Atomic emission spectroscopy (AES), more commonly referred to as emission spectroscopy, is a spectroscopic technique which examines the wavelengths of photons emitted by atoms or molecules during their transition from an excited state to a lower energy state. Each element emits a characteristic set of discrete wavelengths according to its electronic structure; by observing these wavelengths the elemental composition of the sample can be determined. AES detectors operate by passing a continuous stream of target vapor to a burner where it is combusted by a hydrogen flame, resulting in excited state ions. The photoemission from the flame is passed to a diffraction grating and the resulting emission spectrum is then detected by a photo detector array. In this way, spectral lines for all elements in a sample may be recorded simultaneously.   AES is most useful for samples that are dissolved or suspended in aqueous or organic solutions. AES is typically employed as a bench top instrument.  It is a mature technology available from a number of manufacturers.