Legea Lambert-Beer

Legea Lambert-Beer

Legea Lambert-Beer stanileste legaturile matematice intre cantitatea de radiatii electromagnetice emise respectiv absorbite si concentratie in cazul analizei spectroscopice cantitative. Intensitatea fasciculului (I) are expresia:

Unde: k- coeficient de absorbtie dependent de frecventa, b- grosimea stratului absorbant, c- concentratia atomilor liberi care absorb.

Aceasta lege reprezinta legea de baza folosita in analizele sau determinarile spectrofotometrice.

Sa consideram o radiatie incidenta monocromatica, Io, care cade pe o celula continand proba. Celula are lungimea l iar concentratia substantei ce absoarbe lumina, C. Conform schitei din figura, intensitatea finala, I, este mai mica decat cea initiala, Io in urma absorbtiei luminii, la trecerea prin celula.

Daca lungimea l provoaca o reducere cu un anumit procent a intensitatii initiale, Io, de exemplu cu 50%, un nou strat de lungime l, egala cu primul, va actiona, conform legii Lamber - Beer, in acelasi mod, adica va diminua tot la jumatate noua radiatie incidenta.

Absorbtia luminii in cazul legii Lambert-Beer

Bibliografie

Encyclopedia of spectroscopy & spectrometry 2000 Vol 1-3.

2. Chimie Analitica si Instrumentala, Horea Iustin NASCU Lorentz JANTSCHI, Academic Pres & Academic Direct 2006

3. The Chemistry of Nanomaterials Synthesis, Properties and Applications in 2 Volumes, Volume 1, C. N. R. Rao, A. Mušller, A. K. Cheetham (Eds.)

4. Raman Spectroscopy for Chemical Analysis CHEMICAL ANALYSIS A SERIES OF MONOGRAPHS OF ANALYTICAL CHEMISTRY AND ITS APPLICATIONS, Editor J. D. WINEFORDNER, VOLUME 157

5. Handbook of infrared spectroscopy of ultrathin films, Valeri P. Tolstoy, Irina V. Chernyshova, Valeri A. Skryshevsky