Direct extraction and detection of malachite green from marine sediments by magnetic nano-sized imprinted polymer coupled with spectrophotometric analysis

Molecularly Imprinted SERS Plasmonic Sensor for the Detection of Malachite Green

Malachite green (MG) is a highly toxic dye commonly used in industries and aquaculture, leading to significant environmental contamination and health hazards. Therefore, sensitive and selective detection of MG in real samples is urgently needed. This study presents the development of a molecularly imprinted surface-enhanced Raman spectroscopy (MI-SERS) plasmonic sensor for the rapid and sensitive detection of MG. The sensor consists of a gold nanostar (Au NS) layer as the SERS substrate and an imprinted polydopamine layer containing specific recognition sites for MG. Taking full advantage of the plasmonic effect of SERS and selective recognition capability of imprinted materials, under optimized conditions, the sensor demonstrated high sensitivity, with a detection limit of 3.5 × 10-3 mg/L, excellent selectivity against interference from other organic dyes, and robust performance with recoveries of 90.2-114.2% in real seawater samples. The MI-SERS sensor also exhibited good reproducibility, stability, and reusability. These findings suggest that the MI-SERS sensor is a promising tool for real-time monitoring of MG contamination in complicated samples.

Preparation of surface molecularly imprinted polymers with Fe3O4/ZIF-8 as carrier for detection of Dimethoate in cabbage

In this study, molecularly imprinted polymers (MIPs) were prepared for the specific recognition of organophosphorus pesticides and a rapid, efficient and simple method was established for the detection of dimethoate (DIT) in food samples. Fe3O4 magnetic nanoparticles were synthesized by co-precipitation, and Fe3O4/ZIF-8 complexes were prepared by a modified in-situ polymerization method, and then magnetic molecularly imprinted polymers (MMIPs) were prepared and synthetic route was optimized by applying density functional theory (DFT). The morphological characterization showed that the MMIPs were coarse porous spheres with an average particle size of 50 nm. The synthesized materials are highly selective for the organophosphorus pesticide dimethoate with an adsorption capacity of 461.50 mg·g-1 and are effective resistance to matrix effects. A novel method for the determination of DIT in cabbage was developed using the prepared MMIPs in combination with HPLC. The practical results showed that the method can meet the requirements for the determination of DIT in cabbage with recoveries of 85.6-121.1 % and detection limits of 0.033 μg·kg-1.

A Dimode Scattering Method for Ultratrace Dinitrofuran Detection with Nanopalladium Molecularly Imprinted Polymer Nanocatalytic Probe

With four nanoparticles as the nanomatrix, dinotefuran (DNF) as the template molecule, N-isopropylacrylamide as the functional monomer, trimethylolpropane and trimethacrylate as the cross-linker, four nanosurface molecularly imprinted polymer (MIP) bifunctional probes were prepared by microwave synthesis. It was found that palladium nanosurface MIP (Pd@MIP) not only recognized DNF but also had the strongest catalytic effect on the new nanogold indicator reaction of acrylic acid-HAuCl4, which was evaluated quickly with the slope procedure developed by us. The generated gold nanoparticles (AuNPs) not only possessed the resonance Rayleigh scattering (RRS) effect but also strong surface-enhanced Raman scattering (SERS) activity. The combination of Pd@MIP with DNF enhanced the catalytic effect by coupling the nanosurface electrons with π-electrons, thus enhancing both scattering signals. A new Pd@MIP nanoprobe catalytic-SERS/RRS dual-mode analytical platform was developed for the specific and sensitive detection of DNF. The linear ranges of the SERS and RRS methods were 0.075-0.75 and 0.1-0.75 nmol/L, and the limits of detection were 0.03 and 0.06 nmol/L, respectively. The standard deviations were 0.54-2.39%, and the recoveries were 93-105%.

Hexafluorobutanol primary alcohol ethoxylate-based supramolecular solvent formation and their application in direct microextraction of malachite green and crystal violet from lake sediments

