Glyphosate has excellent herbicidal activity, and its extensive use may induce residue in the environment and enter into humans living through the food chain, causing negative impact. Here, water-soluble 1.55 nm size nitrogen-doped carbon quantum dots (NCDs) with strong blue fluorescence were synthesized using sodium citrate and adenine. The maximum excitation and emission wavelengths of NCDs were 380 nm and 440 nm, respectively. The above synthesized NCDs were first used for the construction of a fluorescence sensor for glyphosate detection. It was found that Cu²⁺ could quench the fluorescence of NCDs effectively through the photoinduced electron transfer (PET) process, which was confirmed using fluorescence lifetime measurements. Additionally, the fluorescence was restored with the addition of glyphosate. Hence, a sensitive turn-on fluorescence sensor based on NCDs/Cu²⁺ for glyphosate analysis was developed. The LODs of glyphosate for water and rice samples were recorded as 0.021 μg/mL and 0.049 μg/mL, respectively. The sensor was applied successfully for ultrasensitive and selective detection of glyphosate in environmental water and rice samples with satisfied recoveries from 82.1% to 113.0% using a simple sample pretreatment technique. The proposed strategy can provide a significant potential for monitoring glyphosate residue in water and agricultural product samples.

The chrysanthemum can be consumed in various forms, representing the “integration of medicine and food”. Quantitative analysis of multi-pesticide residues in chrysanthemum matrices is therefore crucial for both product-safety assurance and consumer-risk evaluation. In the present study, a simple and effective method was developed for simultaneously detecting 15 pesticides frequently used in chrysanthemum cultivation in three matrices, including fresh flowers, dry chrysanthemum tea, and infusions. The calibration curves for the pesticides were linear in the 0.01–1 mg kg⁻¹ range, with correlation coefficients greater than 0.99. The limits of quantification (LOQs) for fresh flowers, dry chrysanthemum tea, and infusions were 0.01–0.05 mg kg⁻¹, 0.05 mg kg⁻¹, and 0.001–0.005 mg L⁻¹, respectively. In all selected matrices, satisfactory accuracy and precision were achieved, with recoveries ranging from 75.7 to 118.2% and relative standard deviations (RSDs) less than 20%. The validated method was then used to routinely monitor pesticide residues in 50 commercial chrysanthemum-tea samples. As a result, 56% of samples were detected with 5–13 pesticides. This research presents a method for the efficient analysis of multi-pesticide residues in chrysanthemum matrices.

An analytical method simultaneously detecting pesticide and its metabolites, especially with higher toxicity, was urgently needed for supervision and safety evaluation of agricultural products. In the present study, a modified QuEChERS method coupled with a ultra-high performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) for simultaneous determination of tolfenpyrad (TFP) and its metabolites in tea matrices (fresh tea shoots, green tea, black tea, green tea infusion and black tea infusion) was established. The method validation showed good linearity (correlation coefficients ≥ 0.9945), accuracy (recoveries in 75.38–109.90%), sensitivity (limits of quantification ≤ 0.05 mg kg⁻¹), and precision (relative standard deviations ≤ 19.09%). The established method was then applied to detect 40 market samples, resulting in 60.0% positive rate of TFP, besides, two metabolites including PT-CA, which is more toxic than the parent TFP, and PT-OH were also detected in the samples with high TFP residue (≥0.048 mg kg⁻¹). The method established in the present work was thus of significant importance in comprehensive monitoring and of TFP in tea products.