Determination of residual organophosphorus thioester pesticides in agricultural products by chemical isotope-labelling liquid chromatography-tandem mass spectrometry coupled with in-syringe dispersive solid phase clean-up and in situ cleavage

Advances in Microfluidics Techniques for Rapid Detection of Pesticide Residues in Food

Food safety is a significant issue that affects people worldwide and is tied to their lives and health. The issue of pesticide residues in food is just one of many issues related to food safety, which leave residues in crops and are transferred through the food chain to human consumption. Foods contaminated with pesticide residues pose a serious risk to human health, including carcinogenicity, neurotoxicity, and endocrine disruption. Although traditional methods, including gas chromatography, high-performance liquid chromatography, chromatography, and mass spectrometry, can be used to achieve a quantitative analysis of pesticide residues, the disadvantages of these techniques, such as being time-consuming and costly and requiring specialist staff, limit their application. Therefore, there is a need to develop rapid, effective, and sensitive equipment for the quantitative analysis of pesticide residues in food. Microfluidics is rapidly emerging in a number of fields due to its outstanding strengths. This paper summarizes the application of microfluidic techniques to pyrethroid, carbamate, organochlorine, and organophosphate pesticides, as well as to commercial products. Meanwhile, the study also outlines the development of microfluidics in combination with 3D printing technology and nanomaterials for detecting pesticide residues in food.

Advances of stable isotope technology in food safety analysis and nutrient metabolism research

Food quality, safety, and the regulatory metabolism of food nutrients in cells are primary factors in determining human health. However, residues of undesirable or hazardous compounds in food products and dysregulation in the nutrient metabolism inevitably occur occasionally. For years, chromatography-mass spectrometry technology has been recognized as an essential research tool in food analysis and nutrient metabolism research, and it is more accurate and robust when coupled with stable isotopes. In this study, we summarize the applications of stable isotope technology in the quantification of contaminant residues (pesticides, veterinary drugs, mycotoxins, polycyclic aromatic hydrocarbons, and other hazardous compounds) in foods and in the nutrients (glucose, lipids, amino acids and proteins) metabolism research. The aim of this review was to serve as a reference for providing effective analysis techniques for protecting food quality and human health, and to pave the way for the broader application of stable isotope technology.

In-syringe dispersive solid phase filter extraction cleanup followed by liquid chromatography-triple quadrupole mass spectrometry for fast determination of colchicine in plasma/urine

As an effective treatment for acute gouty arthritis and cardiovascular disease, colchicine is also a toxic alkaloid and may cause poisoning or even death in overdose. The study of colchicine elimination and the diagnosis of poisoning etiology need the rapid and accurate quantitative analysis method in biological matrix. An analytical method was developed for colchicine in plasma and urine by in-syringe dispersive solid phase extraction (DSPE) followed by liquid chromatography-triple quadrupole mass spectrometry (LC-MS/MS). Sample extraction and protein precipitation were proceeded with acetonitrile. The extract was cleaned by in-syringe DSPE. An XBridge™ BEH C₁₈ column（100 mm × 2.1 mm, 2.5 µm）was used to separate colchicine by gradient elution with mobile phase of 0.01% (v/v) ammonia-methanol. The amount and filling sequence of magnesium sulfate (MgSO₄) and primary secondary amine (PSA) suitable for in-syringe DSPE were studied. Scopolamine was screened as the quantitative internal standard (IS) for colchicine analysis according to the consistency of recovery rate, chromatographic retention time and matrix effects. The limits of detection for colchicine in plasma and urine were both 0.06 ng mL^-1 and the limits of quantitation were both 0.2 ng mL^-1. The linear range was 0.04 - 20 ng mL^-1 (Equivalent to 0.2-100 ng mL^-1 in plasma or urine) with a correlation coefficient r > 0.999. By IS calibration, the average recoveries at three spiking levels in plasma and urine were 95.3-102.68% and 93.9-94.8% with the relative standard deviations (RSDs) of 2.9-5.7% and 2.3-3.4%, respectively. The matrix effects, stability, dilution effects and carryover for determination of colchicine in plasma and urine were also evaluated. The elimination of colchicine within 72-384 h post-ingestion was studied for a poisoning patient with the doses of 1 mg d^-1 for 39 days and then 3 mg d^-1 for 15 days).

