Which of the following substances may interfere with the analysis of phenols?

Phenols are analyzed in wastewater to assess the presence of pollutants that can be harmful to the environment and public health. The presence of certain substances can interfere with the accurate measurement of phenols during testing procedures.

Sulfides are particularly notorious for interfering with phenol analysis because they can react with the reagents used to detect phenols, thereby leading to false results or a distortion of the actual concentration of phenols in the sample. In many analytical methods, such as those involving colorimetric techniques, sulfide can produce colors that may mimic or mask the signals from phenolic compounds, resulting in inaccurate readings.

In contrast, other substances like chlorine, ammonia, and nitrate do not typically interfere to the same extent with the analysis of phenols. While they may have their own impacts on various chemical processes within wastewater, their interaction with the compounds used to detect phenol concentrations is generally minimal compared to sulfides. This specific characteristic of sulfide makes it particularly important to monitor and potentially remove from samples prior to phenol analysis to ensure the accuracy of the results.