Microwave digestion is a common technique used by elemental scientists to dissolve heavy metals in the presence of organic molecules prior to analysis by inductively coupled plasma, atomic absorption, or atomic emission measurement. This technique is usually accomplished by exposing a sample to a strong acid in a closed vessel, and raising the pressure and temperature though microwave irradiation. This increase in temperature and pressure of the low pH sample medium thereby increases both the speed of thermal decomposition of the sample, and the solubility of heavy metals in solution. Once these heavy metals are in solution, it is possible to quantitate or quantify the sample through elemental techniques.
H. M. Kingston and Lois B. Jamie. "Introduction to microwave sample preparation: Theory and practice" ACS Professional Reference Book, ACS, Washington, D.C., 1988. Pages xxii + 263.