CODEX-compliant eleven organophosphorus pesticides screening in multiple commodities using headspace-solid phase microextraction-gas chromatography-mass spectrometry

Microextraction of organophosphorus pesticides on a screw coated with PAN/calcined ZnMgAl-LDH electrospun nanofibers

The present research is an attempt to expand the recently reported microextraction on screw method. For this purpose, polyacrylonitrile/calcined ZnMgAl-LDH nanofiber was fabricated by the electrospinning technique on the surface of a screw. It was applied to the extraction of organophosphorus pesticides (OPP) from agricultural samples. The separation and determination of OPPs were carried out by gas chromatography-mass spectrometry. The characterization of the fabricated nanofiber was performed utilizing Fourier transform infrared spectroscopy, field emission scanning electron microscopy, energy-dispersive X-ray spectroscopy, and X-ray diffraction instruments. Effective parameters on the extraction efficiency of the analytes including sample pH, ionic strength, sample flow rate and number of cycles, type, volume, and flow rate of desorption solvent were optimized by one-variable-at-a-time method. Under optimized conditions, the limits of detection were 0.03 and 0.07 μg L^-1 for diazinon and chlorpyrifos, respectively. This method showed wide linearity in the range 0.10-1000 μg L^-1 for diazinon and 0.25-1000 μg L^-1 for chlorpyrifos with R² > 0.996. The intra- and inter-day precisions (RSD%, n = 3) were ≤ 6.4% and ≤ 7.7%, respectively. Also, RSD% values less than 11.1% were obtained for screw-to-screw reproducibility. The applicability of the method for the extraction and determination of the analytes in complex agricultural environments such as cabbage, potato, tomato, cucumber, and beetroot was investigated. The results led to acceptable relative recoveries in the range 81.0-108.2%.

Development of ultrasound-assisted extraction followed by solid-phase extraction followed by dispersive liquid–liquid microextraction followed by gas chromatography for the sensitive determination of diazinon in garden parsley as vegetable samples

A new pretreatment method termed ultrasound-assisted extraction (UAE) which is combined with solid-phase extraction which is combined with dispersive liquid-liquid microextraction (SPE-DLLME) followed by gas chromatography-flame ionization detector (GC-FID) analysis has been developed for the determination of diazinon in garden parsley as vegetable samples. The analyte was extracted from garden parsley sample using ultrasound-assisted extraction followed by solid-phase extraction followed by dispersive liquid-liquid microextraction. Various parameters that affect the efficiency of the extraction techniques have been optimized. The calibration plot was linear in the range of 5.0–1,000 μg kg−1 with detection limit of 1.0 μg kg−1 for diazinon in garden parsley samples. The results confirm the suitability of the UAE-SPE-DLLME-GC-FID as a sensitive method for the analysis of the targeted analyte in garden parsley samples.

Current Applications of Magnetic Nanomaterials for Extraction of Mycotoxins, Pesticides, and Pharmaceuticals in Food Commodities

Environmental pollutants, such as mycotoxins, pesticides, and pharmaceuticals, are a group of contaminates that occur naturally, while others are produced from anthropogenic sources. With increased research on the adverse ecological and human health effects of these pollutants, there is an increasing need to regularly monitor their levels in food and the environment in order to ensure food safety and public health. The application of magnetic nanomaterials in the analyses of these pollutants could be promising and offers numerous advantages relative to conventional techniques. Due to their ability for the selective adsorption, and ease of separation as a result of magnetic susceptibility, surface modification, stability, cost-effectiveness, availability, and biodegradability, these unique magnetic nanomaterials exhibit great achievement in the improvement of the extraction of different analytes in food. On the other hand, conventional methods involve longer extraction procedures and utilize large quantities of environmentally unfriendly organic solvents. This review centers its attention on current applications of magnetic nanomaterials and their modifications in the extraction of pollutants in food commodities.

