Recovery of metallic markers sprayed on soybean plants

Abstract

To understand aspects related to the application of plant protection products, the analysis of spray deposits using metallic markers is a simple and low cost alternative. However, choose the appropriate marker is a challenge. Here, we investigated the recovery of metallic ions used as markers sprayed on soybean plants. The experiment was carried out with soybean plants grown in vases from April to June 2012. The experimental design was completely randomized with 5 treatments, each one composed by the metallic markers: manganese sulfate (MnSO4), zinc sulfate (ZnSO4), copper sulfate (CuSO4), copper hydroxide (Cu(OH)2) and copper oxychloryde (CuCl2.3Cu(OH)2). Each marker was sprayed on soybean leaves in 5 dosages and 2 replications (plants at phenological stages R1 and R2). Furthermore, the metallic markers were applied over the glass laminae due to their inability to absorb. Later on, the markers were washed from soybean leaves and the glass laminae. In this process, samples were submitted to the acid solution (0.2 mol L-1HCl) for 60 minutes and the quantification of the recovered concentration of each ion was accomplished by means of an atomic absorption spectrophotometer. Hence, standard curves of the cations Cu2+, Mn2+, and Zn2+ with concentrations of 0.25, 0.5, 1.0, 2.0 were used. The values were submitted to the statistical analysis of regression. Considering the extraction method used and the rate of recovery, the markers copper hydroxide and copper oxychloride are not recommended for such studies, since these products either on soybean leaves or in a glass laminae showed lower recovery (lower than 97%). Otherwise, the manganese, copper and zinc sulfates (above than 98%) are suitable for studying spray deposits. Appropriated metallic markers to study deposits are discussed.