What does "chain of custody" refer to in water quality testing?

"Chain of custody" in water quality testing refers specifically to the documentation that tracks the possession, handling, and integrity of a sample from the time it is collected until it is analyzed. It ensures that the sample has not been tampered with, contaminated, or otherwise compromised in any way that would affect test results. This record includes details about everyone who handled the sample, along with the times and circumstances under which they took possession of it. This process is crucial for maintaining the integrity of the data and is often required for legal or regulatory purposes.

The other options, while relevant to various aspects of sample management and analysis, do not define the chain of custody itself. A record of chemical analysis pertains to the results obtained from tests, while a timeline of when samples were collected relates to the timing of sampling events. Similarly, a log of environmental conditions documents the context under which the samples were taken but does not include the tracking of sample possession. Hence, the focus on the list of individuals who came into contact with the sample is what specifically aligns with the concept of chain of custody.