Dispersive solid-phase extraction using microporous metal-organic framework UiO-66: Improving the matrix compounds removal for assaying pesticide residues in organic and conventional vegetables

An efficient dispersive solid-phase extraction method was developed to trace pesticide residues in commonly consumed vegetables. In this method, UiO-66 with uniform micropores was used as sorbent, and gas chromatography-mass spectrometry was applied to detect the pesticides. Thanks to the size sieving action of uniform micropores, UiO-66 directly extracted the target pesticides from vegetable matrices and excluded the relatively large matrix compounds. This well eliminated the matrix effect. The important experimental conditions were evaluated by orthogonal array experimental design. In optimized conditions, good linearity (R² ≥ 0.99), detection limits (0.4-2.0 ng/g), recoveries (60.9-117.5%) and precision (relativestandarddeviations < 14.6%) were achieved. Moreover, the sorbent UiO-66 can be reused more than 20 times. These demonstrate a simple, reliable and robust method to screen the pesticide residues in vegetables. Furthermore, the validated method was applied to detect the pesticides in various organic and conventional vegetables.

Review: Microextraction Technique Based New Trends in Food Analysis

Food chemistry is the study and classification of the quality and origin of foods. The identification of definite biomarkers and the determination of residue contaminants such as toxins, pesticides, metals, human and veterinary drugs, which are a very common source of food-borne diseases. The food analysis is continuously demanding the improvement of more robust, sensitive, highly efficient, and economically beneficial analytical approaches to promise the traceability, safety, and quality of foods in the acquiescence with the consumers and legislation demands. The traditional methods have been used at the starting of the 20th century based on wet chemical methods. Now it existing the powerful analytical techniques used in food analysis and safety. This development has led to substantial enhancements in the analytical accuracy, precision, sensitivity, selectivity, thereby mounting the applied range of food applications. In the present decade, microextraction (micro-scale extraction) pays more attention due to its futures such as low consumption of solvent and sample, throughput analysis easy to operate, greener, robotics, and miniaturization, different adsorbents have been used in the microextraction process with unique nature recognized with wide range applications.

Fluorescence sensor for organophosphorus pesticide detection based on the alkaline phosphatase-triggered reaction

The threat of organophosphorus pesticide (OPP) residue to food safety and human health has caused widespread concern. In this paper, a sensitive fluorescence sensor for OPP detection was constructed based on the alkaline phosphatase (ALP) -triggered in situ reaction. In this method, ALP catalyses the dephosphorylation of the substrate l-ascorbic acid 2-phosphate sesquimagnesium salt hydrate (AAP) to generate l-ascorbic acid (AA). AA instantly combines with o-phenylenediamine (OPD) to form 3-(1,2-dihydroxyethyl)furo[3,4-b]quinoxalin-1(3H)-one (DFQ), which contains a quinoxaline core skeleton fluorophore and emits a strong fluorescence intensity at 425 nm. The existence of OPPs inhibits the activity of ALP and the production of AA and DFQ. As a result, the fluorescence intensity obviously decreases. Under optimal conditions, the fluorescence intensity linearly depends on the logarithm of chlorpyrifos concentration over a wide range of 20 pg/mL ∼1000 ng/mL with a detection limit of 15.03 pg/mL (S/N = 3), which is lower than the previously reported values. The sensor with its satisfactory accuracy and precision has been successfully applied to the detection of chlorpyrifos in leeks and celery samples with recoveries of 94.5-106.7% and an inter-assay relative standard deviation (RSD) below 11.51%. OPPs can be semiquantitatively determined by the colour changes in ultraviolet light. The superiority of the sensor is due to its visual simplicity without complex fluorescence labelling procedures and costly instruments.

Simultaneous determination of five organophosphorus pesticide residues in different food samples by solid-phase microextraction fibers coupled with high-performance liquid chromatography

BACKGROUND

Excessive or improper use of organophosphorus pesticides (OPPs) may adversely affect human health through the food chain. In the present study, a simple, rapid and effective analytical method was successfully established and used for the determination of OPPs quinalphos and its analogs in different food samples.

RESULTS

Under the optimized experimental conditions, five OPPs (quinalphos, triazophos, parathion, fenthion and chlorpyrifos-methyl) exhibit a good linearity within a range of 0.02 to 2.0 μg mL^-1 . The detection limit range was 3.0 to 10.0 μg L^-1 (signal-to-noise ratio = 3). The method was successfully used to detect and quantify the residues of quinalphos and its analogs in tomato, cabbage, barley and water samples; all spiked samples gave satisfactory recovery rates for the target analytes of between 82% and 98%, with a relative SD of 3.6% to 7.8%.

