Analysis of Aqueous Extractable Protein in Elastomers ASTM D5712

Scope:

ASTM D5712 determines the amount of protein in different elastomeric products like gloves, shoes, and tires. The rubber-like properties of these substances are derived from proteins and their structure. If there is a change in type and amount of protein, the physical properties of these substances are changed. 

The amount of protein present in elastomeric products is determined for quality control and for designing elastomeric products.

Test Procedure:

In ASTM D5712, water-soluble proteins are extracted in a buffer solution. The buffer solution is then precipitated, concentrating the protein and separating them from other water-soluble substances which may interfere in the analysis. The extracted protein is redissolved and quantified colorimetrically by the modified Lowry method using a protein standard.

Modified lowry method involves the reaction of protein with cupric sulfate and tartrate in an alkaline solution, resulting in the formation of tetradentate copper-protein complexes. When the Folin-Ciocalteu Reagent is added, it is effectively reduced in proportion to these chelated copper complexes, producing a water-soluble product that is blue.

Results:

The total protein concentration is exhibited by a color change of the sample solution in proportion to protein concentration, which is then measured by preparing a curve of absorbance versus micrograms of protein. The curve is used to determine the amounts of protein