Just Published: Journal of Analytical and Applied Pyrolysis

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 Analytical and Applied Pyrolysis
http://rss.sciencedirect.com/publication/science/5247

Selected papers from the latest issue:

Aromatic Hydrocarbon Production by the Online Catalytic Cracking of Lignin Fast Pyrolysis Vapors using Mo2N/γ-Al2O3

30 May 2013, 16:58:57

Publication date: Available online 30 May 2013
Source:Journal of Analytical and Applied Pyrolysis
Author(s): Yan Zheng , Dengyu Chen , Xifeng Zhu
This study investigates the online catalytic cracking of lignin fast pyrolysis vapors using Mo2N/γ-Al2O3 prepared by nitriding an alumina-supported molybdenum oxide precursor with nitrogen hydrogen mixtures though temperature programming. The activity and selectivity of the catalyst toward aromatic hydrocarbons were determined in the pyrolysis-gas chromatography/mass spectrometry system. Results show that the catalyst has a significant function in the pyrolysis process. In the presence of the catalyst, the primary pyrolysis products from lignin are catalytically converted into aromatic products, benzene and toluene, as well as to an insignificant quantities of dimethylbenzene, ethylbenzene, trimethylbenzene, and naphthalene. The highest aromatic hydrocarbon yield of 17.5% is obtained using Mo2N/γ-Al2O3 (the catalyst-to-lignin weight ratio=4) at 700°C; by contrast, this yield is only 1.4% when no catalyst is used. Furthermore, the highest benzene yield of 70.1% is obtained using Mo2N/γ-Al2O3 (catalyst-to-lignin weight ratio=4) at 850°C. Under this condition, the monocyclic aromatic hydrocarbons together contribute >95% of the total aromatic hydrocarbon yield, whereas the selectivity toward naphthalene is only 2.2%.

PAHs emission from the pyrolysis of Western Chinese coal

30 May 2013, 16:58:57

Publication date: Available online 30 May 2013
Source:Journal of Analytical and Applied Pyrolysis
Author(s): Jie Dong , Zhu Cheng , Fan Li
Several organic and inorganic pollutants are released during coal utilization such as polycyclic aromatic hydrocarbons (PAHs). PAHs, due to their carcinogenic properties pose potential health hazards. The current work focus on the behaviour of the 16 PAHs during pyrolysis process, an important step of all coal thermal conversion including combustion, gasification, and carbonization. The experiments were performed using a CDS -5250 pyroprobe which could be heated fast. The pyroprobe was coupled with GC-MS (Thermo DSQII/FOCUS GC) and the pyrolysis products were analyzed in-situ. The emissions of the 16 USEPA priority-controlled polycyclic aromatic hydrocarbons from Western Chinese coal were measured under different pyrolysis conditions. The results showed that the emission concentrations of PAHs reach a maximum at a pyrolysis temperature of 800°C. Emission concentrations of PAHs decreased with increasing rates of pyrolysis heating. PAHs emmissions increased gradually with coal rank under the same pyrolysis conditions. A correlation between the yield of PAHs; coal rank and maceral was also demonstrated. Also in this study, the variety trend of the each specie of 16 PAHs with pyrolysis temperature were observed and the reasons were disccussed.

Exposure to valproic acid and 5,7-dimethoxycoumarin induces pheomelanogenesis in the human melanoma G-361 cells, as demonstrated by Py-GC/MS/MS study

30 May 2013, 16:58:57

Publication date: Available online 27 May 2013
Source:Journal of Analytical and Applied Pyrolysis
Author(s): Ewa Chodurek , Anna Dzierżęga-Lęcznar , Slawomir Kurkiewicz , Krystyna Stępień
Melanogenesis is one of the main markers of the differentiation of normal and neoplastically transformed melanocytes. Valproic acid (VPA) and 5,7-dimethoxycoumarin (DMC), the potential anti-cancer drugs with differentiating activity, were reported to enhance melanin synthesis in melanoma cells. The aim of this study was to examine if the stimulation with VPA and DMC affects the structure of melanin synthesized by the human melanoma G-361 cell line. G-361 cells were cultured with VPA, DMC, and a mixture of the two agents for 7 days. Melanin isolated from the treated and untreated cells were pyrolysed, and the thermal degradation products were analyzed by gas chromatography/tandem mass spectrometry with a triple quadrupole instrument operating in a multiple reaction monitoring mode. After the stimulation with VPA and DMC, the sulfur containing pyrolytic markers of pheomelanin were detected among the thermal degradation products of the pigment isolated from the tumor cells. The levels of pheomelanin markers were the highest after the cell treatment with the combination of both agents. No sulfur compounds were present in the pyrolysate of melanin from the untreated control cells. We have concluded that VPA and DMC are able to induce pheomelanogenesis, and thus alter the structure of melanin produced in the human melanoma G-361 cells.

