用于纳米孔道分析的四通道电化学传感器设计与仿真

纳米孔道技术是一种基于空间限域的超灵敏的单分子分析技术.通过研究单个分子限域于纳米孔道中所产生的离子电流的变化,可在单分子尺度上获取其结构、尺寸、电性及与孔道间弱相互作用的信息.目前主要应用的纳米孔道测量仪器单次实验仅能测量单个纳米孔道,其检测通量较低.本文基于实验室前期自主设计研制的单通道纳米孔道测量仪器Cube-D2上,比较研究了两种互阻放大器的测量特性,从而选择了合适的测量电路设计了四通道电化学传感器放大电路.进一步通过仿真验证了四通道电化学传感器设计方案的可行性,为阵列化高通量纳米孔道单分子电化学测量仪器的设计提供了理论基础.     

Fluorescent sensors for the detection of chemical warfare agents

Along with biological and nuclear threats, chemical warfare agents are some of the most feared weapons of mass destruction. Compared to nuclear weapons they are relatively easy to access and deploy, which makes them in some aspects a greater threat to national and global security. A particularly hazardous class of chemical warfare agents are the nerve agents. Their rapid and severe effects on human health originate in their ability to block the function of acetylcholinesterase, an enzyme that is vital to the central nervous system. This article outlines recent activities regarding the development of molecular sensors that can visualize the presence of nerve agents (and related pesticides) through changes of their fluorescence properties. Three different sensing principles are discussed: enzyme-based sensors, chemically reactive sensors, and supramolecular sensors. Typical examples are presented for each class and different fluorescent sensors for the detection of chemical warfare agents are summarized and compared.     

Elaboration and use of a double channel detection ion chromatographic method for determination of ions in aqueous samples

Summary In this paper we report our research in developing a simple and reliable method for determination of various anions in aqueous samples. Among the several methods existing for determining ions in aqueous samples, ion chromatography is becoming more and more important, due to its reliability and ability to determine the concentration of more ions from one sample. Although several detection methods are available, in this work we used conductivity detection, and indirect UV photometric detection. Because in some cases it can be important to gather more detailed information on the composition of a sample, we present a way to meet this demand by using double channel detection. Presented at Balaton Symposium on High Performance Separation Methods, Siófok, Hungary, September, 1–3, 1999     

Synthesis of C-11 and F-18 labelled compounds for biomedical applications: Current status and challenges for the future

The synthesis of¹¹C and¹⁸F labelled compounds for biomedical applications is a rapidly growing field with applications in Neurology, Cardiology, Oncology and the study of human biochemistry and physiology. Literally hundreds of compounds have been labelled but only a few have made their way into human studies with the bulk being used in animal studies. This review focuses on the production of these isotopes, the chemistry of labelling radiopharmaceuticals with these isotopes, automated chemistry and finally future considerations and applications for both¹¹C and¹⁸F.     

Fluorescence OFF-ON-OFF mechanism for the detection of digoxin,La3+, and epinephrine using bovine serum albumin functionalized molybdenum oxide quantum dots

Herein, we synthesized molybdenum oxide quantum dots using bovine serum albumin as a ligand (BSA-MoO_x QDs) via a simple method. The synthesized fluorescent BSA-MoO_x QDs were stable, and blue fluorescence was noticed upon exposure to UV lamp at 365 nm. When excited at 320 nm, BSA-MoO_x QDs showed an emission peak at 406 nm. Atomic force microscopic images demonstrated that the thickness of BSA layer on the surface of MoO_x QDs is 3.9 ± 1.6 nm. The as-synthesized BSA-MoO_x QDs acted as a sensor for the detection of digoxin, La³⁺, and epinephrine via fluorescence OFF-ON-OFF mechanisms, exhibiting linear ranges of 1–25, 0.125–5, and 0.5–10 μM with lower detection limits of 9.74, 23.08, and 4.58 nM for digoxin, La³⁺, and epinephrine, respectively. This method was successfully demonstrated to be an effective analytical platform for measuring digoxin and epinephrine in pharmaceutical and biofluid samples.     

