P.0 Präsident und andere
Filtern
Dokumenttyp
Sprache
- Englisch (2)
Schlagworte
- Isotope dilution (2) (entfernen)
Organisationseinheit der BAM
- 1.1 Anorganische Spurenanalytik (2) (entfernen)
Quantification of sulphur in copper metals by isotope dilution LA-ICP-MS using polyethylene frits
(2018)
Sulphur is one of the relevant impurities in copper and its alloys affecting their material properties. To ensure the quality of copper products, fast direct solid sampling techniques are very attractive. However, for the calibration suitable matrix reference materials are required. For the certification of such reference materials appropriate, SI-traceable analytical methods are essential. Therefore, a procedure was developed to quantify total sulphur in copper by combining the classical isotope dilution (ID) technique and laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS).
Here, for the first time, polyethylene (PE) frits were used to prepare appropriate solid samples for the sulphur quantification in copper metals (alloyed/unalloyed) by isotope dilution LA-ICP-MS. The properties of the PE frit meet the requirements as porous material with high absorption efficiency, thermal and chemical resistance as well as low sulphur blank. Different copper reference materials were used to develop and validate the procedure. The copper samples were spiked with 34S, digested with nitric acid and then the digests were absorbed on PE frits. After drying, the frits were analysed by LA-ICP-IDMS using a Nd:YAG laser at 213 nm coupled to an ICP sector field mass spectrometer. It could be demonstrated, that the sample solution dispersed on the frits did not influence the 32S/34S ratio significantly even though the sulphur intensities were fluctuating along the scanned lines. Relative standard deviations of the isotope ratios were below 5 % in average between three line scans (except for the pure spike solution and procedure blank). The measurement results were validated by comparing them with the results obtained by conventional ICP-IDMS after analyte-matrix separation. Plotting the mass fraction of sulphur in copper obtained by LA-ICP-IDMS versus those obtained by ICP-IDMS yields a linear curve with a correlation coefficient of 0.9999 showing a strong agreement between both techniques.
The metrological traceability to the SI from the kg down to the sulphur mass fraction in copper is established by an unbroken chain of comparisons, each accompanied by an uncertainty budget. Thus, the measurement results are considered reliable, acceptable and comparable within the stated measurement uncertainty.
The therapeutic dose of lithium (Li) compounds, which are widely used for the treatment of psychiatric and hematologic disorders, is close to its toxic level; therefore, drug monitoring protocols are mandatory. Herein, we propose a fast, simple, and low-cost analytical procedure for the traceable determination of Li concentration in human serum, based on the monitoring of the Li isotope dilution through the partially resolved isotope shift in its electronic transition around 670.80 nm using a commercially available high-resolution continuum source graphite furnace atomic absorption spectrometer. With this technique, serum samples only require acidic digestion before analysis. The procedure requires three measurements—an enriched 6Li spike, a mixture of a certified standard solution and spike, and a mixture of the sample and spike with a nominal 7Li/6Li ratio of 0.82. Lanthanum has been used as an internal spectral standard for wavelength correction. The spectra are described as the linear superposition of the contributions of the respective isotopes, each consisting of a spin-orbit doublet, which can be expressed as Gaussian components with constant spectral position and width and different relative intensity, reflecting the isotope ratio in the sample. Both the spectral constants and the correlation between isotope ratio and relative band intensity have been experimentally obtained using commercially available materials enriched with Li isotopes. The Li characteristic mass (mc) obtained corresponds to 0.6 pg. The procedure has been validated using five human serum certified reference materials. The results are metrologically comparable and compatible to the certified values. The measurement uncertainties are comparable to those obtained by the more complex and expensive technique, isotope dilution mass spectrometry.