A new type of hexafluorobutanol (HFB) primary alcohol ethoxylate (AEO)-based supramolecular solvent (SUPRAS) with density higher than water was prepared for the first time. HFB acted as AEO micelle-forming agent and density-regulating agent for SUPRAS formation. The prepared SUPARS was applied as extraction solvent for vortex-assisted direct microextraction of malachite green (MG) and crystal violet (CV) from lake sediment followed by high-performance liquid chromatographic determination. In the present work, SUPRASs prepared from AEO with different carbon chains as the amphiphiles and various coacervation agents were investigated. SUPARS formed from MOA-3 and HFB provided better extraction efficiency in comparison with other SUPRASs. Parameters influencing the extraction recovery of target analytes including the type and volume of AEO, volume of HFB, and vortex time were investigated and optimized. Under optimized conditions, linearity in the range of 2.0-400 μg g-1 for MG and 2.0-500 μg g-1 for CV with a correlation coefficient higher than 0.9947 was obtained. Limits of detection of 0.5 μg g-1 and relative standard deviations in the range of 0.9-5.8% were obtained. Compared to conventional extraction techniques for analysis of analytes in solid samples, the proposed method reduced sample usage and eliminated a primary extraction process by using a toxic organic solvent. The proposed method is simple, fast, and green and can be used for the analysis of target analytes in solid samples.

A review on magnetic sensors for monitoring of hazardous pollutants in water resources

Water resources have long been of interest to humans and have become a serious issue in all aspects of human life. The disposal of hazardous pollutants in water resources is one of the biggest global concerns and poses many risks to human health and aquatic life. Therefore, the control of hazardous pollutants in water resources plays an important role, when it comes to evaluating water quality. Due to low toxicity, good electrical conductivity, facile functionalization, and easy preparation, magnetic materials have become a good alternative in recent years to control hazardous pollutants in water resources. In the present study, the idea of using magnetic sensors in controlling and monitoring of pharmaceuticals, pesticides, heavy metals, and organic pollutants have been reviewed. The water pollutants in drinking water, groundwater, surface water, and seawater have been discussed. The toxicology of water hazardous pollutants has also been reviewed. Then, the magnetic materials were discussed as sensors for controlling and monitoring pollutants. Finally, future remarks and perspectives on magnetic nanosensors for controlling hazardous pollutants in water resources and environmental applications were explained.

Graphene Oxide Molecularly Imprinted Polymers as Novel Adsorbents for Solid-Phase Microextraction for Selective Determination of Norfloxacin in the Marine Environment

In this study, a novel sample pretreatment strategy of solid-phase microextraction using graphene oxide molecularly imprinted polymers as adsorbents coupled with high-performance liquid chromatography was developed to detect norfloxacin in the marine environment. As a carrier, the imprinted polymers were synthesized by precipitation polymerization with graphene oxide. Compared with graphene oxide non-imprinted polymers, the graphene oxide molecularly imprinted polymers exhibited higher adsorption capacity towards norfloxacin. The synthesized polymeric materials were packed into a molecularly imprinted solid-phase microextraction cartridge, and critical parameters affecting the extraction process were optimized. Under the optimized molecular imprinted solid-phase microextraction condition, the proposed method was applied to the analysis of norfloxacin for seawater and fish with satisfactory recovery (90.1–102.7%) and low relative standard deviation (2.06–5.29%, n = 3). The limit of detection was 0.15 μg L⁻¹ and 0.10 μg kg⁻¹ for seawater and fish, respectively. The study revealed that the proposed molecularly imprinted solid-phase microextraction represents an attractive sample pretreatment strategy for the analysis of norfloxacin in the marine environment.

Porous Biomass Carbon Derived from Clivia miniata Leaves via NaOH Activation for Removal of Dye

Clivia miniata (CM), is an important ornamental plant and has been widely cultivated all over the world. However, there are no reports on Clivia miniata-based porous biomass carbon (CMBC). In this study, for the first time, CM leaves were used to generate porous biomass carbon via NaOH activation. The structures and surface characteristics were determined using scanning electron microscopy, N2 adsorption/desorption, TGA, FT-IR, X-ray diffraction, Raman and X-ray photoelectron spectra tests. CMBC has a large SSA (2716 m2/g) and a total pore volume of 1.95 cm3/g. To test the adsorption performance via adsorption experiments, the cationic and synthetic dye, malachite green (MG), was utilized as the adsorption model. The CMBC had a greatest adsorption capacity of 2622.9 mg/g at a pH value of 8 and had a fastest adsorption capacity of 1161.7 mg/g in the first 5 min. To explain MG adsorption into CMBC, the Freundlich isotherm and the pseudo-second-order kinetic model were used. The adsorption mechanism of MG was also investigated. After 10 cycles, the adsorption efficiency of CMBC to MG could still reach 85.3%. In summary, CMBC has excellent potential in dyeing wastewater pollution treatment.