The bound conformation of microtubule-stabilizing agents: NMR insights into the bioactive 3D structure of discodermolide and dictyostatin

A protocol based on a combination of NMR experimental data with molecular mechanics calculations and docking procedures has been employed to determine the microtubule-bound conformation of two microtubule-stabilizing agents, discodermolide (DDM) and dictyostatin (DCT). The data indicate that tubulin in assembled microtubules recognizes DDM through a conformational selection process, with minor changes in the molecular skeleton between the major conformer in water solution and that bound to assembled microtubules. For DCT, the deduced bound geometry presents some key conformation differences around certain torsion angles, with respect to the major conformer in solution, and still displays mobility even when bound. The bound conformer of DCT resembles that of DDM and provides very similar contacts with the receptor. Competition experiments indicate that both molecules compete with the taxane-binding site. A model of the binding mode of DDM and DCT to tubulin is proposed.     

Nanomaterials based non-enzymatic electrochemical and optical sensors for the detection of carbendazim: A review

Carbendazim sensors with high sensitivity and selectivity have become imperative for the welfare of the food industry, agriculture, aquaculture, and forestry. The design and development of sensors with high sensitivity and selectivity require deeper insights into the chemistry of nanomaterials. Driven by these needs, we intend to offer a concise discussion of diverse materials and various analytical techniques employed for carbendazim detection. This review focuses on interpreting the performance of well-recognized techniques integrated with keenly engineered nanomaterials, critical discussions on the drawbacks of the available sensors, and subsequent advances in nano-tailored materials. This review also provides constructive ideas for the requirement of maiden electrochemical and optical sensors, as well as existing challenges and future prospects.     

Rapid and inexpensive method for the simple fabrication of PDMS‐based electrochemical sensors for detection in microfluidic devices

The fabrication of PDMS microfluidic structures through soft lithography is widely reported. While this well‐established method gives high precision microstructures and has been successfully used for many researchers, it often requires sophisticated instrumentation and expensive materials such as clean room facilities and photoresists. Thus, we present here a simple protocol that allows the rapid molding of simple linear microchannels in PDMS substrates aiming microfluidics‐based applications. It might serve as an alternative to researchers that do not have access to sophisticated facilities such as clean rooms. The method developed here consists on the use of pencil graphite leads as template for the molding of PDMS channels. It yields structures that can be used for several applications, such as housing support for electrochemical sensors or channels for flow devices. Here, the microdevices produced through this protocol were employed for the accommodation of carbon black paste, which was utilized for the first time as amperometric sensor in microchip electrophoresis. This platform was successfully used for the separation and detection of model analytes. Ascorbic acid and iodide were separated within 45 s with peak resolution of 1.2 and sensitivities of 198 and 492 pA/μM, respectively. The background noise was ca. 84 pA. The analytical usefulness of the system developed was successfully tested through the quantification of iodide in commercial pharmaceutical formulations. It demonstrates good efficiency of the microfabrication protocol developed and enables its use for the easy and rapid prototyping of PDMS structures over a low fabrication cost.     

A pattern recognition based fluorescence quenching assay for the detection and identification of nitrated explosive analytes

Herein we report a differential array of micelle-solubilized fluorophores for the detection and identification of small nitrated analytes, such as the explosives TNT, tetryl, RDX and HMX. The quenching ability of the analytes can be used to correlate their analyte identity, wherein the quenching patterns generated from the differential array are used in linear discriminant analysis (LDA). LDA results in a well-clustered two-dimensional plot, and a jack-knife analysis of the data suggests that this system can be used to identify unknown samples of analyte with 96 % accuracy and with a detection limit of 19 muM.     

Laser-induced breakdown spectroscopy for detection of explosives residues: a review of recent advances, challenges, and future prospects

In this review we discuss the application of laser-induced breakdown spectroscopy (LIBS) to the problem of detection of residues of explosives. Research in this area presented in open literature is reviewed. Both laboratory and field-tested standoff LIBS instruments have been used to detect explosive materials. Recent advances in instrumentation and data analysis techniques are discussed, including the use of double-pulse LIBS to reduce air entrainment in the analytical plasma and the application of advanced chemometric techniques such as partial least-squares discriminant analysis to discriminate between residues of explosives and non-explosives on various surfaces. A number of challenges associated with detection of explosives residues using LIBS have been identified, along with their possible solutions. Several groups have investigated methods for improving the sensitivity and selectivity of LIBS for detection of explosives, including the use of femtosecond-pulse lasers, supplemental enhancement of the laser-induced plasma emission, and complementary orthogonal techniques. Despite the associated challenges, researchers have demonstrated the tremendous potential of LIBS for real-time detection of explosives residues at standoff distances. Figure This review discusses the application of laser-induced breakdown spectroscopy (LIBS) to the problem of explosive residue detection. LIBS offers the capability for real-time, standoff detection of trace amounts of residue explosives on various surfaces     

