Direct Current Glow Discharge Mass Research Articles

Silicon and indium as secondary cathodes for the analysis of solid alumina and sapphire by slow-flow direct-current glow discharge mass spectrometry

We demonstrate and compare the capabilities of indium and silicon as secondary cathodes for the analysis of flat, solid alumina and sapphire matrices by direct current glow discharge mass spectrometry (dc-GDMS).

Application of 7N In as secondary cathode for the direct current-glow discharge mass spectrometry analysis of solid, fused high-purity quartz.

Direct current glow discharge mass spectrometry with an indium-based secondary cathode technique is used to analyze solid, nonconducting, fused high-purity quartz regarding metallic impurities of relevance to the solar industry. Details of the analytical routines are presented. In this work, the secondary cathode design and glow discharge conditions are optimized beyond the commonly applied practices. In addition, relative sensitivity factors (RSFs) for these optimized conditions are established and compared to previously published results. The results indicate that the technique enables stable measurements with detection limits down to the part per billion (ppb) range.

AMPEROMETRIC DETERMINATION OF CERIUM (III) USING 2,7-DINITROZO-1,8- DIHYDROXYNAPHTHALENE-3,6-DISULFONIC ACID SOLUTION

Cerium and its compounds are widely used in the production of electronic devices and semiconductors, which is why these substances will enter the environment more often in the future. There is a need for effective express methods that can determine the trace amounts of cerium and other rare earth elements with high accuracy to control and study the possible negative impact of cerium compounds on the ecosystems. The objective of this research paper was to elaborate on an express method capable of producing accurate and reliable results on the content of cerium in wastewaters in the presence of other rare earth elements. The elaboration of the express method was carried out based on the amperometric titration method studying the effect of various buffer solutions on cerium determination. Moreover, the effect of strontium, lutetium, iron, yttrium, samarium, niobium, holmium, praseodymium, gadolinium, and erbium ions on acquisition accuracy of the cerium (III) ions in samples of process water was studied. The research results presented a method for the amperometric determination of cerium (III) applying 2,7-dinitroso-1,8-dihydroxynaphthalene-3,6-disulfonic acid on a rotating platinum disk microelectrode. The extraction-amperometric method of analysis was proposed for the analysis of process water. The optimal concentrations of background electrolytes and buffer mixtures and the voltage values, were determined; the stability constant of the complex was calculated; the lower limit of the determined cerium content was defined. No interfering influence of foreign ions on the determination of cerium (III) ions was observed. The developed method for determining cerium (III) has a simpler hardware design than the previously described method of pulsed direct current glow discharge mass spectrometry but has a higher detection limit.

Determination of relative sensitivity factors of elements in a copper matrix by using microsecond-pulsed and continuous direct current glow discharge mass spectrometry

The relative sensitivity factors of 72 elements in microsecond-pulsed and continuous direct current (dc) modes were determined and compared by preparing the calibration samples by using Element GD type glow discharge mass spectrometry (GD-MS).

The direct quantification by glow discharge mass spectrometry with the universal relative sensitivity factors without matrix-matched standards

Direct measurement of the elemental components of bulk conductors or semiconductors is the main application area of direct current glow-discharge mass spectrometry (dc-GDMS). The quantification by GDMS usually requires the matrix-matched standards to obtain the relative sensitive factors (RSFs) of the target elements. Unfortunately, the matrix types of the analytes are far beyond the available matrix-matched standards. To overcome this limitation of GDMS, we attempted to establish a direct quantification method by GDMS with a set of universal RSFs (u-RSFs) instead of the matrix-matched standards. To explore the intrinsic relationship between the RSFs and the operational parameters of GDMS, we studied the impact of the discharge current, discharge voltage, discharge gas flow rate, and the ion transmission system voltage on the RSFs of the representative elements with a GDMS instrument. Only the discharge gas flow rate was identified significant on RSFs. Based on the optimum parameters, a set of u-RSFs were obtained by averaging the RSFs in certified reference materials (CRMs) covering most common matrixes. The direct quantification by GDMS was accomplished by u-RSFs. This method was further validated in several scenarios, and the accuracy of 10%~30% was achieved.

Development and application of a porous cage carrier method for detecting trace elements in soils by direct current glow discharge mass spectrometry

By using a porous cage carrier method, interferences were removed and the signal of Si was improved.

