A flame spectrophotometer measures light emitted or absorbed by atoms to determine the chemical composition of substances. It works best for metals and can measure quantities down to parts per million. The equipment is simple but requires precise calibration. Spectroscopy has a long history and has been used to build machines based on the flame spectrophotometer effect.
A flame spectrophotometer, also known as an atomic emission spectrophotometer, is a device for measuring light as it interacts with or is emitted from atoms to determine the chemical composition of substances. Light waves are measured when they are absorbed by an atom as it adds energy to it and pushes electrons towards a higher energy shell, or the light emitted when these excited electrons return to a lower energy shell is measured. Spectroscopy can be used to determine the amount of elements present in essentially any substance, but it works best for metals such as sodium, potassium and copper. This is because metals are easily excited to higher energy states with a low temperature in flame spectrophotometric analysis.
An atomic absorption spectrometer only works with visible light. A flame spectrophotometer can bombard an atom with ultraviolet light, however, if fluorescence spectroscopy is used to examine atomic compositions as well. These wavelengths of light can be directly related to changes in the energy states of outer shell electrons in atoms. Other types of spectroscopy, such as the study of X-ray emissions, are used to examine changes in the energy states of electrons in the inner energy shells of atomic structures. Molecular compounds also have unique rotational states between the atoms involved, leading to spectroscopic emissions in the microwave bands for their study.
The intensity of light in a flame spectrophotometer is directly related to the amount of an element present in a sample. The emission colors, or spectral lines, are distinct enough that elements can easily be distinguished from one another. The process used by a flame spectrophotometer for elementary samples is considered so precise that it can measure quantities of an element down to parts per million in a sample.
Equipment designed to perform flame spectrophotometric analysis is considered to be built on fairly simple instruments. The temperature required to provide atomic excitation, however, is high and is usually achieved by burning acetylene or propane at temperatures between 3.632° and 5.432° Fahrenheit (2,000° and 3,000° Celsius). The light emitted by the sample is passed through optical filters for analysis. It is also channeled to impact a photomultiplier detector which converts it into an electrical signal to record light intensity for elemental concentration measurements.
Spectrophotometers are popular laboratory machines used in clinical research or to determine the presence of metals in environmental samples. Their major drawback is that they require precise calibration against established standards to produce reliable readings, especially with complicated sample mixes. The history of the spectroscopy process can be traced back as far as Aristophanes’ study of the crystalline lens in 423 BC Only in the 1800s was the fundamental law of atomic absorption quantified and made it possible to build machines based on the flame spectrophotometer effect, which states that matter absorbs light at the same wavelength as it emits light.
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