Practical real world uses for Colorimetry

[crybllrd]

I need to give a short presentation about Colorimetry in my chemistry class.
I plan on using the first five minutes giving an example procedure about determining the concentration using MicroLAB's spectrophotometer hardware in our lab.
I would like to use that last five minutes of my presentation talking about what industries use colorimetry, and perhaps use some real world uses that we could relate it to.
Any ideas?

 

[Nemus]

One that goes on in every single hospital all over the world is to measure hemoglobin content of blood as a health indicator. I'd guess it is the most common.
In many research labs (like mine) we use colorimetry as a quick test for different elements before we send out for expensive certified analysis.
When we make proteins and purify on nickel columns we often use the reagent dimethylglyoxime to check for traces of nickel.

 

[crybllrd]

Thanks a lot, that is exactly what I was looking for.
Do you mind elaborating on the "make proteins and purify on nickel columns we often use the reagent dimethylglyoxime to check for traces of nickel" part? I am trying to do some further research on these topics.
Thanks again.

 

[Nemus]

A convenient way to make small amounts of mutated proteins is to edit in a "tag" with six histidines at the end. It has an affinity for nickel and there are columns e.g. "Histrap" with nickel bound to a chelator. You pour the bacterium lysate through the column and only your favourite protein sticks. You then elute with an imidazole buffer (competitive for nickel) and collect your protein. Occasionally some nickel ions tag along. They give a red color with dimethyl glyoxime.

 

[epenguin]

Google 'Lowry protein assay'.

Very widely used there is also a caution, which is a matter of principle for your talk.

It is good enough for a lot of work for e.g. serum protein concentration and much else (v. widely used). OK when you are looking at relative values, e,g, variations of proein concentration. It is usually standardised, calibrated, using bovine serum albumin.

But if you were to use it to determine the concentration of a particular pure protein and the absolute concentration is important I know for a fact that wrong and misleading results can be obtained if you do not calibrate it using the same protein whose absolute concentration is known by some other method. Maybe this example to too advanced for your talk but in general since there can be interferences for any colorimetric method by other substances in mixtures, it should be standardised with solutions as far as possible resembling those you are going to be testing, I don't know if I have been clear.

 

[epenguin]

There are zillions of improvements, modifications, adaptations, tweaks, kits deriving from the phosphomolybdate method for determination of inorganic phosphate that originate from Fiske and SubbaRow [(1925) J. Biol. Chem. 66, 375] , anyone in your biochemistry department can give you a protocol e.g. from manufacturers' pamphlets and catalogs etc. Very widely used.a perspective
http://www.garfield.library.upenn.edu/classics1981/A1981LY47200001.pdf

 

[lisab]

I use it to measure formaldehyde emissions. PM me if you'd like more details.