Molecular Characteristics of Vermicompost and Their Relationship to Preservation of Inoculated Nitrogen-Fixing Bacteria

30 May 2013, 16:58:57

Publication date: Available online 27 May 2013
Source:Journal of Analytical and Applied Pyrolysis
Author(s): Dariellys Martinez-Balmori , Fábio Lopes Olivares , Riccardo Spaccini , Kamilla Pereira Aguiar , Marcelo Francisco Araújo , Natália Oliveira Aguiar , Fernando Guridi , Luciano Pasqualoto Canellas
The chemical nature of organic matter during the process of vermicomposting of cattle manure and filter cake from a sugar factory was characterized by thermochemolysis. The pyrolysates were mainly constituted of lignin moieties from propanoic acid units and short-chain (<C20) fatty acids (as methyl esters); alkanes, alkenes, terpenes and steroids were minor compounds. Nitrogen containing compounds were noticeable in filter cake vermicompost (VC) as were carbohydrate moieties. Despite thermochemolysis had shown low sensitivity for carbohydrates, the presence of a number of carbohydrate derivatives was indicative of extensive biological transformation of organic matter during vermicomposting. A high content of long-chain alcohols was found only in filter cake VC. At the end of VC maturation, the content of hydrophobic compounds (lignins plus fatty acids) in filter cake residues was higher than in cattle manure. This mature VC exhibited the highest natural density of culturable diazotrophic bacteria compared to cattle manure VC (approximately 10⁴ times cells g⁻¹ VC), and when the diazotrophic bacterium Herbaspirillum seropedicae was introduced to both types of VC, the population numbers were higher in filter cake VC at 10 months of storage after inoculation. We found an apparent relationship between molecular characteristics of organic matter and the harboring or preservation of diazotrophic bacteria introduced to VC, which is a step toward understanding the relationship between the molecular characteristics of organic matter and the microbial activities.

Thermal stability characterization of n-alkanes from determination of produced aromatics

30 May 2013, 16:58:57

Publication date: Available online 24 May 2013
Source:Journal of Analytical and Applied Pyrolysis
Author(s): Xiaomei Qin , Hai Chi , Wenjun Fang , Yongsheng Guo , Li Xu
The thermal stability of n-nonane and n-undecane, as the model endothermic hydrocarbon fuels, was evaluated by determining the content change of produced aromatics during the thermal cracking process. The ¹H nuclear magnetic resonance spectroscopy (¹H NMR), along with the high-performance liquid chromatography (HPLC) and the gas chromatography/mass spectrometry (GC/MS) analyses, is mainly considered to follow the formation of aromatics in the liquid cracking residues of the n-alkanes. The results of the aromatic contents obtained from these three analytical methods show satisfactory agreements. The ¹H NMR method also gives the olefin content and the branching index of the liquid residues. The changes of the aromatics, olefins and branching index against the temperature directly reflect the thermal stability of the n-alkanes. Based on the results from ¹H NMR, HPLC and GC/MS, a scheme of the formation of aromatics from the thermal cracking of n-alkanes is discussed.

Pyrolysis reactions of coniferyl alcohol as a model of the primary structure formed during lignin pyrolysis

30 May 2013, 16:58:57

Publication date: Available online 21 May 2013
Source:Journal of Analytical and Applied Pyrolysis
Author(s): Takeo Kotake , Haruo Kawamoto , Shiro Saka
It has been suggested that cinnamyl alcohol-type structures are formed during lignin primary pyrolysis using model dimers. In this article, the pyrolysis reactions of trans-coniferyl alcohol (CA) bearing a guaiacyl moiety were studied under N2 at temperatures in the range of 200–350°C, with particular emphasis on the evaporation/degradation processes. Some (less than 15%) of the CA evaporated without undergoing any degradation reactions, whereas large portions of the CA were converted to polymerization products together with monomers (up to ∼15% in total) with various side-chains. The cis-isomer of CA and 4-vinylguaiacol with a C2 side-chain were also identified. Methylation of the phenolic OH group of CA substantially reduced the formation of polymerization products, whereas the influence of the methylation on the side-chain-converted monomers was limited. Since the methylated CA was not effective for quinine methide formation, quinine methide and radical pathways were indicated as more important reaction mechanisms for the polymerization and side-chain-conversion processes, respectively. These results suggest that CA, if it was formed through pyrolytic cleavage of lignin β-ether linkages, tended to be degraded before it could be recovered through evaporation. Furthermore, the recovery of different monomers suggested the process was greatly dependent on the relative evaporation/degradation efficiencies.

