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World Congress on Biosensors 2014

World Congress on Biosensors 2014
Biosensors 2014

Thursday, 31 May 2012

Save the date!


Informa Life Sciences' 2nd Annual Analytical Method Development conference brings together industry practitioners from across large, medium and small pharma to deliver Europe's only conference addressing these three aspects of holistic method development in one conference. Visit the event website to see which hot topics will be discussed, plus download the brochure for the full speaker line up. http://www.informaglobalevents.com/CQ5194JCFACE

Just Published: Trends in Analytical Chemistry


A new issue of this journal has just been published. To see abstracts of the papers it contains (with links through to the full papers) click here:
Selected papers from the latest issue:

Advances made on many different fronts

31 May 2012, 09:59:40
Publication year: 2012
Source:TrAC Trends in Analytical Chemistry, Volume 36
Andrea Jaquins Gerstl, I. Mitch Taylor, Zhan Shu, Hong Zhang, Stephen G. Weber

Chemical monitoring activity for the implementation of the Water Framework Directive

31 May 2012, 09:59:40
Publication year: 2012
Source:TrAC Trends in Analytical Chemistry, Volume 36
Philippe Quevauviller, Mario Carere, Stefano Polesello

Chemical monitoring and emerging pollutants in the Common Implementation Strategy of the Water Framework Directive

31 May 2012, 09:59:40
Publication year: 2012
Source:TrAC Trends in Analytical Chemistry, Volume 36
Mario Carere, Stefano Polesello, Caterina Sollazzo, Bernd Manfred Gawlik
This Foreword gives an overview on the last two mandates on Chemical Monitoring under the Common Implementation Strategy of the Water Framework Directive. It describes the development from 2005 until today, highlighting the various topics being addressed by the expert group. It sets the work into the relationship of the policy-making process as regards chemical-monitoring aspects for priority substances and emerging contaminants.

Guidance for sediment and biota monitoring under the Common Implementation Strategy for the Water Framework Directive

31 May 2012, 09:59:40
Publication year: 2012
Source:TrAC Trends in Analytical Chemistry, Volume 36
Mario Carere, Valeria Dulio, Georg Hanke, Stefano Polesello
The Environmental Quality Standards Directive 2008/105/EC (EQSD) marks an important step in the use of sediments and biota as matrices for chemical-status assessment under the Water Framework Directive 2000/60/EC (WFD). Analysis of contaminants in sediments and biota is indeed widely recognized as a cost-effective approach in water-quality monitoring to describe the general contamination level, to supply reference values for local and regional monitoring and to identify areas of concern where additional monitoring effort is needed. Because of the explicit reference in the EQSD to the use of sediments and biota as preferred matrices for the monitoring of substances with accumulation potential – especially for the assessment of long-term trends, but also for compliance checking, wherever appropriate – Member States of the European Union (EU) asked the European Commission to publish a guidance document to enhance the degree of harmonization among EU countries in chemical monitoring of sediments and biota, taking into account best available techniques, standard procedures and common practices. This article presents the key features of that guidance document, its main recommendations for chemical monitoring of sediments and biota and the scope for further improvement in current monitoring practices.

Highlights

► The European Commission developed Guidance on monitoring of sediment and biota. ► The Guidance addresses harmonization on monitoring sediment and biota in EU countries. ► Practically applying Water Framework and Environmental Quality Standards Directives.

Chemical-monitoring on-site exercises to harmonize analytical methods for priority substances in the European Union

31 May 2012, 09:59:40
Publication year: 2012
Source:TrAC Trends in Analytical Chemistry, Volume 36
Georg Hanke, Giulio Mariani, Sara Comero, Robert Loos, Giovanni Bidoglio, Stefano Polesello, Sara Valsecchi, Marianna Rusconi, Jan Wollgast, Javier Castro-Jiménez, Luisa Patrolecco, Nicoletta Ademollo
In support of the implementation of the Water Framework Directive (WFD, 2000/60/EC), three intercomparison exercises were carried out on European rivers (Po, Danube and Meuse) in order to assess the current state of monitoring methodologies. Laboratories from European Union (EU) Member States (MSs) were invited to gather at the selected EU river and sample together, each laboratory with its own method. Participants simultaneously sampled the river water and analyzed according to their protocols. A selection of priority substances (PSs) [i.e. polybromodiphenyl ethers (PBDEs), polycyclic aromatic hydrocarbons (PAHs) and alkyl phenols (APs)] included in Directive 2008/105/EC were analyzed in standard solutions, extracts from river waters and river-water samples in order to investigate variabilities in different steps of the analytical process. Concentrations measured in river samples using WFD-monitoring protocols showed that even some of the most challenging WFD PSs (e.g., PAHs, PBDEs and APs) can be measured at WFD-relevant concentrations with methods currently applied in MSs, but variability is still too great and not all laboratories meet required limits of quantification. Hindrance to the implementation of the monitoring requirements is therefore not the technical feasibility of analysis at these concentration levels, but rather communication, knowledge exchange and harmonization among the laboratories involved.

Highlights

► European intercomparison for implementation of the Water Framework Directive. ► Current state of monitoring methods for PAHs, PDBEs and alkyl phenols in EU rivers. ► Harmonization of monitoring procedures among laboratories is needed.

Testing sample stability in short-term isochronous stability studies for EU-wide monitoring surveys of polar organic contaminants in water

31 May 2012, 09:59:40
Publication year: 2012
Source:TrAC Trends in Analytical Chemistry, Volume 36
Bernd Manfred Gawlik, Robert Loos, Giovanni Bidoglio, Gisela Fauler, Xinghua Guo, Ernst Lankmayr, Thomas Linsinger
The article introduces the European Union (EU)-wide monitoring concept as run by the European Commission’s Joint Research Centre (JRC) and specifically addresses the issue of stability tests for environmental specimen and samples using the so-called isochronous stability-test design. We briefly describe the underlying statistical concept and apply it to water samples being collected in the context of the JRC’s EU-wide environmental monitoring activities. The stability of spiked tap-water and river-water samples and their containers was assessed at 4°C, 20°C and 40°C using ibuprofen, gemfibrozil, ketoprofen, diclofenac, bezafibrate, naproxen, perfluoroheptanoate (PFHpA), perfluorooctanoate (PFOA), perfluorooctane sulfonate (PFOS), carbamzepine, sulfamethoxazole, terbutylazine and triclosan as test substances in two different stability-testing schemes. The stability of the samples decreased as expected with an increase in the storage temperature. Uncertainty contributions were calculated and it was concluded that this type of sample remains stable for ca. 6weeks if stored at 4°C.

Highlights

► We developed a non-probabilistic, pan-European snapshot mechanism for water samples. ► It is used to derive benchmarks and links to regional chemical-monitoring programs. ► We addressed the issue of analyte stability in water samples. ► We applied the isochronous stability test used for reference materials. ► We used data directly to feed into policy implementation.