The formation of an oscillating system during the sputtering of sapphire single crystal with pulsed glow discharge

Sapphire (α-Al2O3, transparent corundum) single crystals were analyzed with pulsed direct current glow discharge mass spectrometry. Combined hollow cathode was used as a discharge cell. To obtain stable sputtering of dielectric material, a formation of initial surface conductivity via preliminary vacuum deposition of thin metallic layer was proposed. Al and Ta film of different thickness (30–200 nm) were considered for this purpose. The approach was found to provide the effective sputtering of dielectrics. The formation of an oscillating system was shown during the sputtering of sapphire samples in a tantalum combined hollow cathode cell. For oriented sapphire single crystals, periodic oscillations of 27Al+ intensity were acquired. This phenomenon was observed only for dielectric single crystals and not for other dielectric samples, e.g. alumina ceramic or fused quartz. The linear dependence of oscillation period on the duration of discharge pulse was found. The origin of these oscillations seems to be attributed to periodic fluctuations of surface conductivity. Oscillation periods calculated for two different orientations of sapphire single crystals (001 and 012) were found to be proportional to the main period of sapphire lattice. Therefore, an assumption that the crystal internal structure of the sample might be the cause of the oscillations is discussed.

Determination of trace impurity elements in MnZn ferrite powder by direct current glow discharge mass spectrometry

An analytical method for the determination of 26 impurity elements (such as Li, Be, Na, Mg, Al, Si, P, S, K, Ca, Sc, Ti, V, Cr, Co, Ni, Ga, Ge, Y, Nb, Mo, Ag, Cd, Sb, W and Pb) in MnZn ferrite powder by direct current glow discharge mass spectrometry (GD-MS) was established. MnZn ferrite powder was mixed with copper powder, used as a conductor, and pressed. The effects of MnZn ferrite powder preparation conditions and glow discharge parameters for the sensitivity and stability of signal analysis were investigated. By determining the choice of isotope and the application of the mass resolutions of 4000 (MR, medium resolution) and 10000 (HR, high resolution), mass spectral interference was eliminated. The contents of impurity elements in MnZn ferrite powder was calculated by subtraction after normalizing the total signal of Mn, Zn, Fe, O and Cu. The results showed that the detection limit of 26 kinds of impurity elements was between 0.002 and 0.57 μg/g, and the relative standard deviation (RSD) was between 3.33% and 32.35%. The accuracy of this method was verified by the ICP-MS. The method was simple and practical, which is applied to the determination of impurity elements in MnZn ferrite powder.

Determination of trace elements in high purity alumina powder by helium enhanced direct current glow discharge mass spectrometry

Trace impurities in high purity alumina powder were determined by fast flow direct current glow discharge mass spectrometry (GD-MS). The non-conductive samples were prepared with high purity graphite powder and used as a sample binder and as a secondary cathode. To improve the sensitivity of the GD-MS analysis, helium was introduced as an additional glow discharge gas to argon plasma. The quantification results of the GD-MS measurement were calculated by external calibration with matrix matched certified reference materials. The GD-MS results for the determination of Na, Mg, Si, Ca, Ti, V, Cr, Fe, Cu, Zn and Ga in the alumina samples agreed well with the certified values of a reference material and the results of chemical analysis using wet sample digestion with inductively coupled plasma atomic emission spectrometry (ICP-AES) and inductively coupled plasma mass spectrometry (ICP-MS). The GD-MS analysis is a rapid analysis technique to determine trace elements in non-conductive alumina to below mg·kg−1 levels.

Studies of rare earth elements to distinguish nephrite samples from different deposits using direct current glow discharge mass spectrometry

Nephrite is an interesting gemstone of wide versatility that is used for ritual objects, decoration, utilitarian objects, carving or jewellery around the world. It is necessary to demonstrate a possible relationship between the concentrations of characteristic elements and differences in the quality or deposit. In this study, direct current glow discharge mass spectrometry (dc-GD-MS) was used to determine the rare earth elements (REEs) of 14 nephrite samples from different deposits by using a tantalum (Ta) pin for the electrical connection, and this method has successfully overcome interferences in the REE analyses. After the optimization of discharge conditions, the characteristics of REEs were studied for nephrite minerals obtained from different deposits. Principal component analysis using REEs and other minor and trace elements successfully separated some nephrites from specific deposits. The dc-GD-MS was an effective tool for the classification of nephrites from different deposits.

