Mária Mörtl

Determination of phenols and chlorophenols as trimethylsilyl derivatives using gas chromatography-mass spectrometry

A rapid and simple method is described for the simultaneous determination of 6 phenols (phenol, o-, m-, p-cresol, catechol and resorcinol) and 19 chlorophenols (all mono-, di-, tri-, and tetrachlorophenol isomers and pentachlorophenol) present in aqueous samples. The method is based on derivatization with trimethylsilyl-N,N-dimethylcarbamate (TMSDMC). In contrast to other derivatization agents, TMSDMC instantaneously reacts with the phenolic compounds at room temperature and no further sample processing is necessary prior to instrumental analysis. The determination of the derivatives was performed by capillary gas chromatography-mass spectrometry (GC-MS). The stability of the most instable trimethylsilyl derivative (pentachlorophenol) was studied using different excess levels of the derivatization reagent. The derivatization method was tested on spiked water samples preconcentrated by solid phase extraction on Isolute ENV+ cartridge. The overall method gave detection limits of 0.01-0.25 microg/L for all compounds and < 0.05 microg/L for 17 of them.

Monitoring Pesticide Residues in Surface and Ground Water in Hungary: Surveys in 1990–2015

Over 2000 surface, ground and raw drinking water samples have been analyzed in the frame of different monitoring projects in Hungary and watercourses in neighboring countries between 1990 and 2015. Effects of pesticide contamination on ecological farming and drinking water supply have been assessed. Main water pollutant ingredients of agricultural origin in Hungary are herbicides related to maize production. After EU pesticide re-registration, diazinon, atrazine, and trifluralin gradually disappeared as contaminants. High levels of water soluble pollutants (e.g., acetochlor) in surface water result in temporarily enhanced levels in raw drinking water as well. Extreme levels observed for herbicide residues were of agrochemical industrial origin.

Neonicotinoid insecticides inhibit cholinergic neurotransmission in a molluscan (Lymnaea stagnalis) nervous system

Neonicotinoids are highly potent and selective systemic insecticides, but their widespread use also has a growing impact on non-target animals and contaminates the environment, including surface waters. We tested the neonicotinoid insecticides commercially available in Hungary (acetamiprid, Mospilan; imidacloprid, Kohinor; thiamethoxam, Actara; clothianidin, Apacs; thiacloprid, Calypso) on cholinergic synapses that exist between the VD4 and RPeD1 neurons in the central nervous system of the pond snail Lymnaea stagnalis. In the concentration range used (0.01-1 mg/ml), neither chemical acted as an acetylcholine (ACh) agonist; instead, both displayed antagonist activity, inhibiting the cholinergic excitatory components of the VD4-RPeD1 connection. Thiacloprid (0.01 mg/ml) blocked almost 90% of excitatory postsynaptic potentials (EPSPs), while the less effective thiamethoxam (0.1 mg/ml) reduced the synaptic responses by about 15%. The ACh-evoked membrane responses of the RPeD1 neuron were similarly inhibited by the neonicotinoids, confirming that the same ACh receptor (AChR) target was involved. We conclude that neonicotinoids act on nicotinergic acetylcholine receptors (nAChRs) in the snail CNS. This has been established previously in the insect CNS; however, our data indicate differences in the background mechanism or the nAChR binding site in the snail. Here, we provide the first results concerning neonicotinoid-related toxic effects on the neuronal connections in the molluscan nervous system. Aquatic animals, including molluscs, are at direct risk while facing contaminated surface waters, and snails may provide a suitable model for further studies of the behavioral/neuronal consequences of intoxication by neonicotinoids.

Optical waveguide lightmode spectroscopy technique-based immunosensor development for aflatoxin B1 determination in spice paprika samples.

