The benzidine test is most commonly used for the detection of blood in the feces, and was therefore singled out for investigation.

What is the benzidine method?

: a sensitive test for the presence of blood (as in urine or feces) based on the production of a blue color upon contact with a solution of benzidine, hydrogen peroxide, and glacial acetic acid.

How do you test for benzidine in urine?

Pipet 100 mL urine into a 180-mL glass bottle. Start a blank control urine sample (100 mL) and two control urine samples (100 mL) spiked with benzidine (0.3 to 1.0 µg) at this point. 5. Add 0.2 g NaCl to the pH-adjusted urine.