Chemical water monitoring under the Water Framework Directive with Certified Reference Materials

31 May 2012, 09:59:40
Publication year: 2012
Source:TrAC Trends in Analytical Chemistry, Volume 36
Marina Ricci, Ivan Kourtchev, Hendrik Emons
In the field of environment protection, a series of European Directives with special emphasis on the water bodies has been approved as a cascade after the milestone Water Framework Directive (WFD) of the year 2000. The most recent piece of legislation, Directive 2009/90/EC, points out the necessity of ensuring the quality of the analytical data and prescribes that the laboratories appointed by the Member States as responsible for the chemical water monitoring shall “demonstrate their competences…by…analysis of available reference materials…”. Certified Reference Materials (CRMs) are the anchor points for comparability of measurement results, in both space and time, ensuring their traceability to a common reference. In this article, we present a critical overview of existing matrix CRMs, related to WFD monitoring needs. Our survey concerns available water, biota and sediment matrix CRMs for the 33 Priority Substances (PSs) (and the eight “other certain pollutants”) listed in the WFD, together with a reference to discontinued CRMs. Tables providing a more synoptic view are available on-line as supplementary information. For the four priority metals (Cd, Pb, Hg and Ni), there are sufficient CRMs for all matrices considered to cover the needs of the monitoring laboratories, but there is a serious lack of matrix CRMs for most of the organic PSs. Also, for the matrix water, there are no materials available for organic pollutants that could be classified as CRMs as commonly understood. We also briefly discuss pure compounds and solution CRMs for calibration purposes. In the final section, we show how a CRM could be used in the estimation of measurement uncertainty for checking compliance at the Environmental Quality Standard level, according to the technical specifications given in Directive 2009/90/EC.

Highlights

► Quality and comparability of water chemical monitoring results should be ensured. ► CRMs are necessary for quality assurance and quality control of measurement results. ► Water, biota and sediment matrix CRMs for Cd, Pb, Hg and Ni are generally available. ► There are no water-matrix CRMs for organic priority substances under the WFD. ► Biota and sediment CRMs exist only for some organic priority substances under the WFD.

Monitoring of contaminants in suspended particulate matter as an alternative to sediments

31 May 2012, 09:59:40
Publication year: 2012
Source:TrAC Trends in Analytical Chemistry, Volume 36
Birgit Schubert, Peter Heininger, Martin Keller, Evelyn Claus, Mathias Ricking
The Water Framework Directive (WFD) requires Member States of the European Union to achieve good status of all waters in 2015. The survey of chemical status focuses on checking compliance of the quality of water systems against environmental quality standards and temporal trend monitoring of contaminants in sediments and/or biota. As sediments appropriate for monitoring contaminants may not always be available, we discuss the use of suspended particulate matter (SPM) as an alternative. We describe and discuss differences in quality and quantity of sediments and SPM collected by different sampling techniques with regard to the respective advantages and drawbacks for various monitoring purposes. Often, both contaminant concentrations in sediments and in SPM may give the required information. However, selection of the technique applied for collecting SPM should take into consideration, inter alia, the purpose of the monitoring, as well as the hydrodynamic and morphological conditions of the area monitored. We illustrate general conclusions with field applications from the European rivers Rhine and Elbe.

Highlights

► Suspended particulate matter (SPM) and sediments accumulate hydrophobic contaminants. ► The WFD requires trend monitoring of contaminants in sediments and/or biota. ► We compare the use of SPM and sediments for contaminant monitoring. ► Contaminant monitoring may be carried out for various purposes. ► The techniques described are applicable to rivers, estuaries and coastal systems.

The analytical problem of measuring total concentrations of organic pollutants in whole water

31 May 2012, 09:59:40
Publication year: 2012
Source:TrAC Trends in Analytical Chemistry, Volume 36
N. Ademollo, L. Patrolecco, S. Polesello, S. Valsecchi, J. Wollgast, G. Mariani, G. Hanke
The Water Framework Directive (WFD) (2000/60/EC) of the European Union provides protection from chemical pollutants through the Environmental Quality Standards (EQS) Directive (2008/105/EC), which sets EQSs for priority substances (PSs) and certain other pollutants, according to the requirements set out in Article 16(8) of the WFD. For organic PSs, these EQSs are expressed as total concentrations in the whole-water sample. Total concentrations can be obtained by direct analysis of the whole-water sample or by separate determinations on filterable and solid phases. Both solutions have their advantages and drawbacks, which we critically discuss in the present review. Analysis of data in the literature and experience from standardization activities show that it is possible to find a simple extraction method for analyzing whole water without time-consuming separation steps. The solid-phase extraction disk is now subject to standardization efforts as the most promising technique to achieve this goal. We discuss limitations of this approach in the light of the consequences for chemical-status assessment.

Highlights

► Whole-water analysis is carried out by direct analysis or separate determinations. ► We discuss the ways to analyze organics in whole water without separation. ► It is possible to use membrane-disk extraction for whole-water analysis. ► For whole-water analysis, membrane disks are validated in standardization activities. ► Limitations in whole-water analysis in the light of chemical-status assessment.

Sediment and biota in trend monitoring of contaminants in transitional waters

31 May 2012, 09:59:40
Publication year: 2012
Source:TrAC Trends in Analytical Chemistry, Volume 36
C. Maggi, A. Ausili, R. Boscolo, F. Cacciatore, A. Bonometto, M. Cornello, D. Berto
According to Directive 2008/105/EC, the Italian Parliament issued in 2010 the Legislative Decree 219, which determined the environmental quality standard (EQS) for sediment of marine coastal areas, lagoons and coastal ponds. For the purpose of trend monitoring, sediment and biota are the most suitable matrices for many substances. Directive 2008/105/EC gives an indication of the substances that should be taken into consideration for trend monitoring and sets an integrated water-management plan, which has to be prepared for each river-basin district. This article illustrates the criteria that were applied to draw the plan with the aim of assessing the trends of several substances in sediment and biota of the Lagoon of Venice, taking into account the recommendations of Directive 2000/60/EC and the daughter Directives. For this purpose, contaminant concentrations coming from a survey conducted in 2005 were compared with the Italian EQS. Results allowed for the evaluation of spatial and temporal trends of several contaminants in sediments and mollusks of the Lagoon of Venice. They allowed us to focus on which compounds need further monitoring and, most of all, which pollutants require measures to reduce inputs.

Highlights

► We assessed the trend monitoring of contaminants in the Lagoon of Venice. ► For the purpose of trend monitoring, we investigated sediment and biota. ► Directive 2008/105/EC states Member States must set Integrated Water Management Plans. ► Results used for the Sediment Monitoring Plan (2010–2012) for the Lagoon of Venice.

Biomonitoring of lake sediments using benthic macroinvertebrates

31 May 2012, 09:59:40
Publication year: 2012
Source:TrAC Trends in Analytical Chemistry, Volume 36
R. Bettinetti, B. Ponti, L. Marziali, B. Rossaro
The Water Framework Directive (2000/60/EC) is an innovative piece of legislation aimed at protecting the quality of all continental and coastal waters in Europe through an ecological evaluation of the ecosystems. Since it is widely acknowledged that the greater the ecological realism the greater the difficulty of its definition, we describe the different uses of benthic organisms as a tool for assessing the quality of sediment in lakes. We review the responses from single species to the community. We focus on studies in the laboratory and in the field, and we also critically consider the use of predictive models for these evaluations. Our discussion of the information collected underlines the importance of the relation between sensitivity of single species and contaminants. Moreover, the recent approach in developing mechanistic models to predict the response of natural communities seems to be particularly powerful for community ecology, and we strongly recommend more effort along these lines.

Highlights

► Macroinvertebrates are used as indicators of lake sediment toxicity in laboratory and field tests. ► Biomarkers provide early warning of contamination of lake sediments in the field. ► Mesocosms can assist study of the response of a community to toxic contamination. ► Biotic indices and species traits can measure community structure and functioning as response to toxic contamination.

