Orthogonal array optimization of a multiresidue method for cereal herbicides in soils

The status of organochlorine pesticide contamination in Greek agricultural soils: the ghost of traditional agricultural history

Inadequate information regarding pesticide contamination in Greek agricultural soils is currently available, while national soil monitoring programs have not been initiated yet. The aim of the present study was to assess the levels, compositions, and distribution of thirty three organochlorine pesticides (OCPs) in Greek agricultural soils, due to the environmental threat posed by these compounds, even after decades from their abrogation from the market. Determination of the organochlorine pesticides was achieved using gas-chromatography-mass spectrometry, following a QuEChERS sample preparation method. A total of 60 soil samples, from two soil horizons (up to 60 cm), were obtained from agricultural lands in Greece throughout 2019-2020. The major findings presented DDTs, γ-HCH, alachlor, and 4,4- DCBP in the examined soil samples, with DDTs being the major compounds with their maximum cumulative concentration (ΣDDTs) reaching 1273.4 μg kg-1 d.w. Compositional profile and diagnostic ratios suggested that the occurrence of DDT residues was due to historical inputs. Most of the samples did not exceed the target values set by the Netherlands and Canadian guidelines for DDTs in soil; however, there was one exception in the case of Aegina Island. Finally, based on the environmental exposure assessment conducted, the vast majority of the analytes presented lower concentrations compared to the predicted environmental concentrations, with an exemption for DDE metabolite where the measured and predicted concentrations were almost equal.

Monitoring of glyphosate and AMPA in soil samples from two olive cultivation areas in Greece: aspects related to spray operators activities

The persistence of glyphosate and its primary metabolite AMPA (aminomethylphosphonic acid) was monitored in two areas in Southern Greece (Peza, Crete and Chora Trifilias, Peloponnese) with a known history of glyphosate use, and the levels of residues were linked to spray operators' activities in the respective areas. A total of 170 samples were collected and analysed from both areas during a 3-year monitoring study. A new method (Impact Assessment Procedure - IAP) designed to assess potential impacts to the environment caused by growers' activities, was utilised in the explanation of the results. The level of residues was compared to the predicted environmental concentrations in soil. The ratio of the measured concentrations to the predicted environmental concentrations (MCs/PECs) was > 1 in Chora the first 2 years of sampling and < 1 in the third year, whilst the MCs/PECs ratio was < 1 in Peza, throughout the whole monitoring period. The compliance to the instructions for best handling practices, which operators received during the monitoring period, was reflected in the amount of residues and the MCs/PECs ratio in the second and especially the third sampling year. Differences in the level of residues between areas as well as sampling sites of the same area were identified. AMPA persisted longer than the parent compound glyphosate in both areas.

Occurrence and distribution of trifluralin, ethalfluralin, and pendimethalin in soils used for long-term intensive cotton cultivation in central Greece

In the present study, a soil monitoring program was undertaken in Greek cotton cultivated areas in 2012. Twenty-seven soil samples were collected from the entire Thessaly plain in early summer of 2012, corresponding to approximately three months (current use of pendimethalin), up to one year (for the banned ethalfluralin), and three years (for the also banned trifluralin), after the last dinitroaniline application. Low but not negligible levels of dinitroanilines were detected, ranging from 0.01 to 0.21 μg g^-1 d.w. for trifluralin and 0.01-0.048 μg g^-1 d.w. for pendimethalin, respectively. Trifluralin was the herbicide most frequently detected (44.4%). The high historic application of trifluralin and its high persistence and accumulation potential is in line with the abundance of the detected residues. The present data indicate that soil samples contain extractable residues of banned trifluralin, but based on the comparison of the theoretical PECplateau for trifluralin (0.277 µg g^-1) and the maximum Measured Environmental Concentration, it was concluded that the detected residues should be attributed to previous years' application. The latter suggested the need for continual monitoring of the dinitroaniline family of pesticides, including the banned substances, aiming thus to an improved environmental profile for agricultural areas.

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.

Thiacloprid suspension formula optimization by a response surface methodology

A response surface methodology with four factors at five levels was adopted to optimize a model thiacloprid suspension concentrate.