Determination of total protein content in biomedical products by the PDMS-assisted lab-in-a-syringe assay using 3D printed scaffolds removal

The aim of our work was to develop a low-cost, portable device for the fast and easy determination of total protein content by using PDMS-based lab-in-a-syringe technology with removal of 3D-printed channels. We proposed two designs with a one-step PDMS curing and a two-step PDMS-curing fabrication procedure. The one-step PDMS microdevices were found to be the best in the view of preparation, repeatability, and stability of the reagent. This design was then applied for the determination of total protein content in biomedical products using the Bradford assay.

Sensitive and selective determination of imidacloprid with magnetic molecularly imprinted polymer by using LC/Q-TOF/MS

In this paper, magnetic-molecularly imprinted polymer was used for the preconcentration of trace levels of imidacloprid in water and apple samples prior to liquid chromatography-quadrupole-time-of-flight mass spectrometric determination. The selectivity of the magnetic polymer was united with the sensitivity and the high resolving power of the chromatographic system. The developed method showed a linear range from 10.0 to 500.0 µg/L. The quantitative recoveries were obtained for water and apple samples in the range of 92.0%–99.0 %. The relative standard deviations of intra-day and inter-day tests were found to be in the range of 0.8%–1.2% and 1.2%–1.6 %, respectively. In addition, the same magnetic-molecularly imprinted polymer (MMIP) can be used at least ten cycles for the determination of imidacloprid. The preconcentration factor of the method was found to be 2.5, and the total preconcentration procedure can be completed in 1 h. Characterization of synthesised particles were executed with various techniques. Due to its suitable limit of detection, dynamic linear range, sensitivity and selectivity, the developed method seemed to be ideal for the determination and preconcentration of imidacloprid in water and fruit samples.

Simultaneous Quantification of Trace and Micro Phenolic Compounds by Liquid Chromatography Tandem-Mass Spectrometry

The simultaneous quantification of trace and micro metabolites is a bottleneck in food and biological analysis. Phenolic compounds are the most widely distributed and have various physiological functions. In this study, the strategy for the simultaneous liquid chromatography tandem-mass spectrometry (LC-MS/MS) quantification of 13 trace and micro phenolic compounds was proposed by taking product ions and isotopic ions as quantitative ions. The method validation results showed that the limits of detection (LODs) were from 0.01 to 9.84 μg/kg, and the limits of quantification (LOQs) were from 0.03 to 32.8 μg/kg. The intra-day precision and inter-day precision were below 8.4% and 14.4%, respectively. The recoveries ranged from 81.9% to 117.2%, and the matrix effects ranged from -11.5% to 13.7%, which indicated that the method has high sensitivity and suitable stability. The developed analytical method was applied to determine trace and micro constituents in rapeseed samples. The analysis results indicated that the contents of sinapine have significantly different between high and low total phenolic content rapeseeds. This method provides a reference strategy for the simultaneous quantitative analysis of other micro- and trace antioxidants.

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.

Facile extraction and determination of organophosphorus pesticides in vegetables via magnetic functionalized covalent organic framework nanocomposites

Facile enrichment and determination of trace organophosphorus pesticides (OPPs) in foods has been a constantly pursuing goal in food safety field. Herein, Zr⁴⁺-immobilized covalent organic frameworks (Fe₃O₄@COF@Zr⁴⁺) have been first constructed and utilized as the powerful adsorbents for magnetic solid-phase extraction (MSPE) of OPPs. Owing to the π-π stacking interaction, hydrogen bonding and Zr⁴⁺-phosphate coordination reaction, the composites exhibited excellent selectivity and superior affinity to OPPs. Under optimized conditions, the proposed MSPE method coupled with GC-FPD showed good linearity (R² ≥ 0.9990) and yielded low limits of detection (0.7-3.0 μg kg^-1) for OPPs. Moreover, the developed method was successfully employed for the quantitation of OPPs in spiked vegetable samples and obtained satisfactory recoveries in the range of 87-121% with the relative standard deviations (RSDs) ≤ 8.9%. These results demonstrated that the prepared nanoparticles hold unique advantages for trace OPPs analysis in foodstuffs.