Orthotolidine Solution

Testing of fluids such as urine and blood is a part of routine diagnostic forensic testing. As well, such testing can yield useful forensic evidence of disease, presence of toxins and other chemicals, and even genetic material.

While fluid testing can involve sophisticated instruments, simple and reliable tests that can be done at the scene of an accident or death are still in popular use. Several urine-based tests utilize a chemical known as orthotolidine.

In the past, orthotolidine was a popular chemical used to monitor swimming pool water for the presence of excess chlorine. While that use has been supplanted by other chlorine monitoring methods, orthotolidine has remained popular in routine diagnostic testing and in forensic investigations.

The presence of glucose in the urine can be detected using a paper strip impregnated with orthotolidine and two enzymes—glucose oxidase and peroxidase. A yellow dye is also infused into the strip. When the paper strip is immersed in the glucose-containing urine, the glucose is catalytically converted by glucose oxidase in the presence of air to gluconic acid and hydrogen peroxide. Subsequently, peroxidase converts the hydrogen peroxide into a compound that reacts with orthotolidine. The result is a blue color.

The blue reacts with the yellow dye in the strip to form a potential spectrum of color ranging from light green to a dark blue color. The intensity of the color depends on the amount of glucose present in the urine.

This simple test, which can be done within a minute, allows a forensic examiner to gauge if the victim or deceased was diabetic.

Orthotolidine can be combined with another chemical, toluidine, to assess the presence of myoglobin in urine. Presence of the latter is characteristic of a malady called myoglobinuria. If myoglobin (or hemoglobin , as the test cannot distinguish between the two) is present in urine, the orthotolidine-toluidine chemical pair forms a blue color.

Both orthotolidine-based examinations can help identify a victim or corpse.