Decontamination Procedure for Sorghum and Coffee Leaves Sprayed With Zinc and a Surfactant

Decontaminating leaf samples from crops sprayed with pesticides and nutrient solutions is important for foliar analysis. This study evaluated the effect of different washing methods in coffee and sorghum foliage that had been sprayed with zinc (with or without surfactant). The plants were sprayed with a 3 g L-1 zinc sulfate solution, with and without surfactant. Seven days later, leaves were collected and washed. The experiment was completely randomized in a 2 x 2 x 3 + 2 factorial, with three replications. The first factor represents foliar zinc applications with or without surfactant, the second represents the number of washes (1 or 2) and the third represents the concentration of the wash solution (detergent + hydrochloric acid) at (0 + 0 mL L-1; 1.0 + 3.5 mL L-1 and 2.0 + 7.0 mL L-1). The last one represents two additional treatments without washing (zinc sprayed with and without surfactant). Surfactant strengthens contact between zinc and foliage and enhances absorption. Washing is an indispensable pretreatment for leaf analysis and our study showed that a single wash with detergent + hydrochloric acid (1.0+ 3.5 mL L-1) was the most effective washing method for coffee and sorghum.