Preparation of protein-free filtrate: 3 mL of distilled water and 0.5 mL of blood
were taken in a dry test tube and mixed well. 1.5 mL of 10% TCA was added,
thoroughly mixed, and allowed to stand for 10 minutes before it was filtered
into a dry test tube.
Development of color: Standard glucose solutions were taken in 6 test tubes
in the range of 0.2 to 1 mL, 1 mL of protein-free filtrate was taken in a seventh
test tube. To all these tubes, 5 mL of o-toluidine was added and mixed thoroughly.
The tubes were kept in boiling water bath for 10 minutes, cooled, and the
optical density read at 620 mm.