Stereoselective Analysis and Dissipation of Propiconazole in Wheat, Grapes, and Soil by Supercritical Fluid Chromatography-Tandem Mass Spectrometry

Study on the Bioactivity, Toxicity, Stereoselective Fate, and Risk Assessment of Chiral Fungicide Isopyrazam in Five Kinds of Fruits and Vegetables

Isopyrazam (IPZ) is a new chiral fungicide. For bioactivity, there was a 3.37-1578 times difference among the four stereoisomers. For Alternaria alternata and Phoma multirostrata, cis-(1S,4R,9S)-IPZ had the greatest activity. Using cis-IPZ might improve the efficacy and reduce the dosage of the racemate by 54.7-72.2% for A. alternata and P. multirostrata. To zebrafish, trans-IPZ showed the highest acute toxicity (LC50, 0.096 mg/L). The degradation half-lives of IPZ stereoisomers in the five crops ranged from 3.50 to 15.2 days. Cis-IPZ was preferentially degraded in grape, pear, and celery. The residual concentrations of IPZ in grape and celery were still higher than the maximum residue limit, and the acute and chronic dietary intake risks of IPZ in celery were unacceptable (RQa: 146-250%, HQ: 117-200%), which were worthy of further researching. Based on the research results, it is safer and more reasonable to use IPZ in the form of a racemate with a high ratio of cis-IPZ.

Metabolism of a fungicide propiconazole by Cunninghamella elegans ATCC36112

The metabolic breakdown of propiconazole by fungi was examined, and it was found that the microbial model (Cunninghamella elegans ATCC36112) efficiently degrades the triazole fungicide propiconazole through the action of cytochrome P450. This enzyme primarily facilitates the oxidation and hydrolysis processes involved in phase I metabolism. We observed major metabolites indicating hydroxylation/oxidation of propyl groups of propiconazole. Around 98% of propiconazole underwent degradation within a span of 3 days post-treatment, leading to the accumulation of five metabolites (M1-M5). The experiments started with a preliminary identification of propiconazole and its metabolites using GC-MS. The identified metabolites were then separated and identified by in-depth analysis using preparative UHPLC and MS/MS. The metabolites of propiconazole are M1 (CGA-118245), M2(CGA-118244), M3(CGA-136735), M4(GB-XLIII-42-1), and M5(SYN-542636). To further investigate the role of key enzymes in potential fungi, we treated the culture medium with piperonyl butoxide (PB) and methimazole (MZ), and then examined the kinetic responses of propiconazole and its metabolites. The results indicated a significant reduction in the metabolism rate of propiconazole in the medium treated with PB, while methimazole showed weaker inhibitory effects on the metabolism of propiconazole in the fungus C. elegans.

Stereoselective study on chiral fungicide metconazole in four kinds of fruits: Absolute configuration, SFC-MS/MS enantioseparation, degradation and risk assessment

Metconazole is a novel chiral fungicide with two chiral carbon atoms, but the research on its stereoselective behavior is limited. Therefore, the stereoselective behaviors of metconazole in four fruits, including grape, peach, pear and jujube, were summarized in this study. After determining the absolute configuration of metconazole stereoisomers, a chiral separation method through supercritical fluid chromatography/tandem triple quadrupole mass spectrometry was first developed, which combined an improved QuEChERS method obtained the recoveries of 71.6-113 % with RSD ≤ 19.8 %. The LOD and LOQ were 4.30-95.9 and 10.5-143.2 ng/kg, respectively. Different stereoselective and diastereoselective behaviors were observed in four fruits. Dietary risk assessments of rac-metconazole were performed in populations with different ages and genders. Both acute (RQa, 0.0124-0.140 %) and chronic (HQ, 0.0234-0.0794 %) intake risks were acceptable. The results of this study would contribute to more complete risk assessments of metconazole and provide data for chiral studies.

