A new carbon nanomaterial solid-phase microextraction to pre-concentrate and extract pesticides in environmental water

Thin-film solid-phase microextraction of pesticides from cereal samples using electrospun polyvinyl alcohol/modified chitosan/porous organic framework nanofibers

In this study, a coating of electrospun polyvinyl alcohol/modified chitosan/hydroxy-containing porous organic framework (PVA/MCS/HC-POF) was fabricated and applied as a novel sorbent for thin-film solid-phase microextraction of pesticides from cereal samples, followed by HPLC-UV. The successful fabrication of PVA/MCS/HC-POF was confirmed through characterization tests. The functional group of MCS and a large number of hydroxyl groups on the HC-POF structure contributed to the co-extraction of pesticides. Under the optimum conditions, the calibration plots were linear within the range of 5.0-800 ng mL-1 (r2 ≥ 0.978), and the limits of detection were obtained below 4.0 ng mL-1. The method's precision was investigated through intra-day, inter-day, and film-to-film RSD (%) measurements, all of which were less than 6.5 %, 8.2 %, and 10.0 %, respectively. Furthermore, satisfactory recoveries ranging from 63.3 % to 79.0 % were obtained. Accordingly, the proposed method can be considered a suitable alternative for measuring trace amounts of pesticides in cereal samples.

Development of In-Needle SPME Devices for Microextraction Applied to the Quantification of Pesticides in Agricultural Water

The chemical industry explosion in the 20th century has led to increased environmental pollution, affecting fauna, flora, and waterways. These substances alter water's taste, color, and smell, making it unfit for consumption or toxic. Agricultural water networks face threats from pollution before and after treatment. Some chemical contaminants, like pesticides, are embedded in natural biogeochemical cycles. In this study, we developed a simple and low-cost procedure for the fabrication of needles coated with polydimethylsiloxane (PDMS) as an efficient sorbent for the microextraction of organic pollutant traces from water. The prepared needles were used as an alternative for commercial solid-phase micro-extraction (SPME) devices in analytical chemistry. The PDMS polymeric phase was characterized by Fourier-transform infrared spectroscopy (FT-IR), thermogravimetry (TGA), and scanning electron microscopy (SEM). The PDMS-coated needles were used for extraction of thirteen pesticides by direct-immersion solid-phase microextraction (DI-SPME) from contaminated waters, followed by determination with gas chromatography-mass spectrometry (GC-MS). The developed analytical method showed limits of detection (LODs) between 0.3 and 2.5 ng mL-1 and RSDs in the range of 0.8-12.2%. The homemade needles were applied for the extraction of pesticides in surface and ground aqueous samples collected from an agricultural area. Several target pesticides were identified and quantified in the investigated water samples.

A novel honeycomb-like 3D-printed device for rotating-disk sorptive extraction of organochlorine and organophosphorus pesticides from environmental water samples

In this study, 3D-printing based on fused-deposition modeling (FDM) was employed as simple and cost-effective strategy to fabricate a novel format of rotating-disk sorptive devices. As proof-of-concept, twenty organochlorine and organophosphorus pesticides were determined in water samples through rotating-disk sorptive extraction (RDSE) using honeycomb-like 3D-printed disks followed by gas chromatography coupled to mass spectrometry (GC-MS). The devices that exhibited the best performance were comprised of polyamide + 15 % carbon fiber (PA + 15 % C) with the morphology being evaluated through X-ray microtomography. The optimized extraction conditions consisted of 120 min of extraction using 20 mL of sample at stirring speed of 1100 rpm. Additionally, liquid desorption using 800 µL of acetonitrile for 25 min at stirring speed of 1100 rpm provided the best response. Importantly, the methodology also exhibited high throughput since an extraction/desorption platform that permitted up to fifteen simultaneous extractions was employed. The method was validated, providing coefficients of determination higher than 0.9706 for all analytes; limits of detection (LODs) and limits of quantification (LOQs) ranged from 0.15 to 3.03 μg L-1 and from 0.5 to 10.0 μg L-1, respectively. Intraday precision ranged from 4.01 to 18.73 %, and interday precision varied from 4.83 to 20.00 %. Accuracy was examined through relative recoveries and ranged from 73.29 to 121.51 %. This method was successfully applied to analyze nine groundwater samples from monitoring wells of gas stations in São Paulo. Moreover, the greenness was assessed through AGREEprep metrics, and an overall score of 0.69 was obtained indicating that the method proposed can be considered sustainable.

