palintest Ammonia Duo, User Manual

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7
2 BACKGROUND INFORMATION
Introduction to Colorimetric Measurement
Palintest tests are based on measuring the intensity of
colours produced by Palintest reagents and using
Palintest photometers to measure that intensity of
colour. This is colorimetry and can be defined as any
technique used to evaluate an unknown colour in
reference to known colours.
To avoid subjective measurement between test samples
and colour standards, a colorimeter can be used for
quantitative measurement of the amount of coloured
light absorbed by a sample (with reagents added) in
reference to an untreated sample (blank).
White light is made up of many different wavelengths
of light.
A colorimeter passes a white light beam through an optical
filter which transmits only one particular band of wavelength
of light to the photodetector where it is measured.
The difference in the amount of coloured light transmitted
by a colourless sample (blank) and the amount of coloured
light transmitted by a coloured sample is a measurement
of the amount of coloured light absorbed by the sample.
The use of filters improves the sensitivity of this process
and choice of the correct optical filter (and therefore the
correct wavelength) of light is important.