[Zel]

I am doing a practical involving the HPLC of paracetamol and caffeine, and need to select a single wavelength which will absorb both of these components.
Paracetamol has a wavelength max at 248nm, Caffeine at 274nm.
What would be a suitable wavelength? Would 243 seem appropriate?

Thank you in advance

[Arkcon]

Try to find the complete spectra, preferably with the same ordinate scale, so you can overlay the pages (or maybe find them on the same graph.)  And see if you can pick the best wavelength for both.  You should try to avoid lambda max for either of them, and also inflection points.  At those points, the slope of the curve is changing rapidly.  A slight misalignment of the detector can cause wide, random signal fluctuations.

[Babcock_Hall]

Picking a wavelength of 243 nm does not sound like a good choice, even with the present amount of information.  Why not?