?1 concentrations of most elemental impurities are determined in an arsenic matrix by spark-source mass spectrometry when working with a cut ion-sensitive plate. The mass spectrum of arsenic is relatively simple and the lines for almost all analytically important ions are interference free, at the mass resolution used (ca. 4000). In order to have semi-quantitative results at least, one element should be accurately determined by an independent technique, such as atomic absorption spectrometry. The measurements are then semi-quantitative.     

Determination of hydrogen in stainless steels by spark-source mass spectrometry

A spark-source mass spectrometric (SSMS) method capable of determining traces of hydrogen in micro-volumes of metals was developed by using a pointed metal probe technique. The hydrogen background was decreased to μg g^?1 levels by the combination of a method in which the sample in the ion source is baked under vacuum at 323–343 K for more than 25 ks and a liquid nitrogen or liquid helium cryogenic pump method. This method was applied to the analysis of austenitic stainless steels at μg g^?1 hydrogen levels, and the relative standard deviation was within 20% for samples with hydrogen concentrations ranging from 2 to 4 μg g^?1. The relative sensitivity coefficent was 2.3 (Fe=1).     

Applications of spark-source mass spectrometry for localized microanalysis,film analysis and depth analysis

Spark-source mass spectrometry, which is a typical bulk analysis technique, can also be used to study lateral profiles extending over millimeter distances, and for in-depth, layer and microsample analysis. Such analyses require knowledge of the influence of instrumental parameters such as breakdown voltage, pulse repetition frequency, pulse length and slit settings on the material consumed per spark pulse or per unit time, on the crater dimensions and on the ion yield. A study for over 20 matrices is reported. Applications are for lateral analysis (diffusion profile of beryllium in a Cu/CuBe diffusion couple), in-depth analysis (diffusion profile of nickel in copper), layer analysis (carbon in 3-μm gold layers, 3-μm GaAs epitaxial layer) and of microsample analysis (water residues). The effect of the amount of material sampled per analysis on the obtainable precision is demonstrated.     

Accelerator mass spectrometry of small biological samples

Accelerator mass spectrometry (AMS) is an ultra-sensitive technique for isotopic ratio measurements. In the biomedical field, AMS can be used to measure femtomolar concentrations of labeled drugs in body fluids, with direct applications in early drug development such as Microdosing. Likewise, the regenerative properties of cells which are of fundamental significance in stem-cell research can be determined with an accuracy of a few years by AMS analysis of human DNA. However, AMS nominally requires about 1 mg of carbon per sample which is not always available when dealing with specific body substances such as localized, organ-specific DNA samples. Consequently, it is of analytical interest to develop methods for the routine analysis of small samples in the range of a few tens of microg. We have used a 5 MV Pelletron tandem accelerator to study small biological samples using AMS. Different methods are presented and compared. A (12)C-carrier sample preparation method is described which is potentially more sensitive and less susceptible to contamination than the standard procedures.     

Analysis of thin layers by means of spark-source mass spectrometry

Summary A device has been constructed with which the surface of a specimen can be scanned with a spark drawn from a fixed counter electrode. The mean depth of penetration is of the order of microns and limits of detection of 0.1 ppm are possible. Repeated scanning allows profile analysis, too.

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Analyse dünner Schichten mit Hilfe der Funken-Massenspektrometrie

Zusammenfassung Eine Anordnung wurde konstruiert, mit der eine sich drehende Probenoberfläche durch eine feste Gegenelektrode abgetastet werden kann. Die mittlere Eindringtiefe pro Funkenentladung liegt in der Größenordnung von Mikrometern. Nachweisgrenzen von 0,1 ppm sind möglich. Durch wiederholtes Abtasten können auch Profilanalysen durchgeführt werden.

     

Improvement of reproducibility of trace analysis by spark-source mass-spectrometry

Summary Mechanisms responsible for poor reproducibility of analysis by spark-source mass-spectroscopy are discussed. A new scheme for the output cascade of a radiofrequency generator has been developed. It allows for stabilizing both the charge and impurity mass-spectrum composition at changing the width of the interelectrode gap over a wide range. The causes of transient irreproducibility in mass-spectrometric analysis have been studied and traced to temporal variation in the discharge-circuit parameters. Methods of eliminating this irreproducibility are proposed.

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Verbesserung der Reproduzierbarkeit der funkenmassenspektrometrischen Spurenanalyse

Zusammenfassung Die Ursachen der schlechten Reproduzierbarkeit der mit Hilfe der Fun-kenmassenspektrometrie durchgeführten Spurenanalyse wurden erörtert. Ein neues Schema der Ausgangsstufe des Hochfrequenzgenerators wurde ausgearbeitet. Dies ermöglicht die Konstanthaltung sowohl der Ladung wie der Zusammensetzung des Massenspektrums auch bei weitgehender Veränderung des Elektroden-Zwischenraumes. Die Ursachen der vorübergehenden Nicht-Reproduzierbarkeit massenspektrometrischer Analysen wurden untersucht. Diese wird von der zeitlichen änderung der Ladungsparameter verursacht. Vorschläge für die Behebung dieser Nicht-Reproduzierbarkeit wurden gemacht.

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Presented at the 8th International Microchemical Symposium, Graz, August 25–30, 1980.     

Applications of mass spectrometry in the trace element analysis of biological materials

The importance of mass spectrometry for the analysis of biological material is illustrated by reviewing the different mass spectrometric methods applied and describing some typical applications published recently. Though atomic absorption spectrometry is used in the majority of analyses of biological material, most mass spectrometric methods have been used to some extent for trace element determination in biomedical research. The relative importance of the different methods is estimated by reviewing recent research papers. It is striking that especially inductively coupled plasma mass spectrometry is increasingly being applied, partly because the method can be used on-line after chromatographic separation, in speciation studies. Mass spectrometric methods prove to offer unique possibilities in stable isotope tracer studies and for this purpose also experimentally demanding methods such as thermal ionization mass spectrometry and accelerator mass spectrometry are frequently used.     

Rapid multi-element analysis of groundwater by high-resolution inductively coupled plasma mass spectrometry

A rapid and sensitive method was developed to determine, with a single dilution, the concentration of 33 major and trace elements (Na, Mg, Si, K, Ca, Li, Al, P, S, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, As, Se, Sr, Mo, Cd, In, Sn, Sb, Cs, Ba, Re, Hg, Pb, Bi, U) in groundwater. The method relies on high-resolution inductively coupled plasma mass spectrometry (HR ICP-MS) and works across nine orders of magnitude of concentrations. For most elements, detection limits for this method are considerably lower than methods based on quadrupole ICP-MS. Precision was within or close to ±3% (1) for all elements analyzed, with the exception of Se (±10%) and Al (±6%). The usefulness of the method is demonstrated with a set of 629 groundwater samples collected from tube wells in Bangladesh (Northeast Araiharzar). The results show that a majority of tube well samples in this area exceed the WHO guideline for As of 10 g L^–1, and that those As-safe wells frequently do not meet the guideline for Mn of 500 µg L^–1 and U of 2 µg L^–1.