Determination of urobilinogen in urine

As with bilirubin, the principle of azocoupling reaction with a stable diazonium salt (eg 4-methoxybenzenediazonium tetrafluoroborate) is used to determine urobilinogen in urine. The indication zone turns pink to red in the presence of urobilinogen. The faint pink color still corresponds to the physiological excretion of urobilinogen. In the presence of bilirubin, the color is yellow, which turns green to blue after 1 minute.

Some heterocyclic nitrogenous substances produced by bacteria in urinary tract infections can cause false positives. High concentrations of ascorbate can cause false negatives.

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