Transformation of sulfur during pyrolysis of inertinite-rich coals and correlation with their characteristics

30 May 2013, 16:58:57

Publication date: Available online 21 May 2013
Source:Journal of Analytical and Applied Pyrolysis
Author(s): Meijun Wang , Yongfeng Hu , Jiancheng Wang , Liping Chang , Hui Wang
Sulfur transformation of inertinite-rich coals, which were sampled from three Western China coal mines, Xinjiang Hami (HM), Ningxia Lingwu (LW) and Shendong (SD), during pyrolysis is studied through measuring the release of H2S and COS gases by gas chromatography with flame photometric detector and through analyzing the sulfur forms in raw coals and chars from pyrolysis by X-ray absorption spectroscopy (XAS). It is revealed that the transformation of sulfur during coal pyrolysis is closely linked with coal properties, such as the vitrinite/inertinite ratio, alkaline mineral contents (especially calcium compounds) and H/C atomic ratio for three inertinite-rich coals. Comparisons are performed with a coal sample taken from Pingsuo (PS) coal mine located in North China, of which the properties are significantly different. The maximal release temperature of sulfur-containing gases for the pyrolysis of inertinite-rich coal is higher than that of the PS coal. The release of the S-containing gases in inertinite-rich coals has a maximal temperature interval around 600°C and this is associated with the conversions of inorganic sulfur species, such as pyrite transforming to FeS observed by the XAS in chars of these coals. During the process of pyrolysis, the organic sulfur compounds in inertinite-rich coal can be oxidized to form sulfoxide-like species due to the decomposition of oxygen-containing function groups in the coal matrix, but the active sulfur in PS coal can react with fresh char to form relatively stable thiophene structures. The formation of COS during the pyrolysis of inertinite-rich coals is mainly due to secondary reactions between H2S with CO and/or CO2. 

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Oxford Instruments announces ‘Nanoscale Plasma Processing Seminars’ in Beijing and Taiwan

Continuing on from the success of their previous program of Chinese Seminars which have attracted  over 200 participants, Oxford Instruments, leaders in the manufacture of plasma etch and deposition systems, will be holding two additional one day Seminars in Asia focussing on Nanoscale Plasma Processing. These events  are being held on the 14th May (Beijing, China) and 16th May (ITRI, Hsinchu, Taiwan), and will feature talks by a number of invited guest speakers, specialists from China, Taiwan and Europe, in addition to Process and Applications experts from Oxford Instruments Plasma Technology.

These academic and industrial experts will discuss topics including Atomic Layer Deposition (ALD), Photovoltaics (PV), Deep Silicon Etch, Power Devices, HBLED and Ion Beam technologies during the full one day programme.

Prof. Yang Fuhua, Institute of Semiconductors, CAS, Beijing is very pleased to be involved with the Beijing seminar, “We hosted a similar event with Oxford Instruments two years ago and it was a great success with attendance of over 100 people. The content was excellent with very informative talks from a diverse range of speakers. The events are a great means of finding out about new techniques in an informal setting, with plenty of time to speak to the experts!”

Jeffrey Seah, Asia Business Manager for Oxford Instruments Plasma Technology, who will open the Seminar comments: “We are anticipating a large audience at these Seminars in China and Taiwan, and are extremely honoured that so many distinguished speakers have accepted our invitation to speak about their work in Plasma Processing. Our Seminars are a great opportunity for the Plasma Processing community to come together, to share their experiences, and to learn more from leading international experts in their field.”

Based on the success of their previous Seminars in Beijing and Shanghai, Oxford Instruments anticipates a very high level of interest from both academic and production participants, attracted by such an interesting programme and prestigious speakers.

The event is free to attend, but booking is essential via process.news@oxinst.com,   lingling.wang@oxinst.com (Beijing seminar) or Maggie.tsai@oxinst.com (ITRI, Taiwan seminar)

Just Published: Chemometrics and Intelligent Laboratory Systems

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:

Chemometrics and Intelligent Laboratory Systems
http://rss.sciencedirect.com/publication/science/5232

One-class partial least squares (OCPLS) classifier

30 May 2013, 09:25:22

Publication date: 15 July 2013
Source:Chemometrics and Intelligent Laboratory Systems, Volume 126
Author(s): Lu Xu , Si-Min Yan , Chen-Bo Cai , Xiao-Ping Yu
One-class partial least squares (OCPLS) classifier is investigated as a tool for multivariate statistical quality control (MSQC). According to the OCPLS score distance (SD) and absolute centered residual (ACR) of predicted response, an object can be classified into one of the four groups: regular points (with a small SD and a small ACR), class outliers (with a small SD and a large ACR), good leverage points (with a large SD and a small ACR) and bad leverage points (with a large SD and a large ACR). The correlation between OCPLS distance measures and some existing methods, including D-statistic, Q-statistic and correlation coefficient (Pearson's r), is briefly discussed. OCPLS is applied to non-targeted detection of adulterations in whole milk powder using near-infrared (NIR) spectroscopy. The results demonstrate OCPLS can provide an effective tool for MSQC by including both SD and ACR of predicted response.

Quantitative Raman spectrometry: The accurate determination of analytes in solution phase of turbid media

30 May 2013, 09:25:22

Publication date: 15 July 2013
Source:Chemometrics and Intelligent Laboratory Systems, Volume 126
Author(s): Jing Yang , Zeng-Ping Chen , Juan Zhang , Jing-Wen Jin , Yao Chen
The presence of scatterers in turbid media could severely distort the Raman measurements and thereby prevent accurate determination of analytes in turbid media. To address this issue, in this contribution, an advanced model, multiplicative effects model (MEM), has been derived to explicitly model the effects of scatterers on Raman measurements. Preliminary experimental results for a proof of concept system with varying turbidity levels demonstrated that MEM could effectively account for the detrimental multiplicative effects of scatterers and ultimately achieved accurate quantitative analysis of analyte of interest in turbid media with a relative prediction error of about 4.3%. The enhanced levels of accuracy obtained with MEM open up an avenue for prospective prediction studies in turbid media such as biological tissues by Raman spectrometry.

