Fabrication of benzenesulfonic acid groups modified magnetic microspheres as an MSPE adsorbent for fast determination of paraquat and diquat in human urine combined with UPLC-HRMS.

In this study, novel benzenesulfonic acid groups modified magnetic microspheres (Fe3O4@SiO2@poly(4-VB)) were synthesized and characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier-transform infrared spectrometry (FTIR), and vibrating sample magnetometer (VSM). The as-prepared Fe3O4@SiO2@poly(4-VB) was employed as a magnetic-phase extraction (MSPE) adsorbent for rapid determination of paraquat (PQ) and diquat (DQ) in human urine samples coupled with ultra-high performance liquid chromatography-high resolution mass spectrometry (UPLC-HRMS). Moreover, this paper had expounded systematically the mass spectrum cracking mechanisms of PQ and DQ. And a zwitterionic functionalized SIELC Obelisc R column was employed for separation and retention of the above two polar herbicides using 50 mmol/L ammonium formate (pH = 3.7)-acetonitrile as the mobile phase. Besides, the adsorption and desorption conditions of Fe3O4@SiO2@poly(4-VB) toward PQ and DQ were optimized in spiking urine samples to obtain the best adsorption and desorption efficiencies. And the adsorption mechanisms of Fe3O4@SiO2@poly(4-VB) toward PQ and DQ referred to synergetic effect of electrostatic attraction and π-π interaction. Under the optimal conditions, the inter-day and intra-day spiking recoveries of the proposed method were in the range of 86.7-109.9% with RSDs less than 10%. The limits of detection (LODs) were obtained by spiking in blank urine samples at a series of low concentrations and were found to be 0.12 µg/L and 0.14 µg/L for PQ and DQ, respectively, which were lower than the comparing literatures. The developed analytical method was proven to be simple, rapid, sensitive, and accurate for clinical poisoning analysis.

A general strategy to prepare SERS active filter membranes for extraction and detection of pesticides in water.

An important feature in the fabrication of surface-enhanced Raman scattering (SERS) platforms is, together with the high efficiency, to allow the rapid collection and analysis of a vestigial analyte. Conventional substrates based on rigid solid materials or metal hydrosols are not suitable for sample extraction, limiting their application in areas such as water quality monitoring. Herein, we have developed a strategy to fabricate SERS active substrates (Ag/LCP) based on liquid-crystal polymer (LCP) textile fibers decorated with Ag nanoparticles (NPs). Two distinct methods for substrate preparation envisaging the SERS detection of the pesticide thiram have been explored in this research. In a first stage, we have investigated the usefulness of both approaches using ethanolic solutions of the pesticide thiram, and after real samples spiked with thiram were used to explore the analysis in real environment. The SERS analysis of thiram dissolved in Aveiro Estuary water and in fruit juices have provided enhancement factors of 1.67 × 107 and 3.86 × 105, respectively, using the Ag/LCP composites. Noteworthy, in the latter case, the detection limit (0.024 ppm) achieved is lower than the maximal residue limit (MRL) of 5 ppm in fruit, as prescribed by European regulations (EU) 2016/1. Moreover, the selectivity of the SERS substrates for different pesticides was also evaluated, analyzing distinct pesticides such as paraquat and sodium diethyldithiocarbamate. SERS active Ag/LCP/PA filter membranes were also prepared using Ag/LCP composites supported by a polyamide (PA) filter, which can be an easy alternative to prepare simple, highly efficient and low-cost SERS active filter membranes for water analysis.

Prognostic comparison of goal-oriented hemoperfusion and routine hemoperfusion combined with continuous venovenous hemofiltration for paraquat poisoning.

