Spark Source Mass Spectrometry Research Articles

Multi‐Element Analysis of 15 International Standard Rocks by Isotope‐Dilution Spark Source Mass Spectrometry

The concentrations of 25 trace elements have been determined in 15 international standard rock samples by isotope‐dilution spark source mass spectrometry (ID‐SSMS). This technique yields reliable data down to the ppb concentration range. The agreement between most of our data and recommended values is within 10%. However, for reference samples with low trace element contents (BIR‐1, NIM‐N, PCC‐1, DTS‐1), differences between our data and the literature can be as large as a factor of 80.

Trace impurities determination in lead by spark-source mass spectrometry

Very low concentrations of many elemental impurities are determined in a lead matrix by spark-source mass spectrometry using photoplate detection. In order to obtain semiquantitative results, at least one element /antimony/ should be accurately determined by an independent technique such as atomic absorption spectroscopy in order to be used as an internal standard.

Quantitative analysis in spark source mass spectrometry

The ionization mechanism in the rf vacuum spark is considered. It is shown that anode and cathode plasma can be studied by means of liquid metal ion sources in the cathode or anode mode. Equilibrium isothermal plasma with kT = 6 eV and n e = 10 19 cm −3 was found to occur upon explosion of cathode microprotrusions. On expansion into a vacuum isothermal plasma transforms into nonisothermal plasma in which the ion temperature is proportional to the charge. The main parameters of nonisothermal anode plasma have been determined: particle concentration 10 16 cm −3, temperature of singly-charged ions kT = 0.6 eV. It was found that the ions pulled out from the spark interelectrode gap are formed in explosive emission cathode plasma, and the ions originating in anode plasma are not involved in the formation of the mass spectrum. Based on these investigations, analytical expressions for calculating the impurity-matrix ionization ratio are suggested. The use of ionization ratios allows the accuracy of impurity analysis in spark source mass spectrometry to be improved.

Determination of rare earth elements in a glass matrix by spark source mass spectrometry

A study of the REEs in the glass standard SRM-610 from the NBS by spark source mass spectrometry (SSMS) is presented. A careful study of possible interferences was done prior to the measurements. A comparison between the obtained values and some other published values based on the application of another technique showed satisfactory agreement between the two sets of results

High-sensitivity Nb analysis by spark-source mass spectrometry (SSMS) and calibration of XRF Nb and Zr

A new spark-source mass spectrometric (SSMS) technique for precise analysis of low Nb abundances in geological samples has been developed. The main improvements in precision, accuracy and detection power have stemmed from application of isotope dilution for accurate analysis of the internal standard element Zr, high mass resolution for sensitive measurement of low-abundance Nb peaks and precise determination of the element sensitivity of Nb for calibration. Nb concentrations of 5 ppb to 500 ppm (5 orders of magnitude) can be measured by this technique. Only small sample amounts (∼ 50 mg) are needed for an analysis. Precision and accuracy are better than ∼ ± 4%, ∼ ± 8% and ∼ ± 12% for Nb concentrations higher than 1, 0.1 and 0.01 ppm, respectively. To demonstrate the capability of the technique, 16 international standard rocks have been analysed. Our investigations yield the first reliable Nb and Zr abundances of some standard samples. The agreement for most of our data and compiled literature data is within 10% for Nb concentrations > 5 ppm and Zr > 40 ppm. However, for samples with low Nb and Zr concentrations (e.g., DTS- 1), differences between our data and the literature can be as large as a factor of 70. These standard data have been used to calibrate X-ray fluorescence (XRF) analyses of Nb and Zr. Careful attention to spectral interferences and matrix corrections combined with long counting times (giving precision between ± 0.4 and ± 0.2 ppm 2σ on Nb) leads to a calibration for 13 standards with MSWD of ∼ 0.9 for Nb, and ∼ 2.7 for Zr. This demonstrates that the SSMS data may be used to obtain consistent, high-precision calibrations for Nb analysis at many XRF laboratories worldwide.

