The molar absorption coefficient of tryptophan

Radiation of wavelength 280 nm passed through 1.0 mm of a solution that contained an aqueous solution of the amino acid tryptophan at a concentration of 0.50 mmol dm . The light intensity is reduced to 54 per cent of its initial value (so T = 0.54). Calculate the absorbance and the molar absorption coefficient of tryptophan at 280 nm. What would be the transmittance through a cell of thickness 2.0 mm  

For the transmittance through the thicker cell, we use T= 10 and the value of calculated here. 

These units are convenient for the rest of the calculation (but the outcome could be reported as 5.4 x 10 dm mol cm if desired). The absorbance is 

That is, the emergent light is reduced to 29 per cent of its incident intensity. 

One measure of the intensity of a transition is the maximum value of the molar absorption coefficient, f ax- However, because absorption bands generally spread over a range of wavenumbers, the absorption at a single wavenumber might not give a true indication of the intensity. The latter is best reported as the integrated absorption coefficient, the area under the plot of the molar absorption coefficient against wavenumber (Fig. 12.8). 

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