Objective To investigate the impact of goal-oriented hemoperfusion (HP) with monitoring of the paraquat concentration on the prognosis of patients with acute paraquat poisoning. Methods This prospective observational study involved patients with acute paraquat poisoning admitted from March 2012 to September 2015. The patients received either goal-oriented or routine HP. All other treatments were the same between the two groups. The primary endpoint was 28-day mortality after poisoning. The secondary endpoints were the incidence of organ dysfunction within 7 days and 7-day mortality. Results Eighty-four patients were enrolled (49 in the control group and 35 in the goal-oriented group). The two groups were similar in terms of clinical characteristics. There was no significant difference in the incidence of organ dysfunction between the two groups within 1 week of admission. Mortality on day 7 was significantly lower in the goal-oriented than control group, but there was no difference on day 28. However, 28-day mortality was significantly lower in the goal-oriented group among patients with an oral dose of ≤50 ml. Conclusions HP with monitoring of the urine paraquat concentration as goal-oriented therapy can reduce the early mortality of paraquat poisoning.

One-step green synthetic approach for the preparation of multicolor emitting copper nanoclusters and their applications in chemical species sensing and bioimaging.

One-step green microwave synthetic approach was developed for the synthesis of copper nanoclusters (Cu NCs) and used as a fluorescent probe for the sensitive detection of thiram and paraquat in water and food samples. Unexpectedly, the prepared Cu NCs exhibited strong orange fluorescence and showed emission peak at 600 nm, respectively. Under optimized conditions, the quenching of Cu NCs emission peak at 600 nm was linearly proportional to thiram and paraquat concentrations in the ranges from 0.5 to 1000 µM, and from 0.2 to 1000 µM, with detection limits of 70 nM and 49 nM, respectively. In addition, bioimaging studies against Bacillus subtilis through confocal fluorescence microscopy indicated that Cu NCs showed strong blue and green fluorescence signals, good permeability and minimum toxicity against the various bacteria species, which demonstrates their potential feasibility for chemical species sensing and bioimaging applications.

Ionic liquid-modified silica-coated magnetic nanoparticles: promising adsorbents for ultra-fast extraction of paraquat from aqueous solution.

In the present study, ionic liquid-modified silica-coated magnetic nanoparticles (Fe3O4@SiO2@IL) were synthesized and applied as adsorbents for extraction and determination of paraquat (PQ) followed by high-performance liquid chromatography. For assurance of the extraction efficiency, the obtained results were compared with those obtained by bared magnetic nanoparticles (MNPs). Experimental design and response surface methodology were used for optimization of different parameters which affect extraction efficiency of paraquat using both adsorbents. Under the optimized conditions, extraction recoveries in the range of 20-25 and 35-40 % with satisfactory repeatability values (RSDs%, n = 4) less than 5.0 % were obtained for bared MNPs and Fe3O4@SiO2@IL, respectively. The limits of detection were 0.1 and 0.25 µg/L using Fe3O4@SiO2@IL and bared MNPs, respectively. The linearity was obtained in the range of 0.25 to 25 µg/L and 0.5 to 25 µg/L for Fe3O4@SiO2@IL and bared MNPs, respectively, with the coefficients of determination better than 0.9950. Finally, Fe3O4@SiO2@IL was chosen as superior adsorbent due to more dispersion ability, higher extraction recovery, lower detection limit, as well as better linearity and repeatability. Calculated errors (%) were in the range of 3 to 10 % depicting acceptable accuracy for the analysis of PQ by the proposed method. Finally, the method was successfully applied for extraction and determination of PQ in some water and countryside soil samples.

Magnetic single-walled carbon nanotubes-dispersive solid-phase extraction method combined with liquid chromatography-tandem mass spectrometry for the determination of paraquat in urine.

In this study, magnetic single-walled carbon nanotubes (MSWCNTs) were prepared by impregnating magnetic Fe3O4 nanoparticles onto the surfaces of carboxylic single-walled carbon nanotubes based on electrostatic interactions. The prepared MSWCNTs were used as the adsorbent for the dispersive solid-phase extraction (DSPE) of paraquat from human urine. After adsorption, the paraquat was quantitatively desorbed with 5%TFA in acetonitrile and determined by HPLC-MS. Extraction parameters such as the type of CNT adsorbent, extraction time, sample volume, wash solvent, and the type and volume of desorption solvent were optimized to obtain high DSPE recoveries and extraction efficiencies. Under the optimized conditions, the calibration curve was linear in the range 3.75-375.0 µg/L with a correlation coefficient of 0.999 45. The LOD (S/N=3) and LOQ (S/N=10) were 0.94 and 2.82 µg/L, respectively. The recoveries ranged from 92.89 to 108.9% for spiked real urine samples with RSDs below 3.21%. Finally, the new method was successfully used to determine paraquat in urine samples of suspected paraquat poisoning patients. The MSWCNTs exhibited suitable properties and a high adsorption capacity for the extraction of paraquat.

