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- Copper (4)
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Eingeladener Vortrag
- nein (24)
Mass spectrometric detection can play a prominent role in the assessment of different reactions occurring at varied temperatures in a milled ZnO/Al mixture. This is the first time that online mass spectrometric information was used as a tool for monitoring and understanding the chemical reduction process mechanism. We have observed four different types of reaction taking place: (1) distillation of Zn metal, (2) reduction of ZnO by activated Al, (3) melting of Al and finally (4) reduction of ZnO by inactivated Al. The experimental conditions and results observed by QMS were supported with literature data and physical measurement data from X-Ray Diffraction (XRD) which gave us an idea about the complex reaction cascade which occurred during the formation of the zinc metal.
Detection and monitoring of volatile elements released during the preparation of ultra high purity zinc by vacuum distillation (VD) is reported using online quadrupole gas source mass spectrometry (QMS). The theoretically calculated vapour pressures (pv) for the volatile impurity elements using Dushman constants and the practically observed mass spectra were found to be consistent (S. Dushman and J. M. Lafferty, Scienific Foundations of Vacuum Technique, 2nd ed., Wiley, New York, 1962). This is the first time that the potential ability of an online mass spectrometer was used for monitoring and understanding the process mechanism during the purification of metals (Zn) using VD. We here also illustrate our findings with the results from high resolution glow discharge mass spectrometer (HR-GDMS) analysis before and after the purification of Zn.
Ultra high purity Zn (m6N5) was obtained through triple vacuum distillation using an m4N5 Zn as input material. High-volatile impurities were removed from the zinc matrix by vacuum evaporation, while traces having lower volatility than the matrix remained in the residual material after finishing of the entire purification process. The time required for the removal of the main high-volatile impurity (Cd) was monitored using a connected gas source mass spectrometer. During distillation the Zn vapor of the distillate was condensed on the cap of a glassy carbon crucible which was water cooled by a movable copper block. The temperatures were optimized for the removal of the volatiles and for the distillation process using vapor pressure data. High resolution glow discharge mass spectrometry was applied for the analysis and purity evaluation of the distilled and input zinc. The analysis confirmed the reduction of the metallic impurities from 43 mg kg-1 to 0.5 mg kg-1 (m6N5) after three consecutive vacuum distillations. An increase in the grain size and a decrease in the micro-hardness were observed for the purified Zn material.
The hollow cathode (HC) effect was investigated in non-cooled 15 mm deep drilled flat metallic analytical samples that were easy to prepare. The deep cavity used ("complete HC" in contrast to "recessed HC" with 2-3 mm deep cavity) intensified the HC effect notably and therefore distinctly improved the detection power of the common GD-OES with planar cathodes. A signal enhancement of up to a factor of 150, not reported earlier, in comparison with flat conventional samples was achieved. A better separation of the analytical lines from spectral interferences was observed when the HC assembly was applied. Additionally, an effect of strongly enhanced intensities of atomic lines and somewhat decreased intensities of ionic lines was detected in the case of HC in comparison to usual planar cathodes. The investigations were carried out with samples of copper, steel and zinc matrices using both the same and individually optimised glow discharge (GD) electrical parameters.
Synthetic pressed metal powder standards doped with standard solutions were used for the calibration of both commercially available high resolution GD-MS instruments Element GD and VG 9000 for zinc matrix. Different quantification procedures (IBR, Standard RSF, matrix matched RSF from the calibration with CRMs and use of doped synthetic standards) are compared using zinc matrix as an example, whereas the calibration with doped pellets turned out to be the best quantification technique for high-purity materials. The applicability of the Standard RSF concept is scrutinised. In this context, RSF values for several Matrices (Co, Cu, Fe, In and Zn) are reported additionally.
