Quantification of ziram and Zineb (cas 12122-67-7) residues in fog-water samples

Add time:08/03/2019    Source:sciencedirect.com

The present paper describes the extractive quantification of zinc-dithiocarbamate fungicides, i.e. ziram (zinc bis-dimethyldithiocarbamate) and Zineb (cas 12122-67-7) (zinc ethylene-1,2-bis-dithiocarbamate) in fog-water samples. The method is based on the releasing of equivalent amount of zinc from the fungicides and its subsequent determination by visible spectrophotometry or by flame-atomic absorption spectrometry (flame-AAS). For spectrophotometry, the sample contained up to 48 μg of ziram and 42 μg of zineb was first equilibrated with chloroform. The recovery results show that only ziram content was extracted into chloroform. Then, the sample was treated with NH4SCN and surfactants (i.e. CPC and TX-100) solutions, and extracted with toluene to remove interference of inorganic zinc and other metal ions, if present in the sample. The residue was further used for zineb determination. The chloroform extract and residue were then digested separately with nitric acid to release Zn(II), which were then analyzed spectrophotometerically with 4-(2-pyridylazo)-resorcinol in the micellar medium (TX-100) for the determination of ziram and zineb, respectively. The complex shows λmax at 495 nm. The molar absorptivity in terms of ziram/zineb was determined to be (8.05) × 104 L mole−1 cm−1. The detection limits for ziram and zineb were calculated to be 20 and 21 μg L−1 (with R.S.D. < 1.5%), respectively. Whereas, the optimum concentration ranges were 0.08–1.6 and 0.07–1.4 mg L−1, respectively. Alternatively, the Zn contents present in chloroform extract and in residue were directly analyzed using flame-AAS without undergoing the digestion procedure, and ziram and zineb were determined, respectively. The optimum concentration ranges were 0.9–4.8 and 0.8–4.3 mg L−1, while the detection limits were calculated to be 145 and 144 μg L−1, respectively with R.S.D. < 2.5%. The methods are free from interference of almost all ions [including Zn(II)] and other dithiocarbamate pesticides, which can commonly associate with ziram/zineb in fog-water.

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