Determination of doping elements of synthetic crystals by direct current glow discharge mass spectrometry

Direct current glow discharge mass spectrometry (dc-GD-MS) was applied for the determination of doping elements in synthetic crystals. To get stable discharge, the surface coating method and tantalum carrier method were used to support the sputtering and ionization of samples respectively. For the analysis of BaF2, Y3Al5O12 (YAG), Bi4Si3O12 (BSO), La3Ga5SiO14 (LGS), CsI and Pb(Mg1/3Nb2/3)O3-PbTiO3 (PMN-PT), the stable discharge current and the matrix signals were investigated by using these two methods. While for the analysis of CaF2 and γ-Al2O3, the tantalum carrier method could sustain much stable discharge to achieve fine intensity of matrix elements compared to the surface coating method. Furthermore, two Y3Al5O12 (YAG) samples were also studied by inductively coupled plasma optical emission spectrometer (ICP-AES) to validate the precision, accuracy and reproducibility of these two methods. The results suggested that the dc-GD-MS would be a good choice to determine the doping elements in synthetic crystals by these two methods.

Direct current glow discharge mass spectrometric analysis of non-conducting materials using a surface coating method

A surface coating method was developed to analyze some non-conducting materials using the pin cell of a direct current glow discharge mass spectrometer (dc-GD-MS). As the materials were non-conducting there were many problems associated with sustaining a dc glow discharge, and this could be overcome by coating the surface with a very thin layer of conducting material. During the sample preparation process the melted indium was coated manually onto the surface of the sample, thus supporting the sputter process and causing the sample to be sputtered and ionized for analysis. After optimization of the plasma conditions, the prepared samples could be analyzed directly by dc-GD-MS with satisfactory detection limits, stability and reproducibility. Two NIST standard reference materials were used to validate the precision, accuracy and reproducibility of this method. The results showed that this method could avoid grinding, sustain the relatively stable discharge and enhance the stability of signals compared to the method of using a cathode made from indium pin rolled in the sample powder.

H 2/Ar direct current glow discharge mass spectrometry at constant voltage and pressure

The addition of hydrogen to a direct current (dc) - argon glow discharge (GD) coupled to a time of flight mass spectrometer has been studied using a fixed voltage between the electrodes and a fixed discharge pressure. Hydrogen contents investigated were 0.5%, 1% and 10% v/v in the argon discharge and the samples under study consisted of a copper-base, a nickel-base and an iron-base homogeneous materials. Also, the in-depth profile analysis of a tin plate was investigated. Results have shown that hydrogen addition gives rise to significant changes in the slope of the linear relationship between the electrical current and the discharge voltage. Clearly, the electrical resistance of the discharge at the typical operation voltages in the interval 600–1000 V increases with hydrogen added to pure argon. A decrease of the sputtering rates was observed the higher the hydrogen concentrations. Besides, the “reduced sputtering rates”, i.e. the sputtering rates divided by the corresponding electrical current, were also lower for the H 2/Ar discharges than for pure argon. However, the analytical ion signals observed using discharge voltages higher than 900 V turned out to be higher in a 0.5% H 2/Ar discharge than in pure argon for the copper and nickel materials. Besides, for the three samples investigated the ion yields were from 1.5 up to 3 times higher in 0.5% H 2/Ar discharges as compared to the pure argon. Finally, the effect of 0.5% H 2 addition to the Ar discharge on the in-depth profile of a tin plate has also been investigated. As compared to the use of a pure Ar GD, higher sensitivity for major and minor components of the coating were observed without loss of the relative depth resolution achieved.

Neptunium determination by dc glow discharge mass spectrometry (dc-GDMS) in Irish Sea sediment samples

Direct current glow discharge mass spectrometry (dc-GDMS) has been applied for the direct analysis of 237Np in marine sediment samples from the Irish Sea. The secondary cathode technique was exploited to promote the sputtering of the sediment samples once compacted into a pellet. A certified marine sediment doped with a certified 237Np solution was used for obtaining matrix-matching samples for calibration purposes. Acquiring 100 points over an integration time of 300 ms a detection limit down to 80 pg g−1 was obtained. Results on 237Np were in agreement with those obtained by the determination of 233Pa by γ-spectrometry.

