Determination of the water solubility of the fungicide chlorothalonil

Abstract

A UV-Visible spectrophotometric analytical procedure was developed and used to measure the water solubility of chlorothalonil at temperatures ranging from 8.5 to 37.5 °C. The effect of formulation chemicals present in BRAVO®500, a pesticide formulation containing chlorothalonil, on the apparent water solubility of chlorothalonil was also assessed. The water solubility was measured using a generator column technique while the apparent solubility enhancement of chlorothalonil by formulation chemicals in diluted formulation was evaluated by both generator column and batch shake techniques. A water solubility of 0.492 to 1.85 mg/L was found for a temperature range of 8.5 to 37.5 °C. The enthalpy of solution was found to be 7.96 kcal/mole. The apparent solubility enhancement due to formulation chemicals in dilute BRAVO®500 solution was 0.942 mg/L at 23 °C, which yielded a log Kdoc of 4.24. Based upon these results and typical formulation application rates, it is unlikely that the formulation chemicals present in the BRAVO® 500 formulation would increase the mobility of chlorothalonil in the environment.