Hi, Muhammad!

Could you give a little more information as to what your solution contains (if it is a solution)? Am I correct in assuming that this does not happen when kept at room temperature? Also, I doubt you will receive *all* possible assumptions, but you might get a few. :D

regards,

Daniel

"Blueshift" means decrease in absorption wavelength. There may be several reasons for blueshift. You need to check the cause happening behind storage in refrigerator for few day.

In addition, I would like to mention that the opposite of blueshift is "redshift" which means increased absorption wavelength. 

Many thanks!

I discovered it's a spectrometer malfunction.  

and i am waiting the service engineer to fix it up.

   The change in the wavelength of the typical  'absorption' or :emission" spectra of a sample  after some processing " like :keeping in a fridge for some days " is expressed in terms of blue or red shift-decrease in wavelength is called "blue shift" while increase is called red shift.

No, it means that you have workout the mechanism responsible for the shift-could be a new interesting result. Try it.