A novel fluorimetric method for glyphosate and AMPA determination with NBD-Cl and MCR-ALS

Determination of glyphosate with a novel optic membrane sensor

Glyphosate has been a widely used herbicide since the 1970s. However, glyphosate causes serious health problems if exposed to it for a long time. Therefore, quick and reliable determination of glyphosate becomes an important issue. This study proposes a solution to this issue with a highly selective and sensitive fluorescent polymeric membrane sensor for glyphosate determination with a wide linear working range (1-18 ppb) and low detection limit (0.84 ppb). The developed sensor can measure glyphosate at pH 8.0 and is applicable to real samples with recovery percentages varying between 98.4 and 111.5. Additionally, this sensor can respond in a short time and can be reused up to 200 times. The repeatability of the method was found to be 10.47 ± 0.11 at a 95 % confidence level and the relative standard deviation was 1.76 for the analysis results of 10 ppb samples. All these features make proposed method, an ambitious alternative tool for glyphosate detection.

The first spectrofluorimetric-based approach for studying stability-indicating assay and quantifying midodrine in its bulk powder, prescribed matrices; application to content homogeneity testing and sustainability evaluation

A novel application of a spectrofluorimetric method has been developed and validated for the stability analysis and quantification of midodrine hydrochloride in tablets and crude form. This study describes a technique based on the selective derivatization of midodrine's (MDN) primary amine group with NBD-Cl reagent under a borate buffer system (pH 8.5), yielding a highly fluorescent benzofurazan derivative. The product was measured at λex = 462 nm and λem = 537 nm, demonstrating a linear range of 30-600 ng/mL (r = 0.9998). The method's detection (8.9 ng/mL) and quantitation (26.98 ng/mL) limits were determined. Validation followed ICH guidelines, confirming precision, accuracy (recovery: 98.9-100.7 %), and absence of excipient interference in commercial formulations (tablets and oral drops). The method was applied to assess stress-induced degradation (acid, alkali, oxidation, aqueous, and photolytic conditions) and determine degradation kinetics under each condition. Additionally, content uniformity analysis of tablets was performed per USP guidelines, demonstrating robustness for quality control applications.

A portable smartphone-based detection of glyphosate based on inhibiting peroxidase-like activity of heptanoic acid/Prussian blue decorated Fe3O4 nanoparticles

The rapid and onsite detection of glyphosate in tobacco products is still a great challenge. In this study, a novel smartphone-assisted sensing platform for the detection of glyphosate has been successfully proposed through the peroxidase-like activity of Fe3O4-based nanozyme. Heptanoic acid/Prussian blue (PB) decorated Fe3O4 nanoparticles (Fe3O4@C7/PB) could catalyze and oxidize 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS, colorless) into a steel blue colored product in the presence of hydrogen peroxide. Glyphosate could specifically inhibit the peroxidase-like activity of Fe3O4@C7/PB by occupying the active site, thereby the glyphosate detection could be accomplished within 10 min by monitoring the color change of ABTS. This study has developed a smartphone-based portable detection platform for online analysis of glyphosate with a detection limit of 0.1 μg mL-1. The absorbance response curve of glyphosate showed good linearity in the concentration range of 0.125-15 μg mL-1 at 415, 647, and 730 nm. Moreover, by employing a co-precipitation technology and inhibiting the peroxidase-like activity, the glyphosate analysis would be less affected by the tobacco sample matrix. The nanosensor possesses excellent selectivity and anti-interference ability, which has application value in actual samples for onsite screening.

A dual-signal sensing strategy based on ratiometric fluorescence and colorimetry for determination of Cu2+ and glyphosate

Herein, a dual-signal sensing strategy based on ratiometric fluorescence and colorimetry for Cu²⁺ and glyphosate determination was constructed. Fluorescence silicon nanoparticles (SiNPs) were prepared by hydrothermal reaction, which has maximum fluorescence intensity under the excitation of 355 nm. o-Phenylenediamine (OPD) was oxidized through Cu²⁺ to generate 2,3-diaminophenazine (oxOPD). The obtained oxOPD showed a strong absorption peak at 417 nm and quenched the fluorescence of SiNPs at 446 nm due to fluorescence resonance energy transfer (FRET). Meanwhile, oxOPD produced a new fluorescence emission at 556 nm forming a ratiometric state. With increasing Cu²⁺, the original solution changed from colorless to yellow. When glyphosate was present, the interaction between Cu²⁺ and the functional groups of glyphosate could reduce the oxidation of oxOPD, resulting in the enhancement of fluorescence at 446 nm and the decrease of fluorescence at 556 nm. Furthermore, the addition of glyphosate changed yellow solution to colorless. Under the optimal conditions of OPD (1 mM), 20 mM Tris-HCl buffer (pH 7.5), and incubation time (4 h), the ratiometric fluorescence sensor had good selectivity and showed a wide linear range of 0.025-20 μM with the LOD of 0.008 μM for Cu²⁺ and 0.15-1.5 μg/mL with the LOD of 0.003 μg/mL for glyphosate, respectively. Besides, it is worth mentioning that this developed sensing system showed good performance in real samples, providing a simple and reliable dual-signal detection strategy.

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.

NBD-Based Environment-Sensitive Fluorescent Probes for the Human Ether-a-Go-Go-Related Gene Potassium Channel

Three environment-sensitive probes were developed for the hERG channel based on the nitrobenzoxadiazole fluorophore herein. After careful evaluation, probes M1 and M3 were found to have a high affinity for imaging the hERG channel in the cell-based experiment. Compared with other fluorescent labeling technologies (such as fluorescent proteins), these probes afford a convenient and economical method to determine hERG channel in vitro and in cellulo. Therefore, these probes are expected to be applicable for usage in physiological and pathological studies of hERG channels and have the potential to establish a screening system for hERG channels.

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.

Analytical methods to analyze pesticides and herbicides

This paper reviews studies published in 2019, in the area of analytical techniques for determination of pesticides and herbicides. It should be noted that some of the reports summarized in this review are not directly related to but could potentially be used for water environment studies. Based on different methods, the literatures are organized into six sections, namely extraction methods, electrochemical techniques, spectrophotometric techniques, chemiluminescence and fluorescence methods, chromatographic and mass spectrometric techniques, and biochemical assays. PRACTITIONER POINTS: Totally 141 research articles have been summarized. The review is divided into six parts. Chromatographic and mass spectrometric techniques are the most widely used methods.