Calibration of two commercially available glow discharge double focusing mass spectrometers, the VG 9000 and Element GD, is described using synthetic pin standards pressed from solution doped copper and zinc matrices. A special pressing die was developed for this purpose and optimal results were obtained with the highest possible pressures, i.e., 95 kN·cm- 2. This calibration approach permits the determination of trace element mass fractions down to µg·kg- 1 with small uncertainties and additionally provides traceability of the GD-MS results in the most direct manner to the SI (International System of Units). Results were validated by concurrent measurements of a number of compact copper and zinc certified reference materials. The impact of the sample pin cross-section (circular or square) was investigated with the use of a new pin-sample holder system for the Element GD. The pin-sample holder was designed by the manufacturer for pin-samples having circular cross-section; however, samples with square pin cross-section were also shown to provide acceptable results. Relative Sensitivity Factors for some 50 analytes in copper (VG 9000, Element GD) and zinc matrices (VG 9000) are presented. The field of applicability of GD-MS may be considerably extended via analysis of pin geometry samples based on their ease of preparation, especially with respect to the accuracy and traceability of the results and the enhanced number of analytes which can be reliably calibrated using such samples.
In supplementary work to the one published earlier, experiments with SF6, NF3, CF4 and H2 as new modifier gases for the matrix studied were performed. Our investigations were continued to improve the described analytical method and to achieve additional insights into the mechanism of analyte release. Our new survey is split in two parts. At first fluorinating modifiers were used to investigate the behaviour of a variety of trace elements (Ag, Al, As, Au, Bi, Cd, Co, Cr, Fe, Mg, Mn, Ni, P, Pb, Sb, Se, Si, Sn, Te, Ti, Zn and Zr). Most of them (exceptions Au, Se, and Te) could be effectively released from the copper matrix by thermo-halogenation reactions and by partial sub-sample evaporation. Using SF6 and NF3 as modifier gases, low limits of quantification (LOQs) were achieved for the 19 well released trace elements (typical ≤0.1 mg kg-1). Most elements (exceptions Ag, Mg, and Ni) could be calibrated by using aqueous calibration solutions without any sample pretreatment. For the trace determination of Se, Te, and Au, a further analytical method of ETV-ICP OES is described in the second part based on thermo-hydrogenation reactions by using a hydrogen/argon mixture as a modifier gas. The determination of Se and Te with very high analytical performance (LOQ < 0.1 mg kg-1) can either be carried out in a second analytical step succeeding the halogenation procedure, or the sub-sample is directly treated with H2 without previous halogenation procedure whereby the sub-sample can either be partially or totally evaporated. In this case some other analytes (Ag, Au, As, Bi, Cd, Fe, Mg, Ni, Pb, Sb, Sn, and Zn) can additionally be quantified simultaneously with Se and Te.
Inspired by the globule arc technique a new electrothermal vaporization inductively coupled plasma optical emission spectrometry (ETV-ICP OES) method was developed for the analysis of high-purity copper materials. The performance of the method was investigated for the analytes Ag, Al, As, Bi, Cd, Co, Cr, Fe, Mg, Mn, Ni, P, Pb, S, Sb, Se, Si, Sn, Te, Ti, Zn and Zr. ETV parameters were optimized regarding the release of the analytes, the transport efficiency and the quality of analytical results in terms of precision, trueness and power of detection. The influence of CCl2F2, CHClF2, C2H2F4 and CHF3 as gaseous halogenation modifiers was investigated. A sufficient in situ analyte matrix separation was achieved by using CHF3 as halogenating reagent avoiding a high matrix input from the molten copper sample into the ETV system and the plasma. A complete release from the samples was obtained for all investigated analytes except Se and Te. Acceptable results for the determination of the trace elements Ag, Al, As, Bi, Cd, Co, Cr, Fe, Mg, Mn, Ni, P, Pb, S, Sb, Si, Sn, Ti, Zn and Zr in high-purity copper were achieved. The method includes a preceding sample preparation step of oxidizing the surface of copper samples which results in a significantly enhanced sensitivity. In addition to the calibration with copper samples, the feasibility of the calibration with liquid multi-element solutions was investigated. Except for Ag, Mg and Ni all analytes could be analyzed using aqueous calibration solutions. The trueness of the method was tested by the determination of analyte contents of certified reference materials. Limits of quantification ranging from 0.6 ng g-1 to 29 ng g-1 were achieved. The developed direct solid sampling method is time and cost effective and well suited for the characterization of high-purity copper materials. The method can be automated to a large extent and is applicable for processes accompanying analyses. In contrast to all other investigated trace elements, Se and Te were not released from the matrix at measurable levels under the used conditions. The determination of these elements is still under investigation and will be reported in a succeeding publication.