Optical waveguide lightmode spectroscopy (OWLS) technique has been applied to label-free detection of aflatoxin B1 in a competitive immunoassay format, with the aim to compare the analytical goodness of the developed OWLS immunosenor with HPLC and enzyme-linked immunosorbent assay (ELISA) methods for the detection of aflatoxin in spice paprika matrix. We have also assessed applicability of the QuEChERS method prior to ELISA measurements, and the results were compared to those obtained by traditional solvent extraction followed by immunoaffinity clean-up. The AFB1 content of sixty commercial spice paprika samples from different countries were measured with the developed and optimized OWLS immunosensor. Comparing the results from the indirect immunosensor to that obtained by HPLC or ELISA provided excellent correlation (with regression coefficients above 0.94) indicating that the competitive OWLS immunosensor has a potential for quick determination of aflatoxin B1 in paprika samples.

Study on Soil Mobility of Two Neonicotinoid Insecticides

Movement of two neonicotinoid insecticide active ingredients, clothianidin (CLO) and thiamethoxam (TMX), was investigated in different soil types (sand, clay, or loam) and in pumice. Elution profiles were determined to explore differences in binding capacity. Soil characterized by high organic matter content retained the ingredients, whereas high clay content resulted in long release of compounds. Decrease in concentration was strongly influenced by soil types: both CLO and TMX were retained in loam and clay soils and showed ready elution through sandy soil and pumice. Elution capability of the active ingredients in sandy soil correlated with their water solubility, indicating approximately 30% higher rapidity for TMX than for CLO. Soil organic carbon-water partitioning coefficients () determined were in good agreement with literature values with somewhat lower value for CLO in sandy soil and substantially higher values for TMX in clay soil. High mobility of these neonicotinoid active ingredients in given soil types urges stronger precautionary approach taken during their application.

New N-hydroxy carbamic acid trialkylsilyl derivatives: preparation and thermal reactions

Abstract New N-siloxy- or N-alkoxy-carbamic acid derivatives have been prepared. The crystal structure of N-siloxy-O-tert-butyl carbamate was determined. The thermal behaviour of these compounds was studied in the absence and in the presence of other reaction partners. The reaction products were identified by gas chromatography, gas chromatography-mass spectroscopy, IR spectroscopy and NMR. The experimental results can be explained by the formation of a radical-type transition state (carboxynitrene), detected by mass spectroscopy.

Synthesis and reactions of silylcarbamates with bulky substituents

Abstract New silylcarbamates containing bulky substituents were synthesized in order to study their reactivity with nucleophilic agents as lactones and chloroformates. We suggest a mechanism for these reactions.

Preparation of Mixed Carbamic/ Dithiocarbamic Anhydrides via Silyl Carbamates or Silyl Dithiocarbamates

Abstract The reactions of silyl carbamates and silyl dithiocarbamates with different acid chlorides (carbamoyl/thiocarbamoyl chloride, chloroformates, etc.) have been studied. The obtained mixed anhydrides have different thermal stability.

Reactions of silylcarbamates with ketones

The reaction of N,N-dialkyl-O-trimethylsilyl carbamates with different carbonyl compounds gives enamines under mild conditions in good yields.

Effects of neonicotinoid insecticide formulations and their components on Daphnia magna – the role of active ingredients and co-formulants

ABSTRACT Formulating agents used in pesticide products have been regarded as inactive/inert components; however, several studies confirmed additive, synergistic or antagonistic effects between the active ingredients (AIs) and additives, or the individual toxicity of the formulating agents. The worldwide used neonicotinoid insecticides and their components can reach surface waters, due to their physico-chemical properties (e.g. water solubility) or improper application in chemical plant protection technology, and can adversely affect non-target aquatic organisms. Formulated pesticides were analysed for alkane sulphonate surfactants by using liquid chromatography coupled with tandem mass spectrometry. In acute immobilisation tests on Daphnia magna, differences were found among the toxicity of the investigated neonicotinoid AIs and formulations. The toxicity of a formulated insecticide (Apache 50 WG®– AI: clothianidin) was found to be 46.5 times more toxic than explained by its AI, probably due to toxic effect of the formulating agents on D. magna. In contrast, two preparations (Calypso 480SC® – AI: thiacloprid, Actara 240 SC®– AI: thiamethoxam) were 2–3 times less toxic than their AIs. Results indicate possible synergistic/antagonistic interaction with the AIs.