Importance of dietary uptake of trace elements in the benthic deposit-feeding Lumbriculus variegatus

31 May 2012, 09:59:40
Publication year: 2012
Source:TrAC Trends in Analytical Chemistry, Volume 36
Marina Camusso, Stefano Polesello, Sara Valsecchi, Davide A.L. Vignati
The Water Framework Directive and daughter Directives of the European Union state that a risk-assessment approach should be used to set Environmental Quality Standards (EQSs) for different environmental compartments, including sediments. The derivation of sediment QSs is particularly relevant for substances that accumulate in sediment and could pose a risk through direct toxicity to benthic invertebrates, or to benthic predators through the food chain (secondary poisoning). For metals, total concentrations in sediment are not usually directly related to ecotoxicological effects because of variable natural background levels, and many abiotic and biotic factors can modify their bioaccessibility and bioavailability. The most common methods for incorporating bioavailability correction in QSsediment refer to the medium in which organisms live and determine only the chemical availability (bioaccessibility sensu) of elements, assuming that the available fraction is independent of the organisms to protect. However, there is significant evidence that the bioavailable fraction also depends on the feeding behavior and the ecology of biota, especially when the diet (sediment intake) is the main route of uptake. In the present work, we apply the Biodynamic Model to literature and original unpublished data of trace-element bioaccumulation in the sediment-dwelling oligochaete Lumbriculus variegatus to assess the main factors that affect the bioaccumulation and hence the bioavailable fraction in sediments. Results highlighted that, for L. variegatus, there is not a single, predominant route of uptake for all the elements considered. Ni is accumulated mainly from pore water. Sediment ingestion is the main uptake route for As, Cd, Cu and Zn. Pb body burden seems to depend on both the freely dissolved concentration in pore water and the dietary uptake. When diet is the main route of uptake, trace-element bioaccumulation is strongly controlled by the sediment-ingestion rate, which is itself a function of organic carbon (OC) content. We discuss the implications of these findings for the derivation of QSsediment and explore avenues for future research.

Highlights

► Deposit-feeding Lumbriculus variegatus accumulate trace elements mainly via diet. ► Ingestion rate is a key factor in forecasting trace-element accumulation by diet. ► Organic carbon in sediment influences trace-element intake by changing ingestion rate. ► Dietary uptake of elements must be considered in deriving sediment Quality Standards.

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Wednesday, 30 May 2012

Just Published: Sensors & Actuators B: Chemical


A new issue of this journal has just been published. To see abstracts of the papers it contains (with links through to the full papers) click here:
Selected papers from the latest issue:

Facile synthesis of nanospindle-like Cu2O/straight multi-walled carbon nanotube hybrid nanostructures and their application in enzyme-free glucose sensing

30 May 2012, 09:19:19
Publication year: 2012
Source:Sensors and Actuators B: Chemical, Volume 168
Xuemei Zhou, Huagui Nie, Zhen Yao, Youqing Dong, Zhi Yang, Shaoming Huang
A type of nanospindle-like Cu2O/straight multi-walled carbon nanotubes (SMWNTs) nanohybrids modified electrode for sensitive enzyme-free glucose detection has been fabricated, where the morphology of the nanohybrids were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray powder diffraction (XRD). The electrochemical characteristics of this electrode material were investigated by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The as-prepared nanospindle-like Cu2O/SMWNTs nanohybrids exhibit much higher electrocatalytic activity on the oxidation of glucose than the SMWNTs or Cu2O alone as the electrode modifying material, which attributes to high catalytic active sites provided by the nanospindle-like Cu2O and high electron transfer rate provided by an efficient electrical network formed by Cu2O and SMWNTs. The proposed sensors exhibit linear behavior in the concentration range from 500nM to 2.5mM for glucose with a high sensitivity of 2143μAmM−1 cm−2 and a limit of detection of 200nM (3σ). More importantly, the nanohybrids modified electrode also show good stability, reproducibility and high resistance against poisoning by chloride ion and the commonly interfering species such as ascorbic acid, dopamine, uric acid and acetamidophenol. These good analytical performances make the nanospindle-like Cu2O/SMWNTs nanohybrids promising for the future development of enzyme-free glucose sensors.

Room temperature CO sensing of selectively grown networked ZnO nanowires by Pd nanodot functionalization

30 May 2012, 09:19:19
Publication year: 2012
Source:Sensors and Actuators B: Chemical, Volume 168
Sun-Woo Choi, Sang Sub Kim
Room temperature sub-ppm CO sensing was realized in selectively grown networked ZnO nanowires by functionalizing their surfaces with Pd nanodots. In particular, the γ-ray radiolysis was applied to the Pd nanodot functionalization. The CO sensing characteristics of the Pd-functionalized ZnO nanowires were compared with those of bare ZnO nanowires. The Pd functionalization sharply improved the resistance responses at CO concentrations in the range of 100ppb–2ppm. At room temperature, the Pd-functionalized ZnO nanowire sensors exhibited a response of 1.02 at as low as 100ppb CO. The improvement of sensing capability by the Pd nanodot functionalization seems to be associated with the combined effect of electronic and chemical sensitizations due to the Pd nanoparticles.

A colorimetric and fluorometric dual-modal chemosensor for cyanide in water

30 May 2012, 09:19:19
Publication year: 2012
Source:Sensors and Actuators B: Chemical, Volume 168
Jiang-Fei Xu, Hong-Hai Chen, Yu-Zhe Chen, Zhong-Jin Li, Li-Zhu Wu, Chen-Ho Tung, Qing-Zheng Yang
We have developed a new class of benzothiazolium hemicyanine Cu(II) complex based colorimetric and fluorometric dual-modal chemosensor for the toxic cyanide anion in 100% water solution. This dual-modal response was achieved by the removal of Cu(II) ions from sensor complex in the presence of cyanide to recover the internal charge transfer (ICT) character of the hemicyanine dye. The novel sensor shows good sensitivity with μM-level detection limit, and displays high selectivity to cyanide in the presence of other common interference anions.

Dually tunable inverse opal hydrogel colorimetric sensor with fast and reversible color changes

30 May 2012, 09:19:19
Publication year: 2012
Source:Sensors and Actuators B: Chemical, Volume 168
Jinsub Shin, Sung Gu Han, Wonmok Lee
Through opal-templated photopolymerization of copolymeric hydrogel consisting of 2-hydroxyethyl methacrylate, N-isopropylacrylamide, acrylic acid, and N,N′-methylenebis(acrylamide), a dually tunable inverse opal sensor by temperature and pH has been successfully synthesized. Temperature drop or pH increase induced hydrogel swelling and subsequent color changes of the sensor respectively due to lower critical solution temperature behavior of N-isopropylacrylamide and the altered Donnan potential by acrylic acid units. The color change driven by hydrogel swelling could be quantitatively measured by reflectance spectra. Increased content of N-isopropylacrylamide in the hydrogel resulted in a larger volume change under the same T-drop experiment. On the contrary, higher crosslinker content led to a less swollen hydrogel. From the kinetic investigations, response time for temperature change was measured to be much faster than that for pH variation (0.5s vs. 28s). An exceptionally rapid temperature response could be explained by fast water influx to the thin layers at the top of inverse opal hydrogel after an instantaneous temperature change. A cyclic pH/temperature changes (pH jump–temperature-drop–pH drop–temperature-jump) on a dually tunable sensor showed a perfect restoration of diffraction wavelength as well as the rapid response times for all stimuli. This work facilitates the fabrication of a variety of multi-responsive inverse opal sensors exhibiting rapid response kinetics by simply copolymerizing the individual sensing monomers using the optimized photo-polymerization and the colloidal templating route.