Stereoselective analysis of chiral pesticides: a review

Chiral organic pollutants, including pesticides, herbicides, medicines, flame retardants, and polycyclic musk, represent a significant threat to both the environment and human health. The presence of asymmetric centers in the structure of chiral pesticides introduces stereoisomers with distinct distributions, fates, biomagnification capacities, and cytotoxicities. In aquatic environments, pesticides, as persistent/pseudo-persistent compounds, have been detected in substantial quantities, posing severe risks to non-target species and, ultimately, public health through water supply and food exposures. In response to this environmental challenge, stereoselective analytical methods have gained prominence for the identification of pesticide/drug enantiomers in recent years. This review examines the environmental impact of chiral pesticides, emphasizing the distinct biological activities and distribution patterns of their stereoisomers. By highlighting the advancements in liquid chromatography for enantiomeric analysis, the review aims to underscore the urgent need for a comprehensive understanding of these pollutants to facilitate informed remediation strategies and ensure the safer dispersal of chiral organic pollutants in the environment, thereby addressing the potential risks they pose to ecosystems and human health. Future research should focus on developing sustainable and efficient methodologies for the precise analysis of stereoisomers in complex matrices, particularly in sewage water, emphasizing the importance of sewage processing plants in ensuring water quality.

Comprehensive Stereoselectivity Assessment of Toxicokinetics, Tissue Distribution, Cytotoxicity, and Environmental Fate of Chiral Pesticide Propiconazole

Propiconazole (PRO) has been widely used in the treatment of fungal infection in fruits, vegetables, cereals, and seeds. In this study, a newly established chiral liquid chromatography tandem mass spectrometry method was applied to the systemic stereoselectivity evaluation of PRO enantiomers, including toxicokinetics, tissue distributions, cytotoxicity, accumulation, and degradation. Our results showed that both trans (+)-2S,4S-PRO and cis (-)-2S,4R-PRO had lower Cmax and AUC0-∞ and higher CLz/F values in plasma and lower accumulation concentrations in the liver, heart, and brain. In cytotoxic assays, cis (-)-2S,4R-PRO exhibited the lowest cytotoxicity in PC12 neuronal, N9 microglia, SH-SY5Y neuroblastoma, and MRC5 lung fibroblast cell lines. Moreover, the Eisenia fetida incubation experiment revealed that the accumulations of both trans (+)-2S,4S-PRO and cis (-)-2S,4R-PRO were higher than those of their antipodes in E. fetida. In summary, our findings first suggested that the application of cis (-)-2S,4R-PRO for agriculture would hugely reduce the environmental risk.

Enantioselective Behaviors of Chiral Pesticides and Enantiomeric Signatures in Foods and the Environment

Unreasonable application of pesticides may result in residues in the environment and foods. Chiral pesticides consist of two or more enantiomers, which may exhibit different behaviors. This Review intends to provide progress on the enantioselective residues of chiral pesticides in foods. Among the main chiral analytical methods, high performance liquid chromatography (HPLC) is the most frequently utilized. Most chiral pesticides are utilized as racemates; however, due to enantioselective dissipation, bioaccumulation, biodegradation, and chiral conversion, enantiospecific residues have been found in the environment and foods. Some chiral pesticides exhibit strong enantioselectivity, highlighting the importance of evaluation on an enantiomeric level. However, the occurrence characteristics of chiral pesticides in foods and specific enzymes or transport proteins involved in enantioselectivity needs to be further investigated. This Review could help the production of some chiral pesticides to single-enantiomer formulations, thereby reducing pesticide consumption as well as increasing food production and finally reducing human health risks.

Degradation Dynamics and Residue Analysis of Four Propiconazole Stereoisomers in "Fengtang" Plum during Storage by LC-MS/MS

Herein, an accurate and sensitive method was developed for detecting four stereoisomers of propiconazole in "Fengtang" plum by LC-MS/MS. The mean recovery of four propiconazole stereoisomers ranged from 79.42 to 104.10% at three adding levels with reasonable RSD of 1.54-11.68%, and the LOD and LOQ of the four stereoisomers was 0.0005 mg/kg and 0.004 mg/kg, respectively. In addition, the residue and selective degradation of propiconazole stereoisomers in plums were investigated by storage at 20 °C and 4 °C. The half-lives of propiconazole stereoisomeric during storage were 9.49-15.40 d at 20 °C, and 21.00-28.88 d at 4 °C. The degradation of (2R,4R)-propiconazole and (2R,4S)-propiconazole in stored plums was slightly slower than that of the corresponding enantiomers (2S,4S)-propiconazole and (2S,4R)-propiconazole. The total residues of propiconazole were 0.026-0.487 mg/kg in the plum storage period, and the water washing could remove 49.35% to 54.65% of the propiconazole residue in plum. The hardness of plums treated with propiconazole was generally higher than that of control in the middle and late stages of storage. The effects of propiconazole on the total soluble solid content of plums were different at 20 °C and 4 °C. This study provides a scientific reference for the food safety evaluation of the "Fengtang" plum after the application of propiconazole during the storage period.

