Determination of cereal herbicide residues in environmental samples by gas chromatography

Linking chemical surface water monitoring and pesticide regulation in selected European countries

The progress in chemical analytics and understanding of pesticide dynamics in surface waters allows establishing robust data on compounds with frequent exceedances of quality standards. The current chemical, temporal, and spatial coverage of the pesticide monitoring campaigns differs strongly between European countries. A questionnaire revealed differences in monitoring strategies in seven selected European countries; Nordic countries prioritize temporal coverage, while others focus on spatial coverage. Chemical coverage has increased, especially for non-polar classes like synthetic pyrethroids. Sweden combines monitoring data with agricultural practices for derived quantities, while the Netherlands emphasizes spatial coverage to trace contamination sources. None of the EU member states currently has established a process for linking chemical surface water monitoring data with regulatory risk assessment, while Switzerland has recently established a legally defined feedback loop. Due to their design and objectives, most strategies do not capture concentration peaks, especially 2-week composite samples, but also grab samples. Nevertheless, for substances that appear problematic in many data sets, the need for action is evident even without harmonization of monitoring programs. Harmonization would be beneficial, however, for cross-national assessment including risk reduction measures.

Investigation of the miRNA levels changes to acceptable daily intake dose pesticide mixture exposure on rat mesentery and pancreas

Consumers are constantly exposed to a variety of chemical mixtures as part of their everyday activities and lifestyle. Food, water and commercial products are only some examples of the possible ways people get exposed to these mixtures. However, following federal and local guidelines for risk assessment related to chemical exposure, risk analysis focuses on a single substance exposure scenario and not on a mixture, as in real life. Realizing the pronounced gap of this methodology, the real-life risk simulation scenario approach tries to address this problem by investigating the possible effect of long-term exposure to chemical mixtures closely resembling the actual circumstances of modern life. As part of this effort, this study aimed to identify the cumulative effects of pesticides belonging to different classes and commonly used commercial products on long-term exposure with realistic doses. Sprague Dawley rats were given a pesticide mix of active ingredients and formulation chemicals in a daily acceptable dose (ADI) and 10xADI for 90 days. Following thorough everyday documentation of possible side-effects, after 90 days all animals were sacrificed and their organs were examined. Exposure to pesticides particularly affects the miRNA levels at that point will provide us with more information about whether they can be potential biomarkers.

Miniaturized multiresidue method for the analysis of pesticides and persistent organic pollutants in non-target wildlife animal liver tissues using GC-MS/MS

In order to gain a better insight into pesticide and pollutant exposure of small (non-target) wildlife animals, a QuEChERS sample preparation method was first developed for 5 g liver tissues (e.g. hedgehog samples) and then downscaled for the analysis of 100 mg liver tissues (e.g. bat samples). The optimized (micro) QuEChERS methods used 1% acetic acid in acetonitrile as organic solvent for liquid-liquid extraction (LLE) and salting out was performed with anhydrous magnesium sulfate and sodium acetate (4:1). After a freezing-out step, sample clean-up was carried out with anhydrous magnesium sulfate, PSA, C₁₈, and GCB (150:25:20:5). Overall, 209 pesticides and persistent organic pollutants (POPs) can be analysed within each sample with gas chromatography coupled to tandem mass spectrometry (GC-MS/MS). Both methods were validated with representative analytes according to the European Commission guideline SANTE/12682/2019. Limits of quantification were between 1 and 20 μg kg^-1, and the methods proved to be linear up to 400 μg kg^-1. Additionally, the analytes delivered satisfactory results regarding recovery and precision. As proof of concept, samples of six hedgehog livers were analysed with both methods to prove the accuracy of the micro QuEChERS method. Additionally, six livers of different bat species were analysed with the downscaled method. The newly developed micro QuEChERS method for multiresidue analysis requires only minute amounts of biomaterial and represents a sophisticated novel technique for determining the exposure of small wildlife animals to different contaminants.

