A simple and reliable method for estimation of protein contamination in latex. Detects as low as 25 to 40 μg protein/gm latex (or 25 to 50 ppm). Protein solutions applied to the test strips form compact and symmetrical spots, their diameter being directly proportional to protein concentration. Protn-Latex™ latex protein extraction buffer extracts protein from the latex sample, which is then applied to the test strips and rapidly developed. By measuring the Ø of protein spots with the Protn-Latex™ card, the range of protein concentration in the sample can be determined.