easy-to-do analytical test for ketones in urine using the same nitroprusside compound used in the liquid test for ketone bodies. This test reagent was also a tablet, Acetest; carrying out a test simply involved placing a drop of urine on the surface of the tablet and observing for the development of a purple color indicating ketone bodies. In addition to sodium nitroprusside, the tablet contains glycine and trisodium phosphate. Dip-and-Read Tests In 1956 dip-and-read colorimetric enzymatic tests were introduced as new methods for recognizing glucose in urine (10). Two independent orga nizations provided test systems that had somewhat different forms; one was a unitized reagent strip and the other a reagent-impregnated tape. Clinistix was a product of Ames Divi sion of Miles Laboratories and TesTape was a product of Eli Lilly and Company. The chemical reaction sys tems of the two reagent compositions are similar. Glucose oxidase and per oxidase provide a double sequential enzyme system in which glucose oxi dase catalyzes the oxidation of glucose in the urine with oxygen of the air to form gluconic acid and hydrogen per oxide. In turn, the second enzyme, peroxidase, catalyzes the interaction of hydrogen peroxide and the chromogen orthotolidine to generate a blue color as an indicator of the presence of glucose in the urine. The procedure for using either Clinistix or TesTape is to dip the test composition in a speci men of urine or to moisten it in the urine stream. The reactions involved are:
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glucose (C6H1206) + oxygen (of the air) glucose hydrogen peroxide (H2O2) oxidase + gluconic acid (C6H12O7) orthotolidine (Ci 2 H 16 N 2 ) + H 2 0 2 peroxidase
*• oxidized orthotolidine (blue color)
This basic chemical reaction sequence is still employed in the billions of urine glucose systems that are used throughout the world each year. It is also the basis of practically all of the rapid blood-sugar-measuring systems that have become critical items in the recognition and monitoring of diabe tes. Different chromogens have been used in various reagent systems, but the glucose oxidase-peroxidase oxida tion mechanism for glucose color reac tions is prevalent. The introduction of glucose oxidase ready-to-react systems provided a new dimension to the analytical chemistry testing of urine by the diabetic. The convenience of either TesTape or Clinistix was unexcelled. One simply
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ANALYTICAL CHEMISTRY, VOL. 56, NO. 6, MAY 1984 · 671 A
