Final Answer:
The maximum allowable time between obtaining the first and final portions of a composite sample is 45 minutes.The correct option is C. 45 minutes.
Explanation:
In environmental monitoring and various laboratory analyses, composite sampling is a common practice to ensure representative data. The maximum allowable time between obtaining the first and final portions is crucial to maintain sample integrity. The correct answer is C, 45 minutes. This time frame strikes a balance between practical considerations and the need to capture the sample's true characteristics.
Composite sampling involves combining several smaller samples to create a single, representative sample. The time limitation helps prevent potential changes or degradation in the sample over an extended period. If the time between obtaining the first and final portions exceeds 45 minutes, there is an increased risk of alterations due to environmental factors, evaporation, or chemical reactions. This timeframe is based on scientific understanding and practical experience in sample collection protocols.
To delve into the specifics, consider the nature of the substances being sampled. For instance, volatile compounds may evaporate, leading to inaccurate results. Additionally, chemical reactions within the sample may occur, altering its composition.
The 45-minute limit is a well-established guideline, balancing the need for timely composite sampling with the necessity of maintaining the sample's true representation. Therefore, adherence to this time constraint is essential for reliable and accurate analytical results in various scientific and environmental applications.
The correct option is C. 45 minutes.