Trends of dithiocarbamate residues in raspberries in the Republic of Serbia over the period 2007/2010

Dithiocarbamates (DTC) are among the most commonly used in the world. In the Republic of Serbia almost 300 active substances are registered including five dithiocarbamate fungicides (ziram, mancozeb, metiram, propineb and tiram). For raspberry protection from fungal diseases, only mancozeb combined with metalaxyl-M (Ridomil Gold MZ 68-WG; mankozeb 640 g/kg + metalaxyl-M 40 g/kg), of all dithiocarbamates, is authorized for use in the Republic of Serbia. Dithiocarbamates present in food can be of health concern. They have at least three modes of toxic action. These include: (a) the capacity to generate carbon disulfide (CS2), (b) biotransformation into ethylenethiourea (ETU), (c) the ability to chelate physiologically important ions (e.g., copper). The Serbian government authorities adapted the maximum residue levels (MRLs) to the MRLs set by the European Union in 2010 (The Official gazette 27/2010) but dithiocarbamate levels were not set for all agricultural products. The MRLs for dithiocarbamates in raspberries (dithiocarbamates expressed as CS2, including maneb, mancozeb, metiram, propineb, thiram and ziram) in the EU and the Republic of Serbia is 0.05 mg/kg. The paper presents the method validation results and the results of dithiocarbamate monitoring study. Our study comprised the determination of the dithiocarbamate residues content in 103 raspberry samples from the market of the Republic of Serbia taken during 2007/2010. Over 20% of samples were above the MRLs (0.05 mg/kg), with the highest detected concentration of 0.8 mg/kg. The headspace GC/MS multi-residue method, based on the analysis of carbon disulphide obtained after the treatment of analytes with hydrochloric acid in the presence of tin (II)chloride was used. The averaged recovery from raspberries was spiked in the range of 0.05 - 1.25 mg/kg, is 91.35%. The limits of detection (LOD = 3 x δ baseline noise) and quantification (LOQ = 10 x δ baseline noise) were approximately 0.01 and 0.03 mg/kg, respectively. The linearity obtained without matrix was R2=0.992, and with matrix was R2=0.999. The matrices did not have interfering peaks in the time of CS2 elution.