Capillary electrophoresis-mass spectrometry for the direct analysis of glyphosate: method development and application to beer beverages and environmental studies

Electrochemical Detection of Glyphosate in Surface Water Samples Based on Modified Screen-Printed Electrodes

This study addresses the necessity to monitor the presence of glyphosate (Gly) in waters, highlighting the need for on-site detection of Gly by using electrochemical sensors in environmental and agricultural monitoring programs. Two approaches were employed: (1) modification with graphene decorated with gold nanoparticles (AuNPs-Gr) and dispersed in either dimethylformamide (DMF) or a solution containing Nafion and isopropanol (NAF), and (2) molecularly imprinted polymers (MIPs) based on polypyrrole (PPy) deposited on gold SPEs (AuSPE). Electrochemical characterization revealed that sensors made of AuNPs-Gr/SPCE exhibited enhanced conductivity, larger active area, and improved charge transfer kinetics compared to unmodified SPEs and SPEs modified with graphene alone. However, the indirect detection mechanism of Gly via complex formation with metallic cations in AuNPs-Gr-based sensors introduces complexities and compromises sensitivity and selectivity. In contrast, MIPPy/AuSPE sensors demonstrated superior performance, offering enhanced reliability and sensitivity for Gly analysis. The MIPPy/AuSPE sensor allowed the detection of Gly concentrations as low as 5 ng/L, with excellent selectivity and reproducibility. Moreover, testing in real surface water samples from the Olt River in Romania showed recovery rates ranging from 90% to 99%, highlighting the effectiveness of the detection method. Future perspectives include expanding the investigation to monitor Gly decomposition in aquatic environments over time, providing insights into the decomposition's long-term effects on water quality and ecosystem health, and modifying regulatory measures and agricultural practices for mitigating its impact. This research contributes to the development of robust and reliable electrochemical sensors for on-site monitoring of Glyphosate in environmental and agricultural settings.

Strategies for capillary electrophoresis: Method development and validation for pharmaceutical and biological applications-Updated and completely revised edition

This review is in support of the development of selective, precise, fast, and validated capillary electrophoresis (CE) methods. It follows up a similar article from 1998, Wätzig H, Degenhardt M, Kunkel A. "Strategies for capillary electrophoresis: method development and validation for pharmaceutical and biological applications," pointing out which fundamentals are still valid and at the same time showing the enormous achievements in the last 25 years. The structures of both reviews are widely similar, in order to facilitate their simultaneous use. Focusing on pharmaceutical and biological applications, the successful use of CE is now demonstrated by more than 600 carefully selected references. Many of those are recent reviews; therefore, a significant overview about the field is provided. There are extra sections about sample pretreatment related to CE and microchip CE, and a completely revised section about method development for protein analytes and biomolecules in general. The general strategies for method development are summed up with regard to selectivity, efficiency, precision, analysis time, limit of detection, sample pretreatment requirements, and validation.

A Novel Fluorescent Sensor Based on Aptamer and qPCR for Determination of Glyphosate in Tap Water

Glyphosate (GLYP) is a broad-spectrum, nonselective, organic phosphine postemergence herbicide registered for many food and nonfood fields. Herein, we developed a biosensor (Mbs@dsDNA) based on carboxylated modified magnetic beads incubated with NH2-polyA and then hybridized with polyT-glyphosate aptamer and complementary DNA. Afterwards, a quantitative detection method based on qPCR was established. When the glyphosate aptamer on Mbs@dsDNA specifically recognizes glyphosate, complementary DNA is released and then enters the qPCR signal amplification process. The linear range of the method was 0.6 μmol/L−30 mmol/L and the detection limit was set at 0.6 μmol/L. The recoveries in tap water ranged from 103.4 to 104.9% and the relative standard deviations (RSDs) were <1%. The aptamer proposed in this study has good potential for recognizing glyphosate. The detection method combined with qPCR might have good application prospects in detecting and supervising other pesticide residues.

