Sensitive, rapid and non-derivatized determination of glyphosate, glufosinate, bialaphos and metabolites in surface water by LC–MS/MS

Quantitation of glyphosate, glufosinate, and AMPA in drinking water and surface waters using direct injection and charged-surface ultra-high performance liquid chromatography-tandem mass spectrometry

Herbicides glyphosate (N-(phosphonomethyl)glycine) and glufosinate (2-amino-4-(hydroxymethylphosphinyl)butanoic acid) and the main transformation product of glyphosate, aminomethanephosphonic acid (AMPA), are challenging to analyze for in environmental samples. The quantitative method developed by this study adapts previously standardized dechlorination procedures coupled to a novel charged surface C18 column, ultra-high performance liquid chromatography-tandem mass spectrometry, polarity switching, and direct injection. The method was applied to chlorinated tap water, as well as river samples, collected in the City of Winnipeg and rural Manitoba, Canada. Using only syringe filtration without derivatization, the validated method resulted in good accuracies in both tap and surface water, at both 2 and 20 μg L-1. Method limits of detection (MLD) and quantification (MLQ) ranged from 0.022/0.074 to 0.11/0.36 μg L-1, with precisions of 0.46-2.2% (intraday) and 1.3-7.3% (interday). The mean (SEM) of the pesticides in μg L-1 for tap water were 0.11 (0.007) (AMPA), glufosinate and glyphosate < MLDs; and for Red River water were 0.56 (0.045) (AMPA), glufosinate < MLQ, and glyphosate 0.40 (0.072). For the smaller tributaries, glufosinate was >MLD but < MLQ once and that was for Shannon Creek at 0.2 μg L-1. For the remaining rivers, the mean concentrations ranged from 0.31 to 3.1 μg L-1 for AMPA, and 0.087-0.53 μg L-1 for glyphosate. The method will be ideal for supporting monitoring and risk assessment programs that require high throughput sampling and quantitative methods capable of producing robust results that leverages chromatographic and mass spectrometric paradigms instead of being extraction technology focused.

Investigation of the performance of activated carbon cloth to remove glyphosate, glufosinate, aminomethylphosphonic acid and bialaphos from aqueous solutions by adsorption/electrosorption

The present study investigates the removal of glyphosate, glufosinate, aminomethylphosphonic acid and bialaphos herbicides from their 5 × 10^-5 M aqueous solutions onto activated carbon cloth by adsorption and electrosorption. Analysis of these highly polar herbicides was achieved by UV-visible absorbance measurements, after derivatization with 9-fluorenylmethyloxycarbonyl chloride. The limit of quantification values of glyphosate, glufosinate, aminomethylphosphonic acid and bialaphos were 1.06 × 10^-6 mol L^-1, 1.38 × 10^-6 mol L^-1, 1.32 × 10^-6 mol L^-1 and 1.08 × 10^-6 mol L^-1, respectively. Glyphosate, glufosinate, aminomethylphosphonic acid and bialaphos were removed from their aqueous solutions with higher efficiencies by means of electrosorption (78.2%, 94.9%, 82.3% and 97%, respectively) than of open-circuit adsorption (42.5%, 22%, 6.9% and 81.8%, respectively). Experimental kinetic data were fitted to pseudo-first order and pseudo-second order kinetic models. It was determined that pseudo-second order kinetic model represents experimental data better with satisfactory coefficient of determination, r² (> 0.985) and normalized percent deviation, P (< 5.15) values. Adsorption isotherm data were treated according to Freundlich and Langmuir isotherm models. Based on the r² (> 0.98) and P (< 5.9) values, it was found that experimental data well fitted to Freundlich isotherm model. Adsorption capacities of activated carbon cloth for glyphosate, glufosinate, aminomethylphosphonic acid and bialaphos, expressed in terms of Freundlich constant, were calculated as 20.31, 118.73, 239.33 and 30.68 mmol g^-1, respectively. The results show that the studied ACC can be used in home/business water treatment systems as an adsorbent due to its high adsorption capacity.

Improved Chromatography and MS-Based Detection of Glyphosate and Aminomethylphosphonic Acid Using iTrEnDi

Glyphosate (GLY), a synthetic, nonselective systemic herbicide that is particularly effective against perennial weeds, is the most used weedkiller in the world. There are growing concerns over GLY accumulation in the environment and the attendant human health-associated risks, and despite increased attention in the media, GLY and its breakdown product aminomethylphosphonic acid (AMPA) remain elusive to many analytical strategies. Chemical derivatization coupled with high-performance liquid chromatography-mass spectrometry (HPLC-MS) addresses the challenge of quantifying low levels of GLY and AMPA in complex samples. Here we demonstrate the use of in situ trimethylation enhancement using diazomethane (iTrEnDi) to derivatize GLY and AMPA into permethylated products ([GLY^Tr]⁺ and [AMPA^Tr]⁺, respectively) prior to analysis via HPLC-MS. iTrEnDi produced quantitative yields and resulted in a 12-340-fold increases in HPLC-MS-based sensitivity for [GLY^Tr]⁺ and [AMPA^Tr]⁺, respectively, compared with underivatized counterparts. The limits of detection of derivatized compounds were found to be 0.99 ng/L for [GLY^Tr]⁺ and 1.30 ng/L for [AMPA^Tr]⁺, demonstrating significant sensitivity improvements compared to previously established derivatization techniques. iTrEnDi is compatible with the direct derivatization of Roundup formulations. Finally, as proof of principle, a simple aqueous extraction followed by iTrEnDi enabled the detection of [GLY^Tr]⁺ and [AMPA^Tr]⁺ on the exterior of field-grown soybeans that were sprayed with Roundup. Overall, iTrEnDi ameliorates issues relating to low proton affinity and chromatographic retention, boosting HPLC-MS-based sensitivity and enabling the elucidation of elusive analytes such as GLY and AMPA within agricultural systems.

