The maximum allowable time before analysis, also known as hold time, is regulated by which part of the CFR?

The correct answer is indeed related to Part 136 of the Code of Federal Regulations (CFR). This section specifically deals with the criteria and procedures for the analytical methods used in water quality testing, including the maximum allowable hold times for samples before analysis. These hold times are critical because they ensure the integrity of the sample is maintained, minimizing changes in concentrations of the analytes of interest that could occur due to degradation or adsorption during storage.

Part 136 outlines the specific limits and conditions under which various types of water samples must be analyzed after collection. This includes stipulations for the preservation of samples and the temperature under which they should be stored, as well as the importance of timely analysis to obtain reliable and representative results.

Understanding these regulations is essential for water lab analysts to ensure compliance with federal standards and to produce accurate and reliable analytical results.