A new tool for inorganic nitrogen speciation study: simultaneous determination of ammonium ion, nitrite and nitrate by ion chromatography with post-column ammonium derivatization by Nessler reagent and diode-array detection in rain water samples

The paper presents a new method for a simultaneous determination of inorganic nitrogen species in the oxidized (NO₂⁻, NO₃⁻) and reduced (NH₄⁺) form in rain water samples. The method is based on a system of nitrogen species separation employing ion exchange and diode-array detection. The ions are separated in a strong ion-exchanger, nitrites and nitrates are determined directly at 208 and 205 nm, respectively, while the ammonium ions are determined in the column hold-up time after a post-column derivatization by the Nessler reagent, at 425 nm. The use of a diode-array detector permits a simultaneous identification of the inorganic nitrogen species in 8 min. The detection limits obtained are: NO₂⁻, 0.1 mg L⁻¹; NO₃⁻, 0.05 mg L⁻¹; NH₄⁺, 1 mg L⁻¹. The method proposed has been successfully used for speciation analysis of inorganic nitrogen in precipitation.     

Artificial intelligence-based microfluidic platforms for the sensitive detection of environmental pollutants: Recent advances and prospects

Environmental pollution and its drastic effects on human and animal health have urged governments to implement strict policies to minimize damage. The first step in applying such policies is to find reliable methods to detect pollution in various media, including water, food, soil, and air. In this regard, various approaches such as spectrophotometric, chromatographic, and electrochemical techniques have been proposed. To overcome the limitations associated with conventional analytical methods, microfluidic devices have emerged as sensitive technologies capable of generating high content information during the past few years. The passage of contaminant samples through the microfluidic channels provides essential details about the whole environment after detection by the detector. In the meantime, artificial intelligence is an ideal means to identify, classify, characterize, and even predict the data obtained from microfluidic systems. The development of microfluidic devices with integrated machine learning and artificial intelligence is promising for the development of next-generation monitoring systems. Combination of the two systems ensures time efficient setups with easy operation. This review article is dedicated to the recent developments in microfluidic chips coupled with artificial intelligence technology for the evolution of more convenient pollution monitoring systems.     

The use of Artificial Neural Networks for the selective detection of two organophosphate insecticides: Chlorpyrifos and chlorfenvinfos

Amperometric acetylcholinesterase (AChE) biosensors have been developed to resolve mixtures of chlorpyrifos oxon (CPO) and chlorfenvinfos (CFV) pesticides. Three different biosensors were built using the wild type from electric eel (EE), the genetically modified Drosophila melanogaster AChE B394 and B394 co-immobilized with a phosphotriesterase (PTE). Artificial Neural Networks (ANNs) were used to model the combined response of the two pesticides. Specifically two different ANNs were constructed. The first one was used to model the combined response of B394 + PTE and EE biosensors and was applied when the concentration of CPO was high and the other, modelling the combined response of B394 + PTE and B394 biosensors, was applied with low concentrations of CPO. In both cases, good prediction ability was obtained with correlation coefficients better than 0.986 when the obtained values were compared with those expected for a set of six external test samples not used for training.     