Model NOx emissions by least squares support vector machine with tuning based on ameliorated teaching–learning-based optimization

30 May 2013, 09:25:22

Publication date: 15 July 2013
Source:Chemometrics and Intelligent Laboratory Systems, Volume 126
Author(s): Guoqiang Li , Peifeng Niu , Weiping Zhang , Yongchao Liu
The teaching–learning-based optimization (TLBO) is a new efficient optimization algorithm. To improve the solution quality and to quicken the convergence speed and running time of TLBO, this paper proposes an ameliorated TLBO called A-TLBO and test it by classical numerical function optimizations. Compared with other several optimization methods, A-TLBO shows better search performance. In addition, the A-TLBO is adopted to adjust the hyper-parameters of least squares support vector machine (LS-SVM) in order to build NOx emissions model of a 330MW coal-fired boiler and obtain a well-generalized model. Experimental results show that the tuned LS-SVM model by A-TLBO has well regression precision and generalization ability.

Rough set based wavelength selection in near-infrared spectral analysis

30 May 2013, 09:25:22

Publication date: 15 July 2013
Source:Chemometrics and Intelligent Laboratory Systems, Volume 126
Author(s): Ying Dong , Bingren Xiang , Ying Geng , Wenbo Yuan
Rough set based procedure was proposed as a new methodology to select component-specific wavelengths for near-infrared (NIR) spectral analysis. Information gain (IG) was employed to regulate the size of the discernibility matrix and decrease the memory requirements of rough set based reduction. This procedure involved submitting the resulting subsets of wavelengths to the analytical models in question. The utility of this method was illustrated by an analysis of classification models for phenylalanine (Phe) in plasma. The wavelength selection algorithm was compared with correlation based feature selection (CRFS) method and consistency based feature selection (CSFS) approach. Model fit was assessed using 10-fold cross-validation (10-fold CV) and leave-one out (LOO) approach. The predictability of the model was evaluated by an external prediction set. Furthermore, another two NIR data sets, obtained from the published literatures, were used to develop the quantitative models and validate the rough set based wavelength selection method. This study demonstrates conclusively that reducts of rough set could preserve the spectra–structure relationship and provide reliable model variables for NIR analysis. The results also indicate that rough set algorithm may hold promise for application as an additional feasible technique to NIR band assignment. As a fast, simple and noninvasive measurement, it is hopeful to find a clinical use in the diagnosis of unusual Phe elevation with further research.

A chemometric approach to prediction of transmembrane pressure in membrane bioreactors

30 May 2013, 09:25:2

Publication date: 15 July 2013
Source:Chemometrics and Intelligent Laboratory Systems, Volume 126
Author(s): Hiromasa Kaneko , Kimito Funatsu
Membrane bioreactors (MBRs) have been widely used to purify wastewater for reuse. However, MBRs are subject to fouling, which is the phenomenon whereby foulants absorb or deposit on the membrane. To enable chemical cleaning to be performed at an appropriate time, membrane fouling must to be predicted in the long term. There has been research on correlations among fouling phenomena, water quality variables, and operating conditions. Therefore, in this paper, we aimed to construct a chemometric or statistical model between the increase in the transmembrane pressure (TMP) and MBR parameters such as water quality variables and operating conditions and use this model to predict TMP. We analyzed three data sets measured in real industrial MBR plants and then confirmed that the constructed model could predict TMP over time with high accuracy. By applying the proposed method to process control, MBR plants will be operated effectively and stably.

A SEVA soft sensor method based on self-calibration model and uncertainty description algorithm

30 May 2013, 09:25:22

Publication date: 15 July 2013
Source:Chemometrics and Intelligent Laboratory Systems, Volume 126
Author(s): Liu Yiqi , Huang Daoping , Li Zhifu
Soft sensors are widely used to estimate process variables that are difficult to measure online. However, due to poor quality of input data and deterioration of prediction model as time passes, soft sensors make poor performance. We have been constructing a principal component analysis (PCA) model before performing a prediction. Furthermore, the just-in-time (JIT) learning model has been improved and served as prediction model for self validating (SEVA) soft sensors. The proposed soft sensor not only carries out internal quality assessment but also generates multiple types of output data, including the prediction values (PV), input sensor status (ISS), validated measurement (VM), output sensor status (OSS) and the uncertainty values (UV) which represent the credibility of soft sensors' output. The effectiveness of the proposed SEVA soft sensors is demonstrated through a case study of a wastewater treatment process.

