Selective Identification of Maneb and Mancozeb via Mn²⁺ and Zn²⁺ Coordination and Mass Fragmentation Mechanism

Maneb and mancozeb fungicides have very similar structures, with the main difference being the presence of an additional zinc ion in mancozeb. Specificity is the constant challenge raised in previously developed methods for identifying these compounds. Therefore, a more reliable and effective identification method was introduced, enabling the sensitive and accurate detection of structurally similar manganese-containing fungicides. In this study, 2-imidazolidinethione (ETU) was detected at a retention time of 9.22 min as the hydrolyzed product, and permanganate was formed as the oxidized product of those two fungicides, which were used to confirm the ligand and the manganese ion, respectively. Additionally, simple direct UV-visible measurements successfully identified the characteristic spectra of both maneb and mancozeb. The limit of detection (LOD) values of maneb and mancozeb were 0.007 and 0.008 ppm, respectively, and the determination coefficient (R ²) for maneb and mancozeb was 0.9999. Interday and intraday precision were 1.58 and 1.62%, and 1.41 and 1.57% for maneb and mancozeb, respectively. The developed method demonstrated high accuracy for both fungicides, with recovery rates ranging from 99.2 to 99.8% (±1.1-1.6%) across concentrations of 0.25, 0.50, and 0.75 ppm. A significant degradation was observed following hydrolysis, with 95.63 and 96.67% degradation recorded for maneb and mancozeb, respectively. Moreover, complete oxidation (100%) of each fungicide was achieved. The most important aspect of this study was the precise differentiation of maneb and mancozeb by studying the effect of zinc (Zn²⁺) as well as manganese (Mn²⁺) ions on the ethylenebisdithiocarbamate moiety.