Miniaturized low-cost ion mobility spectrometer for fast detection of chemical warfare agents

Ion mobility spectrometry (IMS) is a well-known method for detecting hazardous compounds in air. Typical applications are the detection of chemical warfare agents, highly toxic industrial compounds, explosives, and drugs of abuse. Detection limits in the low part per billion range, fast response times, and simple instrumentation make this technique more and more popular. In particular, there is an increasing demand for miniaturized low-cost IMS for hand-held devices and air monitoring of public areas by sensor networks. In this paper, we present a miniaturized aspiration condenser type ion mobility spectrometer for fast detection of chemical warfare agents. The device is easy to manufacture and allows single substance identification down to low part per billion-level concentrations within seconds. The improved separation power results from ion focusing by means of geometric constraints and fluid dynamics. A simple pattern recognition algorithm is used for the identification of trained substances in air. The device was tested at the German Armed Forces Scientific Institute for Protection Technologies-NBC-Protection. Different chemical warfare agents, such as sarin, tabun, soman, US-VX, sulfur mustard, nitrogen mustard, and lewisite were tested. The results are presented here.     

Metal Oxide Nanowire and Thin-Film-Based Gas Sensors for Chemical Warfare Simulants Detection

This work concerns with metal oxide (MOX) gas sensors based on nanowires and thin films. We focus on chemical warfare agents (CWAs) detection to compare these materials from the functional point-of-view. We work with different chemicals including simulants for Sarin nerve agents, vescicant gases, cyanide agents, and analytes such as ethanol, acetone, ammonia, and carbon monoxide that can be produced by everyday activities causing false alarms. Explorative data analysis has been used to demonstrate the different sensing performances of nanowires and thin films. Within the chosen application, our analysis reveal that the introduction of nanowires inside the array composed by thin films can improve its sensing capability. Cyanide simulants have been detected at concentrations close to 1 ppm, lower than the Immediately Dangerous for Life and Health (IDLH) value of the respective warfare agent. Higher sensitivity has been obtained to simulants for Sarin and vescicant gases, which have been detected at concentrations close or even lower than 100 ppb. Results demonstrate the suitability of the proposed array to selectively detect CWA simulants with respect to some compounds produced by everyday activities.     

Label-free electrochemical immunoassay for the detection of human chorionic gonadotropin hormone

Here we report on a new and rapid immunoassay for the label-free voltammetric detection of human chorionic gonadotropin hormone (hCG) in urine. Monitoring the changes in the current signals of antibodies (Abs) before and after the binding of the antigen (Ag) provides the basis for an immunoassay that is simple, rapid, and cost-effective. Since hCG is found at highly elevated levels in pregnant female urine with the range of 30,000-200,000 mIU/mL (approximately 30-200 nM) by 8-10 weeks into pregnancy, its label-free electrochemical detection was achieved by using our method. The coverage of the electrode surface with the Ab and the incubation time with the target Ag were optimized for the detection of hCG. The limit of detection of our method was calculated to be 15 pM (n = 3, approximately 15 mIU/mL) in synthetic hCG samples and 20 pM (n = 3, approximately 20 mIU/mL) in human urine. The electrochemical results for the detection of hCG in the urine samples were in agreement with the results obtained using a reference system, enzyme-linked immunosorbent assay. Further research about the intrinsic electroactivity of Abs and their target molecules would surely provide new and sensitive screening assays, as well as extensive data regarding their interaction mechanisms.     

快速cDNA文库筛选和淀粉合成酶基因的分离与鉴定

建立了一种以PCR为基础的快速筛选cDNA文库的方法。该方法利用96孔板和一对特异的引物,逐级从cDNA文加筛选目标克隆,最终获得目标DNA片段。与同位素杂交筛选方法相比,该方法具有快速、简单、省时等优点,数日内即完成目标片段的克隆;同时,还可极大地降低实验费用,且无需使用同位素。本文利用这一方法从水稻南粳隆;同时,还可极大地降低实验费用,且无需使用同位素。本文利用这一方法从水稻南粳隆;同时,还可极大地降低实验费用,且无需使用同位素。本文利用这一方法从水稻南粳37未成熟种子的cDNA文加筛选出了完整的水稻可溶性淀偻合酶基因cDNA序列。我们认为此方法对于筛选其他类型文库同样有借鉴意义。     

A simple and economical chemical neutralization method for the destruction of sulfur mustard and its analogues

A simple and economical chemical neutralization method is developed against highly toxic chemical warfare agent's viz. sulfur mustard (SM), sesquimustard, and their homologues/analogous. The method involves treatment of chemical warfare agents with sodium in inert solvents. This destruction method of sulfur mustards release innocuous products via desulfurization reactions. The products were characterized by GC-MS technique. The method is suitable in particular, for bulk destruction of heel of mustard stockpiles.     