Determination of glyphosate and AMPA in indoor settled dust by hydrophilic interaction liquid chromatography with tandem mass spectrometry and implications for human exposure

The widespread application of glyphosate leads to significant contamination of outdoor environmental compartments, notably air and soil, which can contaminate indoor air and dust. This study assessed the contamination of indoor household dust for the first time in France and potential exposure to glyphosate through the inadvertent ingestion of dust. A specific and new analytical method was developed using HILIC MS/MS (hydrophilic interaction liquid chromatography with tandem mass spectrometry) to measure polar pesticides, such as glyphosate, aminomethylphosphonic acid, and glufosinate, in indoor dust, with a low quantification limit (25 ng/g). The dust from vacuum cleaner bags of 60 rural and urban households (Brittany, France) was analyzed. All samples contained glyphosate (median 1675 ng/g for rural dwellings (n = 29), 457 ng/g for urban dwellings (n = 31)), more than 90 % contained aminomethylphosphonic acid, and none contained glufosinate. Concentrations were influenced by the rural or urban setting, the proximity of crops, and the use of weed killers on driveways or lawns. Glyphosate exposure via indoor dust ingestion was < 1 % of both acceptable daily intake and dietary intake. However, the high quantification limit of the glyphosate concentration in the food analysis method probably leads to overestimation of the dose from food.

Determination of Glyphosate, Glufosinate, and Their Major Metabolites in Tea Infusions by Dual-Channel Capillary Electrophoresis following Solid-Phase Extraction

In this study, two analytical procedures were developed and validated using dual-channel capillary electrophoresis-coupled contactless conductivity detection (CE-C4D) followed by solid-phase extraction (SPE) for simultaneous determination of glyphosate (GLYP), glufosinate (GLUF), and their two major metabolites, aminomethylphosphonic acid (AMPA) and 3-(methylphosphinico) propionic acid (MPPA), respectively, in a popular beverage such as tea infusions. GLYP, GLUF, and AMPA were analyzed in the first channel using background electrolyte (BGE) of 1 mM histidine (His) adjusted to pH 2.75 by acetic acid (Ace). In contrast, MPPA was quantified in the second channel with a BGE of 30 mM His adjusted to pH 6.7 by 3-(N-morpholino) propanesulfonic acid (MOPS) and 10 µM of cetyltrimethylammonium bromide (CTAB). In addition, the samples of tea infusions were treated using SPE with 10 mL of 0.5 mM HCl in methanol as eluent. At the optimized conditions, the method detection limit (MDL) of GLYP, GLUF, AMPA, and MPPA is 0.80, 1.56, 0.56, and 0.54 μg/l, respectively. The methods were then applied to analyze four target compounds in 16 samples of tea infusions. GLYP was found in two infusion samples of oolong tea with concentrations ranging from 5.34 to 10.74 µg/L, and GLUF was recognized in three samples of green tea infusion in the range of 45.1-53.9 µg/L.

Glyphosate, aminomethylphosphonic acid, and glufosinate ammonium in agricultural groundwater and surface water in China from 2017 to 2018: Occurrence, main drivers, and environmental risk assessment

Glyphosate and glufosinate ammonium are the main herbicides used to control weeds in no-tillage agricultural fields in China. However, their leaching risk to groundwater and ecological risk to aquatic organisms remain unclear. From the agricultural basins among 10 provinces of China, glyphosate, its main metabolite aminomethylphosphonic acid (AMPA), and glufosinate ammonium were detected in 1.01%, 0.86%, 0% of 694 groundwater samples with the maximum concentrations of 2.09, 5.13, and <0.05 μg/L, and were detected in 14.3%, 15.8%, and 2.6% of 196 surface water samples with the maximum levels of 32.49, 10.31 and 13.15 μg/L. Furthermore, to evaluate the main drivers of exposure to the targets in water bodies, the fate models were used. The model simulation indicated that spray drift and overflow runoff were the key factors affecting the exposure to targets in surface water adjacent to rice field, whereas the spray drift deposition, runoff, and erosion induced the exposure to the targets in pond water close to dry land crop fields under different meteorological conditions and soil characteristics. The targets in groundwater posed a low risk to water consumption, while fish embryos might be at unacceptable risk due to glufosinate ammonium exposure in surface water with median risk quotient (RQ) equal to 55.6. The results highlight the spatial and seasonal distribution of glyphosate, AMPA, and glufosinate ammonium in groundwater and surface water in agricultural basins of China, providing the first evidence to the environmental risk of the targets to drinking water consumption and aquatic organism safety in China agriculture system.