BLE - Beer Lambert Law

what is spectrophotometry?

measurement of how much light is absorbed or transmitted by a given sample

when light passes through a coloured solution, some of the light is absorbed

what are the parts of a spectophotometer?

light source, filter to allow the generation of light of the chosen wavelength, cuvette holder, photocell, amplifier to detect transmitted light and recording device to measure the light intensity

transmittance

the amount of monochromatic light passing through a uniform solution

incident light

light coming from the light source

transmitted light

how much light gets through the sample

absorbance

the measurement of how much light is absorbed by the sample

beer lambert law

the extinction is directly proportional to the concentration of the absorbance material and the path length (absorbance is directly proportional to concentration)

A=Ɛcl where A is absorbance, Ɛ is molar absorption, c is concentration of absorbing medium and l is the path length of absorbing light in cm - usually 1cm

Beer Lambert standard curve

• a plot of unknown concentration versus extinction with result in a straight line through the origin which generates a standard curve

  • the concentration of an unknown sample can be determined using this standard curve