Response of soil bacterial and fungal community structure succession to earthworm addition for bioremediation of metolachlor

Synergistic biodegradation of earthworms and soil microorganisms plays a key role in the removal of organic pollutants in soil, yet microbially mediated processes remain unclear, especially regarding the succession of soil microbial interactions. Herein, soil biochemical evaluation, microbial community characterization, and interaction network construction were combined to understand the mechanisms dominating microbial community succession during synergistic bioremediation of metolachlor-polluted soils. The results of the network analysis indicated that metolachlor could render more complex relations but weaker connection strength among soil microorganisms. The addition of earthworms significantly alleviated the stress of metolachlor on soil microbial interactions and resulted in the restoration of interactions to a great extent. Additionally, the soil physicochemical properties, enzyme activities, and microbial community changed greatly with the addition of metolachlor and earthworms. Some soil microorganisms became significantly correlated with soil properties, metolachlor concentrations, and enzyme activities. These results, dominated by the succession of soil microbial communities, provide a new perspective for assessing the remediation effect of contaminated soil by organic pollutants.

Pesticide residue concentration in soil following conventional and Low-Input Crop Management in a Mediterranean agro-ecosystem, in Central Greece

The present study was focused on the comparative evaluation of pesticide residues, determined in soil samples from Kopaida region, Greece before and after the implementation of Low-Input Crop Management (LCM) protocols. LCM has been suggested as an environmental friendly plant protection approach to be applied on crops growing in vulnerable to pollution ecosystems, with special focus on the site specific problems. In the case of the specific pilot area, the vulnerability was mainly related to the pollution of water bodies from agrochemicals attributed to diffuse pollution primarily from herbicides and secondarily from insecticides. A total of sixty-six soil samples, were collected and analyzed during a three-year monitoring study and the results of the determined pesticide residues were considered for the impact evaluation of applied plant protection methodology. The LCM was developed and applied in the main crops growing in the pilot area i.e. cotton, maize and industrial tomato. Herbicides active ingredients such as ethalfluralin, trifluralin, pendimethalin, S-metolachlor and fluometuron were detected in most samples at various concentrations. Ethalfluralin, which was the active ingredient present in the majority of the samples ranged from 0.01 μg g(-1) to 0.26 μg g(-1) soil dry weight. However, the amount of herbicides measured after the implementation of LCM for two cropping periods, was reduced by more than 75% in all cases. The method of analysis was based on the simultaneous extraction of the target compounds by mechanical shaking, followed by liquid chromatography mass spectrometric and gas chromatography electron capture (LC-MS/MS and GC-ECD) analysis.

Development of multi-residue analysis of herbicides in cereal grain by ultra-performance liquid chromatography-electrospray ionization-mass spectrometry

A rapid and sensitive method was developed for the determination of 50 herbicides in cereal grain by ultra-performance liquid chromatography-electrospray ionization-mass spectrometry (UPLC-ESI-MS). Using acetonitrile effectively extracted 22 kinds of triazine and other basic herbicides, and using 90:10 v/v acetonitrile-phosphate buffer (pH = 7.5) effectively extracted other 28 herbicides. Chromatographic separation was achieved using gradient elution with acetonitrile-water as a mobile phase for 22 triazine and phenylurea herbicides and with 5mM ammonium acetate aqueous solution containing 0.1% formic acid-acetonitrile as a mobile phase for other 28 herbicides. Using matrix-matched standard calibration curve effectively reduced the indirect matrix effects, ensured accurate quantification for these herbicides. The response was linear over two orders of magnitude with a correlation coefficients (r(2)) higher than 0.992. The limits of quantification for the herbicides varied from 0.2 to 25.6 μg kg(-1). The intra- and inter-day precisions (relative standard deviation, RSD) were 2.2-9.3% and 5.7-17.1%, respectively. The recovery varied from 61.6% to 110% with the RSD of 1.6-11.8%. Analyzing soybean, corn and wheat samples from 17 counties evaluated this method. The developed and validated method has high sensitivity, satisfactory recovery and precision, can ensure the multi-class multi-residue analysis at low μg kg(-1) level for the most herbicides in cereal grain.

