Paraquat and Diquat: Recent Updates on Their Pretreatment and Analysis Methods since 2010 in Biological Samples.

Paraquat (PQ) and diquat (DQ) are quaternary ammonium herbicides which have been used worldwide for controlling the growth of weeds on land and in water. However, PQ and DQ are well known to be toxic. PQ is especially toxic to humans. Moreover, there is no specific antidote for PQ poisoning. The main treatment for PQ poisoning is hemoperfusion to reduce the PQ concentration in blood. Therefore, it is essential to be able to detect PQ and DQ concentrations in biological samples. This critical review summarizes the articles published from 2010 to 2022 and can help researchers to understand the development of the sample treatment and analytical methods for the determination of PQ and DQ in various types of biological samples. The sample preparation includes liquid-liquid extraction, solid-phase extraction based on different novel materials, microextration methods, and other methods. Analytical methods for quantifying PQ and DQ, such as different chromatography and spectroscopy methods, electrochemical methods, and immunological methods, are illustrated and compared. We focus on the latest advances in PQ and DQ treatment and the application of new technologies for these analyses. In our opinion, tandem mass spectrometry is a good choice for the determination of PQ and DQ, due to its high sensitivity, high selectivity, and high accuracy. As far as we are concerned, the best LOD of 4 pg/mL for PQ in serum can be obtained.

Adsorption of the herbicides diquat and difenzoquat on polyurethane foam: Kinetic, equilibrium and computational studies.

This work reports a study about the adsorption of the herbicides diquat and difenzoquat from aqueous medium employing polyurethane foam (PUF) as the adsorbent and sodium dodecylsulfate (SDS) as the counter ion. The adsorption efficiency was shown to be dependent on the concentration of SDS in solution, since the formation of an ion-associate between cationic herbicides (diquat and difenzoquat) and anionic dodecylsulfate is a fundamental step of the process. A computational study was carried out to identify the possible structure of the ion-associates that are formed in solution. They are probably formed by three units of dodecylsulfate bound to one unit of diquat, and two units of dodecylsulfate bound to one unit of difenzoquat. The results obtained also showed that 95% of both herbicides present in 45mL of a solution containing 5.5mgL-1 could be retained by 300mg of PUF. The experimental data were well adjusted to the Freundlich isotherm (r2 ≥ 0.95) and to the pseudo-second-order kinetic equation. Also, the application of Morris-Weber and Reichenberg equations indicated that an intraparticle diffusion process is active in the control of adsorption kinetics.

Analytical characterization using surface-enhanced Raman scattering (SERS) and microfluidic sampling.

With the rapid development of analytical techniques, it has become much easier to detect chemical and biological analytes, even at very low detection limits. In recent years, techniques based on vibrational spectroscopy, such as surface enhanced Raman spectroscopy (SERS), have been developed for non-destructive detection of pathogenic microorganisms. SERS is a highly sensitive analytical tool that can be used to characterize chemical and biological analytes interacting with SERS-active substrates. However, it has always been a challenge to obtain consistent and reproducible SERS spectroscopic results at complicated experimental conditions. Microfluidics, a tool for highly precise manipulation of small volume liquid samples, can be used to overcome the major drawbacks of SERS-based techniques. High reproducibility of SERS measurement could be obtained in continuous flow generated inside microfluidic devices. This article provides a thorough review of the principles, concepts and methods of SERS-microfluidic platforms, and the applications of such platforms in trace analysis of chemical and biological analytes.

Development of LC-MS/MS analytical method for the rapid determination of Diquat in water and beverages.