CONCLUSION

The results obtained show that the proposed method is an accurate, rapid and reliable sample pre-treatment method with respect to giving a good enrichment factor and detection limit for determining quinalphos pesticide residues in different food samples. © 2019 Society of Chemical Industry.

Ratiometric fluorescence sensor for organophosphorus pesticide detection based on opposite responses of two fluorescence reagents to MnO2 nanosheets

The detection of organophosphorus pesticides (OPs) has received considerable attention for their great harm to human beings. Herein, a novel ratiometric fluorescence biosensor was constructed for the determination of OPs by using Scopoletin (SC) and Amplex Red (AR) as probe pairs that have opposite responses to MnO₂ nanosheets (MnO₂ NS). MnO₂ NS possess peroxidase-like catalytic activity, which could quench the fluorescence of SC as well as enhance the fluorescence of the non-fluorescent substance AR by oxidation. In the absence of OPs, acetylcholinesterase (AChE) hydrolyzed acetylcholine chloride (ATCh) into choline (TCh) and acetate. TCh led the decomposition of MnO₂ NS to manganese ions (Mn²⁺), increasing signal of SC and decreasing signal of AR. In the presence of OPs, the activity of AChE was inhibited and the decomposition of MnO₂ NS was hindered, therefore the fluorescence intensity of SC was weak and the fluorescence intensity of AR had an obvious increase. Moreover, under the optimal conditions, the ratio of fluorescence intensity response recorded on the AR/SC increases with increasing the concentration of DDVP. The method has wider linear range of 5.0 pg/mL ∼500 ng/mL with a detection limit of 1.6 pg/mL, which is superior to previously reported methods. This strategy has also been applied to a visual observation based on the color change of the solution under UV light.

Preparation and application of chlorpyrifos molecularly imprinted solid-phase microextraction probes for the residual determination of organophosphorous pesticides in fresh and dry foods

A solid-phase microextraction probe was prepared on the surface of a stainless-steel wire through molecular sol-gel imprinting technology using chlorpyrifos as a template molecule, tetraethoxysilane as a sol-gel precursor, and acrylamide and β-cyclodextrin as functional monomers. The polymer was characterized by infrared spectrometry and scanning electron microscopy. Moreover, the selectivity and the parameters including the type and volume of the extraction solvents, ionic strength, pH, temperature, extraction time, stirring speed, and desorption time affecting extraction performance were evaluated. Under the optimum solid-phase microextraction and gas chromatography conditions, the linear ranges were 0.25-25.0 μg/L for chlorpyrifos, quinalphos, triazophos, pirimiphos-methyl, and chlorpyrifos-methyl with the correlation coefficient above 0.99. The detection limits (S/N = 3) were in the range of 0.02-0.07 μg/L and the RSDs were <7.3%. The developed method was successfully used to determine the multi-residues of chlorpyrifos, quinalphos, triazophos, pirimiphos-methyl, and chlorpyrifos-methyl in green peppers and cinnamon with satisfactory recoveries.

Simultaneous determination of three organophosphorus pesticides in different food commodities by gas chromatography with mass spectrometry

A sensitive and selective gas chromatography with mass spectrometry method was developed for the simultaneous determination of three organophosphorus pesticides, namely, chlorpyrifos, malathion, and diazinon in three different food commodities (milk, apples, and drinking water) employing solid-phase extraction for sample pretreatment. Pesticide extraction from different sample matrices was carried out on Chromabond C18 cartridges using 3.0 mL of methanol and 3.0 mL of a mixture of dichloromethane/acetonitrile (1:1 v/v) as the eluting solvent. Analysis was carried out by gas chromatography coupled with mass spectrometry using selected-ion monitoring mode. Good linear relationships were obtained in the range of 0.1-50 μg/L for chlorpyrifos, and 0.05-50 μg/L for both malathion and diazinon pesticides. Good repeatability and recoveries were obtained in the range of 78.54-86.73% for three pesticides under the optimized experimental conditions. The limit of detection ranged from 0.02 to 0.03 μg/L, and the limit of quantification ranged from 0.05 to 0.1 μg/L for all three pesticides. Finally, the developed method was successfully applied for the determination of three targeted pesticides in milk, apples, and drinking water samples each in triplicate. No pesticide was found in apple and milk samples, but chlorpyrifos was found in one drinking water sample below the quantification level.