Monitoring of Heavy Metals in As‐Implanted Simox with Surface Photovoltage

Heavy metals in concentrations of E‐16‐E‐18 cm−3 are commonly found in SIMOX samples implanted in high current implanters (100 mA). In the present study, surface photovoltage (SPV) was used successfully to measure the heavy metal concentration in as‐implanted SIMOX. An initial correlation has been established between the minority carrier diffusion length measured on the back of a SIMOX wafer and Fe concentration measured by SIMS and spark source mass spectrometry in as‐implanted SIMOX films. A correlation between the leakage current of MOS transistors and the heavy metal contamination level as measured by SPV was established. SPV measurements are quick, nondestructive, and do not require any additional sample preparation. They can therefore be used as a QC method to monitor heavy metals in as‐implanted SIMOX layers.

Spark source mass spectrometry applied to the determination of the isotopic composition of samples containing lithium, boron or iron

Spark source mass spectrometry has been used to determine the isotopic composition of Li and B and the 55Fe/58Fe and 59Fe/58Fe isotope ratios in enriched lithium-7 hydroxide, boric acid and irradiated disodium pentacyanonitrosylferrate, respectively. The experimental procedure followed in each instance is explained. Appropriate standards were used to check accuracy. Some modifications were introduced into the standard data handling to improve the precision when necessary. A careful study of possible interferences was performed in each instance. When there were doublets present in the element investigated, the mass lines were identified through the calculation of exact masses.

Applications of fuzzy theory to spatially resolved analysis of solids

Fuzzy theory is applied to compare response profiles and surfaces in spatially resolved materials analysis. Different options are proposed for the type of membership function, the definition of spreads, and specially defined similarity values. These similarity values are expressed analytically, thus permitting the development of a fast computer program. A special normalization in the calculation of the similarity values allows a set of distributions to be arranged hierarchically by clustering; the distributions are displayed as a dendrogram. The fuzzy techniques are also used to judge the homogeneity of a solid with respect to the distribution of chemical elements on its surface. Depth profiles from Rutherford back-scattering spectrometry and results of surface analysis by spark-source mass spectrometry are investigated as practical examples.

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).

Preparation of elemental Si from SiO 2

A method was developed to prepare elemental Si from SiO 2 in quantities up to 500 mg. SiO 2 is first converted to K 2[SiF 6] which is then submitted to a metallothermic reduction with Al. The gray α-modification of Si is formed by this procedure. The material is of high purity, as verified by electron microprobe, X-ray diffraction and spark source mass spectrometry analyses.

The ultrapurification of tellurium

High-purity tellurium is used in the preparation of II–VI compounds, particularly CdTe and Cdx Hg1−x Te. Distillation of tellurium under low-pressure H2 reduces the concentrations of iron and silicon. The addition of CdTe to tellurium prior to zone refining, in a quantity less than the eutectic concentration, has been observed to change the segregation behavior of Ca, K, Ga and As, which enables more efficient refining. Emission spectroscopy, spark source mass spectroscopy and the evaluation of Cd0.21Hg0.79 Te have been used to characterize these effects.

A photoplate calibration technique applied to the determination of hafnium in zirconium by SSMS

A photoplate calibration procedure is suggested for spark source mass spectrometry /SSMS/ with photoplate detection. The technique uses the Churchill two-line method applied to the two stable isotopes of copper. The calibration curve thus obtained is split into fragments and each fragment is approximated by a polynomial. The method was applied for the quantitative determination of Hf as impurity in zirconium sponge obtained from a pilot plant dedicated to the depletion of the hafnium content in zirconium by fractional crystallization.

Degradation of the mass spectrum due to reflected ions in spark source mass spectrometry employing an electrical detection system

The experience of using an electrical detection system in spark source mass spectrometry, with particular reference to the presence of diffuse peaks at the mass numbers of interest, is reported. A possible solution to the problem of these diffuse peaks is also reported.

