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level: Level 3

Questions and Answers List

Fundamental Laws of Spectrophotometry

level questions: Level 3

QuestionAnswer
Radiation in the wavelength range __ is passed through a solution of a compound200-700 nm
The electrons in the bonds w/in the molecule become excited so that they occupy a higher state and in the process absorb some of the energy passing thru the solution.
Uv-Vis Spectroscopy Applications in pharmaceutical analysis:1 A robust method for the quantification of drugs 2 Determine pka, partition coefficient and solubilities of drugs 3 Determine the release of drugs from formulation with time ( e.g. dissolution) 4 UV spectrum can be used as pharmacopeial identity checks 5 Monitor reaction kinetics of drug degradation
Spectroscopy STRENGTHS and LIMITATIONSSTRENGTHS 1 Easy to use, robust, good precision 2 Routine method for determining physico-chemical properties of drugs LIMITATIONS 1 Only moderately selective 2 Not really applicable to the analysis of mixtures
CONCENTRATION of solution↑; transmitted radiant beam ↓Beer-lambert law
THICKNESS of solution↑, transmitted radiant beam ↓LAMBERT’S OR BOUGUER’S LAW
Ratio of the radiant power transmitted by the solution to the radiant power transmitted by the blank (solvent)Transmittance (T)
Also called optical density, absorbancy, extinction coefficient Measure of the amount of light absorbed by the sampleAbsorbance (A)
Graph obtained when A is plotted against λAbsorption Spectrum/ Spectral Absorbance (SA)
Graph obtained when C is plotted against A A is directly proportional to C C is directly proportional to A ↑ C ↑ ABeer’s Plot