Apr. 16th, 2010

maradydd: (Default)
My friend [livejournal.com profile] feonixrift, who is allergic to latex, recently had an unexpected reaction to a roll of athletic tape that was sold as "latex-free". Whilst commiserating with her, I remarked that there really ought to be a straightforward way to determine whether latex was present in a product or not. Reading about the composition of latex, I noted that allergic responses to latex typically have to do with an antigenic protein in the stuff, and she observed that synthetic elastics shouldn't contain protein. I immediately considered and discarded the idea of an ELISA or a Western blot, since both of those tests are not the kind of thing you can do with common household items. However, a little more research turned up the biuret test, which confusingly uses no actual biuret, but does work as an indicator of the presence of protein and is even kind of quantitative.

The biuret test involves small amounts of copper (II) sulfate and potassium or sodium hydroxide, all reagents which I happened to have in my cellar lab. (I get them at the hardware store; USAians can probably find NaOH as drain cleaner and CuSO4 as pool algaecide [h/t [livejournal.com profile] palecur].) As I had never done a biuret test before and did not know what to expect, I decided to find out what to expect by performing a biuret test on something which I knew had protein in an aqueous solution -- in this case, whole milk.

[livejournal.com profile] chocolatecoffee took pictures. Here is how you do it. )

It also occurs to me that there are lots of aqueous solutions out there for which protein or an excess thereof is a Bad Thing, e.g., urine. While I do not particularly want to induce proteinuria in myself, I am inclined to find out what my baseline urinary protein levels are like (which will involve working out a way to measure light absorption at 540 nm, i.e., building that spectrometer I've been meaning to build).

More news once I've tested actual latex and some latex-bearing and latex-free athletic tapes. But for now, you can test things for the presence of peptides too!


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