Theoretical and practical aspects of flame emission spectroscopy

Abstract

When excited by an external source of energy, such as a flame, an electric arc, or a spark, the electrons of the atoms in their ground states are excited to more energetic states and, when they return to their lower energy states, they emit photons. The use of this physical process for quantitative analytical purposes is known as atomic emission spectroscopy. If a flame is used as the energy source, it is called flame atomic emission spectroscopy, or simply flame photometry. The physical processes involved are very rapid because the lifetimes of the excited states are short. Despite this, they can still be used in educational experiments in teaching laboratories of general chemistry and analytical chemistry. Modern emission spectroscopy equipment is currently widely used in geochemistry and mineralogy, water and mineral analysis, soil, plant, and fertilizer analysis, biochemistry, and medicine. In industry, it is routinely used for the quality control of reagents and other products, such as metal alloys, glass, cement, and ceramics. In this paper, the characteristics, uses, and limitations of flame atomic emission spectroscopy as an analytical technique are presented simply and straightforwardly, and well-known educational experiments are used to illustrate the theory. Throughout the text, some highlighted questions are given to encourage the reader to seek answers in the literature.