Ortho Toluidine test is used for detecting?

Appeared in: WCL Staff Nurse - 2019

Explanation

The Ortho-tolidine (OT) test is a standard colorimetric test specifically used to measure the concentration of residual chlorine in treated water.
The principle of the test involves adding ortho-tolidine reagent to a water sample, which reacts with free and combined chlorine to produce a yellow-colored compound.
The intensity of the resulting yellow color is proportional to the amount of chlorine present, which can be measured against a set of color standards to quantify the concentration.

Option B: The primary test for nitrites is the Griess test, not the Ortho-tolidine test. The Griess test produces a characteristic pink or red color in the presence of nitrites.
Option C: Nitrates are detected using reagents like diphenylamine or brucine, which produce blue or yellow colors, respectively. The Ortho-tolidine test is not used for nitrate detection.
Option D: Ammonia is detected using Nessler's reagent. This reaction produces a color that ranges from yellow to brown, depending on the ammonia concentration.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Water quality testing methods as background academic context rather than a clinical decision trigger.
Public health nurses are responsible for ensuring the safety of community water supplies, which includes monitoring for adequate disinfection.
Testing for residual chlorine is a key task to confirm that water is protected from microbial contamination throughout the distribution system.
A residual chlorine level of 0.5 mg/L is the recommended minimum to ensure water safety at the consumer's end.

How to Approach the Question

This is a factual recall question based on concepts from Preventive and Social Medicine (Community Health Nursing).
Identify the core subject of the question, which is the 'Ortho Toluidine test'.
Access your knowledge base regarding water purification and testing methods.
Recall that chlorination is the most common method of water disinfection and that tests are needed to check for adequate 'residual chlorine'.
Connect the 'Ortho Toluidine test' specifically to the detection of 'chlorine'. A useful mnemonic is to associate the yellow color produced by the test with the yellowish-green nature of chlorine gas.
Eliminate the other options by recalling the specific tests for them (e.g., Griess test for nitrites).

Concept Tested & Keywords

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E6 Parks TextBook of Preventive & Social Medicine part 2 — Subpart B (pp 233-449 of 464) p. 32-34

Practise the full WCL Staff Nurse - 2019

Attempt every question from this paper in a timed mock, then review the full solution for each one.