The Ion Formation and Quantitative Response of Isoprene, Monoterpenes and Terpenoids in Ion Mobility Spectrometry with Atmospheric-Pressure Chemical Ionization as a Function of Temperature.

Ion mobility spectrometry is successfully used as a sensor technology for different applications. A feature of this method is that characteristic ion mobility spectra are obtained for each measurement rather than a sum signal. The spectra result from the different drift velocities of ions in a drift tube at atmospheric pressure.

In Situ Water Quality Monitoring Using an Optical Multiparameter Sensor Probe.

Optical methods such as ultraviolet/visible (UV/Vis) and fluorescence spectroscopy are well-established analytical techniques for in situ water quality monitoring. A broad range of bio-logical and chemical contaminants in different concentration ranges can be detected using these methods. The availability of results in real time allows a quick response to water quality changes.

Membrane inlet-ion mobility spectrometry with automatic spectra evaluation as online monitoring tool for the process control of microalgae cultivation.

The cultivation of algae either in open raceway ponds or in closed bioreactors could allow the renewable production of biomass for food, pharmaceutical, cosmetic, or chemical industries. Optimal cultivation conditions are however required to ensure that the production of these compounds is both efficient and economical. Therefore, high-frequency analytical measurements are required to allow timely process control and to detect possible disturbances during algae growth.

Drift Time Corrections Based on a Practical Measurement of the Depletion Zone to Allow Accurate and Reproducible Determination of the Reduced Mobility of Ions in DT-IMS.

The reduced mobility of an ion is a key parameter for identifying ions and comparing spectra in drift time ion mobility spectrometry. As the resolution of spectrometers improves, accurate determination of the reduced mobility is increasingly important. The drift time, used to calculate the reduced mobility, is affected by the ion gate, and this effect has previously been compensated with a linear correction.

Molecularly Imprinted Polymer-Based Sensors for Priority Pollutants.

Globally, there is growing concern about the health risks of water and air pollution. The U.S.

Rational Design of Molecularly Imprinted Polymers Using Quaternary Ammonium Cations for Glyphosate Detection.

Molecularly imprinted polymers have emerged as cost-effective and rugged artificial selective sorbents for combination with different sensors. In this study, quaternary ammonium cations, as functional monomers, were systematically evaluated to design imprinted polymers for glyphosate as an important model compound for electrically charged and highly water-soluble chemical compounds. To this aim, a small pool of monomers were used including (3-acrylamidopropyl)trimethylammonium chloride, [2-(acryloyloxy)ethyl]trimethylammonium chloride, and diallyldimethylammonium chloride.

Application of Low-Cost Electrochemical Sensors to Aqueous Systems to Allow Automated Determination of NH and HS in Water.

Usage of commercially available electrochemical gas sensors is currently limited by both the working range of the sensor with respect to temperature and humidity and the spikes in sensor response caused by sudden changes in temperature or humidity. Using a thermostatically controlled chamber, the sensor response of ammonia and hydrogen sulfide sensors was studied under extreme, rapidly changing levels of humidity with the aim of analyzing nebulized water samples. To protect the sensors from damage, the gas stream was alternated between a saturated gas stream from a Flow Blurring® nebulizer and a dry air stream.

Humidity Effect on the Drift Times of the Reactant Ions in Ion Mobility Spectrometry.

The effect of moisture content on the drift times of NH and HO reactant ions at different temperatures was experimentally and theoretically studied using an ion mobility spectrometer (IMS). The peak positions of the ions shifted to higher drift times as the humidity of the drift gas increased. The peak displacements were attributed to the consecutive formation of hydrated ion clusters, RI(HO).

Molecularly Imprinted Polymer Materials as Selective Recognition Sorbents for Explosives: A Review.

Explosives are of significant interest to homeland security departments and forensic investigations. Fast, sensitive and selective detection of these chemicals is of great concern for security purposes as well as for triage and decontamination in contaminated areas. To this end, selective sorbents with fast binding kinetics and high binding capacity, either in combination with a sensor transducer or a sampling/sample-preparation method, are required.

Negative electrospray ionization ion mobility spectrometry combined with paper-based molecular imprinted polymer disks: A novel approach for rapid target screening of trace organic compounds in water samples.