Electrochemical detection of hydroquinone with a gold nanoparticle and graphene modified carbon ionic liquid electrode

30 May 2012, 09:19:19
Publication year: 2012
Source:Sensors and Actuators B: Chemical, Volume 168
Song Hu, Yuhua Wang, Xiuzheng Wang, Li Xu, Jun Xiang, Wei Sun
An ionic liquid 1-ethyl-3-methylimidazolium tetrafluoroborate (EMIMBF4) modified carbon paste electrode was fabricated and used as the substrate electrode. Then a gold nanoparticle and graphene (GR) composite film was co-electrodeposited on the carbon ionic liquid electrode (CILE) surface by immersing CILE in the graphite oxide and tetrachloroauric acid dispersion solution with cyclic voltammetric reduction. The fabricated Au–GR/CILE exhibited good electrochemical performances with higher conductivity and lower electron transfer resistance. Electrochemical behaviors of hydroquinone (HQ) were further investigated on the modified electrode by cyclic voltammetry and differential pulse voltammetry. A pair of well-defined redox peaks appeared with the peak-to-peak separation (ΔE p) as 0.077V in 0.1mol/L pH 2.5 PBS, indicating a fast quasi-reversible electron transfer process. The result could be attributed to the presence of high conductive Au–GR nanocomposites on the electrode surface. The electrochemical parameters of HQ on the Au–GR/CILE were calculated and the experimental conditions were optimized. Under the optimal conditions, the linear relationship between the oxidation peak current of HQ and its concentration can be obtained in the range from 0.06μmol/L to 800.0μmol/L with the detection limit as 0.018μmol/L (3σ). The coexisting catechol exhibited no interference and Au–GR/CILE was applied to the detection of HQ in synthetic wastewater samples with satisfactory results.

Multi-wall carbon nanotube gas sensors modified with amino-group to detect low concentration of formaldehyde

30 May 2012, 09:19:19
Publication year: 2012
Source:Sensors and Actuators B: Chemical, Volume 168
Haifen Xie, Changhao Sheng, Xin Chen, Xingyan Wang, Zhi Li, Jia Zhou
Gas sensors with multi-wall carbon nanotubes (MWCNTs) modified with amino-groups on interdigitated electrodes (IDE) were fabricated to detect low concentration of formaldehyde at room temperature. Effects of content of amino groups on sensing responses against various interfering circumstances and low concentration of formaldehyde were investigated. The sensor behaved high relative resistance changes to formaldehyde and lower response to interfering gases such as acetone, carbon dioxide, ammonia, toluene and ethanol. When the concentration of formaldehyde was 20ppb, the relative resistance changes of the sensor modified with 18.19% amino-group reached 1.73%. The sensor displayed high chemical selectivity, fast response and good reproducibility to low concentration of formaldehyde, which was attributed to the properties of MWNTs and the interaction between the surface of MWCNTs and amino-group.

Enhanced acetone sensing performance of Au nanoparticles functionalized flower-like ZnO

30 May 2012, 09:19:19
Publication year: 2012
Source:Sensors and Actuators B: Chemical, Volume 168
Xin-jun Wang, Wei Wang, Yan-Li Liu
ZnO flowers functionalized by Au nanoparticles (NPs) with various Au contents have been developed. The gas sensing properties of the sensors fabricated from these materials were examined and compared at varied working temperatures. Improved sensor response, selectivity and short response and recovery times to acetone vapor were achieved by suitably modulating the weight percent of Au NPs. Experimentally, the formation of Au/ZnO hybrids and surface coarsening of ZnO flowers were found to lead to apparent further enhancement of the sensor performance.

Highly sensitive phenolic biosensor based on magnetic polydopamine-laccase-Fe3O4 bionanocomposite

30 May 2012, 09:19:19
Publication year: 2012
Source:Sensors and Actuators B: Chemical, Volume 168
Yunyong Li, Cong Qin, Chao Chen, Yingchun Fu, Ming Ma, Qingji Xie
New polydopamine (PDA)-laccase (Lac)-Fe3O4 magnetic polymeric bionanocomposites (MPBNCs) were prepared through one-pot Lac-catalyzed oxidation of dopamine in an aqueous suspension containing Lac, magnetic Fe3O4 nanoparticles and dopamine. A PDA-Lac-Fe3O4/Au electrode was prepared by facile and efficient magnetic separation/immobilization of the MPBNCs on a magnetic Au electrode for biosensing of hydroquinone (HQ), giving a sensitivity of 374μAmmol−1 Lcm−2, a limit of detection of 30nmolL−1, as well as good selectivity and stability. The biosensing electrode was also used for HQ analysis in real sample matrices with satisfactory results.

Rapid colorimetric detection of sulfide using calix[4]arene modified gold nanoparticles as a probe

30 May 2012, 09:19:19
Publication year: 2012
Source:Sensors and Actuators B: Chemical, Volume 168
Alok Pandya, Kuldeep V. Joshi, Nishith R. Modi, Shobhana K. Menon
An advanced and proficient colorimetric sulfide sensor based on gold nanoparticles (AuNP) modified calix[n]arene assembly has been designed and synthesized by generation of strongly binding dithiocarbamate(DTC). This molecular receptor competently and selectively recognizes sulfide ion via H-bonds. The assembly was characterized by TEM, DLS, UV–vis, FT-IR and 1H NMR spectrometry which demonstrates the higher binding affinity for sulfide via hydrogen bonding. The optimum range for determination of sulfide is from pH 7 to 10. The lower detection limit is found to be 10nM. This method is simple and relatively free from interference of closely associated ions and is successfully applied to the determination of sulfide in real samples of spiked water and leather waste water.

Miniaturized F−-selective all-solid-state potentiometric sensors with conductive polymer as an intermediate layer

30 May 2012, 09:19:19
Publication year: 2012
Source:Sensors and Actuators B: Chemical, Volume 168
Alexey Matusevich, Mariusz Pietrzak, Elżbieta Malinowska
In this work, miniaturized F-selective all-solid-state potentiometric sensors were prepared and characterized. Poly(3,4-ethylenedioxythiophene) doped with poly(styrenesulfonate) (PEDOT:PSS) was used as an intermediate layer between gold internal electrode and polymer membrane of fluoride-selective sensors. The method of PEDOT:PSS deposition was optimized in order to prepare a layer with the best parameters for sensors preparation. Fluoride-selective ionophores working according to different carrier mechanisms (neutral and charged one) and appropriate lipophilic ionic additives were used for membrane preparation. The influence of membrane components on PEDOT:PSS intermediate layer properties has been evaluated. It is shown that the use of PEDOT:PSS deposited between fluoride-selective membrane and sensor internal electrode can enhance charge transfer between them only if membrane is able to provide sufficient cation movement. Working parameters of electrodes with membranes made of polyurethane (PU) and various amounts of plasticizer or non-plasticized PU were compared with electrodes based on conventional poly(vinyl chloride) (PVC) membranes. It was found that non-plasticized PU can successfully replace plasticized PVC in membranes doped with Al-based fluoride-selective ionophores, while for Zr-based ionophore it caused dramatic deterioration of electrodes’ working parameters. Using PU as membrane matrix, the best working parameters were achieved for electrodes based on Al(III)-tetra-tert-butyltetraazaporphine ( log   K F − , Y − pot . : Cl −3.9, Br −3.8, NO3 −3.6, SCN −2.1, ClO4 −2.5). As a result of studies, miniaturized fluoride-selective all-solid-state potentiometric sensors with response time less than 12s, lifetime more than 3 months and enhanced standard potential (E 0) stability, were prepared.

