Atomic emission spectroscopy (AES) is an analytical technique used to determine the elemental composition of a sample by analyzing the light emitted from excited atoms. In AES, atoms in a sample are excited to higher energy levels by thermal energy from high-temperature sources, such as plasma, arcs, or sparks. When these excited atoms return to lower energy states, they emit light at specific wavelengths characteristic of each element. The resulting atomic emission spectrum, which consists of discrete lines corresponding to these wavelengths, allows for identifying and quantifying various elements within the sample.

AES instrumentation shares similarities with atomic absorption spectrometers but with specific adaptations for emission detection. High-temperature sources, particularly inductively coupled plasma (ICP), are essential in AES as they achieve sufficient energy to excite atoms to their emission states. Other plasma sources include microwave-induced plasma (MIP) and direct current plasma (DCP). The most widely used source, ICP, reaches temperatures up to 10,000 K, creating a stable environment for consistent excitation and emission. ICP-AES, also known as ICP-OES (optical emission spectrometry), enables multielement analysis by positioning multiple detectors in a semicircular array around the emission source to capture simultaneous readings across a range of wavelengths.

AES offers several advantages over traditional atomic absorption methods, such as flame and electrothermal techniques. Due to the high-temperature sources that dissociate complex molecules, AES is less susceptible to chemical interferences, enabling cleaner spectral readings. The technique allows for simultaneous multielement analysis, significantly improving analytical efficiency. Additionally, AES covers a wider concentration range, making it suitable for diverse sample types.

Despite these advantages, AES has limitations. The complex spectra produced by high-temperature sources increase the likelihood of spectral interferences, complicating quantitative analysis. To address these challenges, AES instruments require high-resolution optical systems, often more expensive than those used in atomic absorption spectrometry. Furthermore, while AES is powerful for multielement analysis, atomic absorption techniques remain valuable for single-element analysis due to their simplicity, cost-effectiveness, and precision.

AES is widely used in environmental monitoring, materials science, and clinical laboratories to analyze metals, trace elements, and other inorganic substances. Its ability to perform rapid, multielement analysis makes AES particularly useful for testing soil, water, and biological samples. The high sensitivity and broad elemental range of AES instruments enable accurate measurements at both trace and significant concentrations, making it a versatile tool for elemental analysis across various scientific fields.

In AES, quantitative analysis relies on measuring the intensity of the emitted light, which is proportional to the population of excited atoms. According to the Boltzmann distribution, this excited-state population depends on the temperature of the excitation source, with higher temperatures yielding greater emissions. Calibration curves, often linear over several orders of magnitude, are created by analyzing known standards to correlate emission intensities with elemental concentrations. Standardization techniques are crucial to control for variations in excitation efficiency and other instrumental factors, enabling accurate quantification of elements in diverse samples.