直流ヘリウムグロー放電質量分析法によるステンレス鋼分析

直流ヘリウムグロー放電質量分析法によるステンレス鋼分析

Comparison between the use of direct current glow discharge mass spectrometry and inductively coupled plasma quadrupole mass spectrometry for the analysis of trace elements in nuclear samples.

The quantitative determination of trace elements in nuclear samples by GDMS and ICP-MS is presented and compared. Spectral interferences, matrix effects, detection limits, precision and accuracy are discussed. Results for selected samples demonstrated that both techniques are complementary. The use of a multi-standard solution provides the most accurate results in ICP-MS, whereas in GDMS this is achieved by relative sensitivity factors (RSF) matrix matched. Nevertheless, the use of standard RSF allows a fast screening.

Investigation of mechanisms of corrosion due to diffusion of impurities by direct current glow discharge mass spectrometry depth profiling

A glow discharge mass spectrometer was used to study the incorporation of impurities, such as lithium, boron and zinc, in ZrO2 layers grown on Zircaloy samples by two different techniques: (1) through heat treatment in an autoclave, under thermodynamic conditions and in a chemical environment similar to the primary cooling system used in pressurised water nuclear reactors (PWR), and (2) by reactive sputter deposition on aluminium and silicon substrates. The results obtained show a lithium intake in the oxide layer and confirmed the beneficial effect of the addition of boron to the corrosive environment by the decrease of the oxide layer thickness by a factor of 4, although not being incorporated in the oxide structure. The influence of zinc, used in boiling water reactors (BWR), on the corrosion behaviour could not be identified but its presence in the oxide network was clearly determined. The need for the application of the secondary cathode technique for the determination of the depth profile of insulating ZrO2 layers, as an alternative to the use of radiofrequency powered glow discharge techniques, is established.

Suppression of gas species signals in direct current glow discharge time-of-flight mass spectrometry

The possibility of suppressing gas species in direct current glow discharge mass spectrometry (dc-GDMS) with a linear time-of-flight mass analyzer was investigated. With this dc-GD ion source, a ‘clean’ mass spectrum rich in analyte could be obtained when the dc-GD was operated under a discharge current of 15–30 mA and a gas pressure of 300–500 Pa, in contrast to the strong signals of gas species in conventional dc-GDMS, which operates at lower currents and pressures (typically 1–5 mA and 100 Pa). Such an experimental result is believed to be due to increased sputtering at higher pressures and currents, and the different ionization mechanisms of analyte and gas species. For a possible GD design to eliminate the background gas ions, a new discharge configuration was developed by attaching a TM 010 microwave resonator to the GD ion source. The mass spectrum of the cathode sample showed a low gas species background when the microwave-induced plasma (MIP) discharge was ‘off’ under different dc-GD parameters. The mass spectra of analyte and gas species obtained with ‘MIP+dc-GD’ and ‘MIP only’ modes are also compared and discussed. It was found that the analyte signals decrease and the gas species signals increase in the presence of the MIP, and that the analyte signals nearly disappear in the ‘MIP only’ mode. Preliminary results suggest that, for specific discharge conditions and with a suitable design of the GD source, an efficient suppression of gas species in dc-GDMS detection could be realized.

Direct Current Glow Discharge Mass Spectrometry for Elemental Characterization of Polymers

A direct current glow discharge mass spectrometer has been used for a novel application, the sputtering and subsequent analysis of polymers. This was made possible by the application of a secondary cathode, a tantalum diaphragm placed in front of the nonconducting sample. Different types of polymers were measured (polytetrafluoroethylene, polycarbonate, and poly(vinyl chloride)). Important to note is that the mass spectra obtained are predominantly characterized as atomic, a major difference from the radio frequency GDMS spectra of polymers reported earlier. This facilitates quantitative elemental analysis for several reasons.

Quantitative Analysis of Zirconium Oxide by Direct Current Glow Discharge Mass Spectrometry Using a Secondary Cathode

A dc GD mass spectrometer has been used for the analysis of ZrO 2 samples with known amounts of artificial impurities. For this purpose the secondary cathode technique has been used. The research work focused both on the methodological aspects of the atomization of the ZrO 2 and on some quantitative aspects, with direct analytical interest. The reproducibility was found to be better than 10% RSD in most cases; the accuracy of the ‘standardless’, raw results was within a factor of 2–3 of the known concentration.