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

Dithiocarbamates (DTC) are among the most commonly used pesticides in the world. In the Republic of Serbia almost 300 active substances are registered including five dithiocarbamate fungicides (ziram, mancozeb, metiram, propineb and tiram). In the 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: the capacity to generate carbon disulfide (CS2), biotransformation of ethylenethiourea (ETU), the ability to chelate physiologically important ions (e.g. cooper). 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 wee not set for all agricultural products. The MRL for dithiocarbamates in rasperries (dithiocarbamates expressed as CS2, including maneb, mancozeb, metiram, propineb, thiram and ziram) in the EU and Republic of Serbia is 0.05 mg/kg. The paper presents the method validation results and the results of dithiocarbamate monitoring study. Our studies comprised the determination of the dithiocarbamate residues content in 93 raspberry samples from the market of the Republic of Serbia taken during 2007-2010. Over 20% of samples were above the MRL (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, spiked in the range of 0.05-1.25 mg/kg, is 91.35%. The limits of detection (LOD = 3 x sigma baseline noise) and quantification (LOQ = 10 x sigma baseline noise) are approximately 0.01 and 0.03 mg/kg, respectively. The linearity obtained without matrix is R**2=0.992, and with matrix is R**2=0.999. The matrices do not have interfering peaks in the time of CS2 elution.