Q: Cytosine has a molar extinction coefficient of 6*10³ at 270 nm at pH 7. Calculate the absorbance and percent transmission of 1*10^-4 and 1*10^-3 M cytosine solution in a 1-mm cell.

Solution

For 1*10^-4M, the absorbance A is given as,

A = log(I₀/I) = e * b * c = 6*10³ * 0.1 * 1*10^-4 = 0.06

in percent transmission, I/I₀ * 100,

A_% = 10^-0.06 * 100 = 10^1.94 (%) = 87.10 %

Similarly, for 1*10^-3M, the absorbance A is given as,

A = log(I₀/I) = e * b * c = 6*10³ * 0.1 * 1*10^-3 = 0.6

in percent transmission, I/I₀ * 100,

A_% = 10^-0.6 * 100 = 10^1.4 (%) = 25.12 %