A toolbox to explore NMR metabolomic data sets using the R environment

30 May 2013, 09:25:22

Publication date: 15 July 2013
Source:Chemometrics and Intelligent Laboratory Systems, Volume 126
Author(s): Stéphane Balayssac , Sébastien Déjean , Julie Lalande , Véronique Gilard , Myriam Malet-Martino
We describe herein the implementation of graphical and statistical tools developed in the R free software environment to explore metabolomic data sets. This toolbox, available upon request from the authors for the latest releases, includes univariate, bivariate and multivariate existing approaches accompanied with various graphical displays and interactive facilities. Concretely, very basic knowledge in R is required: from Excel data files as input to graphical and numerical outputs the user is led through a set of questions he only has to answer. We illustrate the potential of the toolbox on a data set coming from a ¹H NMR metabolomic study of cerebellums from a murine model of Alzheimer's disease. We show the complementarity of various graphical techniques in order to provide information easier to interpret. In particular, a simple correlation study can be highly meaningful, and competitive with a more sophisticated multivariate analysis, when using ad hoc graphical representations depending on the level of interest: global, multiple or single metabolite focus. 

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Wyatt Calypso Succeeds in ABRF-MIRG Study

Wyatt Technology is pleased to report the success of the Calypso composition-gradient multi-angle light scattering (CG-MALS) system in a study conducted by the Molecular Interactions Research Group (MIRG) of the Association of Biomolecular Research Facilities (ABRF). The conclusions of the 2012 MIRG study were announced at the ABRF 2013 annual meeting in Palm Springs earlier this month.
In the study, a pair of unknown proteins, prepared and characterized by the ABRF, was sent out to multiple labs to determine affinity and stoichiometry of binding. In a single afternoon consisting of 2 CG-MALS runs, the Wyatt Calypso system correctly determined that one molecule of Protein Y (26.3 kDa) binds 2 molecules of Protein X (11.9 kDa), one with K_D of 10 nM and the other with 14 µM. This analysis agreed perfectly with the extensive AUC and ITC measurements performed by ABRF prior to distributing the samples.
The CG-MALS measurement was the only solution-based measurement among the participating labs. The others used surface plasmon resonance (SPR) instruments which require immobilization of one of the binding partners. Only 4 of 13 SPR labs correctly measured and interpreted the data, typically taking 1-2 days even though the chip immobilization recipe and regeneration were provided by the organizers.
Interestingly, the affinities determined by SPR were significantly weaker than those found by any of the solution-based measurements (AUC, ITC, CG-MALS), indicating that, in this instance, immobilization modifies the interaction.
The successes of Wyatt’s products continue after the recent nomination of the Optilab UT-rEX for an Editors award at PITTCON 2013. To learn more about Wyatt’s innovative products please visit www.wyatt.com or email info@wyatt.com. A copy of the study is available by visiting

http://www.abrf.org/ResearchGroups/MolecularInteractions/Studies/ABRF2013-MIRGsession1-Yamniuk.pdf.

UK Trade and Investment joins hands with Randox Laboratories Ltd. UK to organise healthcare seminars in Pakistan

Randox Laboratories Ltd. UK in association with UK Trade and Investment Pakistan organised seminars in Karachi, Lahore and Islamabad from 22nd to 24th May, on “Improving Healthcare and Laboratory performance in Pakistan.”

The seminars were targeted to the pathologists and lab professionals of private and public hospitals in Pakistan. 

Stephen Doherty, a representative of Randox Laboratories Ltd, was the key note speaker with his main topic of discussion being how hospitals and laboratories in Pakistan can improve patients’ results reported by the clinical laboratories through External Quality Assurance and Internal Quality Control.

Dr. Adnan Zuberi, a Consultant Chemical Pathologist at Ziauddin University Hospital, also was one of the speaker’s during the seminars who discussed the cost saving benefits of early errors detection and correct patient diagnosis.

Randox Laboratories Ltd was established in 1982 in the UK and for over 30 years they have played a pioneering role in healthcare. Today, as a world leader in in-vitro diagnostics, they supply a wide range of diagnostic instruments and tests for rapid and reliable disease detection. Randox have been distributing in Pakistan through Muslim Trading for almost 25 years and have established business with both public and private sector healthcare customers.

British Deputy High Commissioner and Director UK Trade and Investment, Pakistan, Francis Campbell said: 

“We are very pleased to organise these seminars with Randox to improve healthcare system in Pakistan. UK Trade and Investment’s main role in Pakistan is to help British business grow and Randox’s success in this market sets up a fine example of successful British companies operating in Pakistan.”

