What is the measure that cannot be determined analytically but indicates the concentration of chloramines?

The measure that indicates the concentration of chloramines and cannot be determined analytically is combined chlorine residual. Combined chlorine refers to the amount of chlorine that has reacted with organic and inorganic substances in the water, primarily forming chloramines. These compounds are responsible for residual disinfection in water systems but do not have the same efficacy as free chlorine.

Analyzing combined chlorine residual specifically involves calculating it from total chlorine and free chlorine measurements. Since combined chlorine cannot be directly measured with standard analytical methods and is derived from those other measurements, it can be challenging to quantify it independently.

In contrast, total chlorine residual encompasses all forms of chlorine, including both free and combined chlorine. Free chlorine residual represents the amount of unreacted chlorine still available in the water for disinfection. Breakpoint chlorine refers to a specific point in water treatment where chlorine is applied and a certain reaction level is achieved, leading to a significant reduction in combined chlorine. This indicates that each of those measurements has distinct characteristics and methods for determination, while combined chlorine residual is primarily inferred rather than directly analyzed.