Sensitive determination of paraquat by square wave anodic stripping voltammetry with chitin modified carbon paste electrode.

A novel analytical approach has been developed and evaluated for the quantitative analysis of paraquat herbicides which can be found at trace levels in olive oil and olives. The aim of this work is to optimize all factors that can influence this determination by a carbon paste electrode modified with chitin (Chit-CPE). The best responses were obtained with square wave potential in diluted Na2SO4 as supporting electrolyte. The influence of various parameters on the Chit-CPE was investigated. Under the optimized working conditions, calibration graphs were linear in the concentration ranges of 5.0 × 10(-9)-1.0 × 0(-5) mol L(-1). For 180 s preconcentration, detection limits of 2.67 × 10(-10) mol L(-1) (peak 2) was obtained at the signal noise ratio (SNR) of 3. To evaluate the reproducibility of the newly developed electrode, the measurements of 1.0 × 10(-5) mol L(-1) PQ were carried out for seven times at Chit-CPE and the relative standard deviation was 5.2%. The analytical methodology was successfully applied to monitor the paraquat content in olives and olive oil.

A bioconjugated design for amino acid-modified mesoporous silicas as effective adsorbents for toxic chemicals.

A general synthetic method for functionalization of mesoporous silica with amino acid has been developed. The carboxylic acid functionalized SBA-15 was conjugated with l-phenylalanine (Phe) and l-tryptophan (Trp) to obtain nontoxic amino acid-conjugated functionalized mesoporous silica materials. The materials were used as adsorbents for the removal of the herbicide Paraquat (PQ) and its analog, ethyl viologen dibromide (EVB) from aqueous solutions. In comparison to the commercially available activated carbon adsorbents, the silica-based adsorbents prepared in this study exhibited relatively higher PQ removal efficiency in aqueous solutions at room temperature and pH 7.0. The silica-based adsorbents, pendant with amino acid moieties exhibited greater adsorption capacities toward PQ and EVB than the analogs but without the amino acid moiety, suggesting that there is a benefit for the enhanced π-π interaction between the aromatic groups of the conjugated amino acid moieties and the adsorbate. This bioconjugated method developed here provides a promising new tool to synthesize new materials for detoxification of herbicides in clinical trials.

Preparation of acrylic acid-modified chitin improved by an experimental design and its application in absorbing toxic organic compounds.

Chitin grafted poly (acrylic acid) (chi-g-PAA) is synthesized and characterized as an adsorbent of toxic organic compounds. Chi-g-PAA copolymers are prepared using of ammonium cerium (IV) nitrate (Ce(4+)) as the initiator. The highest grafting percentage of AA in chitin obtained using the traditional technique is 163.1%. A maximum grafting percentage of 230.6% is obtained using central composite design (CCD). Experimental results are consistent with theoretical calculations. The grafted copolymer is characterized by Fourier transform Infrared spectroscopy and solid state (13)C NMR. A representative chi-g-AA copolymer is hydrolyzed to a type of sodium salt (chi-g-PANa) and used in the adsorption of malachite green (MG), methyl violet (MV), and paraquat (PQ) in aqueous. The monolayer adsorption capacities of these substances are 285.7, 357.1, and 322.6 mg/g-adsorbent, respectively. Thermodynamic calculations show that the adsorption of MG, MV, and PQ are more favored at diluted solutions. The high adsorption capacity of chi-g-PANa for toxic matter indicates its potential in the treatment of wastewater and emergency treatment of PQ-poisoned patients.

An improved approach for extraction and high-performance liquid chromatography analysis of paraquat in human plasma.

