Which of the following describes a simple assay?

• A. A test to determine whether a sample is pure.
• B. A test to measure the exact concentration of a compound.
• C. A qualitative test to identify the compound's structure.
• D. Indicator test to determine the presence of a compound.

Answer: (D)

A simple assay is a quick, easy test that gives a yes-or-no answer about whether a target compound is present, typically using an indicator that produces an observable signal such as a color change. This makes it useful for rapid screening or field checks where precise measurement isn’t needed. It focuses on presence rather than quantity or detailed information.

Purity testing looks for how clean the sample is and often requires more detailed analysis. Determining the exact concentration requires quantitative methods and a calibration curve to measure how much of the compound is there. Identifying a compound’s structure involves structural analysis and often spectroscopy or other advanced techniques, not just a straightforward presence test. Hence, the indicator test to determine the presence of a compound best fits a simple assay.