DETERMINATION OF GLYPHOSATE AND AMINOMETHYLPHOSPHONIC ACID IN SOILS BY HPLC WITH PRE-COLUMN DERIVATIZATION USING 1,2-NAPHTHOQUINONE-4-SULFONATE

Three-dimensional polymer phenylethnylcopper/nitrogen doped graphene aerogel electrode coupled with Fe3O4 NPs nanozyme: Toward sensitive and robust photoelectrochemical detection of glyphosate in agricultural matrix

BACKGROUND

Presently, glyphosate (Gly) is the most extensively used herbicide globally, Nevertheless, its excessive usage has increased its accumulation in off-target locations, and aroused concerns for food and environmental safety. Commonly used detection methods, such as high-performance liquid chromatography and gas chromatography, have limitations due to expensive instruments, complex pre-processing steps, and inadequate sensitivity. Therefore, a facile, sensitive, and reliable Gly detection method should be developed.

RESULTS

A photoelectrochemical (PEC) sensor consisting of a three-dimensional polymer phenylethnylcopper/nitrogen-doped graphene aerogel (PPhECu/3DNGA) electrode coupled with Fe3O4 NPs nanozyme was constructed for sensitive detection of Gly. The microscopic 3D network of electrodes offered fast transfer routes for photo-generated electrons and a large surface area for nanozyme loading, allowing high signal output and analytical sensitivity. Furthermore, the use of peroxidase-mimicking Fe3O4 NPs instead of natural enzyme improved the stability of the sensor against ambient temperature changes. Based on the inhibitory effect of Gly on the catalytic activity Fe3O4 NPs, the protocol achieved Gly detection in the range of 5 × 10-10 to 1 × 10-4 mol L-1. Additionally, feasibility of the detection was confirmed in real agricultural matrix including tea, maize seedlings, maize seeds and soil.

SIGNIFICANCE

This work achieved facile, sensitive and reliable analysis towards Gly, and it was expected to inspire the design and utilization of 3D architectures in monitoring agricultural chemicals in food and environmental matrix.

Bifunctional Cu(II)-containing PDA-PEI copolymer dots: Demonstration of a dual-mode platform for colorimetric-fluorescent detection of glyphosate in the environment

The reliable and accurate detection of glyphosate is urgently demanded because it is related to food and environmental safety. In this contribution, a PDA-PEI/Cu2+ complex that possesses peroxidase-mimetic activity and stimulus-responsive fluorescence was fabricated by coordinating Cu2+ with polydopamine-polyethyleneimine copolymer dots (PDA-PEI CPDs). With the introduction of Cu2+, the fluorescence intensity of PDA-PEI CPDs dropped sharply owing to the electron transfer effect. As a peroxidase-mimicking nanozyme, the PDA-PEI/Cu2+ complex owns catalytic capacity to oxidize the colorless 3,3',5,5'-tetramethylbenzidine (TMB) into blue oxTMB, leading a further fluorescence quenching by internal filtering effect by oxTMB. Once the glyphosate participated, the fluorescence signal of PDA-PEI CPDs is recovered significantly because of the formation of more stable Glyp-Cu2+ complexes, meanwhile the peroxidase-mimicking activity of PDA-PEI/Cu2+ complex could be strongly hindered. According to this principle, a novel and extremely convenient 'turn off' colorimetric and 'turn on' fluorescence sensing platform can be established for dual-mode detection of glyphosate. The favorable sensitivity and selectivity and were verified in the analysis of glyphosate in the environment through the marriage of dual-signal sensing platform. The detection limit of the dual-mode glyphosate sensing platform was 103.82 ng/mL for colorimetric assay and 16.87 ng/mL for fluorescent assay, respectively. Satisfactory recoveries in the range of 96.40%-104.66% were obtained, indicating the potential of this method for application in complicated real sample. Thereby, this strategy broadens the applications of polydopamine nanomaterials and holds a promising application in determination of pesticide residues.

