Which property is used to confirm the presence of bilirubin in urine?

The presence of bilirubin in urine is confirmed through the diazo reaction. This chemical reaction involves the interaction of bilirubin with diazonium salts to produce a color change, typically resulting in a reddish-brown pigment. This makes the diazo reaction a highly specific and reliable method for detecting bilirubin, as bilirubin itself does not react with many other components typically found in the urine.

Colorimetric analysis refers to assessing the concentration of a specific substance based on color intensity but is not a direct test for bilirubin. Instead, it may be used in various qualitative and quantitative assessments, but it does not specifically confirm bilirubin.

The pH test measures the acidity or alkalinity of urine, which does not provide information regarding the presence of bilirubin.

The nitrite test is primarily used for detecting the presence of bacteria in urine, particularly certain types of urinary tract infections, and is not relevant to the detection of bilirubin.

Thus, the diazo reaction is the specific and appropriate test for confirming bilirubin's presence in urine, distinguishing it from the other methods that focus on different substances or properties.