Development and validation of an integrated microfluidic device with an in-line Surface Enhanced Raman Spectroscopy (SERS) detection of glyphosate in drinking water

Glyphosate, also known as N-(phosphonomethyl)glycine, is one of the most widely used herbicides in the world. However, the controversy surrounding the toxicity of glyphosate and its main breakdown product, aminomethylphosphonic acid (AMPA), remains a serious public concern. Therefore, there is a clear need to develop a rapid, sensitive and automated alternative method for the quantification of glyphosate and AMPA. In this context, surface enhanced Raman spectroscopy (SERS) coupled with a microfluidic system for the determination of glyphosate in tap water was developed, optimized and validated. The design of the microfluidic configuration for this application was built constructed to integrate the synthesis of the SERS substrate through to the detection of the analyte. To optimize the microfluidic setup, a design of experiments approach was used to maximize the SERS signal of glyphosate. Subsequently, an approach based on the European guideline document SANTE/11312/2021 was used to validate the method in the range of 78-480 μg/L using the normalized band intensities. The limit of detection and quantification obtained for glyphosate were 40 and 78 μg/L, respectively. Recoveries were in the range 76-117%, while repeatability and intra-day reproducibility were ≤17%. Finally, the method was also tested for the determination of AMPA in tap water matrix and for the simultaneous detection of AMPA and glyphosate.

In-line sample concentration in capillary electrophoresis by cyclodextrin to admicelle microextraction

Cyclodextrins (CDs) as a pseudophase in pseudophase-to-pseudophase microextraction (P2ME) in capillary zone electrophoresis (CZE) are proposed. In this P2ME mode called CD to admicelle ME, a long plug of dilute analyte solution prepared in cetyltrimethylammonium bromide (CTAB) at the critical micellar concentration was injected into the capillary. This formed CTAB admicelles at the interface between the solution and the negatively charged capillary surface, where the analytes were trapped. The injection of CD solution released the admicelles and the analytes from the capillary surface due to the formation of stable CD/CTAB inclusion complexes. The analytes are concentrated at the CD front during injection and voltage separation. Various neutral CDs were found to be effective for CD to admicelle ME. To implement this in-line sample concentration technique in CZE, CD concentration, sample injection time, and sample:CD solution injection ratio were optimized. The optimized conditions for five model anionic analytes, namely, 4-bromophenol, sulindac, sulfamethizole, 4-vinylbenzoic acid, and succinylsulfathiazole, were 20 mM α-CD in 20 mM sodium tetraborate (pH 9.2) solution, sample injection time of 370 s, and CD:sample injection ratio of 1:2. The sensitivity enhancement factors (SEFs) were between 112 and 168. The SEFs of sulindac and sulfamethizole in particular were similar to previously published off-line microextraction techniques, which are typically time-consuming. The calculated values of LOQ, intra-/inter-day (n = 6/n = 10, 3 days) repeatability, and linearity (R2) of CD to admicelle ME were 0.0125-0.05 µg/mL, 1.5-4.6%, 1.8-4.8%, and ≥0.999, respectively. Finally, the potential of CD to admicelle ME to the analysis of artificial urine samples was demonstrated.

Picomolar detection limits for glyphosate by two-dimensional column-coupled isotachophoresis/capillary zone electrophoresis-mass spectrometry

Capillary electrophoresis-mass spectrometry often lacks sufficient limits of detection for trace substances in the environment due to its low loadability. To overcome this problem, we conducted a feasibility study for column-coupling isotachophoresis to capillary electrophoresis-mass spectrometry. The first dimension isotachophoresis preconcentrated the analytes. The column-coupling of both dimensions was achieved by a hybrid capillary microfluidic chip setup. Reliable analyte transfer by voltage switching was enabled by an in-chip capacitively coupled contactless conductivity detector placed around the channel of the common section between two T-shaped crossings in the chip connecting both dimensions. This eliminated the need to calculate the moment of analyte transfer. A commercial capillary electrophoresis-mass spectrometry instrument with easily installable adaptations operated the setup. Prior to coupling isotachophoresis with capillary zone electrophoresis-mass spectrometry, both dimensions were optimized individually by simulations and verified experimentally. Both dimensions were able to stack/separate all degradation products of glyphosate, the most important herbicide applied worldwide. The first dimension isotachophoresis also removed phosphate, which is a critical matrix component in many environmental samples. Enrichment and separation of glyphosate and its main degradation product aminomethylphosphonic acid by the 2D setup provided an excellent limit of detection of 150 pM (25 ng/L) for glyphosate. This article is protected by copyright. All rights reserved.