Nanoporous silicalite-only cantilevers as micromechanical sensors: Fabrication, resonance response and VOCs sensing performance

30 May 2012, 09:19:19
Publication year: 2012
Source:Sensors and Actuators B: Chemical, Volume 168
I. Pellejero, J. Agustí, M.A. Urbiztondo, J. Sesé, M.P. Pina, J. Santamaría, G. Abadal
Nanoporous microcantilevers entirely constituted by silicalite type zeolite have been fabricated by integrating the seeded growth hydrothermal zeolite synthesis step in a conventional microfabrication scheme using Si technologies. The mechanical properties of the as prepared polycrystalline beams, ranging from 200μm to 2000μm in length and 20 to 120μm in width have been fully characterized. In particular, Young modulus and quality factor of silicalite-only cantilevers before and after detemplation process have been determined by using mechanical resonance excitation and optical read-out. As a “proof of concept”, the nanoporous zeolitic cantilevers have been applied to ethanol detection at ppm level. The sensing performance of the as prepared silicalite-only cantilevers has been compared with the exhibited by conventional cantilevers consisting on microfabricated Si beams coated with individual silicalite crystals.

One-pot hydrothermal synthesis of CuO–ZnO composite hollow spheres for selective H2S detection

30 May 2012, 09:19:19
Publication year: 2012
Source:Sensors and Actuators B: Chemical, Volume 168
Sun-Jung Kim, Chan Woong Na, In-Sung Hwang, Jong-Heun Lee
Pure ZnO and CuO–ZnO composite hollow spheres were prepared by one-pot, glucose-mediated hydrothermal reaction with subsequent heat treatment. The pure ZnO hollow spheres could selectively detect C2H5OH at 475°C. The CuO–ZnO hollow spheres prepared from the solutions with the compositions of [Cu2+]/([Cu2+]+[Zn2+])=0.02 and 0.04 showed high responses to 5ppm H2S (R a /R g =13.3 and 32.4, R a : resistance in air, R g : resistance in gas) with negligible cross responses to 100ppm C2H5OH, C3H8, CO and H2 (R a /R g =1.4–1.8) at 336°C. They also showed selective C2H5OH detection at 475°C. The dual selective detection of H2S and C2H5OH by the composite particles was due to electrochemical interactions with H2S of nano-scale p(CuO)–n(ZnO) junctions within the hollow spheres.

Novel protein based pressure transducer

30 May 2012, 09:19:19
Publication year: 2012
Source:Sensors and Actuators B: Chemical, Volume 168
Christopher M. Sponheimer, Corinne S. Lengsfeld
The need for intra-organ pressure measurement can only be facilitated by adapting existing pressure sensing technology to the specific tissues under test. The customization of these sensors has only increased cost and the need to explore new technologies has become increasingly more important. For this article, we explore the use of electrochemical pressure sensing to provide a low-cost pressure sensor to fill this need. Here we show that gelatin exhibits a change in impedance when pressurized if bubbles are first electrolyzed in the gel creating an aerogel. Using electrochemical impedance spectroscopy and model fitting, it is shown that this effect occurs at the aerogel/hydrogel interface and the change in impedance is linearly related to the change in applied pressure. Micrographs were taken of the interface during pressurization and image analysis demonstrates that the change in surface area of the interface is also linearly related to the change in applied pressure.

Highlights

► Surface area of the sol/gel interface of an aerogel is related to its electrochemical properties. ► Impedance of the sol/gel interface is linearly related to the exposed surface area. ► Open circuit voltage of the sol/gel interface is linearly related to the exposed surface area. ► Change in surface area of sol/gel interface is linearly related to the change in applied pressure. ► A linear relationship between pressure and voltage lends itself well to pressure sensors.

Electrochemical study of niclosamide at poly(3,4-ethylenedioxythiophene) modified glassy carbon electrode

30 May 2012, 09:19:19
Publication year: 2012
Source:Sensors and Actuators B: Chemical, Volume 168
Solomon Mehretie, Shimelis Admassie, Merid Tessema, Theodros Solomon
A poly(3,4-ethylenedioxythiophene) (PEDOT) modified glassy carbon electrode was constructed for the determination of niclosamide. Cyclic voltammetry and differential pulse anodic stripping voltammetry were used to study the electrochemical reaction of niclosamide at the modified electrode in pH 7.0 phosphate buffer solution. The PEDOT-modified electrode showed a very good electrochemical behavior with a significant enhancement of the peak current compared to the bare electrode. The pH of the solution, accumulation potential and preconcentration time were optimized and the analytical performance of the modified electrode was investigated. A linear voltammetric response for niclosamide was obtained in the concentration range of 0.075–7.50μM, with a detection limit of 1.09×10−8 M. The method was successfully applied for the determination of niclosamide in pharmaceutical formulation and biological sample.

A novel amperometric sensor based on screen-printed electrode modified with multi-walled carbon nanotubes and molecularly imprinted membrane for rapid determination of ractopamine in pig urine

30 May 2012, 09:19:19
Publication year: 2012
Source:Sensors and Actuators B: Chemical, Volume 168
Hongcai Zhang, Guoyan Liu, Chunyan Chai
Screen-printed electrodes were modified with multi-wall carbon nanotubes (MWCNT) and molecularly imprinted membranes (MIM) were directly synthesized on these modified electrodes using the in situ thermal polymerization techniques. The sensing system was easily established by connecting the screen-printed electrode modified with MWCNT-MIM to an electrochemical analyzer through an electrode slot. The signal for the determination of ractopamine was recorded using differential pulse voltammetry (DPV) and the optimization for the experimental conditions was also conducted. The results showed that the response of the sensor to concentration of ractopamine displayed a linear correlation over a range from 20nM to 200nM with a detection limit of 6nM, demonstrating favorable sensitivity and selectivity for the detection of ractopamine. The recoveries reached 87.7–96.9% based on pig urine samples.

Development of a micro-flame ionization detector using a diffusion flame

30 May 2012, 09:19:19
Publication year: 2012
Source:Sensors and Actuators B: Chemical, Volume 168
Jihyung Kim, Byunghoon Bae, James Hammonds, Taekyu Kang, Mark A. Shannon
A micro-flame ionization detector (micro-FID) design is presented that is targeted for use in a portable gas sensor. Our micro-FID is based on a diffusion flame and features a folded flame structure that is more sensitive than a counter-flow flame designs. Unlike conventional FIDs that use a premixed or open diffusion flame, an air–hydrogen diffusion flame is employed and tested in an encapsulated structure of Quartz–Macor–Quartz layers. Diffusion flames are generally known to be more controllable and stable than premixed flames, where the stability of the micro-FID plays an important role for portable gas sensors. Various channel designs for oxidant and fuel flows meeting with different angles at the burner cavity are tested to obtain a stable flame and high output sensitivity over methane test samples. To verify the empirically designed microchannel, we simulate the temperature distribution in the microchannel by using computational fluid dynamics (CFD) software. To gauge the sensitivity of the device, the collected electric charges per mole (C/mol) is calculated and taken as a reference value of ionization efficiency. The result of the folded flame design is 1.959×10−2 C/mol for methane that is about 34 times higher than the result using a counter-flow flame, which is 5.73×10−4 C/mol for methane, while one of the commercial macro FIDs’ is 10−1 C/mol. This result shows that the micro-FID using the folded flame structure has higher ionization efficiency with less leakage of the analytes than of the classical counter-flow flame design. 

