Ceramics-Silikáty 31, (4) 349 - 363 (1987)

Spektrografická analýza práškových materiálov je mnohoprvkovou metódou nevyžadujúcou chemickú úpravu vzoriek. Optimalizácia metodik umožňuje dosiahnutie dostačujúcej spolahlivosti a súčasne vyhovujúcej dôkazuschopnosti. Práca je venovaná optimalizácii metodiky spektrografického stanovenia vedlajších (Al, Fe, Mg, Si) a niekolkých dôležitých stopových (B, Cr, Mn, Ti) prvkov cementových matrixov modelového zloženia: 70 % CaO, 20 % SiO₂, 5% Al₂O₃, 3% Fe₂O₃ a 2% MgO.

Detailed study showed that optimization that individual steps of spectrographic analysis (evaporation, reproducible excitation, analytical calibration) produced a method for simultaneous determination of the minor elements (Al, Fe, Mg, Si) as well as the important trace elements (B, Cr, Mn, Ti) in a matrix of CaO. The optimization demonstrated that the use of high-resistivity carbon electrodes ensured more extensive and uniform evaporation. A low halogenizing additive LiF changes the character of evaporation of B and partially also of Ti, since it suppresses formation of poorly volatile carbides. However, the Li₂CO₃ additive is more favourable with respect to excitation reproducibility in the DC are and to evaporation proportionality. The Li₂ + Li₂O₃ additive is less suitable for the matrix in question because it leads to non-uniformitv in evaporation and changes the course of calibration lines. Use of the Li₂CO₃ additive with the so-called carrier effect leads to the expected determination precision s_r(c) of 10 % and acceptable results in checking the accuracy of the method. The method is suitable for determination of the minor elements in the following concentration ranges given by analytical calibration: SiO₂ ˂30; 6.3˃ %, Al₂O₃ ˂10; 0.5˃ %, Fe₂O₃ and MgO ˂10; 0.1˃ %. The determinability range for trace elements is given by the upper limit defined as the highest calibration concentration of 1 % of the cement, and the lower limit, associated with the detection limit for the individual elements, which varies between 0.3 ppm (for Mn) and 31 ppm (for B).