Recent progress in analytical capillary isotachophoresis (2018 - March 2022)

This review brings a survey of papers on analytical capillary and microchip isotachophoresis published since 2018 until the first quarter of 2022. Theoretical papers extending fundamental knowledge include those on computer simulations that remain an important research tool useful in the design of electrolyte systems. Many papers are focused on instrumental aspects where new media including microfluidic devices and their hyphenation to various detection techniques bring remarkable results. Papers reporting analytical applications demonstrate the potential of contemporary analytical isotachophoresis. Although it is not being used on a mass scale, its special features are attracting continued interest resulting in applications of isotachophoresis both as a stand-alone analytical method and as a part of multidimensional separation techniques.

Phosphate addition enhances alkaline extraction of glyphosate from highly sorptive soils and aquatic sediments

BACKGROUND

Analytical constraints complicate environmental monitoring campaigns of the herbicide glyphosate and its major degradation product aminomethylphosphonic acid (AMPA): their strong sorption to soil minerals requires harsh extraction conditions. Coextracted matrix compounds impair downstream analysis and must be removed before analysis.

RESULTS

A new extraction method combined with subsequent capillary electrophoresis-mass spectrometry for derivatization-free analysis of glyphosate and AMPA in soil and sediment was developed and applied to a suite of environmental samples. It was compared to three extraction methods from literature. We show that no extraction medium reaches 100% recovery. The new phosphate-supported alkaline extraction method revealed (1) high recoveries of 70-90% for soils and aquatic sediments, (2) limits of detections below 20 μg kg-1 , and (3) a high robustness, because impairing matrix components (trivalent cations and humic acids) were precipitated prior to the analysis. Soil and sediment samples collected around Tübingen, Germany, revealed maximum glyphosate and AMPA residues of 80 and 2100 μg kg-1 , respectively, with residues observed along a core of lake sediments. Glyphosate and/or AMPA were found in 40% of arable soils and 57% of aquatic sediment samples.

CONCLUSION

In this work, we discuss soil parameters that influence (de)sorption and thus extraction. From our results we conclude that residues of glyphosate in environmental samples are easily underestimated. With its possible high throughput, the method presented here can resolve current limitations in monitoring campaigns of glyphosate by addressing soil and aquatic sediment samples with critical sorption characteristics.

Heavy rainfall following a summer drought stimulates soil redox dynamics and facilitates rapid and deep translocation of glyphosate in floodplain soils

We present field data on the effects of heavy rainfall after drought on the mobility of glyphosate and redox conditions in a clayey floodplain soil. By applying glyphosate together with deuterated water as conservative tracer in combination with time resolved in situ redox potential measurements, the spatial and temporal patterns of water infiltration and pesticide transport as well as the concomitant changes of the redox conditions were revealed. Our findings demonstrate that shrinkage cracks in dry soils can serve as effective transport paths for atmospheric oxygen, water and glyphosate. The rain intensity of a typical summer storm event (approx. 25 mm within one hour) was sufficient to translocate deuterated water and glyphosate to the subsoil (50 cm) within 2 hours. Soil wetting induced partial closure of the shrinkage cracks and stimulated microbial activity resulting in pronounced dynamics of in situ soil redox conditions. Redox potentials in 40 to 50 cm depth dropped permanently to strongly reducing conditions within hours to days but fluctuated between reducing and oxidizing conditions in 10 to 30 cm depth. Our findings highlight the close link between the presence of macropores (shrinkage cracks), heavy rainfall after drought, redox dynamics and pesticide translocation to the subsoil and thus call for further studies addressing the effects of dynamic redox conditions as a limiting factor for glyphosate degradation.

