How do you measure the amount of protein on a contact lens with a UV spectrometer and buiret as indicator?

My group and I are working on a science experiment. We are trying to identify the amount of protein build up on contact lens before and after cleaning them with contact solutions. We are trying to see if the different brand contact solutions get the same or different amount of the protein off the contact lense. Therefore, we need to find a good way to measure the amount of protein before and after cleaning the lens with the different solutions. Can anyone help?|||Well, according to Wikipedia:


"Biuret test is used for detecting the presence of peptide bonds. The biuret test relies on the reaction between copper(II) ions and peptide bonds in an alkaline solution. A violet color indicates the presence of proteins. Proteins give a strong biuret reaction because they contain a large number of peptide bonds. It is possible to use the biuret reaction to determine the concentration of proteins because (for most proteins) peptide bonds occur with approximately the same frequency per gram of material. The biuret test works by the peptides forming a matrix by arranging around a Cu2+ ion. This matrix thus has a pink to violet color depending on the amount of protein."





So I'd take some peptid or protein standard to prepare a UV arbsoption vs increasing concentrations of protein curve. Then measure the absorption that yields each of your lenses before and after the cleaning, use a blank (non used) lens to compensate any measure and then plot your results against the curve you built previously. A very similar experiment has been described in this article:





Optometry and Vision Science:Volume 77(10)October 2000pp 503-510