Dear Sir,

In calibration of uv vis spectrometer for resolution we use 0.02% toluene in hexane and calculate the ratio of absorbances at 266 and 269 nm which should be NLT 1.5.

My question is 1) why we use haxane and toluene ? 2) why we should measure at 266 and why not other wavelengths? Please let me know.
Regards,

The usual wavelength to select are the wavelengths that the material of interest (toluene) absorbs strongly, while the solvent (hexane) does not. The control wavelength both materials absorb fairly weakly. This isn't perfect, but it's the best that can be done.

I'd have to look at the UV spectra of Hexane and Toluene to tell you any more.