Highly sensitive visual colorimetric sensor for trichlorfon detection based on the inhibition of metallization of gold nanorods

In this study, a highly sensitive visual colorimetric sensor was designed for the detection of trichlorfon based on inhibiting ascorbate oxidase (AAO)-induced metallization of gold nanorods (Au NRs). Ascorbic acid (AA) can reduce silver ion (Ag⁺) to metal silver (Ag) that will be deposited on the surface of Au NRs, which results in the blue shift of longitudinal localized surface plasmon resonance (LSPR) peak of Au NRs, accompanying by perceptible color changes from red to cyan to red to yellow. In the presence of trichlorfon, the activity of AAO will be inhibited, resulting in less AA is hydrolyzed to dehydroascorbic acid (DHA), and therefore more Ag⁺ is reduced to Ag by AA. Under the optimized conditions, detection of trichlorfon has a wide linear range of 27.8-11111.1 μg/L with a limit of detection as low as 132.6 ng/L. Moreover, the sensor has a good sample spiked recovery (84.7-96.8%) for the determination of trichlorfon in lake water samples. The proposed method can achieve rapid analysis (about 10 min) of trichlorfon with simple operation when there are no other types of organophosphorus pesticides in the real samples.

Capillary electrophoresis applied for the determination of acidity constants and limiting electrophoretic mobilities of ionizable herbicides including glyphosate and its metabolites and for their simultaneous separation

Thermodynamic acidity constants and limiting ionic mobilities were determined for polyprotic non-chromophore analytes using capillary electrophoresis with capacitively coupled contactless conductivity detection. It was not necessary to work with buffers of identical ionic strength as ionic strength effects on effective electrophoretic mobilities were corrected by modeling during data evaluation (software AnglerFish). The mobility data from capillary electrophoresis coupled to conductivity detection were determined in the pH range from 1.25 to 12.02 with a high resolution (36 pH steps). With this strategy, thermodynamic acidity constants and limiting ionic mobilities for various acidic herbicides were determined, sometimes for the first time. The model analytes included glyphosate, its metabolites, and its acetylated derivates (aminomethyl phosphonic acid, glyoxylic acid, sarcosine, glycine, N-acetyl glyphosate, N-acetyl aminomethyl phosphonic acid, hydroxymethyl phosphonic acid). The obtained data were used in simulations to optimize separations by capillary electrophoresis. Simulations correlated very well to experimental results. With the new method, the separation of glyphosate from interfering components like phosphate in beer samples was possible.

Food, Beverage, and Feedstock Processing Facility Wastewater: a Unique and Underappreciated Source of Contaminants to U.S. Streams

Process wastewaters from food, beverage, and feedstock facilities, although regulated, are an under-investigated environmental contaminant source. Food process wastewaters (FPWWs) from 23 facilities in 17 U.S. states were sampled and documented for a plethora of chemical and microbial contaminants. Of the 576 analyzed organics, 184 (32%) were detected at least once, with concentrations as large as 143 μg L^-1 (6:2 fluorotelomer sulfonic acid), and as many as 47 were detected in a single FPWW sample. Cumulative per/polyfluoroalkyl substance concentrations up to 185 μg L^-1 and large pesticide transformation product concentrations (e.g., methomyl oxime, 40 μg L^-1; clothianidin TMG, 2.02 μg L^-1) were observed. Despite 48% of FPWW undergoing disinfection treatment prior to discharge, bacteria resistant to third-generation antibiotics were found in each facility type, and multiple bacterial groups were detected in all samples, including total coliforms. The exposure-activity ratios and toxicity quotients exceeded 1.0 in 13 and 22% of samples, respectively, indicating potential biological effects and toxicity to vertebrates and invertebrates associated with the discharge of FPWW. Organic contaminant profiles of FPWW differed from previously reported contaminant profiles of municipal effluents and urban storm water, indicating that FPWW is another important source of chemical and microbial contaminant mixtures discharged into receiving surface waters.