Laminaria japonica Extract, an Inhibitor of Clavibater michiganense Subsp. Sepedonicum

Bacterial ring rot of potato is one of the most serious potato plant and tuber diseases. Laminaria japonica extract was investigated for its antimicrobial activity against Clavibater michiganense subsp. sepedonicum (Spieckermann & Kotthoff) Davis et al., the causative agent of bacterial ring rot of potato. The results showed that the optimum extraction conditions of antimicrobial substances from L. japonica were an extraction temperature of 80°C, an extraction time of 12 h, and a solid to liquid ratio of 1∶25. Active compounds of L. japonica were isolated by solvent partition, thin layer chromatography (TLC) and column chromatography. All nineteen fractionations had antimicrobial activities against C. michiganense subsp. sepedonicum, while Fractionation three (Fr.3) had the highest (P<0.05) antimicrobial activity. Chemical composition analysis identified a total of 26 components in Fr.3. The main constituents of Fr.3 were alkanes (80.97%), esters (5.24%), acids (4.87%) and alcohols (2.21%). Antimicrobial activity of Fr.3 against C. michiganense subsp. sepedonicum could be attributed to its ability to damage the cell wall and cell membrane, induce the production of reactive oxygen species (ROS), increase cytosolic Ca2+ concentration, inhibit the glycolytic pathway (EMP) and tricarboxylic acid (TCA) cycle, inhibit protein and nucleic acid synthesis, and disrupt the normal cycle of DNA replication. These findings indicate that L. japonica extracts have potential for inhibiting C. michiganense subsp. sepedonicum.

Protective effect of Polygonum orientale L. extracts against Clavibater michiganense subsp. sepedonicum, the causal agent of bacterial ring rot of potato

The Polygonum orientale L. extracts were investigated for antibacterial activity against Clavibater michiganense subsp. sepedonicum (Spieckermann & Kotthoff) Davis et al., the causal agent of a serious disease called bacterial ring rot of potato. The results showed that the leaf extracts of P. orientale had significantly (p<0.05) greater antibacterial activity against C. michiganense subsp. sepedonicum than root, stem, flower extracts in vitro. According to the results of single factor experiments and L(27)3(13) orthogonal experiments, optimum extraction conditions were A1B3C1, extraction time 6 h, temperature 80°C, solid to liquid ratio 1∶10 (g:mL). The highest (p<0.05) antibacterial activity was observed when pH was 5, excluding the effect of control. The extracts were stable under ultraviolet (UV). In vivo analysis revealed that 50 mg/mL of P. orientale leaf extracts was effective in controlling decay. Under field conditions, 50 mg/mL of P. orientale leaf extracts also improved growth parameters (whole plant length, shoot length, root length, plant fresh weight, shoot fresh weight, root fresh weight, dry weight, and number of leaves), in the 2010 and 2011 two growing seasons. Further solvent partition assays showed that the most active compounds were in the petroleum ether fractionation. Transmission electron microscopy (TEM) showed drastic ultrastructural changes caused by petroleum ether fractionation, including bacterial deformation, electron-dense particles, formation of vacuoles and lack of cytoplasmic materials. These results indicated that P. orientale extracts have strong antibacterial activity against C. michiganense subsp. sepedonicum and a promising effect in control of bacterial ring rot of potato disease.

Nano-scale liquid chromatography/mass spectrometry and on-the-fly orthogonal array optimization for quantification of therapeutic monoclonal antibodies and the application in preclinical analysis

Therapeutic monoclonal antibodies (mAbs) constitute a group of highly effective agents for treating various refractory diseases. Nonetheless it is challenging to achieve selective and accurate quantification of mAb in pharmaceutical matrices, which is required by PK studies. Liquid chromatography/mass spectrometry under selected reaction monitoring mode (LC/SRM-MS) is emerging as an attractive alternative to immunoassays because of the high specificity and multiplexing capacity it provides, but may fall short in terms of sensitivity, reliability and quantitative accuracy. Moreover, the strategy for optimization of the MS conditions for many candidates of signature peptides (SP) and the selection of the optimal SP for quantification remains elusive. In this study, we employed a suite of technical advances to overcome these difficulties, which include: (i) a nano-LC/SRM-MS approach to achieve high analytical sensitivity, (ii) a high-resolution nano-LC/LTQ/Orbitrap for confident identification of candidate peptides, (iii) an on-the-fly orthogonal array optimization (OAO) method for the high-throughput, accurate and reproducible optimization for numerous candidate peptides in a single LC/MS run without using synthesized peptides, (iv) a comprehensive evaluation of stability of candidates in matrix using the optimized SRM parameters, (v) the use of two unique SP for quantification of one mAb to gauge possible degradation/modification in biological system and thus enhancing data reliability (e.g. rejection of data if the deviation between the two SP is greater than 25%) and (vi) the utilization of purified target protein as the calibrator to eliminate the risk of severe negative biases that could occur when a synthesized peptide is used as calibrator. To show a proof of concept, this strategy is applied in the quantification of cT84.66, a chimeric, anti-CEA antibody, in preclinical mouse models. A low detection limit of the mAb down to 3.2 ng/mL was achieved, which is substantially more sensitive than established immunoassay methods for anti-CEA antibodies. The quantitative method showed good linearity (within the range of 12.9 ng/mL to 32.3 μg/mL in plasma), accuracy and precision. Additionally, the ultra-low sample consumption (2 μL plasma per preparation) permits the acquisition of an entire set of time course data from the same mouse, which represents a prominent advantage for PK study using small-animal models. The developed method enabled an accurate PK investigation of cT84.66 in mice following intravenous and subcutaneous administrations at relatively low doses over an extended period of time. The strategy employed in this study can be easily adapted to the sensitive and accurate analysis of other mAb and therapeutic proteins.