A simple, sensitive, reliable and economical HPLC method for quantifying paraquat concentration in human plasma has been developed, using diethyl paraquat as an internal standard. The drugs were extracted from the sample and separated on Xtimate C18 column with a mobile phase of 15% acetonitrile in 0.1M orthophosphoric acid containing SDS (150 mg/l). The pH of the mobile phase was adjusted to 3 with triethylamine and the detection wavelength was 256 nm for both paraquat and the internal standard. The average extraction recoveries were 91.9%. Good linearity (R(2)=0.9984) was observed throughout the range of 0.02-10 µg/ml in 0.5 ml plasma. The overall accuracy of this method was 97.6-107.3% and the lower limit of detection was 0.01 µg/ml. The intra- and inter-day variations were lower than 3.65% and 2.64%, respectively. We used this method to examine the paraquat concentrations of 53 patients with acute paraquat intoxication of whom 26 (49.1%) survived. In conclusion, this method was suitable for quantification of paraquat plasma concentration in toxicological samples. It was helpful in both assessing the severity of intoxication and predicting the outcome of paraquat poisoning.

Adsorption of paraquat on goethite and humic acid-coated goethite.

Adsorption of cationic pesticides in soils is generally attributed to mineral clays and organic matter components. However, iron oxides may also contribute to such adsorption or affect it by associating with other components. Using goethite and humic acid as models for iron oxides and organic matter respectively, we studied the adsorption of the cationic pesticide paraquat on goethite and humic acid-coated goethite. At pH 4.0 the adsorption on goethite was not significant, and at pH 10.0, although the surface of the oxide was negatively charged, much less pesticide was adsorbed than on mineral clays. At this pH the adsorption of paraquat decreased as the ionic strength increased, and application of the charge distribution multisite complexation model (CD-MUSIC model) enabled interpretation of the results. At pH 4, the adsorption of paraquat on the humic acid-coated goethite was similar to the adsorption on mineral clays, but was considerably less than the adsorption on humic acid in solution. The lower adsorption on solid organic matter is attributed to a decrease in the number of "active" binding sites on the humic acid as a result of the binding to iron oxide.

Study of the removal of paraquat from aqueous solution by biosorption onto Ayous (Triplochiton schleroxylon) sawdust.

This study concerns the batch biosorption of paraquat on Ayous (Triplochiton schleroxylon) sawdust; the study centers on the evolution of biosorption parameters during the process. It appears that paraquat forms a monolayer on the sawdust surface as evidenced by the good correlation between the experimental data and the Langmuir model. The biosorption which is rather fast (the equilibrium was reached after ten minutes) follows a pseudo-second-order kinetic model and does not obey to the intra-particle diffusion model. According to the mathematical kinetic modeling, pore and surface mass transfer well describe the phenomenon. NaCl reduces the adsorption capacity of the material but has no significant effect on the kinetics. Alkaline solutions enhance the accumulation of the pollutant, the reverse being observed for acidic media. According to the thermodynamic data, this biosorption is a spontaneous and exothermic process. From these results we concluded that the adsorption of the pollutant is mainly due to cation exchange as indicated by the adsorption energy determined by the Dubinin-Radushkevich model (E=12.0736 kJ mol(-1)); some other interactions resulting from the affinity through organophilic interactions between paraquat and sawdust have also been pointed out. Desorption experiments conducted in HCl and HNO(3) solutions confirmed the proposed mechanism.

Competitive and non-competitive adsorption/desorption of paraquat, diquat and difenzoquat in vineyard-devoted soils.