Titanium dioxide-coated core-shell silica microspheres-based solid-phase extraction combined with sheathless capillary electrophoresis-mass spectrometry for analysis of glyphosate, glufosinate and their metabolites in baby foods

Because of their extremely low amount in complex samples, it is quite challenging to accurate determine residues of phosphorus-containing amino-acid-like herbicides (PAAHs) in food products. Here we develop novel core-shell mesoporous silica (CSMS) microspheres coated by titanium dioxide (CSMS@TiO2) for extraction and enrichment of PAAHs in baby foods. After the dispersive solid phase extraction (d-SPE), sheathless capillary electrophoresis-mass spectrometry (sheathless CE-MS) is utilized to achieve efficient separation and sensitive detection. The synthesized CSMS@TiO2 composites are characterized by various spectroscopic techniques, proving TiO2 is uniformly distributed onto the channel surface of CSMS. The composites have essential features that are favorable for adsorption of the analytes on the material for d-SPE, including uniform diameter (1.0 μm with a shell thickness of 133 nm), large perpendicular mesopores (15.6 nm), high surface area (101.1 m2/g) and large pore volume (0.4 cm3/g). Taking glyphosate, glufosinate and their main metabolites (aminomethylphosphonic acid and 3-methylphosphinicopropionic acid) as analytes, selective and efficient enrichment is achieved by CSMS@TiO2-based d-SPE through the affinity interaction between titanium dioxide and phosphate groups. Sensitive detection of target compounds is achieved with low limits of quantitation (LOQs) between 0.3-1.6 ng/mL and excellent inter/intra-day repeatability. The compounds in nine different commercial baby foods from local markets are analyzed using the proposed method. Good recoveries of 82.3-102.6% are achieved with low RSDs (n = 5) of 2.1-8.3%. Our study indicates that the proposed CSMS@TiO2-based d-SPE combined with sheathless CE-MS is an accurate and reliable approach for sensitive determination of trace-amount PAAHs and their metabolites in complex samples.

Porous layer open-tubular column with styrene and itaconic acid-copolymerized polymer as stationary phase for capillary electrochromatography-mass spectrometry

Enhancing the specific surface area of stationary phase is important in chromatographic science, especially in open-tubular column in which the coating only exists on the inner surface. In this work, a porous layer open-tubular (PLOT) column with stationary phase of styrene and itaconic acid-copolymerized polymer was developed. Thermal-initiated polymerization method with strategies like controlling the ratio of reaction reagents to solvents and reaction time, confinement by the narrow inner diameter of capillary were used for preparing the stationary phase with uniform structure and relatively thick layer. Due to the high separation efficiency and capacity, the PLOT column was used for capillary electrochromatography (CEC) separation of multiple groups of analytes like alkylbenzenes, phenyl amines, phenols, vanillins, and sulfonamides with theoretical plates (N) up to 1,54,845 N/m. In addition, due to high permeability of the CEC column and large electroosmotic flow mobility generated by abundant carboxyl groups in the coating material, the PLOT-CEC column was successfully coupled with mass spectrometry (MS) through a sheath flow interface. The developed PLOT-CEC-MS method was used for the analysis of antiseptics like parabens and herbicides like pyridines.

Capillary electromigration methods for food analysis and Foodomics: Advances and applications in the period February 2019-February 2021

This work presents a revision of the main applications of capillary electromigration methods in food analysis and Foodomics. Articles that were published during the period February 2019-February 2021 are included. The work shows the multiple CE methods that have been developed and applied to analyze different types of molecules in foods. Namely, CE methods have been applied to analyze amino acids, biogenic amines, carbohydrates, chiral compounds, contaminants, DNAs, food additives, heterocyclic amines, lipids, secondary metabolites, peptides, pesticides, phenols, pigments, polyphenols, proteins, residues, toxins, vitamins, small organic and inorganic compounds, as well as other minor compounds. The last results on the use of CE for monitoring food interactions and food processing, including recent microchips developments and new applications of CE in Foodomics, are discussed too. The new procedures of CE to investigate food quality and safety, nutritional value, storage and bioactivity are also included in the present review work.

