A novel detector for liquid chromatography (LC) for the determination of dithiocarbamate (DTC) fungicides is presented with a miniaturized dielectric barrier discharge–microplasma molecular emission spectrometer and an online microwave-assisted hydrolysis reactor. DTCs in the sample/standard solutions together with SnCl₂ were pumped to the reactor to be converted to CS₂ with high efficiency, which was then separated from the liquid phase and transformed for the detection of the specific molecular emission at 257.49 nm by the spectrometer. Under optimized conditions, the performance of this new detector was evaluated by its determination of different types of DTC including mancozeb, thiram, zineb, propineb, and metiram, and the limit of detection (LOD) values were found to be in the range 0.1–1.0 μg mL⁻¹. The results from 20 test vegetable and fruit samples determined with the proposed method agreed well with those obtained using the standard headspace gas chromatography–electron capture detector (GC–ECD) method. Preliminary experimental results showed that the proposed method provided slightly higher LOD values than those obtained using GC–ECD. Most importantly, the new LC detector could detect each DTC chemical, whereas the traditional method could not distinguish between analytes of different subclasses of DTC.

Ethephon (ETH), a commonly employed growth regulator, poses potential health risks due to its residue in fruits and vegetables, leading to both acute and subchronic toxicity. However, the detection accuracy of ETH is compromised by the color effects of the samples during the detection process. In this work, a multienzyme reaction-mediated electrochemical biosensor (MRMEC) was developed for the sensitive, rapid, and color-interference-resistant determination of ETH. Nanozymes Fe₃O₄@Au–Pt and graphene nanocomplexes (GN–Au NPs) were prepared as catalysts and signal amplifiers for MRMEC. Acetylcholinesterase (AChE), acetylcholine (ACh), and choline oxidase (CHOx) form a cascade enzyme reaction to produce H₂O₂ in an electrolytic cell. Fe₃O₄@Au–Pt has excellent peroxidase-like activity and can catalyze the oxidation of 3,3′,5,5′-tetramethvlbenzidine (TMB) in the presence of H₂O₂, resulting in a decrease in the characteristic peak current of TMB. Based on the inhibitory effect of ETH on AChE, the differential pulse voltammetry (DPV) current signal of TMB was used to detect ETH, offering the limit of detection (LOD) of 2.01 nmol L⁻¹. The MRMEC method effectively analyzed ETH levels in mangoes, showing satisfactory precision (coefficient of variations, 2.88–15.97%) and recovery rate (92.18–110.72%). This biosensor holds promise for detecting various organophosphorus pesticides in food samples.

Mass spectrometry imaging is a novel molecular imaging technique that has been developing rapidly in recent years. Air flow-assisted ionization mass spectrometry imaging (AFAI-MSI) has received wide attention in the biomedical field because of its features such as not needing a pretreatment sample, having high sensitivity, and wide coverage of metabolite detection. In this study, we set up a mass spectrometry imaging method for analyzing low molecular metabolites in mango fruits by the AFAI-MSI method. Compounds such as organic acids, vitamin C, and phenols were detected from mango tissue by mass spectrometry under the negative ion scanning mode, and their spatial distribution was analyzed. As a result, all the target compounds showed different distributions. Citric acid was mainly distributed in the pulp. Malic acid, quinic acid, and vitamin C universally existed in the pulp and peel. However, galloylglucose isomer and 5-galloylquinic acid were predominantly found in the peel. These results show that AFAI-MSI can be used for the analysis of mango fruit endogenous metabolites conveniently and directly, which will facilitate the rapid identification and in situ characterization of plant endogenous substances.

Triflumezopyrim, a novel mesoionic insecticide used to control planthoppers, is a potential substitute for imidacloprid. In this study, triflumezopyrim and imidacloprid residues in rice were determined using a quick, easy, cheap, effective, rugged, and safe procedure combined with ultra-high-performance liquid chromatography–tandem mass spectrometry. The limit of quantification of both triflumezopyrim and imidacloprid was 0.01 mg kg⁻¹, and the average recovery values were 94–104% and 91–106%, with relative standard deviations (RSDs) of 1.1–1.4% and 2.1–3.4% (n = 5), respectively. The consumer protection level was assessed by calculating the theoretical maximum daily intake using the reported maximum residue limits of triflumezopyrim and imidacloprid. The established method was successfully applied to 200 commercial rice samples collected from four provinces in China, and their potential public health risks were assessed using triflumezopyrim and imidacloprid residues. The risk associated with triflumezopyrim and imidacloprid dietary intake was assessed by calculating the national estimated short-term intake and the acute reference dose percentage (%ARfD). The results show that the theoretical maximum daily intake (NEDI) values of triflumezopyrim and imidacloprid in different age and gender groups were 0.219–0.543 and 0.377–0.935 μg kg⁻¹ d⁻¹ bw, and the risk quotient (RQ) values were 0.188–0.467% and 0.365–0.906%, respectively. The acute reference dose (%ARfD) of triflumezopyrim and imidaclopridin ranged from 0.615 to 0.998% and from 0.481 to 0.780%, respectively.