Methods and Strategies for Biomonitoring in Occupational Exposure to Plant Protection Products Containing Glyphosate

Glyphosate, and the ever growing reliance on its use in agriculture, has been a point of contention for many years. There have been debates regarding the risk and safety of using glyphosate-based herbicides as well as the effects of occupational, accidental, or systematic. Although there have been a number of studies conducted, the biomonitoring of glyphosate poses a series of challenges. Researchers attempting to determine the occupational exposure face questions regarding the most appropriate analytical techniques and sampling procedures. The present review aims to summarize and synthetize the analytical methodologies available and suitable for the purpose of glyphosate biomonitoring studies as well as discuss the advantages and disadvantages of each analytical technique, from the most modern to more well-established and older ones. The most relevant publications that have described analytical methods and published within the last 12 years were studied. Methods were compared, and the advantages and disadvantages of each methods were discussed. A total of 35 manuscripts describing analytical methods for glyphosate determination were summarized and discussed, with the most relevant one being compared. For methods that were not intended for biological samples, we discussed if they could be used for biomonitoring and approaches to adapt these methods for this purpose.

Glyphosate and glufosinate-ammonium in aquaculture ponds and aquatic products: Occurrence and health risk assessment

As the two most commonly used organophosphorus herbicides, glyphosate (Gly) and glufosinate-ammonium (Glu) have unique properties for weed control and algae removal in aquaculture. However, the occurrences and health risks of Gly and Glu in aquaculture ponds are rare known. This study aimed to investigate the occurrences of Gly, AMPA (primary metabolity of Gly) and Glu in surface water, sediment and aquatic products from the grass carp (ctenopharyngodon idella), crayfish (procambarus clarkii) and crab (eriocheir sinensis) ponds around Lake Honghu, the largest freshwater lake in Hubei province, China where aquaculture has become the local pillar industry. Three age groups (children, young adults, middle-aged and elderly) exposure to these compounds through edible aquatic products (muscle) consumption were also assessed by target hazard quotient (THQ) method. The results indicated that Gly, AMPA and Glu were widely occurred in surface water, sediment and organisms in the fish, crayfish and crab ponds. AMPA was more likely to accumulate in the intestine of aquatic products than Gly and Glu. According to the total THQ value (1.04＞1), muscle consumption of grass carp may pose potential risk to children.

New Fluorescent Probes for the Sensitive Determination of Glyphosate in Food and Environmental Samples

In this paper, a dual-functional probe, 2-(benzothiazol)-4-(3-hydroxy-4-methylphenyl) imino phenol (BHMH), was synthesized and characterized for the simultaneous detection of Cu2+ and Fe3+ in dimethyl sulfoxide/4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid (DMSO/HEPES) (1:4, v/v, pH = 6.0). The limits of detections (LODs) for Cu2+ and Fe3+ were 9.05 and 48 nM, respectively. Based on the competitive coordination, the complex BHMH-Cu2+/Fe3+ exhibited good sensitivity and selectivity for glyphosate. The LODs of BHMH-Cu2+ and BHMH-Fe3+ for glyphosate were 0.41 and 0.63 μM, respectively. The probe quantitatively detected glyphosate in tap water, Songhua River water, local water and soil, and food samples. The colorimetric on-site glyphosate sensing through the probe BHMH-Cu2+ was also studied based on smartphones. BHMH and BHMH-Cu2+/Fe3+ exhibited outstanding imaging capabilities for Cu2+, Fe3+, and glyphosate in living cells with low cytotoxicity, especially the first time for glyphosate.