This study aimed to develop simple, fast, and sensitive methods for the determination of diquat (DQ) in various matrices such as water and beverages. For water, direct injection was tested first, however, the sensitivity of the incurred samples were too low and couldn't possibly achieve the targeted limit of quantification. Hence, dilution with "weaker" injection solvents were tested, and the final conditions involved the dilution of water with acetonitrile (0.4 % ammonium hydroxide) which increased the sensitivity by more than ten times. Nevertheless, the beverages samples needed further treatment to achieve acceptable spiked recovery. The final conditions involved extraction using the aforementioned solvent, followed by heating and partitioning. Both of the methods satisfied the validation requirements, with an average recovery ranging from 85.9 to115 % and associated relative standard deviation (RSD %) within the range 3-8. Further applications on real samples were done to test the levels of contamination.

A ratiometric fluorescence method for the detection of diquat by a large Stokes shift fluorescent probe.

Pesticide residues are currently a prominent concern for food safety, and the development of a rapid, convenient, and accurate method for detecting pesticide residues is crucial to ensure the quality of agricultural products. In this study, a small molecule fluorescent probe based on biphenyl disulfonic acid (BDSA) was designed and prepared, and a sensitive, specific, and rapid detection method for diquat (DQ) and paraquat (PQ) was developed. The fluorescent molecule (BDSA-NDA) was synthesized through amide reaction between BDSA and 1,8-naphthalic anhydride, which exhibited cyan fluorescence (480 nm) when excited at 305 nm in aqueous solution with a large Stokes shift (>150 nm). Diquat and paraquat were found to quench the fluorescence of the probe through internal filtration effect (IFE) and photoelectron transfer (PET). Moreover, diquat possessed a large conjugated structure that emitted fluorescence at 340 nm which was assembled into a pair of ratio fluorescence with BDSA-NDA. Under optimized experimental conditions, the developed method achieved detection limits of 0.003 mg/L for diquat and 0.202 mg/L for paraquat. Furthermore, it could identify paraquat doped in diquat formulations. Additionally, when applied to environmental water samples as well as rice and urine, this detection method demonstrated good recovery rates (water: 96.2-100.6 %, rice: 93.5-101.9 %, urine: 96-103.7 %), meeting actual sample detection requirements effectively. This work presents a novel approach for rapidly detecting diquat and paraquat residues which holds practical application value in areas such as pesticide residue analysis in foods, environmental or clinical samples.

Ratiometric emission of Tb(III)-functionalized Cd-based layered MOFs for portable visual detection of trace amounts of diquat in apples, potatoes and corn.

Diquat (DQ) is a typical bipyridine herbicide widely used to control weeds in fields and orchards. The severe toxicity of diquat poses a serious threat to the environment and human health. Metal-organic frameworks (MOFs) have received widespread attention due to their unique physical and chemical properties and applications in the detection of toxic and harmful substances. In this work, a two-dimensional (2D) Tb(III) functionalized MOF Tb(III)@1 (1 = [Cd(HTATB)(bimb)]n·H2O (Cd-MOF), H3TATB = 4,4',4″-triazine-2,4,6-tribenzoicacid, bimb = 1,4-bis((1H-imidazol-1-yl)methyl)benzene) has been prepared and characterized. Tb(III)@1 has excellent optical properties and high water and chemical stability. After the Tb(III) is fixed by the uncoordinated -COO- in the 1 framework, Tb(III)@1 emits the typical green fluorescence of the lanthanide ion Tb(III) through the "antenna effect". It is worth noting that Tb(III)@1 can be used as a dual emission fluorescence chemical sensor for the ratio fluorescence detection of pesticide DQ, exhibiting a relatively low detection limit of 0.06 nM and a wide detection range of 0-50 nM. After the addition of DQ, a rapid color change of Tb(III)@1 fluorescence from green to blue was observed due to the combined effects of IFE, FRET and dynamic quenching. Therefore, a simple test paper box has been designed for direct on-site determination of pesticide DQ. In addition, the developed sensor has been successfully applied to the detection of DQ in real samples (fruits a Yin-Xia Sun and Bo-Tao Ji contributed equally to this work and should be considered co-first authors.nd vegetables) with satisfactory results. The results indicate that the probe developed in this study has broad application prospects in both real sample detection and actual on-site testing.