A rapid, reproducible, on-the-fly orthogonal array optimization method for targeted protein quantification by LC/MS and its application for accurate and sensitive quantification of carbonyl reductases in human liver

Liquid chromatography (LC)/mass spectrometry (MS) in selected-reactions-monitoring (SRM) mode provides a powerful tool for targeted protein quantification. However, efficient, high-throughput strategies for proper selection of signature peptides (SP) for protein quantification and accurate optimization of their SRM conditions remain elusive. Here we describe an on-the-fly, orthogonal array optimization (OAO) approach that enables rapid, comprehensive, and reproducible SRM optimization of a large number of candidate peptides in a single nanoflow-LC/MS run. With the optimized conditions, many peptide candidates can be evaluated in biological matrixes for selection of the final SP. The OAO strategy employs a systematic experimental design that strategically varies product ions, declustering energy, and collision energy in a cycle of 25 consecutive SRM trials, which accurately reveals the effects of these factors on the signal-to-noise ratio of a candidate peptide and optimizes each. As proof of concept, we developed a highly sensitive, accurate, and reproducible method for the quantification of carbonyl reductases CBR1 and CBR3 in human liver. Candidate peptides were identified by nano-LC/LTQ/Orbitrap, filtered using a stringent set of criteria, and subjected to OAO. After evaluating both sensitivity and stability of the candidates, two SP were selected for quantification of each protein. As a result of the accurate OAO of assay conditions, sensitivities of 80 and 110 amol were achieved for CBR1 and CBR3, respectively. The method was validated and used to quantify the CBRs in 33 human liver samples. The mean level of CBR1 was 93.4 +/- 49.7 (range: 26.2-241) ppm of total protein, and of CBR3 was 7.69 +/- 4.38 (range: 1.26-17.9) ppm. Key observations of this study: (i) evaluation of peptide stability in the target matrix is essential for final selection of the SP; (ii) utilization of two unique SP contributes to high reliability of target protein quantification; (iii) it is beneficial to construct calibration curves using standard proteins of verified concentrations to avoid severe biases that may result if synthesized peptides alone are used. Overall, the OAO method is versatile and adaptable to high-throughput quantification of validated biomarkers identified by proteomic discovery experiments.

Soil-dissipation kinetics of twelve herbicides used on a rain-fed barley crop in Spain

This study evaluated the dissipation kinetics under actual field conditions of twelve herbicides in a typical xerofluvent soil in Castilla y León (north central Spain) sustaining barley. The type of soil selected was that typically used in the Castilla y León region to cultivate barley under a rain-fed alternating crop-fallow rotation regimen. Treatments were conducted in spring as two replicates and the soil was sampled every day during the first week, once a week for the following few weeks and thereafter once every month. Soil samples were extracted with a suitable mixture of acetone, water and acetic acid (30:7.5:0.3) before their analysis by GC-MS (gas chromatography-mass spectrometry). Dissipation of the herbicides was well described by a biphasic kinetics pattern. The dissipation times DT50 and DT90 were in general lower than those reported in the literature, owing to a high initial dissipation rate because of volatilization and photolysis processes caused by high environmental temperatures. Herbicide degradation was also enhanced by their lack of sorption by this low colloid-content soil. However, the most persistent herbicides, triallate, flamprop, pendimethalin, terbutryn, and isoproturon, remained for 286 to 372 days in the soil, because low water and organic carbon content impaired microbial growth. In contrast, the phenoxy acid herbicides dissipated rapidly, with no detectable residues detected on harvesting the crop.