Premixed 1% Freon in argon inner gas of various composition (CCl2F2, CHClF2, CHF3) was applied to graphite furnace atomizer to minimize unfavorable effects of carbide formation, such as signal tailing and memory effects in the simultaneous determination of Cr, Mo, Ti and V refractory analytes by electrothermal atomic absorption spectrometry using a multielement atomic absorption spectrometer. The effect of these gaseous additives was investigated when applied separately in atomization, pyrolysis and clean-out steps. The halogenation effects were analytically useful only under the precondition of using ArH2 outer gas to the furnace to all heating steps, and also using this gas in the pre-atomization (drying, pyrolysis) steps. Optimum analytical performance was obtained when mixtures of 1% Freon in argon were applied just before and during the atomization step at a flow rate of 50 mL min- 1 and 2% hydrogen was used as purge gas. Using optimum conditions, signal tailings and carry-over contamination were reduced effectively and good precision (relative standard deviation below 1%) could be attained. Applying 1% CHClF2 and an atomization temperature of 2550 °C, the characteristic masses obtained for simple aqueous solutions were 8.8 pg for Cr, 17 pg for Mo, 160 pg for Ti, and 74 pg for V. The limits of detection were 0.05, 0.2, 2.3 and 0.5 µg L- 1 for Cr, Mo, Ti and V, respectively. The developed method was applied to the analysis of digests of advanced ceramics. The accuracy of the procedure was confirmed by analyzing the certified reference material ERM-ED 102 (Boron Carbide Powder) and a silicon nitride powder distributed in the inter-laboratory comparison CCQM-P74.
The key comparison CCQM-K33 was organized by the Inorganic Analysis Working Group of the CCQM to test the abilities of the national metrology institutes to measure the mass fractions of minor elements in steel. Elements to be analysed were Cr, Mn, Ni and Mo in low alloy steel. The National Metrology Institute of Japan (NMIJ), the National Institute of Standards and Technology (NIST) and the Federal Institute for Materials Research and Testing (BAM) acted as the coordinating laboratories. The participants used various measurement methods, though many of them used ICP-AES. Generally speaking, the agreement of the results was very good for each measurand.
A method, based on electrothermal vaporization (ETV) coupled to inductively coupled plasma optical emission spectrometry (ICP OES), has been optimized for direct solid sampling analysis of soda-lime glass - the most common type of industrially manufactured glass. This method allows fast and reliable quantification of the main elements - Al, Ca, K, Mg, Na, and Si - and trace elements - As, Ba, Cd, Ce, Co, Cr, Cu, Fe, Mn, Mo, Ni, (P), Pb, Sb, (Se), Sn, Sr, Ti, V, Zn, and Zr. In the presented ETV-ICP OES method, calibration is performed predominantly with matrix-free synthetic samples. This metrological advantage is normally not achieved with direct solid sampling methods and is one of the goals of the present study. In a certification interlaboratory comparison for the soda-lime glass CRM BAM-S005c, 2 out of 16 laboratories employed the ETV-ICP OES method. An improved analytical performance was obtained compared with the results of laboratories that used conventional liquid ICP OES. For both methods, the average relative deviations between the laboratory results and certified values as well as the average values of relative standard deviation were with a few exceptions <10%, in most cases even <5%, which indicated high trueness and precision.
ICP-MS analysis of high purity molybdenum used as SI-traceable standard of high metrological quality
(2005)
The need, concept and technical approach for the certification of SI-traceable standards of high metrological quality for chemical analysis of the elements is briefly explained. As an example of problems occurring in the certification of these standards, special technical aspects related to the analysis of high purity Mo by ICP-MS, namely blank reduction for Na, Li and Ni by protective coating of the cones with silicon, as well as dealing with the interferences from the Mo matrix, are discussed.