A SERS-based point-of-care testing approach for efficient determination of diquat and paraquat residues using a flexible silver flower-coated melamine sponge.

Diquat (DQ) and paraquat (PQ) residues in food are potential hazards to consumers' health. Point-of-care testing (POCT) of them remains challenging. Based on surface-enhanced Raman spectroscopy (SERS) technology, we developed a POCT strategy for DQ and PQ on apple surface and in apple juice. A point-of-use composite was fabricated using a piece of porous melamine sponge (MS) modified with silver nanoflowers (AgNFs), combining the specificity of the SERS fingerprint and the excellent adsorption capacity of MS. Using this dual-functional AgNFs@MS, the on-site determination of the DQ and PQ residues was completed within 3 min without pretreatment. Clear trends were observed between SERS intensity and logarithmic concentrations, with r values from 0.962 to 0.984. The limit of detection of DQ and PQ were 0.14-0.70 ppb in apple juice and on apple surface. This study provides a new point-of-use alternative for rapidly detecting DQ and PQ residues in nonlaboratory settings.

Colorimetric and fluorescent dual detection of paraquat and diquat based on an anionic polythiophene derivative.

We have developed a colorimetric and fluorescent dual-response probe for the detection of paraquat and diquat in aqueous solutions based on an anionic polythiophene derivative. The detection limit of this approach can be as low as 10(-9) M by fluorescence measurements.

Development and independent laboratory validation of a simple method for the determination of paraquat and diquat in potato, cereals and pulses.

A new sensitive, fast and robust method for the determination of paraquat and diquat residues in potatoes, cereals and pulses is presented. Different extraction conditions (solvent, time and temperature) have been evaluated using barley grain, potatoes and dry lentils containing incurred residues of diquat and paraquat. The finalised procedure involves extraction with a mixture of methanol/water/hydrochloric acid at 80 °C and analysis by liquid chromatography-tandem mass spectrometry. Diquat D4 and Paraquat D6 internal standards were added to the test portions prior to extraction. A small-scale inter-laboratory validation of the developed method for diquat and paraquat using potato and barley samples was conducted by three laboratories. The precision and accuracy of the method were determined from recovery experiments (five replicates) at 0.01 and 0.1 mg kg(-1). The recoveries obtained (n = 180) were in the range of 92-120 % with associated relative standard deviation (RSD) between 1.4-10 % for all compound/commodity/spiking concentration combinations.

A rapid and reliable immunochromatographic strip for detecting paraquat poinsoning in domestic water and real human samples.

Paraquat (PQ) is one of the most commonly used herbicides, but it has polluted the environment and threatened human health through extensive and improper usage. Here, a new naked-eye PQ immunochromatographic strip was developed to recognize PQ in domestic water and real human samples within 10 min based on a novel custom-designed anti-PQ antibody. The PQ test strip could recognize PQ at a concentration as low as 10 ng/ml, reaching the high-efficiency time-of-flight mass spectrometry detection level and identifying trace amounts of PQ in samples treated with a diquat (DQ) and PQ mixture. Notably, both the performance evaluation and clinical trial of the proposed PQ strips were validated in multiple hospitals and public health agencies. Taken together, our study firstly provide the clinical PQ-targeted colloidal gold immunochromatographic test strip designed both for environment water and human sample detection with multiple advantages, which are ready for environmental monitoring and clinical practice.

In vivo microcapillary sampling coupled with matrix-assisted laser desorption/ionization fourier transform ion cyclotron resonance mass spectrometry for real-time monitoring of paraquat and diquat in living vegetables.

