Rolf Tamm

Improvements in graphite-furnace atomic-absoption microanalysis with solid sampling

SummaryMicroanalysis using mechanized solid sampling with graphite-furnace atomic-absorption gives accurate results in the determination of trace elements in different NBS Standard Reference Materials. Analytical conditions are optimized by use of the method of standard additions, and all capabilities of a microcomputer controlled graphite furnace, such as matrix modification by oxygen ashing, temperature ramping and maximum power heating for atomization are used. Direct calibration against acid standards is possible.ZusammenfassungDie Mikroanalyse von Spurenelementen in verschiedenen NBS Standard-Referenzmaterialien unter Zuhilfenahme eines mechanisierten Zubehörs zur Festprobendosierung ergibt genaue Ergebnisse. Die Optimierung der analytischen Bedingungen wurde mit der Additionsmethode überprüft, wobei alle Möglichkeiten eines modernen mikrocomputer-gesteuerten Graphitrohrofens, wie Matrixmodifikation durch Sauerstoffveraschung, kontrollierter Temperaturanstieg und Atomisierung mit der superschnellen Heizrate ausgeschöpft wurden. Die direkte Messung gegen angesäuerte Bezugslösungen ist möglich.

Characterization of a pressurizable two-step atomizer for atomic absorption spectrometry ☆

A two-step atomizer consisting of a transversely heated atomization tube with integrated contacts and a cup furnace for sample vaporization was constructed. The system could accommodate tubes of various lengths and it could be operated at selected pressures. There was no physical contact between the tube and the cup and mainly diffusion was responsible for the sample vapour transport from the cup to the tube. Under these conditions there was an unavoidable loss by 40% of the peak area signals due to the gap between the cup and the tube. For a 24-mm tube, characteristic masses were on the average three times lower than for the state of the art transverse heated graphite atomizers (THGA). By de-coupling the processes of analyte vaporization and atomization the dynamic working range could be increased by three to six times using conventional measurements by atomic absorption spectrometry (AAS). In this case the cup temperature and hence the rate of analyte transport from the cup to the tube was controlled such that atom density in the tube did not exceed the linear range of the absorbance measurement. Carrying out clean-out steps at reduced pressure decreased memory effects.