Enantioselective effect of chiral prothioconazole on the conformation of bovine serum albumin

As a typical chiral triazole fungicide, the enantioselective toxicity of prothioconazole to environmental organisms is of increasing concern. Herein, the binding mechanism of chiral PTCs to BSA was investigated by multi-spectral technique and molecular docking. Fluorescence titration and fluorescence lifetime experiments fully established that quenching BSA fluorescence by chiral PTCs is static quenching and could spontaneously bind to BSA. Hydrophobic interactions dominate the binding process of chiral PTCs to BSA. Differently, although both chiral PTCs and BSA have a primary binding site, the difference in chiral isomerism leads to a stronger binding ability of S-PTC than R-PTC. Both configurations of PTC can change the conformation of BSA and induce changes in the microenvironment around its amino acid residues, and the effect of S-PTC is more significant. Overall, S-PTC exhibited a more substantial effect on BSA structure relative to R-PTC. That is, S-PTC may lead to more potent potential toxicological effects on environmental organisms. This study provides a comprehensive assessment of the environmental behavior of chiral pesticides and their potential toxicity to environmental organisms at the molecular level and provides a theoretical basis for the screening of highly effective and biologically less toxic enantiomers of chiral pesticides.

Effect of propiconazole on plastic film microplastic degradation: Focusing on the change in microplastic morphology and heavy metal distribution

With the rapid increase in the use of plastic films, microplastic (MP) pollution in agricultural soils has become a global environmental problem. Propiconazole is widely used in agriculture and horticulture; however, its role in plastic film degradation remains elusive. Butylene adipate-co-terephthalate (PBAT) and polyethylene (PE) films were used to analyze the effects of propiconazole on plastic film and MP degradation. We identified the surface morphologies of PBAT and PE at different propiconazole concentrations and soil pH values, as well as the adsorption and release characteristics of heavy metals during the degradation process via scanning electron microscopy, Fourier transform infrared spectroscopy and inductively coupled plasma mass spectrometry. Propiconazole accelerated the degradation of MPs, adsorption of heavy metals (Ni and Zn), and release of Sn at low concentrations (≤40 mg/kg); however, these effects were evidently absent at a high concentration (120 mg/kg). Furthermore, MPs were more prone to degradation in acidic or alkaline soils than in neutral soil when they coexisted with propiconazole. Hence, we suggest that PBAT and PE plastic films may not be suitable for application in acidic and alkaline soils with propiconazole, because of shorter rupture time and more heavy metal adsorption. PBAT degraded faster, absorbed and released more heavy metals than PE. Under all tested conditions, the heavy metal contents in MPs gradually approached those in soil, which proves that MPs are carriers of heavy metal pollutants. These results may help in assessing the impact of MPs on soil environments and provide a theoretical basis for the standardized propiconazole and plastic film usage.

Enantioselective monitoring chiral fungicide mefentrifluconazole in tomato, cucumber, pepper and its pickled products by supercritical fluid chromatography tandem mass spectrometry

