SPECTROPHOTOMETRY and COLORIMETRY
SPECTROPHOTOMETRY
Spectrophotometry is the quantitative measurement of the reflection or transmission properties of a material as a function of wavelength
It involves with the use of a spectrophotometer.
A spectrophotometer is a photometer that can measure intensity as a function of the light source wavelength.
A spectrophotometer is commonly used for the measurement of transmittance or reflectance of solutions, transparent or opaque solids, such as polished glass, or gases.
Principles
A spectrophotometer is employed to measure the amount of light that a sample absorbs. The instrument operates by passing a beam of light through a sample and measuring the intensity of light reaching a detector.
Classes
a.) Single Beam Spectrophotometer Light from the source lamp is passed through a monochromator, which diffracts the light into a "rainbow" of wavelengths and outputs narrow bandwidths of this diffracted spectrum. Discrete frequencies are transmitted through the test sample. Then the photon flux density (watts per metre squared usually) of the transmitted or reflected light is measured by the sensor. The transmittance or reflectance value for each wavelength of the test sample is then compared with the transmission (or reflectance) values from the reference sample.
b.) Double Beam Spectrophotometer
It is to determine the amount of light of a specific wavelength absorbed by an analyte in a sample.
A double beam instrument compares the light intensity between two light paths by splitting the light source into two separate beams. The splitting of the beam is accomplished either statically using a partially transmitting mirror or through attenuation of the beams optical devices.
The diffraction grating and the slit
You are probably familiar with the way that a prism splits light into its component colours. A diffraction grating does the same job, but more efficiently.
The blue arrows show the way the various wavelengths of the light are sent
Spectrophotometry is the quantitative measurement of the reflection or transmission properties of a material as a function of wavelength
It involves with the use of a spectrophotometer.
A spectrophotometer is a photometer that can measure intensity as a function of the light source wavelength.
A spectrophotometer is commonly used for the measurement of transmittance or reflectance of solutions, transparent or opaque solids, such as polished glass, or gases.
Principles
A spectrophotometer is employed to measure the amount of light that a sample absorbs. The instrument operates by passing a beam of light through a sample and measuring the intensity of light reaching a detector.
Classes
a.) Single Beam Spectrophotometer Light from the source lamp is passed through a monochromator, which diffracts the light into a "rainbow" of wavelengths and outputs narrow bandwidths of this diffracted spectrum. Discrete frequencies are transmitted through the test sample. Then the photon flux density (watts per metre squared usually) of the transmitted or reflected light is measured by the sensor. The transmittance or reflectance value for each wavelength of the test sample is then compared with the transmission (or reflectance) values from the reference sample.
b.) Double Beam Spectrophotometer
It is to determine the amount of light of a specific wavelength absorbed by an analyte in a sample.
A double beam instrument compares the light intensity between two light paths by splitting the light source into two separate beams. The splitting of the beam is accomplished either statically using a partially transmitting mirror or through attenuation of the beams optical devices.
The diffraction grating and the slit
You are probably familiar with the way that a prism splits light into its component colours. A diffraction grating does the same job, but more efficiently.
The blue arrows show the way the various wavelengths of the light are sent