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Use of colorimetry in OMMICA

History

Colour (both hue and intensity) has been used as a tool in science for hundreds of years. Newton studied the behaviour of light in Opticks in the early 18th century, helium was discovered in the Sun through study of its spectrum in the 19th century, and colour change of dyes extracted from lichens with pH has been known about since the mediaeval period (forerunner of the litmus test).


Modern colorimetry

Modern scientific colorimetry is the quantitative analysis of colour, and is frequently used to determine the concentration of a species: colour intensity can be directly related to the concentration of a coloured species (this is described in the Beer-Lambert law).


Application in OMMICA

This is used in the OMMICA test to allow determination of test sample concentration, and is why the test kits include a set of standard solutions, to allow the users to prepare calibration curves. These give direct correlation between the sample concentration and the intensity of colour (its absorbance), which is measured at a specific wavelength by a colorimeter (sometimes called a spectrometer). They can then be used to accurately determine the concentration of unknown samples (using the OMMICA supplied calculation spreadsheet, which has safeguards built in to ensure the validity of the curve prepared).


This video demonstrates both the simple use of colour to determine the rough pH of a sample, and also the use of a calibration curve.










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