In 1923 Seibert worked as a postdoctoral fellow at the Otho S.A. Sprague Memorial Institute at the
University of Chicago. She was financed by the Porter Fellowship of the
American Philosophical Society, an award that was competitive for both men and women. She went on to work part-time at the Ricketts Laboratory at the University of Chicago, and part-time at the Sprague Memorial Institute in Chicago. In 1924, she received the University of Chicago's Howard Taylor Ricketts Prize for work she began at Yale and continued in Chicago. She published her pyrogen-free process in the
American Journal of Physiology. It was subsequently adopted by the
Food and Drug Administration, the
National Institutes of Health, and various pharmaceutical firms. She was further recognized in 1962 with the John Elliot Memorial Award from the American Association of Blood Banks for her work on pyrogens. During this time, she met
Esmond R. Long MD PhD, who was working on tuberculosis. In 1932 she agreed to relocate, with Long, to the
Henry Phipps Institute at the
University of Pennsylvania. He became professor of pathology and director of laboratories at the Phipps Institute, while she accepted a position as an assistant professor in biochemistry. Their goal was the development of a reliable test for the identification of tuberculosis. The previous tuberculin derivative,
Koch's substance, had produced false negative results in tuberculosis tests since the 1890s because of impurities in the material. Some sources credit her with successfully isolating the tuberculosis protein molecule during 1937–38, when she visited the
University of Uppsala,
Sweden, as a
Guggenheim fellow to work with Nobel-prize winning protein scientist
Theodor Svedberg. She developed methods for purifying a
crystalline tuberculin derivative using filters of porous clay and nitric-acid treated cotton. In 1943, Seibert received the first Achievement Award from the
American Association of University Women. She remained at the Henry Phipps Institute at the
University of Pennsylvania from 1932 to 1959. She was an assistant professor from 1932 to 1937, an associate professor from 1937 to 1955, a full professor of biochemistry from 1955 to 1959, and professor emeritus as of her official retirement in 1959. In 1968, Seibert published her autobiography -
Pebbles on the Hill of a Scientist. Siebert received the Trudeau Medal from the National Tuberculosis Association in 1938, the
Francis P. Garvan Medal from the
American Chemical Society in 1942, and induction into the
National Women's Hall of Fame in 1990. ==References==