Just Published: Biosensors & Bioelectronics

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:

Biosensors & Bioelectronics
http://rss.sciencedirect.com/publication/science/5223

Selected papers from the latest issue:

Fe3O4 magnetic nanoparticles/reduced graphene oxide nanosheets as a novel electrochemical and bioeletrochemical sensing platform

28 May 2013, 17:37:35

Publication date: 15 November 2013
Source:Biosensors and Bioelectronics, Volume 49
Author(s): Hazhir Teymourian , Abdollah Salimi , Somayeh Khezrian
We have developed Fe3O4 magnetic nanoparticles/reduced graphene oxide nanosheets modified glassy carbon (Fe3O4/r-GO/GC) electrode as a novel system for the preparation of electrochemical sensing platform. Decorating Fe3O4 nanoparticles on graphene sheets was performed via a facile one-step chemical reaction strategy, where the reduction of GO and the in-situ generation of Fe3O4 nanoparticles occurred simultaneously. Characterization of as-made nanocomposite using X-ray diffraction (XRD), transmission electron microscopy (TEM) and alternative gradient force magnetometry (AGFM) clearly demonstrate the successful attachment of monodisperse Fe3O4 nanoparticles to graphene sheets. Electrochemical studies revealed that the Fe3O4/r-GO/GC electrode possess excellent electrocatalytic activities toward the low potential oxidation of NADH (0.05V vs. Ag/AgCl) as well as the catalytic reduction of O2 and H2O2 at reduced overpotentials. Via immobilization of lactate dehydrogenase (LDH) as a model dehydrogenase enzyme onto the Fe3O4/r-GO/GC electrode surface, the ability of modified electrode for biosensing lactate was demonstrated. In addition, using differential pulse voltammetry (DPV) to investigate the electrochemical oxidation behavior of ascorbic acid (AA), dopamine (DA) and uric acid (UA) at Fe3O4/r-GO/GC electrode, the high electrocatalytic activity of the modified electrode toward simultaneous detection of these compounds was indicated. Finally, based on the strong electrocatalytic action of Fe3O4/r-GO/GC electrode toward both oxidation and reduction of nitrite, a sensitive amperometric sensor for nitrite determination was proposed. The Fe3O4/r-GO hybrid presented here showing favorable electrochemical features may hold great promise to the development of electrochemical sensors, molecular bioelectronic devices, biosensors and biofuel cells.

A cardiomyocyte-based biosensor for antiarrhythmic drug evaluation by simultaneously monitoring cell growth and beating

28 May 2013, 17:37:35

Publication date: 15 November 2013
Source:Biosensors and Bioelectronics, Volume 49
Author(s): Tianxing Wang , Ning Hu , Jiayue Cao , Jieying Wu , Kaiqi Su , Ping Wang
Drug-induced cardiotoxicity greatly endangers the human health and results in resource waste. Also, it is a leading attribution to drug withdrawal and late-stage attrition in pharmaceutical industry. In the study, a dual function cardiomyocyte-based biosensor was introduced for rapid drug evaluation with xCELLigence RTCA Cardio system. The cardiomyocyte-based biosensor can monitor the cardiomyocyte growth and beating status simultaneously under the drug effects. Two typical cardiovascular drug, verapamil and flecainide were selected as treatment agents to test the performance of this biosensor. The experiment results showed that the performance of cardiomyocyte-based biosensor verified the basic drug effects by beating status and also tested the drug cytotoxicity by the cell index curves of cardiomyocyte growth. Based on the advanced sensor detection technology and cell culture technology, this cardiomyocyte-based biosensor will be a utility platform for the drug preclinical assessment.

A silver–palladium alloy nanoparticle-based electrochemical biosensor for simultaneous detection of ractopamine, clenbuterol and salbutamol

28 May 2013, 17:37:35

Publication date: 15 November 2013
Source:Biosensors and Bioelectronics, Volume 49
Author(s): Huan Wang , Yong Zhang , He Li , Bin Du , Hongmin Ma , Dan Wu , Qin Wei
A multiplexed electrochemical biosensor has been developed for fast and sensitive detection of ractopamine (RAC), salbutamol (SAL) and clenbuterol (CLB) based on reduced graphene oxide (rGO) and silver–palladium alloy nanoparticles (AgPd NPs). In this paper, rGO with high conductivity was used as an electrode material to immobilize artificial antigens and amplify electrochemical signal. AgPd NPs are used to label antibodies and generate a strong electrochemical signal in phosphate buffered saline (PBS) without any other substrates. Screen-printed carbon electrode (SPCE) and competition strategy were adopted to achieve simultaneous detection of RAC, SAL and CLB without cross-talk between adjacent electrodes. This method can simultaneously detect RAC, SAL and CLB ranging from 0.01 to 100ngmL⁻¹ with detection limits of 1.52pgmL⁻¹, 1.44pgmL⁻¹ and 1.38pgmL⁻¹, respectively. Satisfactory results are achieved in pork sample analysis. The designed strategy provides a promising potential in determination of other biological samples.