Fabrication of an electrochemical sensor based on computationally designed molecularly imprinted polymers for determination of cyanazine in food samples

A computational approach was used for screening functional monomers and polymerization solvent in the rational design of molecularly imprinted polymers (MIPs). It was based on the comparison of the binding energy of the complexes between the template and functional monomers. On the basis of computational results, acrylamide (AAM) and toluene were selected as functional monomer and polymerization solvent, respectively. The MIP, embedded in the carbon paste electrode, functioned as a selective recognition element and pre-concentrator agent for cyanazine determination by using cathodic stripping voltammetric method. The MIP-CP electrode showed very high recognition ability in comparison with NIP-CPE. Some parameters affecting the sensor response were optimized, and then the calibration curve was plotted. A dynamic linear range of 5.0-1000 nM was obtained. The detection limit of the sensor was calculated as 3.2 nM. This sensor was successfully used for cyanazine determination in food samples.

Adsorption and desorption processes of MCPA in Polish mineral soils

Studies on the adsorption and desorption of MCPA (4-chloro-2-methylophenoxyacetic acid) were performed in soil horizons of three representative Polish agricultural soils. The Hyperdystric Arenosol, the Haplic Luvisol and the Hypereutric Cambisol were investigated in laboratory batch experiments. Initially, both the adsorption and desorption proceeded rapidly, and either the equilibrium was reached after approximately 30 min or the process slowed down and continued at a slow rate. In the latter case, the equilibrium was reached after 8 hours. Data on the adsorption/desorption kinetics fitted well to the two-site kinetic model. The measured sorption and desorption isotherms were of L-type. The sorption distribution coefficients (K(ads) (d)) were in the range of 0.75--0.97 for Ap soil horizons and significantly lower in deeper soil layers. The corresponding desorption coefficients (K(des) (d)) were higher and ranged from 1.02 to 2.01. Both the adsorption and desorption of MCPA in all soil horizons was strongly and negatively related to soil pH. It appears that hydrophobic sorption plays a dominant role in the MCPA retention in topsoils whereas hydrophilic sorption of MCPA anions is the dominant adsorption mechanism in subsoils.

Simultaneous determination of three acidic herbicide residues in food crops using HPLC and confirmation via LC-MS/MS

2,4-D, dicamba and 4-CPA with auxin-like activity have been intensively used in agriculture, for the control of unwanted broadleaf weeds. An analytical method involving HPLC coupled with UVD was developed for the simultaneous analysis of these three analytes in Chinese cabbage, apple and pepper fruits (representative non-fatty samples) and brown rice and soybean (representative fatty samples) using liquid-liquid partitioning and column cleanup procedures. The residues were confirmed via tandem mass spectrometry (MS/MS) in ion electrospray ionization (ESI) mode. The standard curves were linear over the range of the tested concentrations (0.25-10 microg/mL), as shown by a marked linearity in excess of 0.9999 (r(2) ). The average recoveries (mean, n = 3) ranged from 94.30 to 102.63 in Chinese cabbage, from 94.76 to 108.47 in apple, from 97.52 to 102.27 in pepper, from 76.19 to 101.90 in brown rice, and from 74.60 to 107.39 in soybean. The relative standard deviations (RSDs) were <9% in all tested matrices. The limits of detection and quantitation were 0.006 and 0.02 mg/kg, respectively. Samples purchased from local markets were analyzed to evaluate the applicability of the methods developed herein. The concentration of the 2,4-D residue was measured at 0.102 mg/kg in the soybean sample; however, this level is exactly the same MRL set by the Korea Food and Drug Administration. This developed method deserves full and complete consideration, as it clearly displays the sensitivity, accuracy and precision required for residue analysis of 2,4-D, dicamba and 4-CPA in food crops.

