Hi Folks, I would like to address a practical aspect of atomic emission spectroscopy related to excitation temperature. In atomic emission spectroscopy, low energy electrons from an atom are excited into higher energy orbitals and light is emitted when the electrons drop back to their ‘ground’ state. When sodium ions are introduced to a Bunsen burner, the characteristic yellow flame is observed because sodium electrons are excited at the temperature of the flame. The practical issue that I am trying to get to relates to the temperatures available from different excitation sources. According to Wikipedia (fountain of all knowledge), temperatures in natural gas flames range between 1200 and 1800 K. Unfortunately, the number of atoms that have electronic energy transitions in this range is fairly small (there is a table in a book called “Vogel’s textbook of analytical chemistry” that tells what elements can be observed with what kind of excitation sources. I will try to remember to look up the page number to post tomorrow). The EPA procedure referenced in the research note uses what is called ICP to excite the cadmium and lead. ICP stands for Inductively Coupled Plasma and can reach temperatures of ~9000 K. While I don’t know that these elements cannot be observed with other excitation sources, my feeling is that if EPA wants to use ICP, it might be because of the temperatures required. Jack