Acetylcholinesterase biosensor based on SnO2 nanoparticles–carboxylic graphene–nafion modified electrode for detection of pesticides

28 May 2013, 17:37:35

Publication date: 15 November 2013
Source:Biosensors and Bioelectronics, Volume 49
Author(s): Long Yang , Qing Zhou , Guangcan Wang , Yun Yang
A sensitive amperometric acetylcholinesterase (AChE) biosensor, based on SnO2 nanoparticles (SnO2 NPs), carboxylic graphene (CGR) and nafion (NF) modified glassy carbon electrode (GCE) for the detection of methyl parathion and carbofuran has been developed. The nanocomposites of SnO2 NPs and CGR was synthesized and characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR), respectively. Chitosan (CS) was used to immobilize AChE on SnO2 NPs–CGR–NF/GCE and to improve electronic transmission between AChE and SnO2 NPs–CGR–NF/GCE. NF was used as the protective membrane for the AChE biosensor. The SnO2 NPs–CGR–NF nanocomposites with excellent conductivity, catalysis and biocompatibility offered an extremely hydrophilic surface for AChE adhesion. The AChE biosensor showed favorable affinity to acetylthiocholine chloride (ATCl) and could catalyze the hydrolysis of ATCl with an apparent Michaelis–Menten constant value of 131μM. The biosensor detected methyl parathion in the linear range from 10⁻¹³ to 10⁻¹⁰ M and from 10⁻¹⁰ to 10⁻⁸ M. The biosensor detected carbofuran in the linear range from 10⁻¹² to 10⁻¹⁰ M and from 10⁻¹⁰ to 10⁻⁸ M. The detection limits of methyl parathion and carbofuran were 5×10⁻¹⁴ M and 5×10⁻¹³ M, respectively. The biosensor exhibited low applied potential, high sensitivity and acceptable stability, thus providing a promising tool for analysis of pesticides.

Electrochemical impedimetric immunosensor for the detection of measles-specific IgG antibodies after measles infections

28 May 2013, 17:37:35

Publication date: 15 November 2013
Source:Biosensors and Bioelectronics, Volume 49
Author(s): Philani Mashazi , Phumlani Tetyana , Sibulelo Vilakazi , Tebello Nyokong
The detection of measles-specific primary antibodies (IgG) using electrochemical impedimetric immunosensors is reported. The optimum conditions for electrode saturation were reached after 40min for 1μgml⁻¹ antibody concentrations. Surface roughness using AFM increased with each immobilization or antigen-antibody reaction step clearly confirming the surface modification and recognition between antigen and antibody. The human serum (HS) and new-born calf serum (NCS) spiked with antigen-specific antibody were studied to mimic the real sample analysis. The HS and NCS sera containing antibodies due to measles exhibited correlation between the increasing antibody serum concentrations and the charge-transfer resistance (electrochemically measured). This work clearly showed the potential use of impedance as the preferred electrochemical method for detecting measles-antibodies in label-free manner.

Ultrasensitive electrochemical immunoassay for DNA methyltransferase activity and inhibitor screening based on methyl binding domain protein of MeCP2 and enzymatic signal amplification

28 May 2013, 17:37:35

Publication date: 15 November 2013
Source:Biosensors and Bioelectronics, Volume 49
Author(s): Huanshun Yin , Yunlei Zhou , Zhenning Xu , Mo Wang , Shiyun Ai
In this work, we fabricated a novel electrochemical immunosensor for detection of DNA methylation, analysis of DNA MTase activity and screening of MTase inhibitor. The immunosensor was on the basis of methyl binding domain protein of MeCP2 as DNA CpG methylation recognization unit, anti-His tag antibody as “immuno-bridge” and horseradish peroxidase labeled immuneglobulin G functionalized gold nanoparticles (AuNPs–IgG–HRP) as signal amplification unit. In the presence of M. SssI MTase, the symmetrical sequence of 5′-CCGG-3′ was methylated and then recognized by MeCP2 protein. By the immunoreactions, anti-His tag antibody and AuNPs–IgG–HRP was captured on the electrode surface successively. Under the catalysis effect of HRP towards hydroquinone oxidized by H2O2, the electrochemical reduction signal of benzoquinone was used to analyze M. SssI MTase activity. The electrochemical reduction signal demonstrated a wide linear relationship with M. SssI concentration ranging from 0.05unit/mL to 90unit/mL, achieving a detection limit of 0.017unit/mL (S/N=3). The most important advantages of this method were its high sensitivity and good selectivity, which enabled the detection of even one-base mismatched sequence. In addition, we also verified that the developed method could be applied for screening the inhibitors of DNA MTase and for developing new anticancer drugs.

Graphical abstract

A label-free electrochemiluminescence cytosensors for specific detection of early apoptosis

