A rapid method for dry weight determination of proteins on a micro scale with an electrobalance

A method to determine the dry weight (0.25-2 mg) of aqueous protein solutions within 1 h, using an electrobalance, is described. The drying of 50-200 mul solution pipetted onto a glass fiber disc is carried out in vacuo at 70 degrees C until the recorded dry weight becomes constant (within 25-40 min). It has been shown that the dried residue can subsequently be used for other purposes, such as quantitative amino acid analyses. The method is also suitable for the determination of moisture content in lyophilized protein samples.