4. The molar absorptivities e of two compounds, A and B were measured with pure samples at two wavelengths. From these data determine the amount of A and B in the mixture.
| at 277 nm (M-1 cm-1) |
at 437 nm (M-1 cm-1) |
|
| A | 14780 | 5112 |
| B | 2377 | 10996 |
The absorbance of a mixture of A and B in a 1.0 cm cell was determined to be 0.886 at 277 nm and 0.552 at 437 nm. Calculate the amount of A and B in the sample.
at 277 nm 0.886 = (14780 x 1.0 x CA) + (2377 x 1.0 x CB)
at 437 nm 0.552 = (5112 x 1.0 x CA) + (10996 x 1.0 x CB)
Solve simultaneously to give: CA = 5.6 x 10-5 M, CB = 2.5 x 10-5 M