Many are scientific methods which analyses qualitatively and quantitively the chemical
composition of solutions. Spectrophotometry and colorimetry are one of them and their
principles, similarities and differences are discussed in this report.
As stated above, spectrophotometry is a technic that uses light in form of electromagnetic
radiations and works on the principle that when radiations pass through a sample in solution,
electrons of the analyte absorb part of the radiation and transmits the rest. Mainly based on
the wavelengths being passed through the sample, that is, the more the transmittance the less
the concentration and the converse holds true.it is essentially for determining the biomolecule
concentration of a solution.
Besides, Colorimetry is another method used to determine the concentration of coloured
compounds in a sample solution. The working principle behind colorimetry implements two
laws, respectively, beer and lambert which states that the intensity of a ray of monochromatic
light decreases exponentially as the concentration of the absorbing medium increases and the
later states that amount of light absorbed is directly proportional to the length and thickness of
the solution being analysed. Thus, the overall law states that the amount of light absorbed by a
colour solution is directly proportional to the concentration of the solution and the length a
light pass through.
In as much as colorimeter and spectrophotometry are similar in such a way that they both
employ a solution put in a “cuvette” and a beam of light in determining the absorbing level of
an analyte, there are some distinctions between the two devices. A spectrophotometer is much
accurate but costly to use that a colorimeter because the former produces device records data
via computer software when the latter produces digitally and in analogue. As already stated,
colorimetry only absorbs only visible light of the spectrum while spectrophotometer detects
the whole spectrum of electromagnetic radiations. Operationally, colorimeters uses a filter to
isolate the broad components of wavelengths.in contrast, spectrophotometer uses a prism and
grating to isolate the narrow band of wavelengths.
Because spectrophotometry and colorimetry are used to analyse the concentrations of
molecules in solutions. For example, detection of impurities and functional groups.
Characterisation of proteins like DNA and RNA. Consequently, it is very important to this effect
that spectrophotometry and colorimetry should be studied and applied in science.