Just Published: Journal of Chromatography A


A new issue of this journal has just been published. To see abstracts of the papers it contains (with links through to the full papers) click here:
Journal of Chromatography A
Selected papers from the latest issue:

Rapid and sensitive solid phase extraction-large volume injection-gas chromatography for the analysis of mineral oil saturated and aromatic hydrocarbons in cardboard and dried foods

30 May 2012, 09:17:25
Publication year: 2012
Source:Journal of Chromatography A, Volume 1243
Sabrina Moret, Laura Barp, Giorgia Purcaro, Lanfranco S. Conte
A rapid off-line solid phase extraction-large volume injection-gas chromatography-flame ionisation detection (SPE-LVI-GC-FID) method, based on the use of silver silica gel and low solvent consumption, was developed for mineral oil saturated hydrocarbon (MOSH) and mineral oil aromatic hydrocarbon (MOAH) determination in cardboard and dried foods packaged in cardboard. The SPE method was validated using LVI with a conventional on-column injector and the retention gap technique (which allowed to inject up to 50μL of the sample). Detector response was linear over all the concentration range tested (0.5–250μg/mL), recoveries were practically quantitative, repeatability was good (coefficients of variation lower than 7%) and limit of quantification adequate to quantify the envisioned limit of 0.15mg/kg proposed in Germany for MOAH analysis in food samples packaged in recycled cardboard. Rapid heating of the GC oven allowed to increase sample throughput (3–4 samples per hour) and to enhance sensitivity. The proposed method was used for MOSH and MOAH determination in selected food samples usually commercialised in cardboard packaging. The most contaminated was a tea sample (102.2 and 7.9mg/kg of MOSH and MOAH below n-C25, respectively), followed by a rice and a sugar powder sample, all packaged in recycled cardboard.

Highlights

► Rapid and sensitive off-line SPE-LVI-GC-FID method for MOSH and MOAH analysis. ► Large volume injection with PTV as an alternative to on-column injection. ► The validated method was proposed as an alternative to the on-line LC–GC method. ► The method was applied to different food extracts.

Low-voltage electrically-enhanced microextraction as a novel technique for simultaneous extraction of acidic and basic drugs from biological fluids

30 May 2012, 09:17:25
Publication year: 2012
Source:Journal of Chromatography A, Volume 1243
Shahram Seidi, Yadollah Yamini, Maryam Rezazadeh, Ali Esrafili
In the present work, for the first time a new set-up was presented for simultaneous extraction of acidic and basic drugs using a recent novel electrically-enhanced microextraction technique, termed electromembrane extraction at low voltages followed by high performance liquid chromatography with ultraviolet detection. Nalmefene (NAL) as a basic drug and diclofenac (DIC) as an acidic drug were extracted from 24mL aqueous sample solutions at neutral pH into 10μL of each acidified (HCl 50mM) and basic (NaOH 50mM) acceptor solution, respectively. Supported liquid membranes including 2-nitrophenyl octyl ether containing 5% di-(2-ethylhexyl) phosphate and 1-octanol were used to ensure efficient extraction of NAL and DIC, respectively. Low voltage of 40V was applied over the SLMs during 14min extraction time. The influences of fundamental parameters affecting the transport of target drugs were optimized using experimental design. Under optimal conditions, NAL and DIC were extracted with extraction recoveries of 12.5 and 14.6, respectively, which corresponded to preconcentration factors of 300 and 350, respectively. The proposed technique provided good linearity with correlation coefficient values higher than 0.9956 over a concentration range of 8–500μgL−1 and 12–500μgL−1 for NAL and DIC, respectively. Limits of detection and quantifications, and intra-day precisions (n =3) were less than 4μgL−1, 12μgL−1, and 10.1%, respectively. Extraction and determination of NAL and DIC in human urine samples were successfully performed. In light of the data obtained in the present work, this new set-up for EME with low voltages has a future potential as a simple, selective, and fast sample preparation technique for simultaneous extraction and determination of acidic and basic drugs in different complicated matrices.

Highlights

► A new set-up of electromembrane extraction at low voltages was designed. ► The set-up was applied for simultaneous extraction of acidic and basic drugs. ► Acidic and basic drugs were extracted into anode and cathode lumens, respectively. ► HPLC–UV was applied for separation and determination of the drugs. ► Determination of the drugs in human urine samples was successfully performed.

Electro membrane extraction followed by low-density solvent based ultrasound-assisted emulsification microextraction combined with derivatization for determining chlorophenols and analysis by gas chromatography–mass spectrometry

30 May 2012, 09:17:25
Publication year: 2012
Source:Journal of Chromatography A, Volume 1243
Liang Guo, Hian Kee Lee
A highly efficient and simple two-step method, electro membrane extraction (EME) followed by low-density solvent based ultrasound-assisted emulsification microextraction (EME–LDS-USAEME) combined with derivatization and analysis by gas chromatography–mass spectrometry (GC–MS), was developed for the determination of trace level chlorophenols in environmental water samples. In the first step, the analytes were extracted, under electrical potential, from the sample solution into the acceptor solution, which was held in a polypropylene membrane sheet with 1-octanol as the supported liquid membrane. The acceptor solution from the first step was then employed as the sample solution for the second step of LDS-USAEME. In this step, the target analytes were extracted into a solvent with lower density than water that was dispersed in the sample solution with the assistance of ultrasound. The extract was separated from the sample solution by centrifugation and collected as the upper layer. Finally, the extract with a derivatization reagent were injected into a GC–MS system for analysis. Six chlorophenols, 2-chlorophenol, 4-chlorophenol, 2,3-dichlorophenol, 2,4-dichlorophenol, 2,4,6-trichlorophenol and pentachlorophenol were selected here as model compounds for developing and evaluating the method. Several factors influencing the extraction and derivatization were investigated. With the EME–LDS-USAEME procedure, high enrichment factors of up to 2198 were achieved. Under the most favorable conditions, good limits of detection (down to 0.005μg/L), linearity (from 0.05–10 to 0.2–10μg/L, depending on the analytes), and repeatability of extraction (RSDs below 9.7%, n =5) were obtained. The proposed method was applied to determine chlorophenols in drainwater samples.

Highlights

► Electro membrane extraction followed by ultrasound emulsification microextraction is reported. ► Flexible pipette allows convenient retrieval of lower density extract in USAEME. ► On-column derivatization avoids separate derivatization and expedites the procedure. ► High extraction efficiency for chlorophenols from aqueous samples obtained. ► The approach is fast and gives low LODs, good linearity and repeatability.