A novel approach for the rapid target screening of water contaminants in trace concentrations was applied for the determination of the artificial sweetener Acesulfame-K, an accepted municipal wastewater indicator. This new method combines the selective enrichment of target analytes on paper-based molecular imprinted polymer disks and the subsequent analysis using a modified ion mobility spectrometer allowing negative electrospray ionization (ESI-IMS). Our developed ion mobility spectrometer permits the sensitive detection of Acesulfame with a limit of detection of 93 µg L within few seconds without sample separation.

Application of open-path Fourier transform infrared spectroscopy for atmospheric monitoring of a CO back-production experiment at the Ketzin pilot site (Germany).

During a controlled "back-production experiment" in October 2014 at the Ketzin pilot site, formerly injected CO was retrieved from the storage formation and directly released to the atmosphere via a vent-off stack. Open-path Fourier transform infrared (OP FTIR) spectrometers, on-site meteorological parameter acquisition systems, and distributed CO point sensors monitored gas dispersion processes in the near-surface part of the atmospheric boundary layer. The test site provides a complex and challenging mosaic-like surface setting for atmospheric monitoring which can also be found at other storage sites.

A new strategy for accelerated extraction of target compounds using molecularly imprinted polymer particles embedded in a paper-based disk.

In this study, a general simple and inexpensive method is introduced for the preparation of a paper-based selective disk-type solid phase extraction (SPE) technique, appropriate for fast and high throughput monitoring of target compounds. An ion exchange molecularly imprinted polymer (MIP) was synthesized for the extraction and analysis of acesulfame, an anthropogenic water quality marker. Acesulfame imprinting was used as an example for demonstrating the benefits of a nanosized, swellable MIP extraction sorbents integrated in an on-site compatible concept for water quality monitoring.

Ion transfer from an atmospheric pressure ion funnel into a mass spectrometer with different interface options: Simulation-based optimization of ion transmission efficiency.

Rationale: We optimized an atmospheric pressure ion funnel (APIF) including different interface options (pinhole, capillary, and nozzle) regarding a maximal ion transmission. Previous computer simulations consider the ion funnel itself and do not include the geometry of the following components which can considerably influence the ion transmission into the vacuum stage.

Methods: Initially, a three-dimensional computer-aided design (CAD) model of our setup was created using Autodesk Inventor.

Ion-exchange molecularly imprinted polymer for the extraction of negatively charged acesulfame from wastewater samples.

Acesulfame is a known indicator that is used to identify the introduction of domestic wastewater into water systems. It is negatively charged and highly water-soluble at environmental pH values. In this study, a molecularly imprinted polymer (MIP) was synthesized for negatively charged acesulfame and successfully applied for the selective solid phase extraction (SPE) of acesulfame from influent and effluent wastewater samples.

Selective mixed-bed solid phase extraction of atrazine herbicide from environmental water samples using molecularly imprinted polymer.

A novel approach for the selective extraction of organic target compounds from water samples has been developed using a mixed-bed solid phase extraction (mixed-bed SPE) technique. The molecularly imprinted polymer (MIP) particles are embedded in a network of silica gel to form a stable uniform porous bed. The capabilities of this method are demonstrated using atrazine as a model compound.

Accuracy of ion mobility measurements dependent on the influence of humidity.

Measurements with sensor techniques in field analytical chemistry can be considerably affected by varying ambient conditions such as humidity. We systematically investigated the way in which ion mobility measurements are influenced by moisture. Both the peak positions of product ions within the spectrum and their relative abundance can vary depending on humidity.

A new strategy for synthesis of an in-tube molecularly imprinted polymer-solid phase microextraction device: selective off-line extraction of 4-nitrophenol as an example of priority pollutants from environmental water samples.

In this study a novel preparation protocol has been developed for the construction of an in-tube molecularly imprinted polymer-solid phase microextraction (MIP-SPME) device. Open tubular capillaries have been molded from a polymer sorbent imprinted for 4-nitrophenol as target molecule. Different parameters like inner diameter and volume of the polymer, porogen volume, swelling and shrinking effects of the polymer tubes, polymerization time, pH of the sample, extraction time, 'salting out' effect and serial connection of the tubes were evaluated and optimized.

