ACTIVITY 4
Flame Test: An application of Spectroscopy
Introduction:
Spectroscopy is a prominent analysis technique within numerous fields of science. One such technique which utilises spectroscopy is the flame test. A flame test is used to determine the presence of elements within an unknown compound (the matter), based on the known characteristic of an elements emission spectrum (the electromagnetic radiation). When an unknown compound is subjected to a flame it will emit a colour. This emittance can be compared to the known emittance of chemicals and therefore our unknown compound can be determined.
Spectroscopy is can be used to help perform prominent analysis technique within numerous fields of science. One such technique which utilises spectroscopy is the flame test. A flame test is used to determine the presence of elements within an unknown compound, based on the known characteristic of an elements emission spectrum. When an unknown compound is subjected to a flame it will emit a colour corresponding to its wavelength. This emittance can be compared to the known emittance of chemicals and therefore our unknown compound can be determined.
A flame test is considered a Qualitative analysis which mean although the compound or element can be determined it offers no insight to the elemental proportions of the compound (think back to your lesson on concentration standards). A Qualitative and Quantitative version of flame test is Flame Emission Spectroscopy (FES) which utilises atomic emittance spectroscopy (AES).Â
You will learn how to read a data output from AES which is a commonly used spectroscopic technique. From spectroscopic analysis we will generate a graph of the emitted spectra represented within our sample. The peak shown on the graph (Figure 3) shows the intensity of the sodium’s light emittance or intensity represented by weak to strong emittance (ranging form 0-100%) at a known wavelength (125nm) of light. This shows Sodium has a peak of 20% intensity at around 125nm. This form of data can be used to determine unknown substances and elements within a solution or compound. When a substance is burned it will emit according to its unique chemical properties, from its unique emittance you can then determine its composition by referring to a reference bank of known substances. Reference banks are commonly used within analytical fields. A reference bank will have the known emittance spectra of numerous chemicals and substances and can therefore be used to help determine the composition of unknowns. This is a similar method to the use of calibration standards as you are utilising known data to determine unknown samples.
FLAME TEST
An Application of Spectroscopy
A short video displaying the basic concept of a spectroscopic technique.
