Herbicidal Ionic Liquids Research Articles

Toxicity evaluation of selected ammonium-based ionic liquid forms with MCPP and dicamba moieties on Pseudomonas putida

Combination of the hydrophilic herbicidal anion with hydrophobic, antimicrobial ammonium cation allows to obtain compounds in ionic liquid form with better properties then conventional herbicides. Both cation and anion can be modified by selection of herbicide and the length of alkyl chains in cation structure. However the knowledge of their potential toxic effects are still limited. Furthermore, the relation between hydrophobicity associated with the length of alkyl chains and toxicity for ionic liquids has not been thoroughly studied. Therefore we investigated toxic effects of herbicidal ionic liquid forms on growth inhibition, given as EC50, of the common soil bacterium Pseudomonas putida. We thereby concentrated on quaternary ammonium salts. Analyzed compounds were composed of dicamba or MCPP moieties and cation with various alkyl chain lengths (n = 6,8,10) We compared them with commercial herbicides, and ammonium-based ionic liquids with neutral anion (Br−). In addition, cis-trans isomerisation of unsaturated membrane fatty acids in Pseudomonas putida was applied as the proxy for toxicity and membrane activity. We showed that toxicity increased with the length of alkyl chains. However, this correlation is only valid for six and eight carbon atom in alkyl chains, where for n = 10 the EC50 values rise by one order of magnitude. In our studies, the herbicidal ionic liquids [C10,C10,C1,C1N][MCPP] and [C10,C10,C1,C1N][dicamba] showed the lowest toxicity among analyzed quaternary ammonium salts and comparable toxicity with corresponding herbicides. No clear increase in toxicity could be followed by changing the anion moieties for ammonium-based ionic liquid forms.

Removal of herbicidal ionic liquids by electrochemical advanced oxidation processes combined with biological treatment

ABSTRACTRecently a new group of ionic liquids (ILs) with herbicidal properties has been proposed for use in agriculture. Owing to the design of specific physicochemical properties, this group, referred to as herbicidal ionic liquids (HILs), allows for reducing herbicide field doses. Several ILs comprising phenoxy herbicides as anions and quaternary ammonium cations have been synthesized and tested under greenhouse and field conditions. However, since they are to be introduced into the environment, appropriate treatment technologies should be developed in order to ensure their proper removal and avoid possible contamination. In this study, didecyldimethylammonium (4-chloro-2-methylphenoxy) acetate was selected as a model HIL to evaluate the efficiency of a hybrid treatment method. Electrochemical oxidation or electro-Fenton was considered as a pretreatment step, whereas biodegradation was selected as the secondary treatment method. Both processes were carried out in current mode, at 10 mA with carbon felt as working electrode. The efficiency of degradation, oxidation and mineralization was evaluated after 6 h. Both processes decreased the total organic carbon and chemical oxygen demand (COD) values and increased the biochemical oxygen demand (BOD5) on the COD ratio to a value close to 0.4, showing that the electrolyzed solutions can be considered as ‘readily biodegradable.’

Frontispiece: Betaine and Carnitine Derivatives as Herbicidal Ionic Liquids

Frontispiece: Betaine and Carnitine Derivatives as Herbicidal Ionic Liquids

Betaine and Carnitine Derivatives as Herbicidal Ionic Liquids.

This study focused on the synthesis and subsequent characterization of herbicidal ionic liquids based on betaine and carnitine, two derivatives of amino acids, which were used as cations. Four commonly used herbicides (2,4-D, MCPA, MCPP and Dicamba) were used as anions in simple (single anion) and oligomeric (two anions) salts. The obtained salts were subjected to analyzes regarding physicochemical properties (density, viscosity, refractive index, thermal decomposition profiles and solubility) as well as evaluation of their herbicidal activity under greenhouse and field conditions, toxicity towards rats and biodegradability. The obtained results suggest that the synthesized herbicidal ionic liquids displayed low toxicity (classified as category 4 compounds) and showed similar or improved efficacy against weed compared to reference herbicides. The highest increase was observed during field trials for salts containing 2,4-D as the anion, which also exhibited the highest biodegradability (>75 %).

