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An absorption spectrophotometer measures the amount of an element in a sample by detecting how much light of a specific frequency is absorbed. It consists of a light source, a sample chamber, a monochromator, and a detector. The sample is usually converted into an aerosol and introduced into a hot flame to convert ions into atoms. It has various applications in geology, environmental protection, and medical fields.
An absorption spectrophotometer is an analytical instrument used to determine the amount of an element present in a sample. It is based on the fact that elements absorb light at a particular frequency within the light spectrum. When an atom is at its lowest energy, or ground state, it can absorb a photon of light with a specific frequency and jump to a higher energy state using the photon’s energy. Therefore, it is possible to detect the element in a sample and determine how much it is present by measuring how much light of the relevant frequency is absorbed by the sample. This technique is widely used in chemistry for elemental analysis.
Typical components of an absorption spectrophotometer include a light source; a chamber or cell in which the sample is exposed to light; a monochromator, which is a device that allows you to select and isolate the frequency of interest; and a detector that measures the intensity of light at that frequency. Since the amount of light absorbed at this frequency is proportional to the concentration of the element, it is possible to calculate how much of the element is present. The data can be viewed on a screen and/or archived electronically.
The light source for an absorption spectrophotometer normally emits light at the specific frequency absorbed by the item being tested. Since the absorption frequency of an element is the same as its emission frequency, the source can use that element to produce light of the required frequency. This can be achieved by an electric discharge in an inert atmosphere, using the element as the cathode. Normally, several light sources are required to test different elements, but in some cases a cathode containing multiple elements is used, to allow for these elements to be tested simultaneously.
In the most widely used type of absorption spectrophotometer, the sample – usually a solution – is converted into an aerosol and introduced into a hot flame, which converts any ions of the element of interest into atoms in their ground state, so that they absorb the light . The type of flame used depends on the element of interest. For many elements, an oxygen-acetylene flame is used; however, some metals can form oxides if there is sufficient oxygen in the flame. In these cases, a non-oxidizing flame can be used. Other methods include using a graphite furnace to heat the sample to a high temperature and electrically heating the sample in a thin carbon rod.
There are a wide variety of applications for the absorption spectrophotometer. A common application in geology is to determine the content of various metals in an ore sample. In the field of environmental protection, this instrument can be used to check the levels of toxic elements in industrial effluents, river and groundwater or to determine the levels of toxic heavy metals in fish. Likewise, it can be used to check the levels of various elements in blood samples, such as essential elements such as sodium, calcium and magnesium, as well as toxic elements.
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