A fast, effective, and environmental-friendly method was developed for enantioseparation and analysis of mefentrifluconazole in vegetables based on supercritical fluid chromatography tandem mass spectrometry. The enantioselective behaviors of mefentrifluconazole enantiomers in tomato, cucumber, and pepper in the greenhouse, and pickled cucumber and pepper during processing were investigated. Mefentrifluconazole enantiomers could obtain baseline separation within 2 min. The average recoveries of all matrices ranged from 78.4% to 119.0%, with relative standard deviations less than 16.8% for two enantiomers. S-(+)-mefentrifluconazole was preferentially degraded in pepper, while there was no enantioselectivity in tomato and cucumber under field conditions. During processing, S-(+)-mefentrifluconazole was reduced preferentially than R-(-)-mefentrifluconazole in pickled cucumber and cucumber brine. Inversely, R-(-)-mefentrifluconazole degraded faster than S-(+)-mefentrifluconazole in pepper brine. But, no obvious enantioselectivity was observed in pickled pepper. The result of this study could contribute to a more accurate dietary risk assessment of mefentrifluconazole in vegetables and processed products.

Study on degradation behaviour, residue distribution, and dietary risk assessment of propiconazole in celery and onion under field application

BACKGROUND

Propiconazole is widely used to control fungal diseases in field crops, including celery and onion. The potential risk to the environment and human health has aroused much public concern. Therefore, it is significant to investigate the degradation behaviour, residue distribution, and dietary risk assessment of propiconazole in celery and onion.

RESULTS

A sensitive analytical method for determination of propiconazole residue in celery and onion was established and validated through high-performance liquid chromatography tandem mass spectrometry. The average recovery rate of propiconazole ranged from 85.7% to 101.8%, with a relative standard deviation of 2.1-6.3%. For the dissipation kinetics, the data showed that propiconazole in celery and onion was degraded, with half-lives of 6.1-6.2 days and 8.7-8.8 days respectively. In the terminal residue experiments, the residues of propiconazole were below 4.66 mg kg^-1 in celery after application two or three times and were below 0.029 mg kg^-1 in onion after application of three or four times with an interval of 14 days under the designed dosages. The chronic and acute dietary exposure assessments for propiconazole were valued by risk quotient, with all values being lower than 100%.

CONCLUSION

Propiconazole in celery and onion was rapidly degraded following first-order kinetics models. The dietary risk of propiconazole through celery or onion was negligible to consumers. The study not only offers a valuable reference for reasonable usage of propiconazole on celery and onion, but also facilitates the establishment of maximum residue limits in China. © 2020 Society of Chemical Industry.

Separation of N'-nitrosonornicotine isomers and enantiomers by supercritical fluid chromatography tandem mass spectrometry

N'-nitrosonornicotine (NNN) is one of the most prevalent and toxic tobacco-specific nitrosoamines. A chiral center at its 2'-position results in R and S enantiomers, the partial double bond character of the NN = O group also results in E and Z isomers, therefore, NNN can form a total of four absolute configurations (E-(R)-NNN, E-(S)-NNN, Z-(R)-NNN, and Z-(S)-NNN). This study investigated the resolution of R/S enantiomers and E/Z isomers of NNN by supercritical fluid chromatography tandem mass spectrometry (SFC-MS/MS). The baseline separation of E/Z-(R,S)-NNN isomers/enantiomers was accomplished through the optimization of chiral columns and co-solvents. Due to the lack of single standard of E/Z isomers, only R-NNN (sum of E-(R)-NNN and Z-(R)-NNN) and S-NNN (sum of E-(S)-NNN and Z-(S)-NNN) were further examined. Through the comprehensive optimization of SFC-MS/MS conditions, R-NNN and S-NNN were separated with a run time of 5 min, the developed method was validated, and its applicability to the determination of NNN enantiomers in burley tobacco samples was demonstrated. This study could be applied to preparative separation of single enantiomer and/or isomer of NNN, and could provide potential benefits to biologic activity studies on these enantiomers and isomers.

New Trend in the Extraction of Pesticides from the Environmental and Food Samples Applying Microextraction Based Green Chemistry Scenario: A Review

This review focused on the green microextraction methods used for the extraction of pesticides from the environmental and food samples. Microextraction techniques have been explored and applied in various fields of analytical chemistry since its beginning, as evinced by the numerous reviews published. The success of any technique in science and technology is measured by the simplicity, environmentally friendly, and its applications; and the microextraction technique is highly successive. Deliberations were attentive to studies where efforts have been made to validate the methods through the inter-laboratory comparison study to assess the analytical performance of microextraction techniques against conventional methods. Succinctly, developed microextraction methods are shown to impart significant benefits over conventional techniques. Provided that the analytical community continues to put forward attention and resources into the growth and validation of the microextraction technique, a promising future for microextraction is forecasted.