An in vivo microcapillary sampling (MCS) method coupled with matrix-assisted laser desorption/ionization fourier transform ion cyclotron resonance mass spectrometry (MALDI-FTICR-MS) analysis was utilized to monitor the real-time bipyridine quaternary ammonium herbicides concentrations and assess their uptake and elimination behaviors in living cabbage plants noninvasively. Under optimized conditions, the proposed method for paraquat (PQ) and diquat (DQ) determination showed wide linear ranges (7.81-500 µg/kg), low limits of detection (0.1-0.9 µg/kg), and good reproducibility. In vivo tracking results demonstrated that different absorption behaviors between PQ and DQ existed in living vegetables and DQ was more easily absorbed. Through decay kinetics model fitting, herbicide half-lives were 1.32 and 1.86 days for PQ and DQ, respectively. To summarize, in vivo MCS method provides valuable information on herbicide risks for agricultural production, which is suitable for temporal, spatial, and longitudinal studies in the same living system and multicompartmental studies in the same organism.

Monolithic spin column extraction and GC-MS for the simultaneous assay of diquat, paraquat, and fenitrothion in human serum and urine.

We present a method based on monolitic spin column extraction and gas chromatography-mass spectrometry as an analytical method for screening diquat (DQ), paraquat (PQ), and fenitrothion in serum and urine. This method is useful for clinical and forensic toxicological analyses. Recovery of DQ, PQ, and fenitrothion from serum and urine, spiked at concentrations between 0.1, 2.5, 20, and 45 µg/ml, ranged from 51.3% to 106.1%. Relative standard deviation percentages were between 3.3% and 14.8%. Detection and quantitation limits for serum and urine were 0.025 and 0.05 µg/ml, respectively, for DQ, 0.1 and 0.1 µg/ml, respectively, for PQ, and 0.025 and 0.05 µg/ml, respectively, for fenitrothion. Therefore, these compounds can be detected and quantified in the case of acute poisoning.

Modified Screen-Printed Potentiometric Sensors based on Man-Tailored Biomimetics for Diquat Herbicide Determination.

Screen-printed platforms integrated with molecularly imprinted polymers (MIP) were fabricated and characterized as potentiometric sensors for diquat (DQ). The synthesized MIP beads were studied as sensory carriers in plasticized poly(vinyl chloride) membranes. The sensors were constructed by using poly(3,4-ethylenedioxythiophene) (PEDOT) as solid-contact material to diminish charge-transfer resistance and water layer potential. Conventional ion-selective electrodes (ISEs) with internal filling solution were used for comparison. The designed electrodes showed near Nernstian slopes of 28.2 ± 0.7 (r² = 0.999) over the concentration range of 1.0 × 10-6-1.0 × 10-2 M with the limit of detection 0.026 µg/mL over the pH range 4.2-9.0. The electrode exhibited good selectivity for diquat cations over a large number of organic and inorganic cations. The sensor was successfully introduced for direct measurement of diquat content in commercial pesticide preparations and different spiked potato samples. The results showed that the proposed electrode has a fast and stable response, good reproducibility, and applicability for direct assessment of diquat content. The proposed potentiometric method is simple and accurate in comparison with the reported HPLC methods. Besides, it is applicable to turbid and colored sample solutions.

Determination of diquat by flow injection-chemiluminescence.

A simple, economic, sensitive and rapid method for the determination of the pesticide diquat was described. This new method was based on the coupling of flow injection analysis methodology and direct chemiluminescent detection; to the authors' knowledge, this approach had not been used up to now with this pesticide. It was based on its oxidation with ferricyanide in alkaline medium; significant improvements in the analytical signal were achieved by using high temperatures and quinine as sensitiser. Its high throughput (144 h(-1)), together with its low limit of detection (2 ng mL(-1)), achieved without need of preconcentration steps, permitted the reliable quantification of diquat over the linear range of (0.01-0.6) microg mL(-1) in samples from different origins (river, tap, mineral and ground waters), even in the presence of a 40-fold concentration of paraquat, a pesticide commonly present in the commercial formulations of diquat.

Simultaneous determination of the quaternary ammonium pesticides paraquat, diquat, chlormequat, and mepiquat in barley and wheat using a modified quick polar pesticides method, diluted standard addition calibration and hydrophilic interaction liquid chromatography coupled to tandem mass spectrometry.

