Microwave-prepared surface imprinted magnetic nanoparticles based electrochemical sensor for adsorption and determination of ketamine in sewage

Construction of an electrochemical sensor based on magnetic molecularly imprinted polymer-zeolite imidazole framework-8 for detection of 3,4-benzopyrene

A novel molecular-imprinted electrochemical sensor for 3,4-benzopyrene (3, 4-BaP) in food samples, with high sensitivity and selective detection, is introduced. Firstly, graphene oxide was modified onto a glassy carbon electrode (GCE) by electroreduction deposition to form an RGO/GCE sensing platform, thereby enhancing the sensitivity and stability of the sensor. Then, magnetic molecularly imprinted polymer-zeolite imidazole framework-8 (MMIP-ZIF-8) was synthesized in one step using the crystal growth method and modified onto RGO/GCE, endowing the sensor with good adsorption capacity and selectivity. The performance of the sensor for 3, 4-BaP was studied using differential pulse voltammetry (DPV), and the detection conditions of the constructed sensor were optimized. The results showed that under the optimal conditions, the constructed sensor exhibited a wide linear range (0.5 ~ 1000 nmol L-1), a low limit of detection (0.16 nmol L-1), and good selectivity and stability for the detection of 3, 4-BaP. It also showed a good recovery (99.74 ~ 102.58%) for the detection of 3, 4-BaP in actual corn meal samples. The MMIP-ZIF-8/RGO/GCE sensor developed has potential application prospects in the precise detection of 3, 4-BaP in food.

Determination of Arylcyclohexylamines in Biological Specimens: Sensors and Sample Pre-Treatment Approaches

Arylcyclohexylamine (ACH) compounds represent a predominant faction within new psychoactive substances. Due to their powerful dissociative effects, they are used in recreational contexts but also in situations of drug-facilitated sexual assault, and therefore, they are a constant target of analysis by forensic experts. In recent years, their consumption has been notably high, especially the use of ketamine, presenting daily challenges for laboratories in the determination of this and other ACH analogues. This review comprises the recent strategies that forensic specialists use to identify and quantify ACH compounds in the laboratory with more traditional analytical techniques and technology, and on the point-of-care testing via sensor technology. The study focuses on analogues of phencyclidine (PCP), ketamine, and eticyclidine, highlighting the consistent need for higher sensitivity in the analysis of various samples collected from real cases and simulations of possible matrices. The review also emphasises the ongoing research to develop more sensitive, quicker, and more capable sensors.

Three-Dimensional Electrochemical Sensors for Food Safety Applications

Considering the increasing concern for food safety, electrochemical methods for detecting specific ingredients in the food are currently the most efficient method due to their low cost, fast response signal, high sensitivity, and ease of use. The detection efficiency of electrochemical sensors is determined by the electrode materials' electrochemical characteristics. Among them, three-dimensional (3D) electrodes have unique advantages in electronic transfer, adsorption capacity and exposure of active sites for energy storage, novel materials, and electrochemical sensing. Therefore, this review begins by outlining the benefits and drawbacks of 3D electrodes compared to other materials before going into more detail about how 3D materials are synthesized. Next, different types of 3D electrodes are outlined together with common modification techniques for enhancing electrochemical performance. After this, a demonstration of 3D electrochemical sensors for food safety applications, such as detecting components, additives, emerging pollutants, and bacteria in food, was given. Finally, improvement measures and development directions of electrodes with 3D electrochemical sensors are discussed. We think that this review will help with the creation of new 3D electrodes and offer fresh perspectives on how to achieve extremely sensitive electrochemical detection in the area of food safety.

An electrochemical sensor for direct and sensitive detection of ketamine

Ketamine is an organic drug with weak electrochemical activity, which makes it difficult to directly detect by electrochemical methods. Herein, an electrochemical sensor, with excellent detection sensitivity, is proposed for direct detection of ketamine based on a weakly conductive poly-L-cysteine molecularly imprinted membrane. Poly-L-cysteine molecularly imprinted membrane sensor (poly-L-Cys-KT-MIM/GCE) is obtained using L-cysteine as a functional monomer and ketamine as a template molecule based on electropolymerization. The green and highly active cysteine is selected as a functional monomer during electropolymerization, which cannot only achieve specific recognition but also improve detection sensitivity. Furthermore, the oxidation mechanism and fingerprint of ketamine on the electrode surface are established by analyzing the corresponding oxidation products using high/resolution mass spectrometry, which will help to promote the application of electrochemistry in the rapid detection of drugs. Under optimal conditions, the as-designed sensor demonstrated a linear response to ketamine within the range of 5.0 × 10^-7 to 2.0 × 10^-5 mol L^-1 and a detection limit of 1.6 × 10^-7 mol L^-1. The proposed method exhibited excellent performance from the viewpoints of selectivity, sensitivity and stability. Notably, the sensor rendered excellent reliability and could be used for the detection of target analytes in hair and urine samples with high recovery rates.

Adsorption of Organic Compounds on Adsorbents Obtained with the Use of Microwave Heating

Activated carbons were obtained by physical and chemical activation of the residue of supercritical extraction of green tea leaves. All the adsorbents obtained were characterized by: elemental analysis, low-temperature nitrogen adsorption, and the contents of acidic and basic oxygen functional groups on the surface of activated carbons by the Boehm method. The activated carbons were micro- or micro-mesoporous with well-developed surface area ranging from 520 to 1085 m²/g and total pore volume from 0.62 to 0.64 cm³/g. The physical activation of the precursor led to the strongly basic character of the surface. Chemical activation with 50% solution of H₃PO₄ of the residue of supercritical extraction of green tea leaves promoted the generation of acidic functional groups. All adsorbents were used for methylene blue and methyl red adsorption from the liquid phase. The influence of the activation method, pH of the dye solution, contact time of adsorbent with adsorbate, the temperature of adsorption, and rate of sample agitation on the effectiveness of organic dyes removal was evaluated and optimized. In the process of methylene blue adsorption on adsorbents, an increase in the sorption capacity was observed with increasing pH of the adsorbate, while in the process of methyl red adsorption, the relation was quite the reverse. The adsorption data were analyzed assuming the Langmuir or Freundlich isotherm models. The Langmuir model better described the experimental results, and the maximum sorption capacity calculated for this model varied from 144.93 to 250.00 mg/g. The results of the kinetic analysis showed that the adsorption of organic dyes on activated carbon was following the pseudo-second-order model. The negative values of the Gibbs free energy indicate the spontaneous character of the process.

Coronas of micro/nano plastics: a key determinant in their risk assessments

As an emerging pollutant in the life cycle of plastic products, micro/nanoplastics (M/NPs) are increasingly being released into the natural environment. Substantial concerns have been raised regarding the environmental and health impacts of M/NPs. Although diverse M/NPs have been detected in natural environment, most of them display two similar features, i.e.,high surface area and strong binding affinity, which enable extensive interactions between M/NPs and surrounding substances. This results in the formation of coronas, including eco-coronas and bio-coronas, on the plastic surface in different media. In real exposure scenarios, corona formation on M/NPs is inevitable and often displays variable and complex structures. The surface coronas have been found to impact the transportation, uptake, distribution, biotransformation and toxicity of particulates. Different from conventional toxins, packages on M/NPs rather than bare particles are more dangerous. We, therefore, recommend seriously consideration of the role of surface coronas in safety assessments. This review summarizes recent progress on the eco-coronas and bio-coronas of M/NPs, and further discusses the analytical methods to interpret corona structures, highlights the impacts of the corona on toxicity and provides future perspectives.