A solid-phase microextraction method for the in vivo sampling of MTBE in common reed (Phragmites australis).

Phytoscreening of phytoremediation-based plantings is discussed as a promising monitoring tool in literature. We developed and applied an analytical procedure for the in vivo sampling of methyl tert-butyl ether (MTBE) in the common reed (Phragmites australis) from a phytoremediation site highly polluted with MTBE. The approach uses solid-phase microextraction (SPME) with the SPME fibre directly introduced into the aerenchyma of the plant stem.

Temperature dependence of ion mobility signals of halogenated compounds.

Ion mobility spectrometry (IMS) as handheld and transportable sensor technique permits the sensitive detection of halogenated compounds with importance in environmental monitoring and process control. The negative ion mobility spectra mostly show one product ion peak which can be attributed to (H(2)O)(n)X(-) ions due to dissociative electron attachments. For minimizing memory effects and contaminations, modern ion mobility spectrometers work at elevated temperatures.

Comparative evaluation of pilot scale horizontal subsurface-flow constructed wetlands and plant root mats for treating groundwater contaminated with benzene and MTBE.

In order to evaluate technology options for the treatment of groundwater contaminated with benzene and MTBE in constructed wetlands (CWs), a scarcely applied plant root mat system and two horizontal subsurface-flow (HSSF) CWs were investigated. The inflow load of benzene and MTBE were 188-522 and 31-90 mg d(-1)m(-2), respectively. Higher removal efficiencies were obtained during summer in all systems.

Performance evaluation using a three compartment mass balance for the removal of volatile organic compounds in pilot scale constructed wetlands.

To perform a general assessment of treatment efficiency, a mass balance study was undertaken for two types of constructed wetlands (CWs), planted gravel filters and plant root mat systems, for treating VOC (benzene; MTBE) polluted groundwater under field conditions. Contaminant fate was investigated in the respective water, plant, and atmosphere compartments by determining water and atmospheric contaminant loads and calculating contaminant plant uptake, thereby allowing for an extended efficiency assessment of CWs. Highest total VOC removal was achieved during summer, being pronounced for benzene compared to MTBE.

Response of halogenated compounds in ion mobility spectrometry depending on their structural features.

Ion mobility spectrometry (IMS) with handheld and transportable devices permits the sensitive detection of chlorinated compounds which are important in environmental monitoring. The ion mobility spectra in negative measuring modus mostly show one product ion peak [(H(2)O)(n)Cl(-)] due to dissociative electron attachments. In this paper, we investigated relevant chlorinated compounds (R-Cl) where R represents allyl-, benzyl-, phenyl-, alkyl- and vinyl-groups.

Capability of headspace based sample preparation methods for the determination of methyl tert-butyl ether and benzene in reed (phragmites australis) from constructed wetlands.

In order to investigate the fate of volatile pollutants such as methyl tert-butyl ether (MTBE) and benzene during the treatment of contaminated water using constructed wetlands, appropriate analytical methods for the analysis of wetland marsh plants, in our case common reed (Phragmites australis), are required. Different sampling procedures and different headspace (HS) based sample preparation techniques were examined to select and establish the most suited procedure for determining the target analytes in plant material. Static HS, dynamic HS and HS solid phase microextraction (SPME) in combination with GC-MS were optimized and evaluated regarding the extraction yields and their capability for quantitative analysis.

Development and application of dynamic air chambers for measurement of volatilization fluxes of benzene and MTBE from constructed wetlands planted with common reed.

Phytoremediation of industrially contaminated groundwater has been a proven technique for several decades. However, mass balances of contaminants are often focused in laboratory investigations. The evaluation of the transfer of volatile organic compounds (VOCs) under field conditions from the saturated and vadose soil zone into the atmosphere, directly or via plants, is rarely part of the research scope.

Aerated treatment pond technology with biofilm promoting mats for the bioremediation of benzene, MTBE and ammonium contaminated groundwater.

A novel aerated treatment pond for enhanced biodegradation of groundwater contaminants was tested under field conditions. Coconut fibre and polypropylene textiles were used to encourage the development of contaminant-degrading biofilms. Groundwater contaminants targeted for removal were benzene, methyl tert-butyl ether (MTBE) and ammonium.