The determination of O, N and H using a microwave induced plasma coupled to carrier gas hot extraction was exploratory investigated. The signal intensities versus time of blanks and calibration materials were recorded. To check for interferences the signal intensities versus wavelength were recorded at the times just before increase and at the maximum of the time dependent analytical signal. O, N and H were investigated at their prominent wavelengths of 777 nm, 174 nm and 486 nm, respectively. Calibration was performed for O, N and H in the ranges of 027 µg, 351000 µg and 343 µg respectively. For concentration values in the middle of the linear part of the investigated calibration interval, a relative precision of 5% at 13 µg, 2% at 74 µg and 0.6% at 23 µg for O, N and H respectively was found. The maximum matrix load to the plasma used was found to be 150 µg min-1. From the signal to noise ratio and the sensitivity obtained, instrumental limits of detection (3s) of 0.01 µg for O, 1 µg for N and 0.1 µg for H were found. Assuming a typical sample mass of 1 g this corresponds to relative LODs of 0.01 µg g-1, 1 µg g-1 and 0.1 µg g-1 for O, N and H respectively.
The special importance of the analysis of non-metals in high purity metals, which will serve as national standards for elemental analysis in Germany, is illustrated for oxygen and nitrogen. The typical range of the mass fraction of oxygen and nitrogen in these materials is below 10.MU.g/g, often close to 1.MU.g/g. The two methods applied at BAM for these measurements are classical carrier gas hot extraction (HE) and carrier gas hot extraction after activation with photons (PAA-HE). The approach, the methods and their advantages and limitations are discussed. Comparative results from the measurement of oxygen and nitrogen in Cu, Fe, Ga, Pb, Sn and W are presented. (author abst.)
An inter-laboratory study was performed by some National Metrology Institutes in order to take a snap shot of the comparability and the capability of performing purity assessments of high purity materials as needed for providing national standards for elemental determination. The measurand was defined as the value of the sum of the mass fractions of Ag, Al, Cu, Fe, Pb and Zn in the bulk of a high purity nickel material and the interim results for the six individual impurities. Whereas for the analytes Ag, Al, Cu and Fe there was no agreement within the target uncertainty of 30%, agreement could be achieved for Pb and Zn. The discrepancies observed for the individual analytes resulted in a variation of a factor of 8 of the reported values for the impurity of nickel with respect to the six defined metallic analytes. The reference measurements using IDMS and for Al using GD-MS confirmed the lower reported values.
The application of metrology in chemical analysis is today hampered by psychological and practical barriers. The argumentation is based on the differences in physical and chemical metrology, which arises mainly from the objects of the measurements. The term measurement is discussed in the realm of analytical chemistry with a special focus on the inherent relation between chemical identification and determination as well as the consequent use of the concept of traceability and uncertainty.
In Germany a system of primary amount of substance standards for elemental analysis is being developed, which forms the material´s basis for the National Standards for element determination. The metrological concept and technical approach is briefly described. The objective of traceability in chemistry, in this case for elemental determination, is illustrated on the example of copper.
A complete metrological traceability system for measurement results of chemical analysis was set up. Core components are pure substances (national standards) characterised at the highest metrological level, primary solutions prepared from these pure substances and secondary solutions deduced from the primary solutions and intended for sale. The relative uncertainty of the element mass fraction of the primary substances and solutions is < 0.01 and < 0.05%, respectively. For the certification of transfer solutions and for stability testing, a precision measurement method for element contents has been developed by means of optical emission spectrometry (ICP OES) by which uncertainties between 0.1 and 0.05% can be achieved. The dissemination to field laboratories is effected with the aid of a calibration laboratory of the German Calibration Service (DKD) which certifies the element content of the secondary solutions with an uncertainty <= 0.3%. Calibration with these solutions enables the user to establish traceability of his measurement results to the International System of Units (SI). Currently, the system comprises Cu, Fe, Bi, Ga, Si, Na, K, Sn, W, and Pb.
