Development of new adsorbent chitin for column preconcentration and spectrophotometric trace determination of Ziram and Zineb in synthetic, commercial samples and food-stuffs

A procedure has been developed for the determination of zinc(II) bis(dimethyldithiocarbamate) (Ziram) or zinc(II) ethylenebisdithiocarbamate (Zineb) present in a large volume of aqueous solution after preconcentration on a column using chitin-1-(2′pyridylazo)-2-naphthol (PAN) as adsorbent. Ziram/Zineb are quantitatively retained on the column as Zn-PAN complex in the pH range 9.0-11.0 and at a flow rate of 1-8 ml/min. Complex adsorbed on chitin was eluted from the column with dimethylformamide (DMF) and absorbance of the eluate was measured at 550 nm against a reagent blank. Beer's law is obeyed over the concentration range 5.3-55.8 μg of Ziram and 6.8-49.0 μg of Zineb in 25 ml of the final DMF solution. Ten replicate determinations on a sample solution containing 45.22 μg of Ziram or 40.86 μg of Zineb gave a mean absorbance of 0.30 with a relative standard deviation 1.6 and 1.8%, respectively. The interference of various ions has been studied. Many alkali metals and metal salts do not interfere. The method has been employed to the determination of Ziram and Zineb in commercial samples and in various foodstuffs and the results were compared with the earlier reported methods.