Evaluation of five fluorescent dyes and triethyl phosphate as atmospheric tracers of agricultural sprays

Abstract

The photostability of five commonly used fluorescent dyes and an organophosphate, triethyl phosphate, was compared on microscope slides or in glass beakers after exposure to sunlight outdoors. Our goal was to determine which chemicals would be most suited for use as tracers for the simulation of long distance transport of herbicides in the atmosphere and as dual tracers for a dual sprayer system for the evaluation of the effects of adjuvants on spray drift potential of agricultural sprays. The dyes and triethyl phosphate were analyzed with a fluorescent spectrometer and a GC (NPD), respectively. Half lives were estimated to be approximately 7 minutes for Tinopal and Eosine, 15 minutes for Fluorescein, 0.75–3 hours for Rhodamine B (RhB) and 0.5 hour for triethyl phosphate. Brilliant sulfaflavine (BSF) was the most persistent chemical, degrading only 11.3% after 8 hours of exposure to sunlight. BSF was selected as the best tracer of those tested, to simulate long distance atmospheric transport of herbicides based on its long persistence. RhB and BSF were selected as the best products for use as dual tracers for a dual sprayer system based on similar persistence over the first hour of exposure to sunlight.