Filtern
Dokumenttyp
Sprache
- Englisch (3)
Referierte Publikation
- ja (3)
Schlagworte
- AAS (1)
- Continuum source molecular absorption spectrometry (1)
- Fluorine determination (1)
- Graphite furnace (1)
- HR-CS-MAS (1)
- High-resolution continuum source absorption spectrometry (1)
- High-resolution continuum source molecular absorption spectrometry (1)
- Molecular absorption (1)
- Niobium oxide (1)
- Slurry sampling (1)
Organisationseinheit der BAM
For the purpose of finding suitable molecules applicable to sulfur determination and to compare their analytical sensitivity systematically, high-resolution overview molecular absorption spectra of sulfides of group 14 elements produced in a graphite furnace were investigated. To that end a modular simultaneous echelle spectrograph (MOSES) was used, which allows recording sub-ranges of spectra out of a total wavelength range from 190 nm to 735 nm. The combined overview spectra show a complex structure with many vibrational bands, each of them consisting of a multitude of sharp rotational lines. The absorption of rotational lines of SiS (282.910 nm), GeS (295.209 nm), SnS (271.578 nm), and PbS (335.085 nm) has been analyzed for optimizing the particular experimental conditions regarding to the sulfur determination. Using the commercial CS AAS instrument contrAA 600 under optimized conditions such as the temperature program, the modification of the platform with Zr and the use of chemical modifiers, the achieved characteristic masses for sulfur are 12 ng (CS), 15.7 ng (SiS), 9.4 ng (GeS), 20 ng (SnS), and 220 ng (PbS). The first four sulfides provide an analytical sensitivity with roughly the same level, but the GeS molecule seems to be the best one with respect to analytical sensitivity and flexibility in molecular formation control. The PbS molecule provides the lowest analytical sensitivity, and together with its low bond strength it is not recommended for sulfur determination.
Aiming for a round-robin test, a new method for the direct determination of fluorine in niobium oxide has been developed. It is based on the use of high-resolution molecular absorption spectra of calcium mono-fluoride (CaF) generated in the graphite tube, combined with the slurry sampling technique. The absorption measurement was performed at the 606.44 nm CaF rotational line. By using graphite tubes with zirconium carbide (ZrC) modified platform, the molecular absorption sensitivity of CaF has been improved by a factor of 20, and no additional chemical modifier was necessary. Generally, non-spectral interferences were observed in the presence of HCl, H2SO4, and H3PO4. For HCl, additional spectral interference occurred due to an overlap of the absorption spectra of CaF and CaCl. However, due to the absence of these mentioned substances in the current material, such interferences do not exist for this application. The characteristic mass found for the CaF 606.44 nm line was 0.1 ng; the limit of detection was 5 mg fluorine per kg solid sample (3σ criterion). The results obtained by the method were within the range of certified values. Comparing to the classical method such as the pyrohydrolysis-photometric method, the developed new method showed clear advantages regarding sensitivity and specificity. The time requirement for one sample analysis was strongly shortened from several hours to only some minutes.
This work aimed to evaluate high-resolution continuum source molecular absorption spectrometry (HR-CS MAS), traditionally used to determine non-metals, for the determination of a new element, metal, vanadium. VO was selected as a target molecule because it is relatively stable and was expected to be spontaneously generated in a flame or a graphite furnace (GF). The high-resolution overview spectra of the molecule were obtained in a wide range of 480–630 nm, and absorption due to the X4Σ−–C4Σ− electronic transition was registered. A unique instrumental setup, comprising a prototype Modular Simultaneous Echelle Spectrograph (MOSES) and a commercial HR-CS MAS apparatus, was applied in the research. Finally, the spectral area centered at 550.6230 nm was selected for analysis. A method was developed to determine V in solutions of catalysts of heavy petroleum oil hydroprocessing using a commercial HR-CS spectrometer in a flame version. Although sensitivity was relatively poor (characteristic concentration 380 mg L−1), an extremely low noise enabled reaching a satisfactory detection limit (20 mg L−1 in solution, i.e. 0.1% m:m in the catalyst). For the first time vanadium was determined using ordinary air-acetylene flame. The obtained results were consistent with the results of atomic absorption spectrometry with N2O-C2H2 flame. Unfortunately, only a small population of VO molecules could have been generated in GF measurements. Furthermore, the observed VO molecules appeared only at unfavorably high temperatures. The work shows the potential of HR-CS MAS as a scientific tool for investigating the mechanism of processes occurring in the GF. This work can inspire other research of new analytes for HR-CS MAS.