In addition to a method of atomization, atomic spectroscopic methods require a means of placing the sample within the device used for atomization. The analysis of seawater for sodium ions requires a means for working with a sample that is in solution. The analysis of a salt-substitute for sodium, on the other hand, requires a means for working with solid samples, which could be first bringing it into solution or working directly with the solid. How a sample is introduced also depends on the method of atomization. Examples of different methods of sample introduction include aspirating a solution directly into a flame, injecting a small aliquot of solution onto a resistive heating mechanism, or exposing a solid sample to a laser or electric spark. More details on specific methods for introducing samples appear in the chapters that follow.