Portable electrochemical surface-enhanced Raman spectroscopy system for routine spectroelectrochemical analysis

A simple, portable electrochemical surface-enhanced Raman spectroscopy (SERS) system is reported, consisting of a small benchtop Raman spectrometer, a laptop computer, and a portable USB potentiostat. Screen printed electrodes modified with silver colloidal nanoparticles are used as the SERS-active electrode, which exhibit long-term stability once prepared. Spectroelectrochemical analyses of para-aminothiophenol and melamine as model systems was conducted. In both cases, an increase in SERS signal is observed upon modulation of the applied voltage, indicating an inherent benefit of such a system wherein the surface charge can be easily tuned. Given the low cost, rapid analysis time, and good sensitivity of this system, this simple setup could be implemented for many on-site sensing applications, ranging from food and drug analysis to environmental monitoring and to chemical and biological warfare agent detection.     

Selective sample cleanup by reusable sol-gel immunoaffinity columns for determination of deoxynivalenol in food and feed samples

The paper describes the development of a simple and highly selective method for the determination of deoxynivalenol (DON) in food and feed samples. It combines sample cleanup with sol-gel immunoaffinity columns containing monoclonal anti-DON antibodies and quantification of DON by high-performance liquid chromatography with ultraviolet detection. The sol-gel immunoaffinity columns are as selective as commercial DON immunoaffinity columns but superior with regard to production costs, storage stability, and reusability. In applying the method for the analysis of maize, wheat, and spaghetti samples, it offers detection limits (LOD, S/N = 3) of 240, 200, and 207 ng/g, and recoveries of 83, 99, and 97%, respectively.     

Electric field-driven strategy for multiplexed detection of protein biomarkers using a disposable reagentless electrochemical immunosensor array

A fast, simple, sensitive, and low-cost method for electrochemical multianalyte immunoassay was developed by combining newly designed electric field-driven incubation with a screen-printed reagentless immunosensor array. The disposable array was prepared by immobilizing respectively horseradish peroxidase (HRP)-labeled antibodies modified gold nanoparticles in biopolymer/sol-gel modified electrodes to obtain direct electrochemical responses of HRP. Upon the formation of immunocomplexes, the responses decreased due to increasing spatial blocking and impedance. At a driving potential of 0.5 V, the incubation process could be accomplished within 2 min. Under optimal conditions, this method could simultaneously detect carbohydrate antigens 153, 125, and 199 and carcinoembryonic antigens ranging from 0.084 to 16, 0.11 to 13, and 0.16 to 15 U mL(-1) and 0.16 to 9.2 ng mL(-1) with a detection time of less than 5 min, and the detection limits corresponding to the signals of 3SD were 0.06, 0.03, and 0.10 U mL(-1) and 0.04 ng mL(-1), respectively. The disposable immunosensor array and simple detection system for fast measurement of panels of tumor markers show significant clinical value for application in cancer screening and provide great potential for convenient point-of-care testing and commercial application.     

Determination of nitrite in drinking water and environmental samples by ion exclusion chromatography with electrochemical detection

An extremely sensitive determination of nitrite in drinking water (tap water and underground water) and environmental samples (rain, lake water, and soil) was achieved by ion exclusion chromatography (IEC) with electrochemical (EC) detection. Potential interferences in the determination of nitrite by the standard spectrophotometric method or by the ion exchange chromatographic method with either conductivity detection or UV detection were eliminated. The detection limit was 0.1 ppb without preconcentration. No nitrite was observed from tap water or underground drinking water. The recoveries of nitrite added to tap water at 0.02, 0.1, and 1 ppm levels were between 96 and 104.5%. The average coefficient of variation was 4.7%. The recovery results were in good agreement with those obtained by the standard spectrophotometric method. Nitrite concentrations between 0.068 and 0.19 ppm were observed in rain within a week period. A greater variation, between 0.015 and 0.26 ppm, was observed in lake water. Amounts of 19.1 ppm and 0.50 ppm nitrite were observed from fertilized and unfertilized soil, respectively.     

