Direct detection of dithiocarbamate fungicides by SALDI/MS using porous TiC ceramic powder as a substrate

Abstract

Dithiocarbamate fungicides (DTCs) have been widely used all over the world. Some of them show toxicities, such as growth toxicity and teratogenicity. Therefore, the analysis of DTCs in environments or crops is very significant. However, their direct and individual analysis was difficult, because most of them are metal complex compounds and have macromolecular properties and a low solubility in water or organic solvents. In the conventional analytical methods for DTCs, the total amount of DTCs was obtained by the quantification of the derivatives of the ligand or by measuring the carbon disulfide formed by the decomposition of the fungicides. Surface assisted laser desorption (SALDI)/MS can detect various compounds, such as metal complexes and macromolecules, present in a nanostructured substrate. The porous titanium carbide (TiC) ceramic powder shows adsorptive properties to various substances and can be used as a substrate for SALDI/MS. In this study, a method for the individual and direct detection of dithiocarbamate pesticides by SALDI/MS using porous TiC ceramics as a substrate has been developed. The dithiocarbamate fungicide was mixed with the porous TiC powder in a mortar, and the mixture was analyzed by SALDI/MS. The deprotonated ion of the ethylene-bis-dithiocarbamate complex, mancozeb or zineb, was detected in the negative ion mode. For the dimethyldithiocarbamate complexes, ferbam and ziram, the ion of the eliminated dithiocarbamate ligand was detected in the positive ion mode. Calibration curves by the present method for Manzeb showed good linearity by using an internal standard material. Based on these results, we concluded that this method is useful for the analysis of DTCs.