A mobile agricultural sprayer (100) is disclosed. The mobile agricultural sprayer (100) is configured to spray a substance at a worksite, and comprises: a chemical tank (268) that holds a chemical fluid (270) to be sprayed at the worksite； a rinse fluid tank (264) that holds rinse fluid (266)； a first sensor (140) coupled to the rinse fluid tank (264) configured to detect a characteristic of the rinse fluid (266) within the rinse fluid tank (264), and, generate a first sensor signal indicative of the characteristic of the rinse fluid (266)； a distribution system (130), including a fluidic pathway (254) and a nozzle (126), configured to pump the rinse fluid (266) from the rinse fluid tank (264) along the fluidic pathway (254) through the nozzle (126) of the sprayer (100)； a second sensor (128) coupled to the fluidic pathway (254) configured to detect a characteristic of the fluid within the fluidic pathway (254), and generate a second sensor signal indicative of the characteristic； and a residue detection system (124) configured to receive the first and second sensor signals and, based on the received sensor signals, determine a concentration of residue within the fluidic pathway (254). Furthermore, a method of determining a concentration of chemical residue is disclosed.