Supramolecular solvent-based micro-extraction of pesticides in food and environmental samples

Supramolecular solvent-based micro-extraction is a very important green technique for the isolation and pre-concentration of pesticide residues in food and environmental samples prior to their chromatographic analysis. The attractive features of supramolecular solvent-based micro-extraction include its simplicity, high pre-concentration factor, fastness, accuracy, low cost, less consumption of chemical reagents and environmental friendliness. The supramolecular solvent is generated from a ternary mixture of amphiphiles, water and a water miscible dispersion and coacervating solvent. Tehydrofuran is one of the solvents commonly used as both a dispersion solvent and a coacervating agent. This paper gives a recent comprehensive review on the application of alkanols as amphiphiles during supramolecular solvent-based micro-extraction of pesticide residues in food and environmental samples. Other researchers used long chain fatty acids as amphiphiles during pesticide analysis in food and environmental samples using supramolecular solvent-based micro-extraction, and this is discussed in this paper. The incorporation of ferrofluids in supramolecular solvents enables phase separation using a magnet instead of the time-consuming centrifugation technique. This paper also gives a detailed review of the application of ferrofluid-based supramolecular solvent micro-extraction of pesticide residues in food and environmental samples.

Soil dissipation of sugarcane billet seed treatment fungicides and insecticide using QuEChERS and HPLC

Chemical treatment of sugarcane seed with fungicides and insecticides prior to planting increases yields of cane and sugar for the perennial, annually harvested crop. However, the fate of the applied chemicals is unknown. Therefore, the purpose of this study was to measure the aerobic dissipation of selected billet seed treatment chemicals in a mineral sugarcane soil from Louisiana. Soil samples from the surface 15 cm were treated with either thiamethoxam, azoxystrobin, fluxapyroxad, propiconazole, or pyraclostrobin and monitored over 100 days under laboratory conditions. Insecticide and fungicide levels were determined by high performance liquid chromatography. Dissipation data were fitted to four kinetic models: simple first-order (SFO), first order multi-compartment (FOMC), double-first order in parallel (DFOP), and hockey-stick (HS). The dissipation half-life (DT₅₀) of thiamethoxam, azoxystrobin, fluxapyroxad, propiconazole, or pyraclostrobin were 275, 100, 144, 74, and 39 d, respectively. Overall, the DT₅₀ for the pesticides in the study indicated medium to long persistence in soil under the conditions of the experiment. This is the first report for several of these pesticides related to the aerobic dissipation in soils used to grow sugarcane.

Enantioselective Analysis and Degradation Studies of Four Stereoisomers of Difenoconazole in Citrus by Chiral Liquid Chromatography-Tandem Mass Spectrometry

Four difenoconazole stereoisomers were well separated on a Superchiral S-OX column. The absolute configurations of the four stereoisomers of difenoconazole eluted in an orderly fashion with the chiral column were confirmed as (2S,4S), (2S,4R), (2R,4R), and (2R,4S)-difenoconazole, respectively, by single-crystal X-ray diffraction. For the first time, a simple and efficient trace detection method for the determination of residues of the four stereoisomers of difenoconazole in a plant sample by HPLC-MS/MS was developed. The mean recoveries were 78.23-104.38% with RSDs of 0.33-9.95%. The limits of detection for the four difenoconazole enantiomers were 0.0002-0.0004 mg/kg, and the limits of quantitation were 0.0044-0.011 mg/kg in citrus leaves and whole fruits. There was no obvious enantioselectivity upon degradation of the four stereoisomers in citrus leaves and whole fruits in Hunan and Guizhou. In Guangzhou, the rate of degradation of (2R,4R)-difenoconazole was the slowest among the four stereoisomers of difenoconazole.