Mobility of agrochemicals in soils plays an important role in the fate and transport of contaminants in the environment. Competitive and non-competitive sorption experiments of three ammonium quaternary herbicides (paraquat, diquat and difenzoquat) onto eight vineyard soils was measured in batch experiments. Non-competitive experiments show that paraquat (PQ) is the most strongly adsorbed (70-97% of added PQ) followed by diquat (DQ) and difenzoquat (DFQ). The best fits were obtained with the Freundlich equation. In competitive experiments with variable mole ratios, it was found a large influence between the divalent cationic herbicides PQ and DQ, and between them and the monovalent herbicide DFQ, but DFQ did only show a scarce influence on PQ and DQ sorption. Desorption of herbicides into CaCl(2) showed very low values: around 11, 19 and 31% for, respectively, PQ, DQ and DFQ. In order to assess the ability of herbicides to displace others, desorption experiments were carried out by replacing Cl(2)Ca by any of the other two herbicides. In this case, the highest percentage of desorption was obtained when DFQ was desorbed with PQ (>72%) and DQ (>73%), but also when PQ was used to desorb DQ (100%) and vice versa (100%).

Preparation of methacrylic acid-modified rice husk improved by an experimental design and application for paraquat adsorption.

Methacrylic acid (MAA) grafted rice husk was synthesized using graft copolymerization with Fenton's reagent as the redox initiator and applied to the adsorption of paraquat. The highest grafting percentage of 44.3% was obtained using the traditional kinetic method. However, a maximum grafting percentage of 65.3% was calculated using the central composite design. Experimental results based on the recipes predicted from the statistical analysis are consistent with theoretical calculations. A representative polymethacrylic acid-g-rice husk (PMAA-g-rice husk) copolymer was hydrolyzed to a salt type and applied to the adsorption of paraquat. The adsorption equilibrium data correlate more closely with the Langmuir isotherm than with the Freundlich equation. The maximum adsorption capacity of modified rice husk is 292.5mg/g-adsorbent. This value exceeds those for Fuller's earth and activated carbon, which are the most common binding agents used for paraquat. The samples at various stages were characterized by solid-state (13)C NMR spectroscopy.

Effect of organic matter and iron oxides on quaternary herbicide sorption-desorption in vineyard-devoted soils.

Herbicide soil/solution distribution coefficients (K(d)) are used in mathematical models to predict the movement of herbicides in soil and groundwater. Herbicides bind to various soil constituents to differing degrees. The universal soil colloid that binds most herbicides is organic matter; however metallic hydrous oxides might also have some influence. The adsorption-desorption of three quaternary ammonium herbicides on soils with different chemical-physical characteristics was determined using a batch equilibration method before and after the following sequential selective dissolution procedures: removal of organic matter, and removal of organic matter plus free iron oxides. The experimentation involved paraquat (PQ), diquat (DQ) and difenzoquat (DFQ) herbicides. The distribution coefficients (K(d)) of the molecules and their correlation to the soil components were determined and a significant negative correlation with organic carbon was highlighted (r<-0.610, p<0.035, n=12). All quats cations experiment high adsorption in the control soils with a Zeta potential at about -21 mV. The order of adsorption on soils (based on K(d)) was the following: PQ>DQ>>DFQ. The adsorption isotherms of these three herbicides on the natural and processed soils were satisfactorily fitted with the Freundlich equation, and a significant correlation with organic carbon was highlighted for quats K(F) (r<-0.696, p<0.012, n=12). The removal of organic matter from soils seems to leave free new adsorption sites for quats on the clay surface, which is no longer occluded by organic matter. This work shows that the amount and nature of the surface that remains available after the removal of single soil constituents is a critical parameter in determining the sorptive behavior of cationic contaminants.

Quaternary herbicides retention by the amendment of acid soils with a bentonite-based waste from wineries.

The agronomic utility of a solid waste, waste bentonite (WB), from wine companies was assessed. In this sense, the natural characteristics of the waste were measured, followed by the monitoring of its effects on the adsorption/desorption behaviour of three quaternary herbicides in acid soils after the addition of increasing levels of waste. This was done with the intention of studying the effect of the added organic matter on their adsorption. The high content in C (294 g kg(-1)), N (28 g kg(-1)), P (584 mg kg(-1)) and K (108 g kg(-1)) of WB turned it into an appropriate amendment to increase soil fertility, solving at the same time its disposal. WB also reduced the potential Cu phytotoxicity due to a change in Cu distribution towards less soluble fractions. The adsorption of the herbicides paraquat, diquat and difenzoquat by acid soils amended with different ratios of WB was measured. In all cases, Langmuir equation was fitted to the data. Paraquat (PQ) and diquat (DQ) were adsorbed and retained more strongly than difenzoquat (DFQ) in the acid soil studied. However, the lowest retention of DFQ in an acid soil can be increased by amendment with organic matter through a solid waste from wineries, and it is enough for duplicate retention a dosage rate of 10t/ha. Anyway, detritivores ecology can still be affected. Detritivores are the organisms that consume organic material, and in doing so contribute to decomposition and the recycling of nutrients. The term can also be applied to certain bottom-feeders in wet environments, which play a crucial role in benthic ecosystems, forming essential food chains and participating in the nitrogen cycle.