Highly effective pre-concentration of thymol and carvacrol using nano-sized magnetic molecularly imprinted polymer based on experimental design optimization and their trace determination in summer savoury, Origanum majorana and Origanum vulgare extracts

To ascertain thymol and carvacrol in pharmaceutical syrups, a valid and effective magnetic molecular imprinted polymer dispersive solid phase microextraction (MMIP-DSPME) process was developed in this study, which was in combination with a high performance liquid chromatography-ultra violet (HPLC-UV) technique for the assessment of thymol and carvacrol separation and pre-concentration. Contact time, eluent kind and volume, pH, the mass of the MMIP were all taken into consideration as key factors. Design expert and multi-objective response surface methodology (RSM) were used to optimize these variables. The mass of the MMIP, sample pH, eluent kind, time of sorption, the volume of eluent, and time of elution were 10 mg, 6, acetonitrile, 28 min, 200 µL, and 5.5 min, respectively, for the maximum extraction recovery of the analytes. The limit of detection (LOD) was 0.042 ng mL^-1 at the optimal conditions, while the value for the limit of quantification (LOQ) was 0.140 ng mL^-1. At the optimized conditions for thymol and carvacrol, the suggested MMIP sorbent had sorption capacities of 64.1 and 72.6 mg g^-1, respectively. Furthermore, for triplicate measurements, the linear dynamic range (LDR) was 0.40-5000 ng mL^-1, and the method's accuracy (RSD %) was 6.26%. The saturation magnetization for the MMIP was 19.0 emu g^-1 obtained by VSM, allowing the sorbent to be separated quickly. The sorption experiments confirmed the large sorption capacity of the MMIP for thymol and carvacrol, as well as its homogeneous binding sites. The extraction recovery for thymol and carvacrol was 96.9-103.8% and 96.6-105.4%, respectively, at all spiked amounts (20, 100, 200, and 500 ng mL^-1). The findings of seven desorption-regeneration cycles using MMIP demonstrated the high stability of the sorbent. The MMIP revealed a particular behavior of sorption for thymol and carvacrol, implying a selective, simple, effective, and flexible analytical method.

The Use of Computational Methods for the Development of Molecularly Imprinted Polymers

Recent years have witnessed a dramatic increase in the use of theoretical and computational approaches in the study and development of molecular imprinting systems. These tools are being used to either improve understanding of the mechanisms underlying the function of molecular imprinting systems or for the design of new systems. Here, we present an overview of the literature describing the application of theoretical and computational techniques to the different stages of the molecular imprinting process (pre-polymerization mixture, polymerization process and ligand-molecularly imprinted polymer rebinding), along with an analysis of trends within and the current status of this aspect of the molecular imprinting field.

Review on molecular imprinting technology and its application in pre-treatment and detection of marine organic pollutants

Molecular imprinting technology (MIT) has been considered as an attractive method to produce artificial receptors with the memory of size, shape and functional groups of the templates and has become an emerging technique with the potential in various fields due to recognitive specificity, high efficient selectivity and mechanical stability, which can effectively remove background interference and is suitable for the pre-treatment and analysis of trace level substances in complex matrix samples. Nearly 100 papers about the application of MIT in the detection of marine pollutants were found through Science Citation Index Expanded (SCIE). On this basis, combined with the application of MIT in other fields, the pre-treatment process of marine environmental samples was summarized and the potential of four types of different molecularly imprinted materials in the pre-treatment and detection of marine organic pollutants (including antibiotics, triazines, organic dyes, hormones and shellfish toxins) samples was evaluated, which provides the innovative configurations and progressive applications for the analysis of marine samples, and also highlights future trends and perspectives in the emerging research field.

Cu-BTC frameworks based electrochemical sensor for hazardous malachite green in aquaculture

Malachite green (MG) has been widely used for controlling external fungi and parasites in the aquaculture. However, MG has been proven to be very hazardous, and the detection of MG in aquaculture environment is crucial for determining whether MG has been used within the allowed limit and for protecting the environment. Herein, a kind of copper based metal-organic frameworks (MOFs) was prepared using copper nitrate and 1,3,5-benzenetricarboxylic acid (H₃BTC) as raw materials. The prepared Cu-BTC materials provide larger active area and higher accumulation capacity for MG, and meanwhile lower the charge-transfer resistance. As a result, the oxidation signal and detection sensitivity of MG are significantly improved by Cu-BTC frameworks. The linear range is 2-500 nM, and the detection limit is 0.67 nM, which is much lower than the reported values. Moreover, other usually-used aquaculture drugs have no interferences, including erythromycin, chloramphenicol, oxytetracycline, furazolidone and nitrofurazone. This method was applied in the water samples, and the results were consistent with those using high-performance liquid chromatography.