A review on the stereospecific fate and effects of chiral conazole fungicides

The production and use of chiral pesticides are triggered by the need for more complex molecules capable of effectively combating a greater spectrum of pests and crop diseases, while sustaining high production yields. Currently, chiral pesticides comprise about 30% of all pesticides in use; however, some pesticide groups such as conazole fungicides (CFs) consist almost exclusively of chiral compounds. CFs are produced and field-applied as racemic (1:1) mixtures of two enantiomers (one chiral center in the molecule) or four diastereoisomers, i.e., two pairs of enantiomers (two chiral centers in the molecule). Research on the stereoselective environmental behavior and effects of chiral pesticides such as CFs has become increasingly important within the fields of environmental chemistry and ecotoxicology. This is motivated by the fact that currently, the fate and effects of chiral pesticides such as CFs that arise due to their stereoselectivity are not fully understood and integrated into risk assessment and regulatory decisions. In order to fill this gap, a summary of the state-of-the-art literature related to the stereospecific fate and effects of CFs is needed. This will also benefit the agrochemistry industry as they enhance their understanding of the environmental implications of CFs which will aid future research and development of chiral products. This review provides a collection of >80 stereoselective studies for CFs related to chiral analytical methods, fungicidal activity, non-target toxicity, and behavior of this broadly used pesticide class in the soil environment. In addition, the review sheds more light on mechanisms behind stereoselectivity, considers possible agricultural and environmental implications, and suggests future directions for the safe use of chiral CFs and the reduction of their environmental footprint.

Deep eutectic solvent-based dispersive liquid-liquid micro-extraction of pesticides in food samples

Deep eutectic solvents are versatile, green and new generation solvents that can be used during dispersive liquid-liquid micro-extraction techniques for pesticides. They have tunable physico-chemical properties that can be easily changed by varying the ratios of hydrogen bond donors and hydrogen bond acceptors in their structures. Deep eutectic solvents are non-flammable, chemically and thermally stable solvents with low vapour pressure. Thus, they have characteristics that are similar to those of ionic liquids. However, they have simpler synthetic procedures, less expensive and are more biodegradable than ionic liquids. One of the limitations of deep eutectic solvents is their toxicity to the environment but they are less toxic than ionic liquids. This paper gives a focused and comprehensive recent review on the applications of deep eutectic solvents during dispersive liquid-liquid micro-extraction of pesticides in food samples for the period starting from 2016 to 2020. Emphasis was placed on the modifications done to the deep eutectic solvent-based dispersive liquid-liquid micro-extraction techniques in order to enhance their greenness during pesticide pre-concentration in food samples. In addition, hyphenated dispersive liquid-liquid micro-extraction techniques were also reviewed and lastly, the paper outlined the challenges associated with the use of DESs during the DLLME techniques.

Application of enantiomeric fractions in environmental forensics: Uncertainties and inconsistencies

The assumption that only biological processes are enantioselective introduces challenges in the reliability of enantioselective analysis as a tool for discriminating biotic and abiotic processes in the environmental fate of chiral pollutants. Enantioselectivity does not depend on the nature of the fate process a chiral contaminant undergoes but on the interaction of the chiral contaminant with homochirality inducing external agents (e.g. chiral molecules, macromolecules or surfaces such as enzymes, blood plasma, proteins, chiral co-pollutants, humic acid and soil organominerals). The environmental behavior of a chiral contaminant is difficult to anticipate because the interactions between the chiral contaminants and the homochirality inducing external agents is often complex and strongly influenced by local environment conditions such as pH, redox conditions, organic carbon, organic nitrogen, humic acid, and redox conditions. Furthermore, the use of enantioselective analysis in environmental forensics depend on the adequate separation and accurate identification and quantification of the enantiomers of the chiral contaminant. Matrix effects, instrument effects, inadequate enantioselective separation, and poor quantification techniques introduce uncertainties in the determination of enantiomeric composition. Here we present the weaknesses of this assumption and recommend using enantiomeric fractions as chemical markers of biotransformation with caution. We recommend using stable isotopes, including abiotic controls to determine if enantioselective sorption occurs, and determining stability of enantiomers in solvent or at elevated temperatures to account for confounding factors arising from matrix effects, enantioselective abiotic processes, and enantiomerization due solvent and thermal lability of the chiral analyte, respectively to maintain the integrity of the utility of enantiomeric composition changes as an environmental forensics tool.

