Solid-state UV–MALDI–MS assay of transition metal dithiocarbamate fungicides

Abstract

The determination of transition metal containing dithiocarbamate fungicides represents a challenging aspect of analytical object. They have a low stability, low solubility and stabilize versatile coordination monomers, dimers, disulfides and/or S-oxidized derivatives. Their diverse biological activities and agricultural implementation encompass plant prevention and crop protection against a variety of plants containing fungi and diseases of 400 pathogens and 70 cultures. Nonetheless, those dithiocarbamates (DTCs) are banned for agricultural use in Europe or have expiration at years 2016-2017 because of their highly toxic degradation products and/or metabolites, in particular ethylene thiourea; they found large-scale implementations in materials research and medicine. Despite the broad interdisciplinary of DTC application, due to the above reasons, they have received little attention in the rapidly growing field of analytical chemistry, and in particular, the analytical mass spectrometry. Therefore, the study reported on qualitative, quantitative and structural analysis of ten DTCs (1-10), using the matrix assisted laser desorption/ionization (UV-MALDI)-Orbitrap-mass spectrometry (MS) contributed considerably to the implementation of the method for environmental and foodstuffs monitoring. Its ultrahigh resolving power and capacity for direct solid-state analysis, at limited number of sample pretreatment steps, at concentration levels of analytes of up to femtogram per gram resulted to achievement of a highly precise analytical information for these non-trivial objects. The presented fully validated method and technique is based on the successful ionization of DTCs embedded in three novel organic salts (M1-M3). In this regard, the reported MS and the single-crystal X-ray diffraction data as well as the quantum chemical one are able to correlate the molecular structures in condense and in the gas phase. Despite the novelty of the fundamental methodological character of the research reported, the promising metrology contributed to the applied aspect of the UV-MALDI-MS as a robust analytical method for environmental and foodstuffs monitoring, which is tested on two commercially available crop protecting products such as Mancozeb® and Antracol®, respectively.

In Vitro Studies of the Activity of Dithiocarbamate Organoruthenium Complexes against Clinically Relevant Fungal Pathogens

“…The multiple fragmentation pattern observed in the ESI-MS spectra corroborates the obtaining of unsymmetrical dinuclear ruthenium complexes in which the dithiocarbamate moiety plays function as bridging ligand, since the presence of fragments that only can be formed through non-equivalent types of ruthenium-sulfur bonds is noticed, and if the compounds would be symmetrical (as in a mononuclear ruthenium complex or in a kind of oligomeric derivative) the fragmentation pattern would be much less complicated; this discussion will be reported further. There is a recent study [63] about the UV-MALDI mass spectrometry investigation of well-known dithiocarbamate complexes (zinc, iron and manganese derivatives) that corroborates our structural proposal, since in this case symmetrical species (monomeric, dimeric, or tetrameric) were obtained and the corresponding mass spectra are not as complicated, as expected, compared to those in this present study. In addition, the analysis of magnetic susceptibility of the studied compounds showed values consistent with the proposed Ru(II)/Ru(III) system.…”

Determination of copper and lead in tequila by conventional matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry and partial least squares regression

“…Beyond any doubt, inductively coupled plasma mass spectrometry (ICP‐MS) is the first‐choice technique for the determination of trace metal/metalloids in any real‐world sample; however, there have also been several applications of conventional MALDI‐HRMS reported, offering a memory‐free, high‐throughput, high‐resolution, micro‐scale alternative with instrument operation costs much lower as compared with ICP‐MS. In this regard, we have recently demonstrated the feasibility of conventional MALDI coupled to time‐of‐flight mass spectrometry (TOFMS) for the determination of mercury and copper in fish tissues.…”

“…At pH close to neutral, the majority of these complexes (excluding arsenic) can be easily extracted into chloroform allowing for solvent evaporation and re‐constitution in a microvolume prior to the sample deposition on the MALDI target. Of note, complexation of metal ions with dithiocarbamates has already been explored within the domain of MALDI‐MS analysis . Despite the low selectivity of diethyldithiocarbamate, interference‐free determination of individual metals can be expected using a high‐resolution mass spectrometer; likewise, the versatility of NaDDTC allows for the selection of suitable internal standards that would be absent in tequila.…”

“…[6][7][8][9][10] In another approach for enhanced determination of small molecules, a considerable effort has been dedicated to the improvement of sample preparation and on the selection of instrumental conditions in conventional MALDI thus avoiding undesired matrix effects. [11][12][13] Beyond any doubt, inductively coupled plasma mass spectrometry (ICP-MS) is the first-choice technique for the determination of trace metal/metalloids in any real-world sample; however, there have also been several applications of conventional MALDI-HRMS reported, [14][15][16][17][18] offering a memory-free, high-throughput, highresolution, micro-scale alternative with instrument operation costs much lower as compared with ICP-MS. In this regard, we have recently demonstrated the feasibility of conventional MALDI coupled to time-of-flight mass spectrometry (TOFMS) for the determination of mercury and copper in fish tissues.…”

“…Of note, complexation of metal ions with dithiocarbamates has already been explored within the domain of MALDI-MS analysis. 15,16 Despite the low selectivity of diethyldithiocarbamate, interference-free determination of individual metals can be expected using a high-resolution mass spectrometer; likewise, the versatility of NaDDTC allows for the selection of suitable internal standards that would be absent in tequila.…”