Determination of trace impurities in cobalt by spark source mass spectrometry

An analytical method, SSMS, for the determination of trace impurities in cobalt is described. This element is used as raw material for the production of60Co in Embalse Nuclear Power Station. Tin, aluminum, lead, silicon, molybdenum, calcium, vanadium, boron, chromium, zirconium, tungsten, nickel, magnesium, iron, zinc and copper were determined. Manganese, analyzed by AAS, was used as an internal standard. The measurements were semiquantitative. The accuracy of the results was compared with that of emission spectrography and atomic absorption spectrometry, the agreement was found to be satisfactory.

Analysis of tellurium by spark source mass spectrometry

Three tellurium standards were analyzed by both spark source mass spectrometry (SSMS) and graphite furnace atomic absorption spectrophotometry (GFAAS). From these results relative sensitivity coefficients (RSC) for spark source mass spectrometry were derived for 24 elements.

Determination of trace impurities in zircaloy-2 and tellurium by spark source mass spectrometry

Determination of trace impurities in zircaloy-2 and tellurium by Spark Source Mass Spectrometry (SSMS) is reported. The advantage of SSMS lies in the fact that along with metallic trace constituents even the nonmetallic impurities and gases including hydrogen can also be determined.

Analysis of gallium arsenide by spark-source mass-spectrometry

A method has been developed for analysing gallium arsenide with a resistance of greater than 10 9Ω by spark-source mass-spectrometry, without the need for pelleting, which introduces a prohibitively high level of contamination and lowers the detection limit for a given exposure. It uses a gold evaporation technique, whereby a thin layer of 99.999% pure gold is deposited on one surface of the GaAs electrodes, in a chamber mounted on the ion-source. No contamination, other than gold, is introduced into the sample at a level of 50 ng/g or greater. It is possible to detect carbon in the sample at the 1–2 μg/g level. The sample preparation time is less than 30 min, and more than one set of samples can be gold-coated at a time.

Impurity segregation in CdxHg1-xTe crystals grown using ACRT

The segregation behaviour of a number of important elements in CdxHg1-xTe (CMT) has been established in crystals grown under conditions of accelerated crucible rotation (ACRT). Chemical analysis by atomic absorption spectrometry (AAS), laser scan mass spectrometry (LSMS) and spark source mass spectrometry (SSMS) has been carried out on both deliberately doped and undoped crystals. Estimates of segregation coefficients have been obtained and these are compared to those found in normal Bridgman grown crystals. In general the segregation coefficients are found to be lower in ACRT material and possible causes for this are suggested.

New developments in spark source mass spectrometry: Improvement of precision and sensitivity

New developments in spark source mass spectrometry: Improvement of precision and sensitivity

The sources and behaviour of impurities in LPE-grown (Cd,Hg)Te layers on CdTe(111) substrates

The sources of background impurities in LPE layers of (Cd,Hg)Te grown on CdTe(111) substrates are investigated using Spark-source mass spectrometry (SSMS) and secondary-ion mass spectrometry (SIMS). The principal sources of impurities were (i) the compounds HgTe and CdTe used in the LPE solution synthesis, (ii) the graphite sliding boat system and (iii) the CdTe substrate. The main impurities and their typical levels in the LPE layers were found to be Li (0.2 ppma), Na (0.3-1.0 ppma), Si (0.1-0.3 ppma), Cl (0.3-0.4 ppma) and K (0.03-0.06 ppma). To reduce the levels various changes in procedure were adopted such as cleaning of the graphite boat parts in aqua regia, the use of elemental starting materials (Hg, Cd, Te), substrate purification and the use of in-situ wash melts. The effect of Hg saturated isothermal annealing on the impurity concentrations and distribution has been studied, revealing rapid surface segregation of the Group IA impurities. The values of the distribution coefficients for several impurities have been calculated from the analytical results, these values being generally in good agreement with other published work.