Supercritical Fluid Extraction of Pesticides and Insecticides from Food Samples and Plant Materials

The principal intention of this study is presenting the attempts carried out for extracting, separating, and determining of the pesticide and insecticide residues existing in food and plant samples. In this regard, a set of content, including the explanations about the supercritical fluid extraction (SFE), supercritical fluid chromatography, and various types of pesticides are indicated. Besides, the parameters affecting the pesticides extraction composed of temperature, pressure, modifier, drying agent, and so on are discussed. Also, examples of insecticides extraction by SFE technique as an important subset of pesticides are indicated. Along with these items, some interesting works, concerning the innovations implemented in the field of SFE of pesticide and insecticide residues from foodstuff and plants are depicted.

Enantioselective Separation and Dissipation of Prothioconazole and Its Major Metabolite Prothioconazole-desthio Enantiomers in Tomato, Cucumber, and Pepper

In this study, a simple and effective chiral analytical method was developed to monitor prothioconazole and prothioconazole-desthio at the enantiomeric level using supercritical fluid chromatography-tandem triple quadrupole mass spectrometry. The baseline enantioseparation for prothioconazole and prothioconazole-desthio was achieved within 2 min on a Chiralcel OD-3 column with CO₂/0.2% acetic acid-5 mmol/L ammonium acetate 2-propanol (85:15, v/v) as the mobile phase at a flow rate of 1.5 mL/min and column temperature of 25 °C. The limit of quantitation for each enantiomer was 5 μg/kg, with a baseline resolution of >3.0. The results of enantioselective dissipation showed that R-(-)-prothioconazole was preferentially degraded in tomato, cucumber, and pepper under greenhouse conditions. S-(-)-prothioconazole-desthio was preferentially degraded in tomato and cucumber; however, R-(+)-prothioconazole-desthio was preferentially degraded in pepper. Results of this study may help to facilitate more accurate risk assessment of prothioconazole and its major metabolite in agricultural products.

Analysis of Enantiomers in Products of Food Interest

The separation of enantiomers has been started in the past and continues to be a topic of great interest in various fields of research, mainly because these compounds could be involved in biological processes such as, for example, those related to human health. Great attention has been devoted to studies for the analysis of enantiomers present in food products in order to assess authenticity and safety. The separation of these compounds can be carried out utilizing analytical techniques such as gas chromatography, high-performance liquid chromatography, supercritical fluid chromatography, and other methods. The separation is performed mainly employing chromatographic columns containing particles modified with chiral selectors (CS). Among the CS used, modified polysaccharides, glycopeptide antibiotics, and cyclodextrins are currently applied.

Assessment of Repeatability in Supercritical Fluid Chromatography with Electrochemical Detection Based on the ISO 11843 Part 7

The present study proposes a method for the assessment of repeatability in supercritical fluid chromatography with electrochemical detection (SFC-ECD), based on the ISO 11843 part 7 (ISO 11843-7:2018) which can theoretically provide detection limits and standard deviation (S.D.) through the stochastic properties of baseline noise without repetitive measurements of real samples. On the baseline noise of SFC-ECD, large-amplitude and periodic noises with less than 0.05 Hz were observed, and the power spectrum of the baseline noise showed 1/f fluctuation (f = frequency). It was found that the present power spectrum analysis, according to the law of error propagation, can provide suitable noise parameters to calculate S.D. of baseline noise and a relative S.D. (RSD) of peak area by ISO 11843-7. The chromatographic determinations of α-, β-, γ- and δ-tocopherol have been taken as examples. In the present SFC-ECD, the RSDs of peak areas for α-, β-, γ- and δ-tocopherol obtained by ISO 11843-7 were within 95% confidence intervals of the RSD of them obtained by repetitive measurements (n = 6). Thus, we found that ISO 11843-7 is applicable to the assessment of repeatability in SFC-ECD for determining tocopherols without repetitive measurements.