Within the National Metrology Institutes (NMIs) and designated laboratories, an interlaboratory comparison, CCQM-P107, was conducted to verify the degree of international comparability concerning the results of purity analysis. The mass fractions of Ag, Bi, Cd, Cr, Ni, Tl at the lower mg/kg-level in a high purity zinc material were determined, but the real measurand in metrological sense was the sum of the six mass fractions. Homogeneity was investigated by glow discharge mass spectrometry, reference values were obtained using isotope dilution mass spectrometry. Six NMIs participated, contributing eight independent data sets. The agreement amongst the results of the participants, their median and the agreement with the reference values were usually excellent and in almost all cases below the target uncertainty of 30% relative. In this manner, the accuracy of results and the comparability between the participants was demonstrated to be established.
Primäre Kalibriernormale für die metrologische Rückführung in der anorganischen chemischen Analytik
(2003)
Special new techniques of atomic spectrometric methods for trace analysis of high purity metals
(2003)
Siliciumcarbid (SiC) ist ein wichtiges technisches Material nicht nur in seinen klassischen Anwendungsbereichen, die auf seinen hervorragenden mechanischen Eigenschaften, insbesondere seiner großen Härte, und seinem besonderen thermischen Verhalten beruhen. Vielfache Anwendungen finden sich auch als Hochleistungskeramik, in der Halbleitertechnik, der Opto- und Mikroelektronik. Für seinen Gebrauch in den verschiedenen Anwendungsgebieten ist die Reinheit des Materials von großer Bedeutung. Die auf der Verwendung von Aufschlusslösungen basierende Analytik ist wegen des erforderlichen zeitaufwendigen Aufschlussverfahrens wenig effektiv. Für größere Analysenserien und für die schnellere Bereitstellung der Ergebnisse sind deshalb direkte Analysenverfahren mit Festprobentechnik von verschiedenen Autoren erprobt und eingesetzt worden. Um zu zuverlässigen und vergleichbaren analytischen Aussagen zu gelangen, sind für einen breiten Einsatz bei den Herstellern validierte und genormte Analysenverfahren erforderlich. Die vorgestellten Ergebnisse sind Bestandteil des Validierungs- und Normungsprozesses. Hierbei wurde für jede der beiden Feststoff-Analysenmethoden mit Multielementcharakter, die optische Emissionsspektrometrie mit induktiv gekoppeltem Plasma und elektrothermischer Verdampfung (ETV ICP OES) und die optische Emissionsspektrometrie mit Gleichstrombogenanregung (DC Arc OES), ein Ringversuch zur Multielement-Spurenbestimmung an sechs vorcharakterisierten Siliciumcarbidpulvern durchgeführt. An diesen Laborvergleichen beteiligten sich mit der ETV ICP OES acht und mit der DC Arc OES neun Laboratorien aus Industrieunternehmen, Forschungseinrichtungen und Universitäten. An jeder der sechs untersuchten Proben wurden sechs parallele Messungen ausgeführt, mit der ETV ICP OES für die Analyten Al, Ca, Cr, Cu, Fe, Mg, Ni, Ti, V und Zr und mit der DC Arc OES für die Analyten Al, B, Ca, Fe, Mg, Ni, Ti und Zr. Für drei der sechs Proben wurden die Gehalte aus den auf der Basis dieser Messungen bestimmten Kalibrierkurven ermittelt, wobei die jeweilige Probe nicht in die Kalibrierung einbezogen wurde. Aus den ermittelten Gehalten wurden nach DIN ISO 5725-2 die Wiederhol- und die Vergleichspräzision beider Analysenverfahren berechnet. Diese stellen wichtige Beiträge zur Verfahrensvalidierung und zur geplanten Normung im Rahmen des DIN NMP 264 "Chemische Analyse von nichtoxidischen keramischen Roh- und Werkstoffen" dar. Ein Eindruck über die Richtigkeit beider Analysenverfahren läßt sich durch Vergleich der Ergebnisse mit den durch rückführbare Messungen zuvor erhaltenen Werten gewinnen. Dabei ist zu beachten, dass diese auch für die Kalibrierung verwendeten Gehaltsangaben der sechs verschiedenen Kalibrierproben nicht in allen Fällen auf einer geraden oder monoton steigenden Kalibrierkurve liegen. Im Nachgang wurde außerdem von der BAM in Kooperation mit der GDMB und unter breiter internationaler Beteiligung eines der sechs SiC-Pulver als Referenzmaterial zertifiziert. Hierdurch wird die Zuverlässigkeit der Aussagen zur Richtigkeit noch weiter erhöht. Die Vergleichs- und die Wiederholpräzision werden als überwiegend gut eingeschätzt, die Richtigkeit als gut bis befriedigend; nur in wenigen Fällen treten größere systematische Abweichungen von den Referenzwerten auf. Damit werden beide Analysentechniken als geeignet zur schnellen Direktanalytik der nur schwer und zeitaufwendig aufzuschließenden Siliciumcarbidpulver bewertet.