PBT screening profile of chemical warfare agents (CWAs)

Chemical warfare agents (CWAs) have been used and disposed of in various fashions over the past decades. Significant amounts have been dumped in the Baltic Sea following the disarmament of Germany after World War II causing environmental concerns. There is a data gap pertaining to chemical warfare agents, environmental properties not the least their aquatic toxicities. Given this gap and the security limitations relating to working with these agents we applied Quantitative Structure-Activity Relationship ((Q)SAR) models in accordance with the European Technical Guidance Document (2003) to 22 parent CWA compounds and 27 known hydrolysis products. It was concluded that conservative use of EPI Suite (Q)SAR models can generate reliable and conservative estimations of chemical warfare agents acute aquatic toxicity. From an environmental screening point of view the organoarsenic chemical warfare agents Clark I and Adamsite comprise the most problematic of the screened CWA compounds warranting further investigation in relation to a site specific environmental risk assessment. The mustard gas agents (sulphur and nitrogen) and the organophosphorous CWAs (in particular Sarin and Soman) are a secondary category of concern based upon their toxicity alone. The undertaken approach generates reliable and conservative estimations for most of the studied chemicals but with some exceptions (e.g. the organophosphates).     

Measurements of chemical warfare agent degradation products using an electrophoresis microchip with contactless conductivity detector

This paper reports on a microfluidic device for the screening of organophosphonate nerve agent degradation products. The miniaturized system relies on an efficient chip-based separation of alkyl methylphosphonic acids (breakdown products of Sarin, Soman, and VX nerve agents) followed by their sensitive contactless conductivity detection. Experimental parameters relevant to the separation and detection processes have been optimized to yield high sensitivity (with 48-86 microg L(-1) detection limits), fast response (50 s for a three alkyl methylphosphonic acid mixture), high precision (RSD = 3.8-5.0%), and good linearity (over the 0.3-100 mg L(-1) range). Applicability to natural (river) water samples is demonstrated. The new microsystem offers promise for monitoring degradation products of chemical warfare agents, with advantages of speed/warning, efficiency, portability, sample size, and cost compared to conventional ion chromatography or capillary electrophoresis systems.     

Voltammetric sensor for general purpose organohalide detection at picogram per liter concentrations based on a simple collector-generator method

With the aim of producing a general purpose sensor for environmental analysis, we describe a simple and sensitive method for organohalide detection, based on an electrochemical collector-generator process. The sensor consists of four coplanar electrodes contacting a solution volume of 300 microL, containing organohalide. At the first working electrode (a Zn/PTFE composite), the analyte is electrolyzed to liberate halide ions. At the second working electrode (Ag), the halide ions are detected by cathodic stripping voltammetry. Using a preconcentration time of 600 s, with differential pulse voltammetry for stripping, the responses to 1-chloropropane, chloroform, carbon tetrachloride, iodoethane, and bromoethane can be plotted on a common calibration curve, with a detection limit of 0.1 nM (1.3 pg L(-1) or less depending on the organohalide). To the best of our knowledge, this is the lowest reported organohalide detection limit by an electrochemical method and is so far the only general purpose electrochemical method sensitive enough for regulatory requirements. The sensor response was invariant for approximately 40 measurements. Analysis of tap water, spiked with chloroform or carbon tetrachloride, gave recoveries within 1.0-2.6% of the recoveries by the standard GC method.     

Discrimination between ricin and sulphur mustard toxicity in vitro using Raman spectroscopy.