Procedures for analysis of atrazine and simazine in environmental matrices

There is an ongoing need to monitor soil and trophic chain samples for residues of triazine herbicides, particularly atrazine and simazine, because these herbicides are among the most used members of their class, are toxic, can be persistent, and are widely distributed in the environment. The main purpose of this review is to provide an overview of principle techniques and approaches used in analyzing atrazine, simazine, and other triazine herbicide residues in environmental matrices. The methods covered generally provide low detection limits, acceptable levels of matrix interferences, and are relatively fast and inexpensive. Atrazine and simazine are popular herbicides used to control a variety of broad leaf and grassy weeds in agriculture and on industrial sites. Because they are widely and frequently used, the environmental contamination of these compounds is considerable. Atrazine, simazine, and other triazines have the ability to translocate in ecosystems. When this occurs, it is often necessary to monitor their residue content in soils, vegetation, biota, and water. There is a vast literature available that addresses the extraction and clean-up of soil, vegetation, animal tissue, and animal fluid samples; unfortunately, few of these publications compare the effectiveness of results obtained on similar matrices. In this review we endeavor to review and provide comparative information on methods dedicated to determining residues of atrazine, simazine, and other triazines in several environment matrices: soil, plants, animal tissues, and water.

Study of the degradation of the herbicides 2,4-D and MCPA at different depths in contaminated agricultural soil

Two phenoxyacid herbicides (2,4-D and MCPA) and their six corresponding phenols were determined in soil by using gas chomatography with electron impact mass spectrometry (GC/MS) for confirmation/quantitation. An automatic extraction (leaching), preconcentration, and cleanup (sorption) module was developed to extract the eight compounds from soil. The average recovery of all species, spiked to soil at microg/kg-mg/kg levels, was 95% (average standard deviation +/- 5%). A plot of agricultural clayey soil (approximately 12 m2) was contaminated with both herbicides (approximately 96 g/m3, depth 10 cm, density 1.23 g/cm3) and irrigated with (17 mm) at variable time intervals. Both herbicides and their corresponding phenol compounds were monitored at different soil depths over a 50 day period. The degradation of both herbicides in the surface layer (t(1/2) approximately 5 days) is a result of photodecomposition and microbial action; in the deeper layers, the degradation products occur in lower proportions by effect of leaching and are also the result of microbial action. The six phenol metabolites are only detected in the surface layer as they form preferentially by photodecomposition. The main metabolites (viz. 2,4-DCP for 2,4-D and 4-C-2-MP for MCPA) are formed within 24 h after the soil is contaminated; their concentration peaks are at day 8 in the absence of irrigation.

Determination of bentazone, dichlorprop, and MCPA in different soils by sodium hydroxide extraction in combination with solid-phase preconcentration

A method for the extraction of bentazone, dichlorprop, and MCPA in three selected Norwegian soils of different textures is described. Initially three different extraction methods were tested on one soil type. All methods gave recoveries >80% for the pesticide mixture, but extraction with sodium hydroxide in combination with solid-phase preconcentration was used for further recovery tests with soils of different properties spiked at four herbicide concentration levels (0.001-10 microg/g of wet soil). The method was rapid and easy and required a minimum of organic solvents. The recoveries were in the range of 82-109, 80-123, and 45-91% for the soils containing 1.4 (Hole), 2.5 (Kroer), and 37.8% (Froland) organic carbon, respectively. Limits of quantification using GC-MS were 0.0003 microg/g of wet soil for bentazone and 0.0001 microg/g of wet soil for both dichlorprop and MCPA.

Laboratory degradation studies of bentazone, dichlorprop, MCPA, and propiconazole in Norwegian soils

Laboratory degradation studies were performed in Norwegian soils using two commercial formulations (Tilt and Triagran-P) containing either propiconazole alone or a combination of bentazone, dichlorprop, and MCPA. These soils included a fine sandy loam from Hole and a loam from Kroer, both of which are representative of Norwegian agricultural soils. The third soil was a highly decomposed organic material from the Froland forest. A fourth soil from the Skuterud watershed was used only for propiconazole degradation. After 84 d, less than 0.1% of the initial MCPA concentration remained in all three selected soils. For dichlorprop, the same results were found for the fine sandy loam and the organic-rich soil, but in the loam, 26% of the initial concentration remained. After 84 d, less than 0.1% of the initial concentration of bentazone remained in the organic-rich soil, but in the loam and the fine sandy loam 52 and 69% remained, respectively. Propiconazole was shown to be different from the other pesticides by its persistence. Amounts of initial concentration remaining varied from 40, 70, and 82% in the reference soils after 84 d for the organic-rich soil, fine sandy loam, and loam, respectively. The organic-rich soil showed the highest capacity to decompose all four pesticides. The results from the agricultural soils and the Skuterud watershed showed that the persistence of propiconazole was high. Pesticide degradation was approximated to first-order kinetics. Slow rates of degradation, where more than 50% of the pesticide remained in the soil after the 84-d duration of the experiment, did not fit well with first-order kinetics.