NPA-Cu2+ Complex as a Fluorescent Sensing Platform for the Selective and Sensitive Detection of Glyphosate

Glyphosate is a highly effective, low-toxicity, broad-spectrum herbicide, which is extensively used in global agriculture to control weeds and vegetation. However, glyphosate has become a potential threat to human and ecosystem because of its excessive usage and its bio-concentration in soil and water. Herein, a novel turn-on fluorescent probe, N-n-butyl-4-(3-pyridin)ylmethylidenehydrazine-1,8-naphthalimide (NPA), is proposed. It efficiently detected Cu2+ within the limit of detection (LOD) of 0.21 μM and displayed a dramatic turn-off fluorescence response in CH3CN. NPA-Cu2+ complex was employed to selectively and sensitively monitor glyphosate concentrations in real samples accompanied by a fluorescence turn-on mode. A good linear relationship between NPA and Cu2+ of glyphosate was found in the range of 10-100 μM with an LOD of 1.87 μM. Glyphosate exhibited a stronger chelation with Cu2+ than NPA and the system released free NPA through competitive coordination. The proposed method demonstrates great potential in quantitatively detecting glyphosate in tap water, local water from Songhua River, soil, rice, millet, maize, soybean, mung bean, and milk with mild conditions, and is a simple procedure with obvious consequences and no need for large instruments or pretreatment.

Sensitive and Fast Determination of Ceftiofur in Honey and Veterinary Formulation by HPLC-UV Method with Pre-column Derivatization

A novel, sensitive and rapid high performance liquid chromatography (HPLC) method for the determination of ceftiofur by pre-column derivatization with 1,2-naphthoquinone-4-sulfonate. Analysis was performed within 5 min on a Kinetex C18 column based on core-shell technology. The mobile phase composed of acetonitrile-water (50:50, v/v) pumped isocratically at a flow rate of 1.0 mL/min under UV detection at 254 nm. The factors affecting the derivatization reaction and separation conditions were carefully evaluated and optimized. The method was linear over the concentration range of 45-450 ng/mL with a limit of detection of 3.29 ng/mL and limit of quantitation of 10.97 ng/mL. The new method was successfully applied for the analysis of ceftiofur in the veterinary formulation and honey with average recoveries of 100.78% and 98. 83%, respectively. The present method is suitable and favorable for the analysis of ceftiofur on account of its sensitivity, rapidity and cost-effectiveness. In addition, it could have significant application for the determination of ceftiofur in other food products.

Enhanced selectivity and sensitivity for colorimetric determination of glyphosate using Mn-ZnS quantum dot embedded molecularly imprinted polymers combined with a 3D-microfluidic paper-based analytical device

We report a novel three-dimensional microfluidic paper-based analytical device (3D-μPAD) with colorimetric detection, using Mn-ZnS quantum dot embedded molecularly imprinted polymer (Mn-ZnS QD-MIP), for selective glyphosate determination in whole grain samples. Detection is based on the catalytic activity of Mn-ZnS QD-MIP in the H₂O₂ oxidation of ABTS. Glyphosate imprinted polymer is successfully synthesized on the Mn-ZnS QD surface using a poly (N-isopropylacrylamide) (NIPAM) and N, N'-Methylenebisacrylamide (MBA) as the functional monomers. The catalytic activity depends on binding or non-binding of glyphosate molecules on the synthetic recognition sites of the Mn-ZnS QD-MIP. Glyphosate selectively binds to the cavities embedded on the Mn-ZnS QD surface, and subsequently turns-off or inhibits the ABTS oxidation and color change to light green. The change of reaction color from dark green to light green depends on the concentration of glyphosate. We report, for the first time, using the relatively new penguard enamel colour to create a hydrophobic barrier. The foldable 3D-μPAD comprises three layers (top/center/bottom), named as the detection zone, immobilized Mn-ZnS QD-MIP disc, and sample loading. Assay on the 3D-μPAD can determine glyphosate by ImageJ detection, over an operating range of 0.005-50 μg mL^-1 and with a detection limit of 0.002 μg mL^-1. Our 3D-μPAD exhibits high accuracy, with a 0.4% (intra-day) and 0.7% (inter-day) relative difference from the certified CRM value. Moreover, the fabricated 3D-μPAD provides good reproducibility (1.7% RSD for ten devices). The developed 3D-μPAD was successfully applied to determine the glyphosate concentration in whole grain samples and shows great promise as an alternative highly selective and sensitive colorimetric method. The 3D-μPAD is well suited to food-quality control and onsite environmental-monitoring applications, without sophisticated instrumentation.

