Which of the following is not a major interference in phenol determination?

The correct choice indicates that hydroxy derivatives of benzene are not considered a major interference in phenol determination. This is due to the structural and chemical properties of phenolic compounds, which share similarities with hydroxy derivatives of benzene. In phenol analysis, such hydroxy derivatives can actually enhance the accuracy of the results rather than disrupt them because they can behave similarly and ideally be quantified alongside phenols.

In contrast, chlorinated solvents, organic acids, and aromatic hydrocarbons can significantly interfere with the determination of phenols. Chlorinated solvents may participate in similar reaction pathways, leading to complicated matrices that affect detection limits. Organic acids can alter stability and solubility, impacting the assay's accuracy. Aromatic hydrocarbons, due to their similar chemical structure, can also create overlapping signals in analytical methods, which can lead to misinterpretation of phenol concentrations.

Therefore, understanding the role of different substances during chemical analyses is crucial in ensuring accurate environmental monitoring, especially in water quality assessments, where phenol concentrations are of interest.