Determination of pesticide residue in marginal lagoons of natural parks in Brazil using an improved calibrate passive sampler

Passive sampling is a sensitive and efficient method for analyzing pesticides in water. This article describes a hollow fiber liquid-phase microextraction (HF-LPME) device that was improved using polypropylene membranes grafted with nanocellulose for the passive sampling of pesticides in water. A comprehensive gas chromatography time-of-flight mass spectrometry (GCxGC/Q-TOFMS) system was used to separate, identify, and quantify pesticides. The sampling rates of 38 moderately hydrophobic to hydrophobic agricultural pesticides (2.18 < log Kow < 6.89) from different chemical classes, including the main triazine, organochlorine and organophosphate compounds, were calculated. A calibration process was applied to evaluate the role of flow velocity and select potential candidates for a possible performance reference compound (PRC). Sampling rates varied between 0.17 mL d-1 and 23.15 mL d-1. The accumulation curves identified linear periods ranging from 3 to 18 days. The new passive sampler device was applied for 8 days in rivers and marginal lagoons of natural parks of the São Francisco basin in Minas Gerais, Brazil and identified 10 target pesticides. Furthermore, 10 non-targeted pesticides were detected by the GCxGC/Q-TOFMS method.

Efficient Validation Strategies in Environmental Analytical Chemistry: A Focus on Organic Micropollutants in Water Samples

This article critically reviews analytical method validation and quality control applied to the environmental chemistry field. The review focuses on the determination of organic micropollutants (OMPs), specifically emerging contaminants and pesticides, in the aquatic environment. The analytical technique considered is (gas and liquid) chromatography coupled to mass spectrometry (MS), including high-resolution MS for wide-scope screening purposes. An analysis of current research practices outlined in the literature has been performed, and key issues and analytical challenges are identified and critically discussed. It is worth emphasizing the lack of specific guidelines applied to environmental analytical chemistry and the minimal regulation of OMPs in waters, which greatly affect method development and performance, requirements for method validation, and the subsequent application to samples. Finally, a proposal is made for method validation and data reporting, which can be understood as starting points for further discussion with specialists in environmental analytical chemistry.

Highly defective copper-based metal-organic frameworks for the efficient adsorption and detection of organophosphorus pesticides: An experimental and computational investigation

Organophosphorus pesticide (OP) residues pose a serious threat to human health, motivating the search for novel adsorbents and detection methods. Herein, defective copper-based metal organic frameworks (Cu-MOFs) were synthesized by the reaction of Cu²⁺ ions and 1,3,5-benzenetricarboxylate linkers in the presence of acetic acid. As the amount of acetic acid increased, the crystallization kinetics and morphology of the Cu-MOFs changed, leading to mesoporous Cu-MOFs with many large surface pores (defects). Adsorption studies of OPs revealed the defective Cu-MOFs showed faster pesticide adsorption kinetics and higher pesticide adsorption capacities. Density functional theory calculations showed that pesticide adsorption in the Cu-MOFs was mainly electrostatic. A dispersive solid phase extraction method was developed based on a defective Cu-MOF-6 for rapidly extracting pesticides from food samples. The method allowed pesticide detection over a wide linear concentration range, low limits of detection (0.0067-0.0164 µg L^-1) and good recoveries in pesticide-spiked samples (81.03-109.55%).

Ionic liquid-functionalized poly-N-phenylpyrrole coated on a NiTi alloy substrate for highly efficient solid-phase microextraction

TiO2–NiO composite nanoflakes were in situ grown, followed by electrochemical polymerization of [C4MIM]PF6@PPPy as a fiber coating for solid phase microextraction.

Iron nanoparticles decorated hierarchical carbon fiber forest for the magnetic solid-phase extraction of multi-pesticide residues from water samples