A novel systematic absence of cross peaks-based 2D-COS approach for bilinear data

A novel approach to use two-dimensional correlation spectroscopy (2D-COS) to analyze bilinear data is proposed. A phenomenon called Systematic Absence of Cross Peaks (SACPs) is observed in a 2D asynchronous spectrum. Two theorems relevant to SACPs have been derived. The SACP-based 2D-COS method has been successfully applied on analyzing bilinear data from mixed samples (including one model system and two real systems). Implicit isolated peaks can be identified and assigned to different components based on characteristic pattern of SACPs even if the time-related profiles of different components are severely overlapped. Based on the results of SACPs, spectra of pure components can be retrieved. Identification of SACPs can still be achieved in the presence of artifacts. Thus, neither noise nor baseline drift can produce significant influence on the results obtained from the approach described in this paper. We have used several well-established chemometric methods, including N-Findr, VCA, and MCR with various initial settings, on two systems that can be successfully solved using the 2D-COS method. The chemometric methods mentioned above cannot provide correct spectra of pure components because of severe problem of rotational ambiguity derived from severe overlapping of the time-related profiles. Only when the information from SACPs in 2D-COS is used as additional constraints in MCR calculation, correct spectra can be obtained. That is to say, the SACP-based 2D-COS method provides intrinsic information which is crucial in the analysis of chromatographic-spectroscopic and analogous data even if the time-related profiles of different components overlap severely.

Analysis of glyphosate and aminomethylphosphonic acid in water, plant materials and soil

There is a need for simple, fast, efficient and sensitive methods of analysis for glyphosate and its degradate aminomethylphosphonic acid (AMPA) in diverse matrices such as water, plant materials and soil to facilitate environmental research needed to address the continuing concerns related to increasing glyphosate use. A variety of water-based solutions have been used to extract the chemicals from different matrices. Many methods require extensive sample preparation, including derivatization and clean-up, prior to analysis by a variety of detection techniques. This review summarizes methods used during the past 15 years for analysis of glyphosate and AMPA in water, plant materials and soil. The simplest methods use aqueous extraction of glyphosate and AMPA from plant materials and soil, no derivatization, solid-phase extraction (SPE) columns for clean-up, guard columns for separation and confirmation of the analytes by mass spectrometry and quantitation using isotope-labeled internal standards. They have levels of detection (LODs) below the regulatory limits in North America. These methods are discussed in more detail in the review.

Degradation dynamics of glyphosate in different types of citrus orchard soils in China

Glyphosate formulations that are used as a broad-spectrum systemic herbicide have been widely applied in agriculture, causing increasing concerns about residues in soils. In this study, the degradation dynamics of glyphosate in different types of citrus orchard soils in China were evaluated under field conditions. Glyphosate soluble powder and aqueous solution were applied at 3000 and 5040 g active ingredient/hm2, respectively, in citrus orchard soils, and periodically drawn soil samples were analyzed by high performance liquid chromatography. The results showed that the amount of glyphosate and its degradation product aminomethylphosphonic acid (AMPA) in soils was reduced with the increase of time after application of glyphosate formulations. Indeed, the amount of glyphosate in red soil from Hunan and Zhejiang Province, and clay soil from Guangxi Province varied from 0.13 to 0.91 µg/g at 42 days after application of aqueous solution. Furthermore, the amount of glyphosate in medium loam from Zhejiang and Guangdong Province, and brown loam from Guizhou Province varied from less than 0.10 to 0.14 µg/g, while the amount of AMPA varied from less than 0.10 to 0.99 µg/g at 42 days after application of soluble powder. Overall, these findings demonstrated that the degradation dynamics of glyphosate aqueous solution and soluble powder as well as AMPA depend on the physicochemical properties of the applied soils, in particular soil pH, which should be carefully considered in the application of glyphosate herbicide.