Mass spectrometric identification and characterization of new clomiphene metabolites in human urine by liquid chromatography–quadrupole time-of-flight tandem mass spectrometry

30 May 2012, 09:17:25
Publication year: 2012
Source:Journal of Chromatography A, Volume 1243
Jianghai Lu, Genye He, Xiaobing Wang, Youxuan Xu, Yun Wu, Ying Dong, Zhenwen He, Xin Liu, Tao Bo, Gangfeng Ouyang
Clomiphene, a selective estrogen receptor modulator, is prohibited by World Anti Doping Agency (WADA) out-of-competition and in-competition. As it is extensively metabolized, further investigation of clomiphene metabolic profile will be essential to routine anti-doping analysis. The metabolic pathway and the different metabolites of clomiphene in human urine collected from three healthy volunteers during 1week were studied by liquid chromatography–quadrupole time-of-flight mass spectrometry (LC–QTOFMS) based on accurate mass measurement. Seven unreported metabolites were identified and characterized, and all of the newly found urinary metabolites belonged to a new metabolic pathway (hydrogenation). An approach for the metabolism study of clomiphene and its analogs by LC–QTOFMS was presented. Two metabolites, 3,4-dihydroxy-dihydro-clomiphene (m/z 440.1991) and 3,4-dihydroxy-dihydro-deethyl-clomiphne (m/z 412.1674), are the potential biomarkers for monitoring oral administration of clomiphene in doping control.

Highlights

► The metabolic pathway and metabolites of clomiphene in human urine were studied. ► Seven unreported metabolites were identified and characterized by LC–QTOFMS. ► Two newly found metabolites are potential biomarkers in doping control analysis.

Three-dimensional cell bioreactor coupled with high performance liquid chromatography–mass spectrometry for the affinity screening of bioactive components from herb medicine

30 May 2012, 09:17:25
Publication year: 2012
Source:Journal of Chromatography A, Volume 1243
Zhao-Li Mou, Xiao-Ni Qi, Rui-Lin Liu, Jing Zhang, Zhi-Qi Zhang
An efficient and convenient method, three-dimensional (3-D) cell bioreactor coupled with high performance liquid chromatography–mass spectrometry was developed for affinity screening and analysis of multiple bioactive components from herbal medicines. Cancer cells were cultured on a porous scaffold to form a 3-D cell bioreactor. After interacting with live and fixed cells, the HPLC fingerprinting chromatograms of herbal medicine extract were compared to evaluate the binding properties of herbal components on cells. Model anticancer drugs (paclitaxel and resveratrol) and non-anticancer drugs (ketoprofen and penicillin G) were chosen to investigate the feasibility. When cell–drug interaction time was 30min, the binding degrees of paclitaxel and resveratrol (each 15μg/ml) were 82.2±7.2% and 66.1±4.1%, and for ketoprofen and penicillin G (each 15μg/ml) were less than 3%. This method was used to screen bioactive components from Polygonum cillinerve (Nakai) Ohwi (PCO) extract, and the binding degrees of two main components in PCO extract (10μg/ml), aristolochic acid A and aristolochic acid B, were 63.0±5.1% and 18.8±0.9%, respectively. These results demonstrated that this method was highly specific, efficient and convenient for affinity screening and analysis of bioactive components interacted with cells.

Highlights

► A three-dimensional (3-D) cell bioreactor was fabricated. ► An affinity screen method was developed by coupling the bioreactor with HPLC/MS. ► The method was used to screen bioactive components in herbal medicine. ► Specific binding components with cells can be screened and analyzed.

Rapid baseline-separation of all eight tocopherols and tocotrienols by reversed-phase liquid-chromatography with a solid-core pentafluorophenyl column and their sensitive quantification in plasma and liver

30 May 2012, 09:17:25
Publication year: 2012
Source:Journal of Chromatography A, Volume 1243
Nadine Grebenstein, Jan Frank
Of the eight natural vitamin E congeners (α-, β-, γ-, and δ-tocopherol and α-, β-, γ-, and δ-tocotrienol), the non-α-tocopherol congeners have unique biological properties that may contribute to human health. Their study in vivo has been complicated by the lack of a simple analytical method that completely resolves and sensitively detects all eight natural tocopherols and tocotrienols in biological matrices. We thus developed and validated (according to the FDA guidelines for bioanalytical method validation) the first reversed-phase liquid chromatographic method for the baseline-separation and quantification of all eight tocopherols and tocotrienols. Analytes were extracted from human plasma or mouse liver and separated on a Phenomenex Kinetex PFP column (2.6μm, 150×4.6mm) by elution with methanol:water (85:15, vol/vol) at a flow rate of 0.8mL/min. The developed RP-LC method used a solid-core pentafluorophenyl stationary phase and achieved baseline separation of all eight vitamin E congeners within 15min at a backpressure of 23MPa, which is suitable for most conventional HPLC systems. The method was fast, linear, accurate, and precise with detection limits of 27–156pg and good recoveries (82–122%) for all analytes. In conclusion, we developed and validated the first RP-LC method for baseline resolution of all eight tocopherols and tocotrienols extracted from plasma and liver, which should be useful for the quantification of individual vitamin E congeners in large epidemiological studies and randomized controlled trials.

Highlights

► A reversed-phase HPLC method for all 8 vitamin E congeners was developed. ► Baseline-separation was achieved on a solid-core pentafluorophenyl column. ► All tocopherols and tocotrienols were resolved in <15min with a LOD of 27–156pg. ► The method was validated for human plasma and mouse liver tissue. ► Reversed-phase separation of all vitamin E congeners is reported for the first time.

Determination of CMPO using HPLC–UV

30 May 2012, 09:17:25
Publication year: 2012
Source:Journal of Chromatography A, Volume 1243
Gracy Elias, Gary S. Groenewold, Bruce J. Mincher, Stephen P. Mezyk
Octyl(phenyl)-N,N-diisobutylcarbamoylmethylphosphine oxide (CMPO) is an extractant proposed for selective separation of radionuclide metals from used nuclear fuel solutions using solvent extraction. Radiolysis reactions can degrade CMPO and reduce separation performance and hence methods for measuring the concentration of CMPO are needed. A novel high performance liquid chromatography (HPLC) method was developed for measuring CMPO in dodecane that featured a low pH buffer, octanol as a co-solvent with 2-propanol, and ultraviolet (UV) detection. Validation data indicated that the HPLC–UV method for CMPO determination provided good linearity, sensitivity, accuracy and precision. Method performance was evaluated using CMPO samples that had undergone radiolysis, and the results showed a decrease in CMPO concentration and the appearance of degradation products. The degradation products were identified using electrospray ionization mass spectrometry, which also showed formation of CMPO–nitric acid complexes that account for the apparent loss of CMPO in an acidic environment, independent of irradiation.

Highlights

► CMPO is a ligand useful for radionuclides extraction in nuclear fuel solutions. ► Developed and applied a novel analytical technique with HPLC–UV for CMPO. ► LC/ESI-MS identified CMPO and a dominant radiolysis product. ► Direct infusion ESI-MS characterized CMPO–HNO3 coordination chemistry.