This study describes a versatile, robust and fast sample pre-concentration novel method based on chemical vapour deposition grown iron nanoparticles dispersed hierarchical carbon fiber forest (Fe-ACF/CNF) for the determination of multi-pesticide residue in water samples. This method was developed by the implementation of Fe-ACF/CNF to magnetic solid-phase extraction method (MSPE) for the adsorption of twenty-nine pesticides of various classes using gas chromatography equipped with an electron capture detector. Fe-ACF/CNF was grown via tip growth mechanism and Fe-nanoparticles are moved to the tip of CNF. The presence of Fe-nanoparticles is responsible for the magnetic property of proposed adsorbents. The Fe-ACF/CNF is competent enough to extract twenty-nine pesticides of different physico-chemical characteristics from water samples. All the predominant parameters including the amount of sorbent desorption time, temperature, sonication effect, regeneration, and reusability of Fe-ACF/CNF were thoroughly investigated. Acceptable linearity was obtained in the range of 20-500 μg/L with a correlation coefficient value ≥ 0.990 for all pesticides. The accuracy of the developed method was evaluated and the obtained recovery of the spiked samples was within 70-120% (standard deviation ≤ 15%) and reusability up to the 4th cycle. The limit of detection and quantification values was in the range of 1.44-5.15 and 4.76-17.0 μg/L, respectively. The obtained results are also cross verified with real water samples from the Gomti river (Lucknow, India) and shown the excellent extraction efficiency of Fe-ACF/CNF.

In situ fabrication of nitrogen doped graphitic carbon networks coating for high-performance extraction of pyrethroid pesticides

The tailor-prepare solid phase microextraction (SPME) coatings with stable and excellent properties to effectively extract analytes from sample matrix still remains a challenge. Herein, a nitrogen doped graphitic carbon networks (NG-CNTW) coated fiber was fabricated by direct carbonization of nanosized ZIF-67 crystals (nano-ZIF-67) that grown on stainless steel wire. The NG-CNTW coated fiber coupled with gas chromatography-tandem mass spectrometry (GC-MS/MS) was applied for enrichment and determination of pyrethroids. The NG-CNTW coating exhibited high surface area and hierarchical porous structures that facilitate diffusion and accessibility of target molecules. Simultaneously, the nitrogen doped and highly graphitic structures endow the coating with high adsorption affinity for aromatic compounds. Under optimum conditions, the SPME-GC-MS/MS method presented wide range of linearity performance (0.08-200.0 ng g^-1), low limits of detection (0.02-0.5 ng g^-1) and good repeatability (RSD < 9.6%) for 8 kinds of pyrethroids. Furthermore, the proposed method was successfully applied in the determination of pyrethroids in grape and cauliflower samples, as the results were in the range of 3.16-15.06 ng g^-1and 2.08-9.29 ng g^-1, respectively. This work not only provides a new method by fabricating carbon nanomaterial coatings in situ derived from MOFs, but also shows great potential of MOFs derivative materials in environmental analysis field.

Temperature and time-controlled hydrothermal growth and sorption selectivity of titania nanowires on titanium fiber for highly efficient solid-phase microextraction

Two kinds of TiO₂ nanowires (TiO₂NWs) with different orientation were in-situ grown on Ti substrates by controlling temperature and time during the hydrothermal process. The adsorption performance was evaluated by using typical aromatic compounds as model analytes coupled to HPLC with UV detection. The results demonstrated that the TiO₂NWs coating grown at higher temperature within longer time had better affinity towards PAHs. For this purpose, the key experimental factors affecting the adsorption performance of the TiO₂NWs coating fabricated at 200 °C for 10 h were further investigated and optimized for the extraction of PAHs. Under the optimized conditions, the proposed method presented linear responses in the concentration ranges of 0.05 to 200 μg·L^-1 PAHs with correlation coefficients more than 0.998. LODs (S/N=3) were 0.008 to 0.034 μg·L^-1. Moreover, RSDs for the single fiber repeatability of the intra-day and the inter-day analyses were less than 5.6% (n=5) and 5.8%, respectively. RSDs for the fiber-to-fiber reproducibility were between 5.1% and 6.5%. Finally, the proposed method was successfully applied to the selective preconcentration and determination of trace PAHs in environmental water samples. In addition, The fabricated Ti fiber can be used at least 200 times due to its high mechanical and chemical stability.

Assessment of pesticides in water using time-weighted average calibration of passive sampling device manufactured with carbon nanomaterial coating on stainless steel wire

