Experiment 7: Techniques in Spectrophotometry Flashcards
When matters interact with electromagnetic radiation…
- Absorption
- Scattering
or - Reflection
of the electromagnetic radiation will take place.
Po in relation to Pb
Po is the incident radiant power or incident irradiance.
Pb is the transmitted irradiance, light after it emerges.
Po is when it goes in solution, pb is once it makes it out.
Quantity T (transmittance)
Fraction of irradiance transmitted through the sample
T=Po/Pb
Irradiance
Energy per secocnd per unit area of the light beam going into or emerging from and irradiated sample. Energy per second is power. It is the radiant power per unit area imparting on or emerging from a sample.
Monochrome
One coloured
The essence of instrumental analysis
The existence of a one-to-one correspondence of signal strength and quantity is the essence of instrumental analysis.
Spectrophotometry
Analytical quantitation techniques based on the interaction of the sample with electromagnetic radiation.
The magnitude of absorptivity depends on…
The wavelength of the traversing radiation
The transmittance of the solution of an absorbing species will vary with…
The wavelength of the impinging light.
Spectrum
Profile of transmittance over a range of wavelengths. Quite unique for pure chemical substances and they furnish structural information of the pure compounds.
Absorbance
Mathematical transformation of transmittance. Has a definition but does not have a physical meaning.
Analytical quantity in Beer’s law because it is directly proportional to concentration.
Absorptivity
absorbance of sample solution of unit concentration in a one centimeter cell
Molar absorptivity
- absorbance (extrapolated) of a one molar solution in a one centimeter cell
- Units are M-1cm-1
- Directly related to the probability of transition between the two quantum states in the “molecular” species.
The absorption spectrum of an analyte is a plot of…
absorbance as a function of the wavelength of the impinging radiation.
