During her long and distinguished career, Florence Seibert made important contributions to science and to the advancement of medicine. Because of her work it became possible to test accurately for tuberculosis, and intravenous drug therapy became safe.
Dr. Seibert succeeded in isolating Purified Protein Derivative, thus making possible the isolation of the active substance of pure tuberculin. This work, done in the l930s, is now the international standard for tuberculin made in the world. She perfected a new distillation process that eliminated pyrogens (fever producing chemicals) from the distilled water used in intravenous therapy, thus making that therapy safe.
Seibert worked until her retirement at the Henry Phipps Institute of the University of Pennsylvania. After retirement she volunteered for 13 more years in programs examining the etiology of cancer.