In this study, a modified Quick Polar Pesticides (QuPPe) method, optimized by a central composite design, was developed to determine quaternary ammonium pesticides (QUATs) residues in barley and wheat by ultra-high-performance liquid chromatographic tandem mass spectrometry (UHPLC-MS/MS) using a hydrophilic interaction chromatography (HILIC) column. Considering the high polarity of these compounds, special conditions of sample preparation and analysis are required. Different mobile phases, extraction procedure and clean-up were evaluated. An isocratic elution with aqueous solution of ammonium formate 60 mmol L-1 (pH 3.7) and acetonitrile, 40:60 (v/v), was selected. Water and acidified methanol as extraction solvent, without heating, and a clean-up with dichloromethane, chitosan and acetonitrile presented good results. The validated method presented satisfactory selectivity, linearity, matrix effect, trueness and precision, providing recoveries from 93 to 110% with RSD < 13% for barley, and 70 to 115% with RSD < 18% for wheat. The complexity of these matrices requires the calibration in matrix and the diluted standard addition calibration (DSAC) procedure has been shown to be an excellent option to compensate for the matrix effect and the losses of the analytes in the extraction. Real samples of barley and wheat were analyzed and 60% presented concentrations of paraquat above the maximum limits allowed by the European Union. The modified QuPPe method combined with DSAC and HILIC-UHPLC-MS/MS demonstrated to be an effective approach to determine QUATs in barley and wheat, and is a good alternative for routine analysis. The use of the biosorbent chitosan is effective, low cost and more ecological when compared to others conventional sorbents.

High throughput residue analysis of paraquat and diquat involving hydrophilic interaction liquid chromatographic separation and mass spectrometric determination.

A selective, sensitive and robust LC-MS/MS method is reported for the determination of the residues of paraquat and diquat in various fruit matrices, including grape, apple and pomegranate. The extraction with acidified water (0.1 M HCl) at 80°C (15 min) offered superior recoveries for both analytes with a significantly lower matrix effects as compared to the extraction with acidified methanol by the methods reported in the existing literature. The optimised HPLC conditions on hydrophilic interaction liquid chromatography (HILIC) columns, when coupled with electrospray ionisation-tandem mass spectrometry, offered their limit of quantification at 0.01 mg kg-1. The analysis on an XBridge HILIC column required a thorough optimisation of the gradient programme to induce chromatographic separation and minimise matrix effects. This was not necessary when a CORTECS HILIC column was used, which provided selective and sensitive analysis within 5 min runtime using isocratic flow. Isotopically labelled internal standards corrected the recoveries of both analytes within 70-120% (RSD < 20%). For the first time, the applications of high resolution accurate mass analysis in the 'time of flight - multiple reaction monitoring' mode have been demonstrated as a complementary means of targeted screening of these compounds at 0.01 mg kg-1 level. The method has a strong potential for applications in both official control and by those involved in food production for checking compliance with the EU MRLs.

Carbon nanotube-based magnetic and non-magnetic adsorbents for the high-efficiency removal of diquat dibromide herbicide from water: OMWCNT, OMWCNT-Fe3O4 and OMWCNT-κ-carrageenan-Fe3O4 nanocomposites.