A Raman spectroscopy cell-based biosensor has been proposed for rapid detection of toxic agents, identification of the type of toxin and prediction of the concentration used. This technology allows the monitoring of the biochemical properties of living cells over long periods of time by measuring the Raman spectra of the cells non-invasively, rapidly and without use of labels (Notingher et al. 2004 doi:10.1016/j.bios.2004.04.008). Here we show that this technology can be used to distinguish between changes induced in A549 lung cells by the toxin ricin and the chemical warfare agent sulphur mustard. A multivariate model based on principal component analysis (PCA) and linear discriminant analysis (LDA) was used for the analysis of the Raman spectra of the cells. The leave-one-out cross-validation of the PCA-LDA model showed that the damaged cells can be detected with high sensitivity (98.9%) and high specificity (87.7%). High accuracy in identifying the toxic agent was also found: 88.6% for sulphur mustard and 71.4% for ricin. The prediction errors were observed mostly for the ricin treated cells and the cells exposed to the lower concentration of sulphur mustard, as they induced similar biochemical changes, as indicated by cytotoxicity assays. The concentrations of sulphur mustard used were also identified with high accuracy: 93% for 200 microM and 500 microM, and 100% for 1,000 microM. Thus, biological Raman microspectroscopy and PCA-LDA analysis not only distinguishes between viable and damaged cells, but can also discriminate between toxic challenges based on the cellular biochemical and structural changes induced by these agents and the eventual mode of cell death.     

Development of catalytic activity protocol for electrochemical reduction of carbon dioxide to value added products

Utilization of carbon dioxide for the production of value added products is a challenging task. Electrochemical reduction of carbon dioxide is one of the most promising techniques to convert the carbon dioxide into value added products. However, the development and selection of a suitable electrocatalyst is not so straightforward. The main problems are non-selectivity of the electrocatalyst toward CO₂ reduction, simultaneous hydrogen evolution reaction, and low efficiency of the process. To overcome these problems, many electrocatalysts have been studied and reported in the literature. However, there is no effective guideline to screen the electrocatalysts in a quick and simple way. Moreover, it is found that the method used for the screening of electrocatalyst is not accurate and has anomalies. Therefore, in this paper, a simple and quick protocol based on half-cell tests is proposed. The method provides a first-hand prediction about the electrochemical activity of an electrocatalyst toward electrochemical reduction of carbon dioxide. The protocol was validated and compared along with confirming the results by product analysis of the electrochemical reduction of CO₂ using full electrochemical reactor. The method was found satisfactory for the preliminary screening of electrocatalyst to reduce carbon dioxide electrochemically.     

Electrochemical detection of DNA hybridization by means of osmium tetroxide complexes and protective oligonucleotides

We have utilized protective oligonucleotides to modify DNA fragments with osmium tetroxide complexes without compromising their ability to hybridize with immobilized thiol-linked probe-SAMs on gold electrodes. Due to reversible voltammetric signals of Os(VI/IV), this method allowed sensitive electrochemical hybridization detection of short (25 bases) and long (120 bases) thymine-containing DNA targets. The detection limit was 3.2 nM for the long target. We found an optimum 40 degrees C hybridization temperature for the short target. No interference by noncomplementary DNA was observed. At least 10 repetitive hybridization experiments at the same probe-SAM were possible with thermal denaturation in between. Such use of protective strands could be useful also for other types of DNA recognition and even for other DNA-modifying agents. Moreover, it is possible to produce electrochemically active oligonucleotides (targets and reporter probes) in ones own laboratory in a simple way.     

Environmentally acceptable sorbents of chemical warfare agent simulants

Development of environmentally acceptable decontaminants of chemical weapons and other highly toxic chemicals is important because of security, economical, health, political, and environmental reasons. The efficiency of natural zeolite (clinoptilolite) and synthetic zeolite, metal oxides, and their mixtures as chemical and physical sorbents of chemical warfare agents (CWA) was investigated. Commonly studied chemical warfare agent simulants dimethyl methylphosphonate (DMMP) and 2-chloroethyl ethyl sulfide (2-CEES) were included in this study. Organic solutions of DMMP and 2-CEES were passed through a column filled with natural and synthetic zeolites and their mixtures with metal oxides. After passing through the column filled with different sorbents, all eluents were filtered and centrifuged before the gas chromatography–mass spectroscopy (GC–MS) analysis. The efficiency of investigated adsorbents was estimated based on the obtained data. All investigated sorbents exhibited absorption efficiency for both simulants of chemical warfare agents. Infrared spectroscopy was used for the detection of DMMP and 2-CEES adsorbed to the investigated adsorbents. Since GC–MS analysis results indicate very good sorption properties of both simulants, the detection of adsorbed CWA simulants was a matter of routine.     