Influence of oligomeric herbicidal ionic liquids with MCPA and Dicamba anions on the community structure of autochthonic bacteria present in agricultural soil

The aim of this study was to evaluate the impact of selected herbicidal ionic liquids (HILs), which exhibit high efficacy in terms of weed control and low toxicity, but may be persistent due to limited biodegradability, on the community structure of autochthonic bacteria present in agricultural soil. Four different oligomeric HILs (with two types of cations and different ratio of herbicidal anions) were synthesized and characterized by employing 1H and 13C NMR. The results of biodegradation assay indicated that none of the tested HILs could be classified as readily biodegradable (biodegradation rate ranged from 0 to 7%). The conducted field studies confirmed that the herbicidal efficacy of the HILs was higher compared to the reference herbicide mixture by 10 to 30%, depending on the dose and weed species. After termination of field studies, the soil treated with the tested HILs was subjected to next generation sequencing in order to investigate the potential changes in the bacterial community structure. Proteobacteria was the dominant phylum in all studied samples. Treatment with the studied HILs resulted in an increase of Actinobacteria compared to the reference herbicidal mixture. Differenced among the studied HILs were generally associated with a significantly higher abundance of Bacteroidetes in case of 1-HIL-Dicamba 1/3 and Firmicutes in case of 2-HIL-Dicamba 1/3.

Herbicidal ionic liquids derived from renewable sources

A new family of herbicidal ionic liquids based on d-glucose and MCPA or 2,4-D anions has been synthesized and the physicochemical, surface active and herbicidal properties of the obtained salts were characterized.

Synthesis, properties and evaluation of biological activity of herbicidal ionic liquids with 4-(4-chloro-2-methylphenoxy)butanoate anion

In this study, fourteen new herbicidal ionic liquids (HILs) based on MCPB with a 1-alkyl-1-methylpiperidinium cation were synthesized and characterized.

Synthesis, Surface Properties and Biological Activity of Long Chain Ammonium Herbicidal Ionic Liquids

Herbicidal ionic liquids exhibit many advantages compared to conventional chemical plant protection agents, which allow for a reduction of the herbicide dose per hectare and decrease of toxicity. Popular herbicides, such as 4-chloro-2-methylphenoxyacetic (MCPA) or 2,4-dichlorophenoxyacetic (2,4-D) acids, can be modified by reaction with long chain ammonium cations in order to obtain novel forms. The aim of this study was to present an alternative method for the synthesis of herbicidal ionic liquids based on a natural cation known as Ethoquad C/12 and to analyze the physicochemical properties and herbicidal activity of the obtained products. New ionic liquids comprising MCPA and 2,4-D as anions were obtained and their chemical as well as thermal stability were evaluated. Furthermore, their biological and surface activity were investigated. The obtained results confirmed that the herbicidal activity has been preserved.

Pyrrolidinium herbicidal ionic liquids

In this work, sixteen new pyrrolidinium herbicidal ionic liquids (HILs) with phenoxycarboxylate anions were synthesized and characterized.

Differences in uptake of Mn by Sinapis alba L. and Triticum aestivum L. after using glyphosate and MCPA-based pesticides and the selected herbicidal ionic liquids

Differences in uptake of Mn by Sinapis alba L. and Triticum aestivum L. after using glyphosate and MCPA-based pesticides and the selected herbicidal ionic liquids

Toxicity of synthetic herbicides containing 2,4-D and MCPA moieties towards Pseudomonas putida mt-2 and its response at the level of membrane fatty acid composition.