Solid‐phase microextraction for the human biomonitoring of environmental chemicals: Current applications and future perspectives

Sample preparation is one of the crucial steps in the analytical chemistry including human biomonitoring studies. Although there are several traditional approaches available, solid‐phase microextraction is emerged as one of the pioneering techniques due to its simplicity, rapidness, wide applicability, and miniaturization of traditional sample preparation (e.g., use of less or no organic solvents). There are few earlier review articles available on the advancements in solid‐phase microextraction and its use for the measurement of environmental chemicals in various types of environmental samples. However, a collective information on applicability and current usage of solid‐phase microextraction for the human biomonitoring of environmental chemicals are scarce, nonetheless, rising demands on innovative analytical approaches for human biomonitoring studies. Hence, in this review article, we covered the application of solid‐phase microextraction as extraction/purification methods for more than 15 classes of environmental chemicals to assess their respective exposure levels and associated health outcomes in various human population reported across the globe. Further, a detailed discussion on various types of matrix used, nature of coupled analytical instrumentations, and limitations and future perspectives of solid‐phase microextraction for human biomonitoring studies is presented in this review.     

Ion‐pair cloud‐point extraction: A new method for the determination of water‐soluble vitamins in plasma and urine

A novel, simple, and effective ion‐pair cloud‐point extraction coupled with a gradient high‐performance liquid chromatography method was developed for determination of thiamine (vitamin B₁), niacinamide (vitamin B₃), pyridoxine (vitamin B₆), and riboflavin (vitamin B₂) in plasma and urine samples. The extraction and separation of vitamins were achieved based on an ion‐pair formation approach between these ionizable analytes and 1‐heptanesulfonic acid sodium salt as an ion‐pairing agent. Influential variables on the ion‐pair cloud‐point extraction efficiency, such as the ion‐pairing agent concentration, ionic strength, pH, volume of Triton X‐100, extraction temperature, and incubation time have been fully evaluated and optimized. Water‐soluble vitamins were successfully extracted by 1‐heptanesulfonic acid sodium salt (0.2% w/v) as ion‐pairing agent with Triton X‐100 (4% w/v) as surfactant phase at 50°C for 10 min. The calibration curves showed good linearity (r² > 0.9916) and precision in the concentration ranges of 1‐50 μg/mL for thiamine and niacinamide, 5–100 μg/mL for pyridoxine, and 0.5–20 μg/mL for riboflavin. The recoveries were in the range of 78.0–88.0% with relative standard deviations ranging from 6.2 to 8.2%.     

Three new turn-on fluorescent sensors for the selective detection of Zn2+: Synthesis,properties and DFT studies

The design and synthesis of three new 1,8-naphthalimide-based fluorescent sensors (1–3) for the detection of Zn²⁺ in aqueous solution is described. The structural architect of these sensors contains 1,8-naphthalimide scaffold as a fluorophore attached to 2,2′-dipicolylamine (DPA) and bis(2-quinolinylmethyl)amine (DQA) receptors through an amide linkage. The addition of Zn²⁺ to the solutions of sensors (1–3) led to enhanced fluorescence intensity, ranging between 2.5 and 14 folds. At physiological pH (pH = 7.4), these sensors exhibited high selectivities for Zn²⁺ over a wide range of competing metal cations, displaying high sensitivities with a limit of detections of 120, 81.7 and 79.2 nM, respectively. This suggests that these sensors can detect chronic Zn²⁺ concentration for freshwater (>1.84 μM), designated by the U.S. Environmental Protection Agency. DFT simulations performed on the more stable stacked conformations of unbound and Zn²⁺ bounded states suggested that the latter display higher density of excited states than the unbound sensors. Moreover, the stacked conformer of sensor 3 was significantly more stable as compared to sensors 1 and 2, which was attributed to a stronger Van Der Waals (VDW) interaction between DQA and 1,8-naphthalimide. The Zn²⁺ binding leads to enhanced electronic coupling between the HOMOs and LUMOs, making excited states more populated which then undergoes geometric relaxation before emitting light and relaxing back to the ground states. The lower energy separation (5.0 eV) between the HOMO and the first Zn²⁺ d-orbital in sensor 3 as compared to sensors 1 and 2 results in enhanced density of the generated states and subsequently higher intensity upon binding with Zn²⁺.     