Electrochemical sensor for organophosphate pesticides and nerve agents using zirconia nanoparticles as selective sorbents

An electrochemical sensor for detection of organophosphate (OP) pesticides and nerve agents using zirconia (ZrO2) nanoparticles as selective sorbents is presented. Zirconia nanoparticles were electrodynamically deposited onto the polycrystalline gold electrode by cyclic voltammetry. Because of the strong affinity of zirconia for the phosphoric group, nitroaromatic OPs strongly bind to the ZrO2 nanoparticle surface. The electrochemical characterization and anodic stripping voltammetric performance of bound OPs were evaluated using cyclic voltammetric and square-wave voltammetric (SWV) analysis. SWV was used to monitor the amount of bound OPs and provide simple, fast, and facile quantitative methods for nitroaromatic OP compounds. The sensor surface can be regenerated by successively running SWV scanning. Operational parameters, including the amount of nanoparticles, adsorption time, and pH of the reaction medium have been optimized. The stripping voltammetric response is highly linear over the 5-100 ng/mL (ppb) methyl parathion range examined (2-min adsorption), with a detection limit of 3 ng/mL and good precision (RSD = 5.3%, n = 10). The detection limit was improved to 1 ng/mL by using 10-min adsorption time. The promising stripping voltammetric performances open new opportunities for fast, simple, and sensitive analysis of OPs in environmental and biological samples. These findings can lead to a widespread use of electrochemical sensors to detect OP contaminates.     

Electrochemical immunosensor for cholera toxin using liposomes and poly(3,4-ethylenedioxythiophene)-coated carbon nanotubes

A sensitive method for the detection of cholera toxin (CT) using an electrochemical immunosensor with liposomic magnification followed by adsorptive square-wave stripping voltammetry is described. Potassium ferrocyanide-encapsulated and ganglioside (GM1)-functionalized liposomes act as highly specific recognition labels for the amplified detection of cholera toxin. The sensing interface consists of monoclonal antibody against the B subunit of CT that is linked to poly(3,4-ethylenedioxythiophene) coated on Nafion-supported multiwalled carbon nanotube caste film on a glassy carbon electrode. The CT is detected by a "sandwich-type" assay on the electronic transducers, where the toxin is first bound to the anti-CT antibody and then to the GM1-functionalized liposome. The potassium ferrocyanide molecules are released from the bounded liposomes on the electrode by lyses with methanolic solution of Triton X-100. The released electroactive marker is measured by adsorptive square-wave stripping voltammetry. The sandwich assay provides the amplification route for the detection of the CT present in ultratrace levels. The calibration curve for CT had a linear range of 10(-14)-10(-7)g mL(-1). The detection limit of this immunosensor was 10(-16) g of cholera toxin (equivalent to 100 microL of 10(-15) g mL(-1)).     

Development of a method for the determination of Fusarium fungi on corn using mid-infrared spectroscopy with attenuated total reflection and chemometrics

A novel method, which enables the determination of fungal infection with Fusarium graminearum on corn within minutes, is presented. The ground sample was sieved and the particle size fraction between >250 and 100 microm was used for mid-infrared/attenuated total reflection (ATR) measurements. The sample was pressed onto the ATR crystal, and reproducible pressure was applied. After the spectra were recorded, they were subjected to principle component analysis (PCA) and classified using cluster analysis. Observed changes in the spectra reflected changes in protein, carbohydrate, and lipid contents. Ergosterol (for the total fungal biomass) and the toxin deoxynivalenol (DON; a secondary metabolite) of Fusarium fungi served as reference parameters, because of their relevance for the examination of corn based food and feed. The repeatability was highly improved by sieving prior to recording the spectra, resulting in a better clustering in PCA score/score plots. The developed method enabled the separation of samples with a toxin content of as low as 310 microg/kg from noncontaminated (blank) samples. Investigated concentration ranges were 880-3600 microg/kg for ergosterol and 310-2596 microg/kg for DON. The percentage of correctly classified samples was up to 100% for individual samples compared with a number of blank samples.