Colorimetric micromethod for the determination of protein in solutions with silver ions and dithizone.

A method of determination of protein based on the measurement of complexed Ag+ and AgCl absorbed on the macromolecules is described. This reaction is carried out in the presence of chloride ions and detergents (Triton X-100 or SDS) in alkaline solution. The silver ions are detected with dithizone. With this method it is possible to estimate 0.1 microgram bovine serum albumin in 0.5 ml sample with a coefficient of variation of 16%, and 1.5 micrograms/sample with a coefficient of variation of 3.6%. The method is simple, rapid, inexpensive, and very sensitive.