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Eingeladener Vortrag
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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.)