Thanks for the reply. I agree that the question does not make any sense. Someone asked me that and I thought that is something that a double beam UV-Vis spectrometer should do automatically because a reference cuvette is always used.

From what I can tell, most UV-Vis absorption spectrometers do not correct for refractive index. I know that the Nanodrop in our lab does not. Since the instruments don't have a mechanism to measure refractive index, and most researchers don't know the index of refraction of their solution precisely, it doesn't make a lot of sense to correct for it. Depending on your solution, you could be altering the index by a few percent which will change the effective wavelength of the light by the same factor: Lambda = Lambda0/n. In other words, the effect of index should be to shift your spectrum. The biggest problem with trying to do this is that it requires you to not only know the index of refraction, but to know the index across a broad spectrum, or know the Sellmeir coefficients of the solution. Here's a paper describing the effect of changing the index:

Article Refractive index effects on the absorption spectra of macromolecules

Thanks John for the reply!

I don't believe any refractive index variations within your sample are sufficient for a routine UV-Vis instrument's readings to be affected. If you really want to minimize any effects of refractive index variation, the most important parameter to control is the temperature of the sample and the operational temperature of the instrument (hard components and light path).