Removal of paraquat from synthetic wastewater using phillipsite-faujasite tuff from Jordan.

A phillipsite-faujasite tuff (faujasite) from Jordan has been activated and characterized to evaluate its efficiency in removing paraquat from synthetic wastewater and to specify optimum conditions with maximum efficiency of the faujasite tuff. Noticed variation in CEC is indicated and explained by selectivity of the faujasite to K(+) and Na(+). Removal of paraquat by using faujasite directly gave average removal efficiency equal to 59%. Thermal activation of the samples enhances their performance. The higher is the temperature of activation the higher the efficiency. Treatment of paraquat effluent using faujasite is a good alternative. Na- or K-loading of the original sample give better results. Loading with Ca and Mg however is not recommended because they always exhibit lower efficiency, which might be related to their lower CEC value. Removal of paraquat from wastewater using charcoal and the non-activated faujasite increased efficiency to about 82%. Thermal activated faujasite at 200 degrees C and 300 degrees C increased the uptake up to about 93% and 99.5%, respectively. Therefore thermal activation of faujasite is necessary to improve its uptake performance.

A novel bioluminescent bacterial biosensor using the highly specific oxidative stress-inducible pgi gene.

A new oxidative stress-responsive bacterial biosensor was constructed using the promoter of the pgi gene fused to the luxCDABE reporter. This strain (PGRFM) responded in a dose-dependent manner to methyl viologen (MV), a model redox chemical that results in oxidative stress. The responses of strain PGRFM to redox chemicals was strongly dependent on the available carbon source. For example, when the strain was grown under nutrient-limited conditions in the presence of glucose or gluconate it was capable of responding to low MV concentrations (0.6-19.3ppm), whereas the same cells grown in LB (a nutrient rich media) only responded to higher concentrations (4.9-625ppm). This allowed us to select PGRFM's growth conditions and extend the range of concentrations at which a stress-inducing chemical could be detected. Further, strain PGRFM responded to structural analogs of MV (i.e., ethyl and benzyl viologen), demonstrating that this strain is responsive to the presence of superoxide radicals, regardless of the chemical by which they are generated. Strain PGRFM's response patterns to these analogs were distinct from each other, which determined their strength to induce oxidative stress. As well, a significant induction was seen when this strain was exposed to hydrogen peroxide, illustrating that strain PGRFM is responsive in the presence of both the superoxide (O(2)(-)) and hydroxyl (OH) radicals.

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.

Removal of paraquat dissolved in a photoreactor with TiO2 immobilized on the glass-tubes of UV lamps.

Experiments were performed to investigate the effects of operating parameters, such as air-inflow rate, UV-light intensity, and film thickness of the photocatalyst, on the photo-decomposition efficiency of paraquat in an immersion-type reactor with TiO2 immobilized by three kinds of methods on the glass tube of UV lamps. As the number of TiO2 coating-time increased from 1 to 4, film thickness on the glass tube by a dip-coating method increased from 355 to 1180 A. The removal efficiency of paraquat using TiO2 prepared by the hydrothermal method was the highest, being 99% in a 12 h operation of 3-type TiO2 immobilized by a sol-gel method and a hydrothermal method, including a commercial product P-25, while that in the absence of TiO2 with only the UV light was the lowest, being 50% in 12 h. The conversion ratios of paraquat at the volumetric flow rates of 5, 10, and 20 mL min(-1) were 46%, 25%, and 17% in 18 h, respectively.