Hi, I wish to know is there anyway to test percentage of protein in
anything fast and accurate without sending them to the laboratory. Is
there portable and cheap kit that can do the job?

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Clarification of Question by josephltt-ga on 21 Oct 2005 18:34 PDT

The material that I wish to test is some food material. Eg, Wheat, Soy
meal, feeds etc.

It would help to know the nature of the material you want to test.  Is
it a solution?  Solid?  Suspension  (e.g., blood)?  What's the nature
of the non-protein material in the sample?

Crude protein is normally determined by measuring the amount of
nitrogen in a sample and then using a conversion factor to estimate
how much protein that represents.  The classic mehtod is the Kjeldahl
Nitrogen assay.  This method is well documented and known by many food
chemists. It is relatively slow and labor intensive.  If you can make
a much bigger investment, there are automated systems that determine
the concentration of nitrogen.  We use one from Leco Corp.  Both these
methods would be laboratory based and not particularly cheap if you
don't already have the equipment.

As far as something cheap and portable, I think you're going to have a
hard time.  If you can be sure that all your protein is soluble, you
can use one of many commercially available kits for soluble protein
concentration.  Most of these depend on the use of a spectrophotometer
or a fluorimeter.  It might be possible to use something like the
Bicinchoninic Acid Assay, and visually compare the color of the
solution to a standardized color chart.  This would only give you a
very rough idea of protein concentration.