Analysis of volatile organic compounds in compost samples: A potential tool to determine appropriate composting time

Changes in volatile organic compound contents in compost samples during pig manure composting were studied using a headspace, solid-phase micro-extraction method (HS-SPME) followed by gas chromatography with mass spectrometric detection (GC/MS). Parameters affecting the SPME procedure were optimized as follows: the coating was carbon molecular sieve/polydimethylsiloxane (CAR/PDMS) fiber, the temperature was 60°C and the time was 30min. Under these conditions, 87 compounds were identified from 17 composting samples. Most of the volatile components could only be detected before day 22. However, benzenes, alkanes and alkenes increased and eventually stabilized after day 22. Phenol and acid substances, which are important factors for compost quality, were almost undetectable on day 39 in natural compost (NC) samples and on day 13 in maggot-treated compost (MC) samples. Our results indicate that the approach can be effectively used to determine the composting times by analysis of volatile substances in compost samples. An appropriate composting time not only ensures the quality of compost and reduces the loss of composting material but also reduces the generation of hazardous substances. The appropriate composting times for MC and NC were approximately 22days and 40days, respectively, during the summer in Zhejiang.

Validation and assessment of matrix effect and uncertainty of a gas chromatography coupled to mass spectrometry method for pesticides in papaya and avocado samples

In this paper a method of using the “quick, easy, cheap, effective, rugged, and safe” (QuEChERS) extraction and gas chromatography coupled to mass spectrometry detection (GC–MS) was developed for the analysis of five frequently applied pesticides in papaya and avocado. The selected pesticides, ametryn, atrazine, carbaryl, carbofuran, and methyl parathion, represent the most commonly used classes (carbamates, organophosphorous, and triazines). Optimum separation achieved the analysis of all pesticides in < 6.5 minutes. Validation using papaya and avocado samples established the proposed method as linear, accurate, and precise. In this sense, the correlation coefficients were > 0.99. The limits of detection (LOD) and quantification (LOQ) in papaya ranged from 0.03 mg/kg to 0.35 mg/kg and from 0.06 mg/kg to 0.75 mg/kg, respectively. Meanwhile for avocado, LOD values varied from 0.14 mg/kg to 0.28 mg/kg and LOQ values ranged from 0.22 mg/kg to 0.40 mg/kg. Recoveries obtained for each pesticide in both matrices ranged between 60.6% and 104.3%. The expanded uncertainty of the method was < 26% for all the pesticides in both fruits. Finally, the method was applied to other fruits.

Development of molecularly imprinted electrochemical sensors based on Fe3O4@MWNT-COOH/CS nanocomposite layers for detecting traces of acephate and trichlorfon

In this study, we developed a novel biomimetic electrochemical sensor sensitized with a Fe3O4@carboxyl-functionalized multiwalled carbon nanotube/chitosan nanocomposite layer using a molecularly imprinted film as a recognition element for the rapid detection of acephate and trichlorfon. The performance of the imprinted sensor was investigated using cyclic voltammetry and differential pulse voltammetry, and the results indicated that the sensor exhibited fast responses to both acephate and trichlorfon. The imprinted sensor had good linear current responses to acephate and trichlorfon concentrations in the ranges from 1.0 × 10(-4) to 1.0 × 10(-10) M and 1.0 × 10(-5) to 1.0 × 10(-11) M, respectively. Under optimal conditions, the imprinted sensor had low limits of detection (signal to noise ratio, S/N = 3) of 6.81 × 10(-11) M for acephate and 8.94 × 10(-12) M for trichlorfon. The developed method was successfully applied to detect acephate and trichlorfon spiked in fortified kidney bean and cucumber samples with good recoveries ranging from 85.7% to 94.9% and relative standard deviations of 3.46-5.18%.