Simultaneous UV-spectrophotometric determination of CS2 and COS using the piperidine, pyrrolidine, ethylenediamine or morpholine reagent

Abstract

The success of a spectrophotometric method for the determination of dithiocarbamate or tetramethylthiuram disulphide (thiram) fungicide residues based on the quantification of the evolved CS2 after an acid hydrolysis of the fungicide depends on the sensitivity and selectivity of the CS2 absorbing reagent. In the present study piperidine, pyrrolidine, ethylenediamine and morpholine and their corresponding optimum reaction conditions with CS2 and COS were spectrophotometrically investigated for their suitability as CS2 and COS absorbing reagents. The CS2-amine and COS-amine adducts, formed after the absorption of the CS2 and COS gases in an alcoholic amine, exhibit different UV-absorption spectra which facilitated the quantification of both CS2 and COS. The sensitivity of the amines to CS2 and COS and the stability of the CS2-amine and COS-amine adducts were found to be dependent on the reaction time between the CS2 and COS with the amine, the concentration and the temperature of the alcoholic amine reagent. Under optimized conditions, ethylenediamine, pyrrolidine and morpholine proved to be equally sensitive to both CS2 and COS just as the previously reported piperidine. Furthermore, the sensitivity of piperidine to COS was improved. The sensitivity optimized amine reagents, dissolved in methanol instead of ethanol and with detection limits for both CS2 and COS down to 0.3 μg/ml, should provide new and cheaper means in the residue analysis of dithiocarbamate and tetramethylthiuram disulphide (thiram) fungicides based on the evolved CS2 and COS after an acid hydrolysis.