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Background: The determination of mancozeb, a fungicide extensively used in agriculture, is a challenge, due to the nature of the compound, a manganese and zinc complex of ethylenebis dithiocarbamate and because of the general instability of the dithiocarbamates. Methods: Mancozeb was analyzed in a GC-EI-MS system after derivatization by CE-UV with detection at 280 nm and in LC-ESI-MS-MS in MRM mode. Results: A comparative study of the performance of three different techniques for the detection of mancozeb was explored, highlighting the advantages and drawbacks of them. The limits of detection and quantification of the techniques were determined; the repeatability was assessed, showing values of relative standard deviation. Gas chromatography, although very sensitive, was not reproducible enough due to fast degradation of the derivatization product, whereas capillary electrophoresis-UV showed problems in run-to-run reproducibility which had the worst limit of detection. LC coupled with tandem mass spectrometry was the most reliable and precise technique and was able to determine the main degradation product of Mancozeb, at the same time. The proposed LC procedure was verified by applying it to a commercial formulation, a fungicide of known concentration, and to Italian white grapes treated with the formulation sprayed during cultivation. Conclusion: Thanks to the simplified sample handling, the proposed method resulted to be simple, fast, green, economic, and suitable for residue analysis in grapes and other fruits. Finally, the method was compared with other similar investigations.