One of the attempts to create more effective herbicidal compounds includes the use of ionic liquids. Herbicidal ionic liquids have more effective biological activity, they are less volatile, more thermally stable, and exhibit superior efficiency in comparison to typically employed herbicides, allowing the reduction of the herbicide dose applied per hectare. However, studies on the environmental toxicity of this group of compounds are very rarely available. Environmental toxicity is an important factor, showing the concentration of compounds that has negative effects on soil bacteria including those responsible for biodegradation processes. Therefore, potential toxicity of four herbicidal ionic liquids (HILs) precursors containing 2,4-D and MCPA moieties was tested with the well investigated model organism for toxicity and adaptation, Pseudomonas putida mt-2. Results were compared to those obtained for commercial 2,4-D and MCPA herbicides. Next to growth inhibition, given as EC50, changes in the isomerisation of cis to trans unsaturated fatty acids were applied as proxy for cellular stress adaptation to toxic substances. The results revealed that all investigated precursors of HILs showed lower toxicity compared to commercialized synthetic herbicides 2,4-D and MCPA. The collected data on toxicity of HILs together with their physico-chemical properties might be useful for assessing the potential risk of the environmental pollution as well as guidelines for setting the legislation for their future use.

ChemInform Abstract: Herbicidal Ionic Liquids Based on Esterquats.

AbstractNovel herbicidal ionic liquids (HILs) containing different anions and cations derived from ammonium esterquats are prepared by employing a simple, inexpensive pathway.

Development of novel ionic liquids based on bentazone

Bentazone is one of the widely used herbicides for controlling sedges and broad-leaf weeds. Due to its high mobility in soils, bentazone has been frequently found among the contaminants detected in surface and ground water and poses a potential threat to aquatic organisms by runoff and leaching. In this work, novel herbicidal ionic liquids (HILs) based on bentazone with four typical cations were synthesized and characterized. The physicochemical properties (water solubility, surface activity, leaching and soil adsorption) and herbicidal activity of HILs were investigated. The result showed that the water solubility of HILs was reduced along with the increasing length of alkyl chains in cations. Compared with bentazone sodium, HILs showed higher adsorption capacity, weaker mobility, and excellent surface activity and Pyr-1 substantially performed higher efficacy under field condition. With high activity of weed control and fascinating physicochemical properties, HILs can reduce the risk of bentazone in aquatic environment and they will be applied widely in the future.

Ionic liquid forms of clopyralid with increased efficacy against weeds and reduced leaching from soils

The excessive application of water-soluble pesticides poses enormous potential risks to groundwater by leaching or in runoff. Ionic liquids can regulate the physicochemical properties of pesticides and surmount their disadvantages. In this study, five herbicidal ionic liquids (HILs) based on clopyralid have been synthesized and characterized to reduce the risks to the aquatic environment and improve the herbicidal activity. The new HILs are prepared by pairing isopropylamine, 1-dodecylamine, 2-benzothiazolamine, 1-methylimidazole, benzyltriethylammonium chloride respectively. The results of the solubility, soil adsorption, surface activity, leaching characteristic and herbicidal activity of HILs show that the physicochemical properties can be optimized by selecting different counter cations. Compared with clopyralid potassium, HILs have better herbicidal activity, greater adsorption capacity and lower leaching characteristic. The HILs of clopyralid can reduce its hazardous impacts on the aquatic environment, suggesting a desirable candidate in clopyralid application in the future.

Metsulfuron-methyl-based herbicidal ionic liquids.

