A rapid colorimetric assay for dry weight.

A rapid, precise colorimetric method for the determination of dry weight in the range 100 1,000 micro grams is reported. The method involves reacting biological materials with an acid solution of dichromate for 20 min at 92 degrees C followed by determination of the optical density at 630 nm of the product formed. The principal advantage of the dichromate method over the standard weight method are: 1) The shorter time required for determination, 2) its greater sensitivity, exactitude and precision using standard laboratory equipment, 3) the method is insensitive to inorganic compounds and therefore can be applied to tissue homogenates prepared in inorganic solutions. The only disadvantage of the method seems to be that dichromate will react specifically with carbon containing groups and therefore the participation of nitrogen, or other elements, in the composition of the biological material, will give proportionately lower absorbances.