Advancements in capacitance-to-digital converter-based C4 D technology for detection in capillary electrophoresis using amplified excitation voltages and comparison to classical and open-source C4 Ds

This work introduces new hardware configurations for a capacitively coupled contactless conductivity detector (C⁴ D) based on capacitance-to-digital conversion (CDC) technology for CE. The aim was to improve sensitivity, handling, price, and portability of CDC-based C⁴ D detectors (CDCD) to reach LODs similar to classic C⁴ Ds with more sophisticated electric circuits. To achieve this, a systematic study on the CDCDs was carried out including a direct comparison to already established C⁴ D setups. Instrumental setups differing in electrode lengths, measurement modes, and amplification of excitation voltages were investigated to achieve LODs for alkali metal ions of 4 to 12 μM, similar to LODs obtained by classic C⁴ D setups. Lowest LODs were achieved for a setup with two 10 mm electrodes at a distance of 0.2 mm and an excitation voltage of 24 V. The detection head was exceptionally lightweight with only 2.6 g and covered only 20 mm of the capillary on total. This allowed the use of multiple detectors along the separation path to enable spatial tracking of analytes during separation. The entirely battery-powered detector assembly weighs less than 200 g, and the data are transmitted wirelessly for possible portable applications. The freely accessible hardware and software were optimized for fully automated measurements with real time data plotting and allowed handling multidetector setups. The new developments were applied to quantify the potassium salt of glyphosate in its herbicide formulation.

Functionalized silver nanoparticles as colorimetric probes for sensing tricyclazole

A colorimetric assay for highly selective and sensitive detection of tricyclazole using fluorescein-functionalized silver nanoparticles (F-AgNPs) as sensing probes was investigated. As the addition of tricyclazole to F-AgNPs, a drastic decrease in the absorbance at 394 nm was detected, which was accompanied with a noticeable color change from yellow to gray. The sensing mechanism involved an interaction between tricyclazole and F-AgNPs, which led to aggregation of the latter, inducing a color change from yellow to gray. An excellent linear calibration curve (R² = 0.9994) was achieved between absorbance at 394 nm and the tricyclazole concentration in the range between 0.06 and 1.0 ppm. Moreover, the detection limit was estimated at 0.051 ppm. The developed colorimetric assay also showed good selectivity and was successfully utilized to quantify tricyclazole in rice samples with satisfactory recoveries. The proposed assay has been successfully applied for monitoring tricyclazole in rice samples.

Validation of a simple ion chromatography method for simultaneous determination of glyphosate, aminomethylphosphonic acid and ions of Public Health concern in water intended for human consumption

The herbicide glyphosate and its main metabolite aminomethylphosphonic acid (AMPA) are generally studied in environmental samples in the investigation of contamination of soil, plants, water and food. Many analytical methods are based on liquid chromatography or high-performance liquid chromatography, with pre-column or post-column derivatization; in addition, the chromatograph can be coupled to mass spectrometers for detection and quantification. Gas chromatography and spectroscopic and electrochemical methods have also been used. In this work, a simple low-cost method is presented for the analysis of water intended for human consumption with the quantification not only of glyphosate and AMPA, but also of other ions of interest to public health (fluoride, chlorite, bromate, chloride, nitrite, nitrate, sulfate and phosphate). Based on ion chromatography with conductivity detection (chemical suppression of eluent conductivity), the key point in this method is the use of gradient elution with two eluents of different pH and ionic strength, not requiring derivatization. There is no interference from the other ions at higher concentrations. The detection limits obtained for glyphosate and AMPA were 15 μg L-1 and 80 μg L-1, respectively. As the method allows the analysis of a large number of samples, it has been successfully applied to monitoring the quality of tap water in 89 municipalities in the northeast region of the State of São Paulo, Brazil.