Modeling the effect of adsorption on the degradation rate of propiconazole in profiles of Polish Luvisols

Laboratory adsorption and degradation studies were carried out to determine the effect of time-dependent adsorption on propiconazole degradation rates in samples from three Polish Luvisols. Strong propiconazole adsorption (organic carbon normalized adsorption coefficients K_oc in the range of 1217-7777 mL/g) was observed in batch experiments, with a typical biphasic mechanism with a fast initial step followed by the time-dependent step, which finished within 48 h in the majority of soils. The time-dependent step observed in incubation experiments was longer (duration from 5 to 23 d), and its contribution to total adsorption was from 20% to 34%. The half-lives obtained at 25 °C and 40% maximum water holding capacity of soil, were in the range of 34.7-112.9 d in the Ap horizon and in the range of 42.3-448.8 d for subsoils. The very strong correlations, between degradation rates in pore water and soil organic carbon and soil microbial activity, indicated that microbial degradation of propiconazole was most likely the only significant process responsible for the decay of this compound under aerobic conditions for the whole of the examined soil profiles. Modeling of the processes showed that only models coupling adsorption and degradation were able to correctly describe the experimental data. The analysis of the bioavailability factor values showed that degradation was not limited by the rate of propiconazole desorption from soil, but sorption affected the degradation rate by decreasing its availability for microorganisms.

Simultaneous enantiomeric analysis of eight pesticides in soils and river sediments by chiral liquid chromatography-tandem mass spectrometry

A rapid and sensitive multi-residue method was developed for the simultaneous quantification of eight chiral pesticides (including diniconazole, metalaxyl, paclobutrazol, epoxiconazole, myclobutanil, hexaconazole, napropamide and isocarbophos) at enantiomeric levels in environmental soils and sediments using chiral liquid chromatography-tandem mass spectrometry based on a combined pretreatment of matrix solid-phase dispersion and dispersive liquid-liquid microextraction (MSPD-DLLME). Under optimized conditions, 0.1 g of solid sample was dispersed with 0.4 g of C18-bonded silica sorbent, and 3 mL of methanol was used for eluting the analytes. The collected eluant was dried and then further purified by DLLME with 550 μL of dichloromethane and 960 μL of acetonitrile as extraction and disperser solvent, respectively. The established method was validated and found to be linear, precise, and accurate over the concentration range of 2-500 ng g^-1 for epoxiconazole, paclobutrazol and metalaxyl and 4-500 ng g^-1 for isocarbophos, hexaconazole, myclobutanil, diniconazole and napropamide. Recoveries of sixteen enantiomers varied from 87.0 to 104.1% and the relative standard deviations (RSD) were less than 10.1%. Method detection and quantification limits (MDLs and MQLs) varied from 0.22 to 1.54 ng g^-1 and from 0.91 to 4.00 ng g^-1, respectively. Finally, the method was successfully applied to analyze the enantiomeric composition of the eight chiral pesticides in environmental solid matrices, which will help better understand the behavior of individual enantiomer and make accurate risk assessment on the ecosystem.

Enantiomeric separation of six chiral pesticides that contain chiral sulfur/phosphorus atoms by supercritical fluid chromatography

Six chiral pesticides containing chiral sulfur/phosphorus atoms were separated by supercritical fluid chromatography with supercritical CO₂ as the main mobile phase component. The effect of the chiral stationary phase, different type and concentration of modifiers, column temperature, and backpressure on the separation efficiency was investigated to obtain the appropriate separation condition. Five chiral pesticides (isofenphos-methyl, isocarbophos, flufiprole, fipronil, and ethiprole) were baseline separated under experimental conditions, while isofenphos only obtained partial separation. The Chiralpak AD-3 column showed a better chiral separation ability than others for chiral pesticides containing chiral sulfur/phosphorus atoms. When different modifiers at the same concentration were used, the retention factor of pesticides except flufiprole decreased in the order of isopropanol, ethanol, methanol; meanwhile, the retention factor of flufiprole increased in the order of isopropanol, ethanol, methanol. For a given modifier, the retention factor and resolution decreased on the whole with the increase of its concentration. The enantiomer separation of five chiral pesticides was an "enthalpy-driven" process, and the separation factor decreased as the temperature increased. The backpressure of the mobile phase had little effect on the separation factor and resolution.