RTI Act
Analysis are performed on pressed pellets for trace elements and fusion glass disks for major elements.
Pressed pellets are prepared using 40 mm aluminium cups filled with Boric acid crystals as binder. Finely powdered sample (-300 mesh) is sprinkled over boric acid and pressed in a 40-ton hydraulic press to produce a circular 40 mm disk. The pressed powder pellets allow trace element determinations, with limits of detection up to 1 ppm for selected elements. The elements determined presently in our lab areK, Ca, Ti, V, Cr, Co,Mn, Fe, Ni, Cu, Zn, Ga, Rb, Sr, Y, Zr, Nb, Ba, La, Ce, Sm, Yb, Th. Light elements like Si, Al, Mg, Na and P are less precise by this method. All major and trace elements are determined on sample pellets for which fused glass disk cannot be made (for e.g. river and marine sediments, soils etc.).
Fused glass Disk is prepared on a Katanax X-300 X-Fluxer triple station fusion instrument in the sample preparation lab of NCESS. One gram of finely powdered sample is mixed with 5 gram of flux (LiT/LiM/LiBR 49.75/49.75/0.50, Pure) in a platinum crucible. It is inserted into the crucible holder which enters the furnace automatically. The door closes and the remaining heating steps are automatically started in sequence and are constantly monitored and displayed. Once the flux is molten at 1050 C, a left-to-right rocking of crucible holder continuously mixes the flux with the sample. When all the sample is dissolved, furnace door opens and the crucible is tilted further to empty its contents into the platinum mold. A set of blowers cool the mold and when completely cooled, the process ends. It is entirely automated and comes preloaded with various fusion programs. It is also possible to create need based programmes.
Fused disks are excellent for analysing major elements as they reduce matrix effects, eliminates particle size effects and provides a homogeneous specimen. Samples which contain higher than normal concentrations of elements like lead, tin, arsenic and/or antimony (as they can seriously damage the platinum ware) and samples which contain organic matter are not suitable for this method of sample preparation. Elements determined by this method are Na, Mg, Al, Si, P, K, Ca, Ti, Mn, and Fe.