In this study, carbon nanotube-based adsorbents, oxidized multi-walled carbon nanotube (OMWCNT) with non-magnetic property and OMWCNT-Fe3O4 and OMWCNT-κ-carrageenan-Fe3O4 nanocomposites with magnetic property, having different structural and surface properties were prepared and their adsorptive properties for the removal of toxic diquat dibromide (DQ) herbicide from water by adsorption were determined in detail. For each adsorption system, the effects of initial DQ concentration, contact time and temperature on the adsorption processes were determined. Equilibrium time was found to be 300 min for DQ solutions. OMWCNT showed faster adsorption and higher maximum adsorption capacity value than magnetic adsorbents. With increasing initial herbicide concentration from 5.43 mg.L-1 to 16.3 mg.L-1, the values of initial sorption rate exhibited a decrease from 29.1 mg.g-1.min-1 to 4.28 mg.g-1.min-1 for OMWCNT-DQ system, from 1.21 mg.g-1.min-1 to 0.823 mg.g-1.min-1 for OMWCNT-Fe3O4-DQ system and from 0.674 mg.g-1.min-1 to 0.612 mg.g-1.min-1 OMWCNT-κ-carrageenan-Fe3O4 system. Maximum adsorption capacity value of OMWCNT was approximately 2.8-fold higher than magnetic OMWCNT-Fe3O4 and 5.4-fold higher than magnetic OMWCNT-κ-carrageenan-Fe3O4 at 25 °C. Adsorption kinetic and isotherm data obtained for all adsorption systems were well-fitted by pseudo second-order and Langmuir models, respectively. Thermodynamic parameters indicated that the adsorption of DQ onto carbon nanotube-based adsorbents was spontaneous and endothermic process. Furthermore, OMWCNT having the highest herbicide adsorption capacity could be regenerated and reused at least five times. This study showed that carbon nanotube-based adsorbents with magnetic and non-magnetic property were of high adsorption performance for the removal of DQ from water and could be promising adsorbent materials for the efficient removal of herbicides from wastewaters.

Capillary electrophoretic analysis of organic pollutants.

Environmental pollutants comprise a variety of compounds from inorganic anions, cations, ionizable organic compounds and moderately hydrophobic organic compounds to highly hydrophobic organic compounds. Correspondingly different separation strategies are required for their separation. In this chapter, we have presented some methods for the separation and the analysis of the organic pollutants such as polycyclic aromatic hydrocarbons, phenoxy acids, dithiocarbamates, paraquat and diquat, endocrine disruptors, toxins and explosives.

Supercritical fluid extraction as an on-line clean-up technique for rapid amperometric screening and alternative liquid chromatography for confirmation of paraquat and diquat in olive oil samples.

A rapid and simple method for the direct screening of paraquat (PQ) and diquat (DQ) in olive oil samples is proposed. The sample screening method involves supercritical fluid extraction (SFE) (clean-up followed by the extraction of the analytes) followed by continuous flow electrochemical detection. Those samples for which the total concentration is close to or above the threshold limit established by the Columbian Society for Social Protection (0.05 microg g(-1)) are subsequently analyzed by liquid chromatography (LC) with diode array detection (DAD). This confirmation method allows the determination of PQ and DQ in the range between 0.04 and 1.0 microg g(-1), with average relative standard deviations lower than 3.5%, and 0.003 and 0.002 microg g(-1) detection limits for PQ and DQ, respectively. The proposed arrangement opens up interesting prospects for the direct determination of polar pesticides in complex samples with a good throughput and a high level of automation.

Determination of quaternary ammonium herbicides in soils. Comparison of digestion, shaking and microwave-assisted extractions.

Very challenging analytical problems arise from the continuous introduction in agriculture of chemical pesticides. Particularly, diquat (DQ), paraquat (PQ) and difenzoquat (DF) are a difficult group of quaternary ammonium herbicides to analyze. This article reviews and addresses the most relevant analytical methods for determining the selected herbicides in soil. We discuss and critically evaluate procedures, such as digestion-based methods, shaking extraction and microwave-assisted extraction (MAE). Clean-up of extracts was performed by solid-phase extraction (SPE) using silica cartridges. Detection of these herbicides was carried out by liquid chromatography (LC) coupled to UV detection and mass spectrometry (MS) as confirmatory technique. Recoveries ranged from 98% to 100% by digestion, from no recovered to 61% by shaking, and from 102% to 109% by MAE with estimated quantification limits between 1.0 microg/kg and 2.0 microg/kg by digestion and 5.0 mug/kg and 7.5 microg/kg by MAE using LC/MS-MS as detection technique. The recoveries obtained under the optimum conditions are compared and discussed with those obtained from digestion extraction and MAE.