Recovery Rate of Tracer Dyes Used for Spray Deposit Assessment

Five fluorescent dyes (BASO Red 546, Brilliant Sulfaflavine, Fluorescein, Uvitex OB, and Rhodamine B) and seven non-fluorescent dyes (Amaranth, Reactive Black 5, Patent Blue Violet, Tartrazine, Lissamine Green B, Erythrosin B, and Ponceau 4R) were tested to determine their potential in tracer application for spray deposit assessment. Laboratory experiments were performed to determine the tracer recovery rate from paper targets, either kept in the dark or exposed to sunlight. Tartrazine was easily extractable and relatively photostable and was chosen for further evaluation on different targets (paper, Mylar and vine leaves), either sprayed or manually treated. Tartrazine was considered suitable for deposit assessment from agricultural sprayers because of no toxicity, simple laboratory procedure, high recovery rate, and relatively low photodegradation. However, field experiments should be properly planned to reduce, or to account for, variability of natural targets (variable extraction rate and possible background deposits) and photodegradation tinder exposure to sunlight.