On-line continuous generation of zinc chelates in the vapor phase by reaction with sodium dithiocarbamates and determination by atomic fluorescence spectrometry

Abstract

The present study shows for the first time that a volatile zinc chelate species can be generated by the on-line continuous merging of an acidified sample solution with an aqueous sodium diethyldithiocarbamate solution followed by rapid separation using a frit-based bubble gas-liquid separator at room temperature. The operating conditions for the generation of the vaporous zinc chelate were preliminarily investigated by non-dispersive atomic fluorescence spectrometry. The possible mechanism of zinc vapor generation is discussed. The study shows that the volatile species is an intermediate species with very similar properties to diethyldithiocarbamic acid and a very short half-life in the acidic solution. Moreover, this species can only be generated by on-line mixing and rapid separation. The efficiency of generation was 33–85% depending on acidity. Under optimal conditions, the flow rates of the sample and Na-DDTC solution were 1.3mlmin−1, the carrier argon flow rate was 225mlmin−1, the acid concentration of the sample solution and the concentration of Na-DDTC were 0.05M and 0.4% (m/v), respectively, the detection limit of zinc was 0.33 (3σ) ngml−1, and the relative standard deviation (RSD) was 1.3%. The accuracy of the method was verified by the determination of zinc in the plant reference materials GBW10015 (spinach) and GBW10045 (rice). The results were in good agreement with the certified reference values.