Analysis of herbicide residues in cereals, fruits and vegetables

The determination of herbicide residues in cereals, fruits and vegetables by chromatographic methods is reviewed. The principal chemical groups of herbicides, like phenoxyacids, benzonitriles, ureas, triazines, dinitroanilines, chloroacetamides, carbamates, uracils, glyphosate and bipyridylium compounds, are considered. This review briefly provides some basic information on food sample extraction, clean-up, derivatization and determination of herbicide residues.

Simultaneous determination of acidic and non-acidic pesticides in natural waters by liquid chromatography-mass spectrometry

There is increasing interest and demand for real multi-residue methods able to simultaneously determine pesticides with a broad spectrum of chemical characteristics in environmental and biological matrices. A method based on solid-phase extraction with a Carbograph 4 cartridge and liquid chromatography with electrospray mass spectrometry (LC-ES-MS) enabling simultaneous determination of non-acidic and acidic pesticides in real water samples is described. On repeatedly (n=5) extracting 4 l of drinking water (spike level 50 ng/l), 2 l of ground water (spike level 100 ng/l) and 1 l of river water (spike level 200 ng/l), recovery of 26 base/neutral pesticides and 13 acidic pesticides were equal to or better than 80%, except for carbendazim (67%), butocarboxim (73%), aldicarb (75%) and molinate (77%). Relative standard deviations ranged between 4 and 15%. Final extracts containing acidic and non-acidic pesticides were analyzed in a single chromatographic run while the ES-MS system was operated in both positive and negative ion modes. With the aim of finding the best operating conditions, in terms of sensitivity, the pH of the LC eluent was varied in the 2.9-8.4 range. Altogether, the best results were obtained by using an LC eluent containing 1 mmol/l formic acid. Over the entire pH range considered, well shaped peaks for both basic and acidic analytes were achieved by the use of a new generation LC column. By extracting selected ion current profiles from the total ion current mass chromatogram relative to analysis of 4 l of drinking water spiked with 50 ng/l of each of the 39 analytes, estimated limits of detection ranged between 0.05 and 1.5 ng/l, except for propyzamide (8 ng/l) and 2,4-DB (3 ng/l).

Determination of chlorophenoxy acid herbicides in water by in situ esterification followed by in-vial liquid-liquid extraction combined with large-volume on-column injection and gas chromatography-mass spectrometry

A new approach for rapidly analysing chlorophenoxy acid herbicides in water is presented. The chlorinated acids are derivatised with dimethyl sulphate in the water sample itself (800 microl) and, next, the methyl esters are extracted with 800 microl of n-hexane. A 200-microl volume of the extract is injected into the GC-MS system. The miniaturisation of both the methylation and extraction steps could be implemented because of the use of large-volume on-column injection and mass spectrometric detection. The optimisation of the methylation reaction for the simultaneous determination of (3,6-dichloro-2-methoxy)benzoic acid, (2-methyl-4-chlorophenoxy)- and (2,4-dichlorophenoxy)acetic acids, (+/-)-2-(4-chloro-2-methylphenoxy)- and 2-(2,4-dichlorophenoxy)propanoic acids and 4-(4-chloro-2-methylphenoxy)- and 4-(2,4-dichlorophenoxy)butyric acids showed that tetrabutylammonium salts act as catalysts. Addition of sodium hydroxide was required to obtain quantitative reaction yields for 4-(4-chloro-2-methylphenoxy)- and 4-(2,4-dichlorophenoxy)butyric acids. The methylation-cum-extraction procedure takes only 3 min per sample for a batch of seven samples. Linear calibration plots were obtained for the complete procedure and the limits of detection were of 10-60 ng/l with a signal-to-noise ratio (S/N) of 6. Relative standard deviations ranged from 8 to 15% (n=7) for analyte concentrations of 0.5 microg/l in surface water.