Ten sulfonylurea-based herbicidal ionic liquids (HILs) were prepared by combining the metsulfuron-methyl anion with various cation types including quaternary ammonium ([bis(2-hydroxyethyl)methyloleylammonium](+), [2-hydroxyethyltrimethylammonium](+)), pyridinium ([1-dodecylpyridinium](+)), piperidinium ([1-methyl-1-propylpiperidinium](+)), imidazolium ([1-allyl-3-methylimidazolium](+), [1-butyl-3-methylimidazolium](+)), pyrrolidinium ([1-butyl-1-methylpyrrolidinium](+)), morpholinium ([4-decyl-4-methylmorpholinium](+)), and phosphonium ([trihexyltetradecylphosphonium](+) and [tetrabutylphosphonium](+)). Their herbicidal efficacy was studied in both greenhouse tests and field trials. Preliminary results for the greenhouse tests showed at least twice the activity for all HILs when compared to the activity of commercial Galmet 20 SG, with HILs with phosphonium cations being the most effective. The results of two-year field studies showed significantly less enhancement of activity than observed in the greenhouse; nonetheless, it was found that the herbicidal efficacy was higher than that of the commercial analog, and efficacy varied depending on the plant species.

Bis(ammonium) ionic liquids with herbicidal anions

The method of synthesis of the novel bis(ammonium) herbicidal ionic liquids with the cation containing two quaternary nitrogen atoms was described.

Herbicidal ionic liquids based on esterquats

Herbicidal ionic liquids (HILs) are candidates for novel, efficient and environmentally friendly plant protection agents.

Glyphosate-Based Herbicidal Ionic Liquids with Increased Efficacy

Eight new glyphosate-based herbicidal ionic liquids (HILs), containing both mono- and dianions of glyphosate (benzalkonium glyphosate, bis(2-hydroxyethyl)cocomethylammonium glyphosate, oleylmethylbis(2-hydroxyethyl)ammonium glyphosate, didecyldimethylammonium glyphosate, di(hydrogenated tallow)dimethylammonium glyphosate, 4-decyl-4-ethylmorpholinium glyphosate, di(benzalkonium) glyphosate, and di(bis(2-hydroxyethyl)cocomethylammonium) glyphosate) were prepared via acid–base reaction between the corresponding ammonium hydroxides (some premade) and glyphosate free acid. The transformation of glyphosate free acid into ionic liquids led to an elimination of melting points in all but one compound and significant change in solubilities. All HILs exhibited higher thermal stability than glyphosate free acid. Greenhouse testing indicated that while at a higher application rate of 360 g/ha the efficacy of all the HILs was comparable to the commercial herbicide control, at a lower application rate of 180 g/ha, the e...

Phenoxy herbicidal ammonium ionic liquids

Ammonium ionic liquids with the 4-chloro-2-methylphenoxyacetate anion were synthesized and characterized. Physicochemical properties, such as thermal stability, phase transition temperatures, viscosity, density, refractive index, as well as surface activity and herbicidal activity were determined. Improved physicochemical properties suggest a reduced environmental impact of newly formed group of herbicidal ionic liquids (HILs). HILs with a longer substituent can be characterized with better herbicidal activity in comparison with commercial products.

Inhibition of germination and early growth of rape seed (Brassica napus L.) by MCPA in anionic and ester form

MCPA (4-chloro-2-methylphenoxy) acetic acid is a common synthetic auxin used as a herbicide. The purpose of this study was to determine the effects of four new forms of MCPA being the herbicidal ionic liquids (HILs) with MCPA as an anion and two previously known formulations (potassium–sodium salt and 2-ethylhexyl ester) on seed germination and seedling development of winter oilseed rape (Brassica napus). Rape plants are susceptible to MCPA and volunteers can be a big problem in crop rotation. Seedling fresh weight and root length were quantified, mitotic activity, as well as lipid, starch, hydrogen peroxide and polyphenol contents were assessed by light and fluorescence microscopy and the computer-aided cytophotometer. In primary roots mitotic activity was almost completely inhibited under the influence of herbicides, cell elongation zones and root hair zones were significantly reduced, and a characteristic bolded root segment formed just above a meristem. In contrast to the traditional salt formulation the new HILs were weak inducers of hydrogen peroxide synthesis, but were potent stimulators of the synthesis of phenolic compounds and storage as well as emergency substances such as lipids and starch. All tested forms of MCPA caused strong phytotoxic effect on winter rape seedlings, but the tested HILs were more effective.