Liquid chromatography coupled to tandem mass spectrometry for the residue determination of ethylenethiourea (ETU) and propylenethiourea (PTU) in water

30 May 2012, 09:17:25
Publication year: 2012
Source:Journal of Chromatography A, Volume 1243
Cristina Ripollés, Juan V. Sancho, Francisco J. López, Félix Hernández
Ethylenethiourea (ETU) and propylenethiourea (PTU) are the main degradation products of dithiocarbamates fungicides, which are widely used in agriculture from several years ago. Their determination in water at low concentrations (e.g. sub-ppb levels) is highly problematic due to their polar character and low molecular size. In the present study, two analytical methodologies have been developed and compared for the selective and sensitive determination of ETU and PTU in various types of waters. Both approaches are based on liquid chromatography coupled to tandem mass spectrometry (LC–MS/MS) with electrospray ionization, using triple quadrupole analyzer. Whereas the first methodology used an on-line solid-phase extraction (SPE) step in order to reach the adequate sensitivity, the second one avoided sample treatment and was based on direct injection into an ultra high performance liquid chromatography (UHPLC–MS/MS) system, making use of a new-generation instrument in order to reach sub-ppb analyte levels in water. Strong matrix effects (typically leading to signal enhancement) were observed for most of the evaluated waters, especially when applying the on-line SPE method, surely due to the higher amount of sample injected into the system. The use of the own analyte (ETU-d4) as isotope-labelled internal standard (ILIS) allowed to compensate these effects and to achieve an accurate ETU quantification at low concentrations. Moreover, three simultaneous transitions, operating in selected reaction monitoring mode, were acquired for both ETU and ETU-d4. This fact together with the evaluation of their relative intensity ratios assured the reliable identification of the analyte in the water samples. The two optimized methodologies were validated by analysis of six different samples (two drinking water, two groundwater and two surface water), spiked at two levels (0.1 and 1.0μg/L), and analyzed each in quintuplicate. Satisfactory accuracy and precision, with recoveries ranging from 73 to 104% and RSDs lower than 20%, were obtained for ETU. Limits of detection for ETU were found to be 0.058μg/L and 0.027μg/L with direct injection and with the on-line methodology, respectively. No satisfactory recoveries were obtained, in general, for PTU despite using its own deuterium-labelled molecule for matrix effects correction. Notable differences in the chemical behaviour between PTU and PTU-d6 were observed, which lead to significant variation in their chromatographic retention time and ionization efficiency. Thus, no satisfactory correction of matrix effects could be reached illustrating that the use of deuterated ILIS can be problematic in some particular cases. Despite the poor correction, a semi-quantitative analysis would be feasible for PTU at sub-ppb levels in water. To the best of our knowledge, this is the first article reporting the use of LC–MS/MS for the trace level determination of these problematic analytes in water.

Highlights

► Dithiocarbamates degradation products ETU and PTU are determined at sub-ppb levels in water. ► Rapid ETU and PTU determination by direct injection in UHPLC–MS/MS QqQ (LOD 0.058μg/L). ► Alternative on-line SPE-LC–MS/MS can be used for ETU in water samples (LOD 0.027μg/L). ► Strong matrix effects observed are corrected for ETU using its own deuterated analyte as ILIS. ► Non satisfactory correction for PTU using PTU-d6 reveals that analyte ILIS may have different chemical behaviour.

Analysis of electrophoretic soil humic acids fractions by reversed-phase high performance liquid chromatography with on-line absorbance and fluorescence detection

30 May 2012, 09:17:25
Publication year: 2012
Source:Journal of Chromatography A, Volume 1243
Oleg A. Trubetskoj, Claire Richard, Ghislain Guyot, Guillaume Voyard, Olga E. Trubetskaya
A combination of reversed-phase high performance liquid chromatography (RP HPLC) with on-line absorbance and fluorescence detection was used for analysis of chernozem soil humic acids (HAs) and their fractions A, B and C+D with different electrophoretic mobility (EM) and molecular size (MS). Samples were injected onto the column at the identical volume and absorbance. All chromatograms exhibit the resolution of seven peaks. The estimation of relative recovery of HAs and fractions from the reverse-phase column has been done. High MS fraction A, which possesses the low EM, is essentially more hydrophobic (73% of the fraction amount remained adsorbed on the column) and aliphatic than medium MS and EM fraction B (33% of the fraction amount remained adsorbed on the column). The most hydrophilic and aromatic properties belong to low MS fraction C+D, which possess the highest EM and practically was not adsorbed on the column. The hydrophobicity of the bulk HAs lies within the range of fractions hydrophobicity. The absorption spectra of bulk HAs, electrophoretic fractions A, B, C+D and corresponding RP HPLC peaks were featureless but had differences in the values of absorbance ratio at 300 and 400nm (A3/A4). For fractions A and B this ratio gradually decreased from peak 1 to 7 (from 3.05 to 2.80 and 3.00 to 2.40, respectively). This trend was less pronounced in HAs and practically absent in fraction C+D, where ratio A3/A4 varied within a small range. The strong relationship between fluorescence properties, EM, MS, polarity and aliphaticity/aromaticity of HAs fractions was found. Humic and protein-like fluorescence had different polarity nature. The protein-like fluorescence is located in humic material which irreversibly adsorbed on the reverse-phase column and not subjected to RP HPLC characterization. The humic-like fluorescence at Ex/Em 270/450nm is mostly located in the hydrophilic peak of low MS fraction C+D. Taking into account that high MS fraction A consisted mainly of aliphatic components it is reasonable to suggest that these associations are capable of organizing into micellar structures. These data could be of great environmental importance, because the different fractions might reflect different soil physical–chemical properties.

Highlights

► RP-UPLC with on-line absorbance and fluorescence of soil humic acids and fractions. ► Relative recovery of humic acid and fractions from the reverse-phase column. ► Relationship between fluorescence, absorbance, polarity and aliphaticity in fractions.

High temperature gas chromatography–time-of-flight-mass spectrometry (HTGC–ToF-MS) for high-boiling compounds

30 May 2012, 09:17:25
Publication year: 2012
Source:Journal of Chromatography A, Volume 1243
P.A. Sutton, S.J. Rowland
High temperature gas chromatography (HTGC) is a routine technique for the analysis of high boiling compounds which are eluted from the column with oven cycling up to >400°C. In contrast, the coupling of HTGC with mass spectrometry (HTGC–MS) has received relatively little attention. This may be due to the availability of GC columns, mass spectrometers and accessories that are able to withstand constant high temperature cycling. We have assembled a HTGC–time of flight-MS (HTGC–ToF-MS) system from readily available products that is capable of rapid (<25min) analysis of ∼C10–100 hydrocarbon boiling equivalents and full mass spectral data recording up to m/z 1850. Here we report initial results from the analysis of diverse substrates including:long-chain (>C60) n-alkanes, n-acid methyl esters up to C64, triacylglycerides (TAGs) with molecular and fragment ions in a single analysis, intact wax esters from C40–64, C80 glycerol alkyl glycerol tetraethers (GDGTs), and C33–44 metallated porphyrins. Mass spectrometry at 430°C was achievable on a routine basis without significant thermal degradation of analytes. The method is applicable to analysis of a wide range of industrial, environmental, biological, geochemical and other samples where high molecular weight analytes are of interest.

Highlights

► HTGC was coupled with a time-of-flight mass spectrometer (HTGC–ToF-MS). ► HTGC–ToF-MS is viable with oven temperatures up to 430°C. ► Molecular and fragment ions were obtained from triglycerides in a single analysis. ► On-line mass spectra were obtained for C40+ n-acid/wax esters and C80 tetraethers. ► On-line mass spectra were obtained for metallated C33 and C44 porphyrins.