Im Beitrag wird außer auf die Ringversuche und ihre Auswertung auch auf methodische Besonderheiten beider direkten Feststoff-Analysenverfahren eingegangen.
Multielement trace determination in high purity advanced ceramics and in high purity metals
Ralf Matschat, Hans-Joachim Heinrich, Michael Czerwensky, Sandra Kuxenko and
Heinrich Kipphardt
Federal Institute for Materials Research and Testing (BAM),
Richard-Willstaetter-Strasse 11, D-12489 Berlin, Germany
Certified reference materials (CRMs) are of high importance to check the trueness of results in chemical analysis. In the field of advanced ceramics two CRMs were developed in the last years by the Federal Institute for Materials Research and Testing - (BAM), one for silicon nitride and one for silicon carbide. The certification of these materials is briefly discussed in this contribution. Both CRMs are not of extremely high purity in the classical sense, but besides their application by industry they are appropriate to be used for the validation of special methods used for trace determination in accordant high purity materials. This is demonstrated for the example of ultrapure silicon carbide which was analyzed by solid sampling electrothermal atomic absorption spectrometry (SS ET AAS). Wet chemical dissolution of this pure material typically introduces blanks which are too high for ultratrace analysis. Therefore SS ET AAS as a direct method was applied which does not need any wet chemical sample preparation. This method can be applied very effectively concerning sample throughput. But, as for all direct solid sampling methods, the calibration is a problem difficult to solve. By using the accordant CRM it could be demonstrated, that the calibration with liquid sample aliquots can be performed without affecting the trueness of the results. The analytical parameters and the performance of the method are discussed.
Besides the so-called matrix CRMs, as reported for silicon nitride and silicon carbide, BAM is also certifying primary pure reference materials used as the National Standards for inorganic analysis in Germany. This work is performed in the frame of an extensive project in co?operation with the sister institute of BAM, the Physikalisch Technische Bundesanstalt (PTB). The crucial point of this project is the certification of the purity of high purity materials, each representing one element of the periodic table. Up to now more than ten primary CRMs are certified or not far from being certified. A variety of different analytical methods was necessary to determine the trace contents of metallic and non-metallic impurities from almost the whole periodic table in the high purity materials. Using high purity copper as an example the application and the results of the different methods applied are demonstrated. Another example presented is high purity iron. In this context the very good comparability of the results from two different methods, used for the determination of metallic traces is demonstrated. One of these methods was the "working horse" - the sector field high resolution ICP mass spectrometry (HR ICP-MS) mainly used in low resolution mode to exploit the good detection power and the other one was the electrothermal atomic absorption spectrometry (ET AAS), which was used to confirm the results of the HR ICP-MS. The analysis of pure molybdenum is presented as a third example. The problems of spectral matrix interference are discussed and different ways of their handling are pointed out. By this example it can also be demonstrated, how the coating of the inlet cones of the ICP mass spectrometer by matrix elements of solutions - which normally is an adverse effect - can be advantageously used to decrease the measured blank values of some analyte elements drastically.