The continued contamination of water sources by pesticides is a problem that involves the life of aquatic organisms and human health, especially in countries whose economy is based on agriculture. The need to know the quality of drinking water under these circumstances is a priority for the public health of any community. Passive sampling methods allow the determination of long-term environmental pollutants through a single sample collection, reducing time and cost of analyses. One advantage of passive sampling is that it is possible to calculate a time-weighted average (TWA) concentration value or an equilibrium concentration value, depending on the type of device used and the exposure time. Passive sampling techniques using carbon nanomaterials (CNMs) have a high potential for pesticide sampling in aquatic systems. A device for passive sampling manufactured with CNMs in a microextraction system and recyclable materials was calibrated in laboratory exposure conditions over 15 days. The calibration results showed linear accumulation periods between 5 and 10 days. Sampling rates were between 0.014 and 0.146 mL day^-1. The sampler was field-tested in the San Francisco river basin in the state of Minas Gerais in Brazil for 7 days. This research allowed for the detection and calculation of TWA concentrations for organochlorine pesticides such as α-HCH, 4,4-DDE, and 4,4-DD in water sources. The manufactured device demonstrated greater sensitivity than the grab sampling processes for the detection of pesticides. The performed passive sampling system using gas chromatography/mass spectrometry (GC/MS) technique allowed for the collection, detection, identification, and quantification of 26 pesticides.

New frontiers and prospects of metal-organic frameworks for removal, determination, and sensing of pesticides

Pesticides have been widely used in agriculture to control, reduce, and kill insects. Humans are also being using pesticides to control insidious animals in daily life. By these practices, a huge volume of pesticides is introduced to the environment. Despite broad-spectrum applicability, pesticides also have hazardous effects on both humans and animals at high and low concentrations. Long-term exposure to pesticides can cause different diseases, like leukemia, lymphoma, and cancers of the brain, breasts, prostate, testis, and ovaries. Reproductive disorders from pesticides include birth defects, stillbirth, spontaneous abortion, sterility, and infertility. Therefore, the application of determination and treatment methods for pre-concentration and removal of these toxic materials from the environment appears a vital concern. To date, different materials and approaches have been employed for these purposes. Among these approaches, multifunctional metal-organic frameworks (MOFs)-assisted adsorption and determination processes have always been in the spotlight. These facts are due to exclusive properties of MOFs in terms of the crystallinity, large surface area, high chemical, and physical stability, and controllable structure as well as unique features of adsorption and determination process in terms of simple, easy, cheap, available method and ability to use in large and industrial scales. In the present work, we illustrate the exceptional features of MOFs as well as the possible mechanism for the adsorption of pesticides by MOFs. The use of these fantastic materials for pre-concentration and removal of pesticides are extensively explored. In addition, the performance of MOFs was compared with other adsorbents. Finally, the new frontiers and prospects of MOFs for the determination, sensing, and removal of pesticides are presented.

New Trend in the Extraction of Pesticides from the Environmental and Food Samples Applying Microextraction Based Green Chemistry Scenario: A Review

This review focused on the green microextraction methods used for the extraction of pesticides from the environmental and food samples. Microextraction techniques have been explored and applied in various fields of analytical chemistry since its beginning, as evinced by the numerous reviews published. The success of any technique in science and technology is measured by the simplicity, environmentally friendly, and its applications; and the microextraction technique is highly successive. Deliberations were attentive to studies where efforts have been made to validate the methods through the inter-laboratory comparison study to assess the analytical performance of microextraction techniques against conventional methods. Succinctly, developed microextraction methods are shown to impart significant benefits over conventional techniques. Provided that the analytical community continues to put forward attention and resources into the growth and validation of the microextraction technique, a promising future for microextraction is forecasted.

Excitation of Surface Plasmon Resonance on Multiwalled Carbon Nanotube Metasurfaces for Pesticide Sensors

With the rapid advances in functional optoelectronics, the research on carbon-based materials and devices has become increasingly important at the terahertz frequency range owing to their advantages in terms of weight, cost, and freely bendable flexibility. Here, we report an effective material and device design for a terahertz plasmonic metasurface sensor (PMS) based on carbon nanotubes (CNTs). CNT metasurfaces based on silicon wafers have been prepared and obvious resonant transmission peaks are observed experimentally. The enhanced resonant peaks of transmission spectra are attributed to the surface plasmon polariton resonance, and the transmission peaks are further well explained by the Fano model. Furthermore, the different concentration gradients of pesticides (2,4-dichlorophenoxyacetic and chlorpyrifos solutions) have been detected by the designed PMSs, showing the lowest detection mass of 10 ng and the sensitivities of 1.38 × 10^-2/ppm and 2.0 × 10^-3/ppm, respectively. Good linear relationships between transmission amplitude and pesticide concentration and acceptable reliability and stability have been obtained. These materials and device strategies provide opportunities for novel terahertz functional devices such as sensors, detectors, and wearable terahertz imagers.