Nanoparticle-based electrochemical immunosensor for the detection of phosphorylated acetylcholinesterase: an exposure biomarker of organophosphate pesticides and nerve agents

A nanoparticle-based electrochemical immunosensor has been developed for the detection of phosphorylated acetylcholinesterase (AChE), which is a potential biomarker of exposure to organophosphate (OP) pesticides and chemical warfare nerve agents. Zirconia nanoparticles (ZrO(2) NPs) were used as selective sorbents to capture the phosphorylated AChE adduct, and quantum dots (ZnS@CdS, QDs) were used as tags to label monoclonal anti-AChE antibody to quantify the immunorecognition events. The sandwich-like immunoreactions were performed among the ZrO(2) NPs, which were pre-coated on a screen printed electrode (SPE) by electrodeposition, phosphorylated AChE and QD-anti-AChE. The captured QD tags were determined on the SPE by electrochemical stripping analysis of its metallic component (cadmium) after an acid-dissolution step. Paraoxon was used as the model OP insecticide to prepare the phosphorylated AChE adducts to demonstrate proof of principle for the sensor. The phosphorylated AChE adduct was characterized by Fourier transform infrared spectroscopy (FTIR) and mass spectroscopy. The binding affinity of anti-AChE to the phosphorylated AChE was validated with an enzyme-linked immunosorbent assay. The parameters (e.g., amount of ZrO(2) NP, QD-anti-AChE concentration,) that govern the electrochemical response of immunosensors were optimized. The voltammetric response of the immunosensor is highly linear over the range of 10 pM to 4 nM phosphorylated AChE, and the limit of detection is estimated to be 8.0 pM. The immunosensor also successfully detected phosphorylated AChE in human plasma. This new nanoparticle-based electrochemical immunosensor provides an opportunity to develop field-deployable, sensitive, and quantitative biosensors for monitoring exposure to a variety of OP pesticides and nerve agents.     

Molecularly imprinted polymer-carbon paste electrode (MIP-CPE)-based sensors for the sensitive detection of organic and inorganic environmental pollutants: A review

The rapidly growing existence of a number of contaminants (i.e. heavy metals, dye compounds, explosives and pesticides etc.) in environment is an alarming concern not only due to their harmful impacts for the environment bur also due to their potential high risk for human health. Thus, the careful and sensitive detection of these environmental contaminants is ver crucial. Electrochemical sensors combined with molecularly imprinted polymers (MIPs) become an attractive area for environmental monitoring. Benefiting from their great features such as high chemical and physical stability, cheap preparation process, excellent selectivity, sensitivity and fast response towards the target compound/s.This review paper aims to present and highlight the latest progresses in the design and development of novel electrochemical sensor systems composed of MIPs and carbon paste electrodes (CPEs) for the sensitive detection of pollutants in environmental samples.     

Electrokinetic sample injection for high‐sensitivity CZE (part 2): Improving the quantitative repeatability and application of electrokinetic supercharging‐CZE to the detection of atmospheric electrolytes

Electrokinetic supercharging (EKS) is defined as a technique that combines electrokinetic sample injection with transient ITP. Quantitative repeatability of EKS‐CZE and the other CE methods using electrokinetic sample injection process is usually inferior in comparison with the CE methods using hydrodynamic or hydrostatic injection. This is due to some effects, such as the temperature change and the convection of the sample solution in the reservoir, as well as the change of the distance between an electrode and a capillary end (D_ec). In particular, we have found that the D_ec change might most seriously affect the repeatability, especially when the electrode is a thin Pt wire that could be unintentionally bent during sampling. By using a Teflon spacer to fix D_ec to 1.1 mm, the RSD of peak area (n=5) was decreased from 20 to 3.4% in EKS‐CZE for several metal cations. This D_ec dependence of the sample amount injected was supported by computer simulation using CFD‐ACE+ software. The improved repeatability (down to 5.1% at n=5, averaged RSD for Co²⁺, Li⁺, Ni²⁺, Zn²⁺ and Pb²⁺) was also experimentally attained by increasing the D_ec to ca. 20 mm, which was also effective to obtain high sensitivity. Since the temperature and the convection effects on the repeatability are comparatively small in a proper laboratory environment, these effects were estimated from the EKS‐CZE experiments using conditions such as warming and agitating the sample solution during EKS process. Finally, EKS‐CZE was applied to the detection of ions from atmospheric electrolytes in high‐purity water exposed to ambient air for 2 h. The microgram per liter levels of anions (chloride, sulfate, nitrate, formate, acetate and lactate) and cations (ammonium, calcium, sodium and magnesium) could be detected using conventional UV detector.