170135_inorganicventures_flipping

13.8 Sample Preparation by Fusion

Lithium carbonate fusions: (cont.)

§ Lithium salts are very soluble. § Lithium has relatively few spectral lines for the ICP-OES user. § Signal quenching (signal suppression by matrix) is relatively less (due to low mass) than the B, Na, or K containing fluxes for the ICP-MS user. § Lithium can be obtained in pure form as the carbonate and is relatively inexpensive. § Li 2 CO 3 melts at relatively low temperatures (relative to the popular sodium carbonate fusion). § You can use graphite crucibles, which are both clean and inexpensive (I prefer glassy carbon which is more expensive, but very clean and not nearly as messy). § Li 2 CO 3 is a basic fusion that will attack many of the refractory metal oxides and sample types attacked by Na 2 CO 3 .

14.1 Ashing

Ashing Techniques: Dry Ashing

§ Dry Ashing is usually performed by placing the sample in an open inert vessel and destroying the combus8ble (organic) por8on of the sample by thermal decomposi8on using a muffle furnace. § Typical ashing temperatures are 450 to 550 ̍C.

§ Magnesium nitrate is commonly used as an ashing aid. § Charring the sample prior to muffling is preferred. § Charring is accomplished using an open flame.