[FreakBean]

I'm trying to find epsilon (molar absorptivity coefficient). The only way I've determined epsilon previously was using Beer's law. But now instead of a standard curve, I have a UV spectrum of absorbance over a range of wavelengths. I've found the wavelength maxima, but I don't know how to find epsilon given this data. Can anyone help me? I've been struggling with this for days.

[Borek]

Can't you read absorbance for a given wavelength from the plot? That will be just one point, but it is better than nothing.

[FreakBean]

Thanks for your reply, Borek. I can read the absorbance at a given wavelength, and I have that. From the graph, I can find the wavelength at which maximum absorbance occurs. This is the optimal wavelength to measure this compound at. But is the absorbance at this point equal to the molar extinction coefficient?

[Borek]

But is the absorbance at this point equal to the molar extinction coefficient?

No, but if you know sample concentration and absorbance, you should be able to calculate the coefficient using Beer's law, just solve for ε (or whatever symbol you use).