ABSTRACT
In 1911 Stanley R. Benedict devised a new and successful formulation of a copper sulfate reagent that is ten times more sensitive for glucose in urine than Fehling's solution and less susceptible to reduction by non-glucose reducing substances. In the 1940s, copper and bismuth reagents were incorporated into a tablet and dry powder, respectively, for semi-quantitative estimation of glucose in urine, as determined by the intensity of the resulting color formation when reacted with urine in a prescribed procedure. The reducing property of glucose is exhibited by many other substances found in appreciable concentration in normal blood, e.g., creatine, creatinine, uric acid, and glutathione. Benedict used larger amounts of blood which were available by venipuncture with hypodermic needle and syringe. Otto Folin and Wu introduced a new copper reduction method as part of a new system of blood analysis. The enzyme's extreme specificity allowed its use for quantitative estimation of urea directly in a mixture as complex as blood.
