A novel liquid chromatography detector based on a dielectric barrier discharge molecular emission spectrometer with online microwave-assisted hydrolysis for determination of dithiocarbamates

Abstract

A novel detector for liquid chromatography (LC) for the determination of dithiocarbamate (DTC) fungicides is presented with a miniaturized dielectric barrier discharge–microplasma molecular emission spectrometer and an online microwave-assisted hydrolysis reactor. DTCs in the sample/standard solutions together with SnCl₂ were pumped to the reactor to be converted to CS₂ with high efficiency, which was then separated from the liquid phase and transformed for the detection of the specific molecular emission at 257.49 nm by the spectrometer. Under optimized conditions, the performance of this new detector was evaluated by its determination of different types of DTC including mancozeb, thiram, zineb, propineb, and metiram, and the limit of detection (LOD) values were found to be in the range 0.1–1.0 μg mL⁻¹. The results from 20 test vegetable and fruit samples determined with the proposed method agreed well with those obtained using the standard headspace gas chromatography–electron capture detector (GC–ECD) method. Preliminary experimental results showed that the proposed method provided slightly higher LOD values than those obtained using GC–ECD. Most importantly, the new LC detector could detect each DTC chemical, whereas the traditional method could not distinguish between analytes of different subclasses of DTC.