Determination of dithiocarbamates; improvements to the method described in EN 12396-1 standard

Abstract

A procedure to improve the performance and reliability of the method described in European standard EN-12396-1 is presented. A CS2 working range of 10–50 µg per 25 mL was validated. The quantification limit was lowered from 0.25 mg kg−1 to 0.05 mg kg−1 (200 g of sample matrix), in agreement with the Maximum Residue Limits for dithiocarbamates (DTCs). The procedure involves the measurement of the average absorbance at 374 nm and 435 nm, to allow for the equilibrium between the two coloured Cupric(II) complexes formed. Two main modifications of the decomposition and distillation apparatus assembly were introduced. One was the stabilization of the colour-forming reagent solution at 0°C to ensure stability of absorbance. The other was the inclusion of a bubbler trap with ethanol, to retain interfering compounds. The possible CS2 contamination by several types of protective gloves was also studied. Vinyl gloves, made according to the AQL 1.5 – EN 455-1/2 standard, did not interfere with the method.