28 May 2013, 17:37:35

Publication date: 15 November 2013
Source:Biosensors and Bioelectronics, Volume 49
Author(s): Lin Zhang , Jin-Huan Jiang , Jian-Jun Luo , Lu Zhang , Ji-Ye Cai , Jiu-Wei Teng , Pei-Hui Yang
A novel electrochemiluminescence (ECL) cytosensors was developed for the detection of early apoptotic cells by the specific interaction between Annexin V and phosphatidylserine(PS) based on ECL signal of CdS-QDs. Immobilization of Annexin V on a L-cysteine-capped CdS-QDs/Polyaniline nanofibers (PANI-NF) resulted in the stable and high loading of Annexin V on the sensor surface and the possibility of sensitivity enhancement. Early apoptotic cells showed an increased exposure of PS on the cell membrane caused by physiological and pathological response reactions, leading to a strong interaction between the apoptotic cells and the sensor surface, which could be probed by the ECL. Using a real of early apoptotic HepG2 cell induced by resveratrol (RVL), the proposed novel strategy has demonstrated its simplicity, high sensitivity, good selectivity and high reproducibility and label-free capability which might hold a great potential for rapid detection of cell apoptosis and drug screening. The results from this approach have showed good agreement with those obtained using inverted microscope, flow cytometry(FCM) and Atomic force microscopy(AFM). The linear range for early apoptotic cells detection ranged from 500 to 1.0×10⁶ cellsmL⁻¹ with a detection limit of 500 cellsmL⁻¹. The reported strategy has provided a promising platform for highly sensitive cytosensing and convenient screening of some clinically anticancer drugs. 

Labnet International announces the Hermle Sieva-2 Filtration centrifuge

The Hermle Sieva-2 Filtration centrifuge offers a wide range of applications in chemical, pharmaceutical, biotech, food processing and research laboratories.  The two options of either perforated or non-perforated rotor baskets make the Sieva-2 ideal for filtration or solid/liquid sedimentation (decantation).  The rotors are designed with cone-shaped centers to guarantee an even spread of filtered material and rinsing agent.  The powerful induction drive motor reaches speeds of 10,000 RPM or 7,825 x g.

Enhanced features include:

• Speed selection from 250 – 10,000 RPM
• Transparent lid to visually monitor samples
• Imbalance detection system for added safety
• 500mL rotor basket with 10 rows of perforations
• Intuitive control panel and large digital LED display

Contact Labnet for additional information:

Labnet International, Inc.
Phone: +1 732 417 0700
Email: labnetinfo@corning.com

Wolfgang Lindner named 2013 CASSS Award Winner

Courtesy Google Images!

Professor Lindner was selected as the 2013 CASSS Award recipient for his outstanding achievements to chromatography. Please join CASSS on October 24, 2013 in the San Francisco Bay Area to recognize and celebrate Professor Wolfgang Lindner for his stellar work in the field of separation science.  The location to be announced soon.  Visit www.casss.org for updates.

Just Published: Analytica Chimica Acta

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:

Analytica Chimica Acta
http://rss.sciencedirect.com/publication/science/5216

Selected papers from the latest issue:

On-line sample processing involving microextraction techniques as a front-end to atomic spectrometric detection for trace metal assays: A review

28 May 2013, 09:59:13

Publication date: 11 June 2013
Source:Analytica Chimica Acta, Volume 782
Author(s): Manuel Miró , Elo Harald Hansen
Within the last decade, liquid-phase microextraction (LPME) and micro-solid phase extraction (μSPE) approaches have emerged as substitutes for conventional sample processing procedures for trace metal assays within the framework of green chemistry. This review surveys the progress of the state of the art in simplification and automation of microextraction approaches by harnessing to the various generations of flow injection (FI) as a front end to atomic absorption spectrometry (AAS), atomic fluorescence spectrometry (AFS) or inductively coupled plasma atomic emission spectrometry or mass spectrometry (ICP-AES/MS). It highlights the evolution of flow injection analysis and related techniques as vehicles for appropriate sample presentation to the detector and expedient on-line matrix separation and pre-concentration of trace levels of metals in troublesome matrices. Rather than being comprehensive this review is aimed at outlining the pros and cons via representative examples of recent attempts in automating green sample preparation procedures in an FI or sequential injection (SI) mode capitalizing on single-drop microextraction, dispersive liquid-phase microextraction and advanced sorptive materials including carbon and metal oxide nanoparticles, ion imprinted polymers, superparamagnetic nanomaterials and biological/biomass sorbents. Current challenges in the field are identified and the synergetic combination of flow analysis, nanotechnology and metal-tagged biomolecule detection is envisaged.

Graphical abstract

On uniqueness and selectivity in three-component parallel factor analysis

28 May 2013, 09:59:13

Publication date: 11 June 2013
Source:Analytica Chimica Acta, Volume 782
Author(s): Nematollah Omidikia , Hamid Abdollahi , Mohsen Kompany-Zareh
Unambiguous recovery of profiles is a distinguishable advantage of Parallel Factor Analysis (PARAFAC) as a trilinear model and has made it a promising exploratory tool for data analysis. Linear dependency in profiles destroys trilinearity and will increase ambiguity in the curve resolution of three-way data sets. PARAFAC uniqueness deteriorates totally or partially in data sets with linearly dependent loadings. Exploiting a reliable method for determination and direct visualization of feasible bands in the PARAFAC model can be helpful not only in full characterization of uniqueness conditions but also in the investigation of the effects of constraints on the PARAFAC feasible solutions. The purpose of this paper is twofold. First, the calculation of rotational ambiguity in the PARAFAC model extends to three components system. The principle behind the algorithm is described in detail and tested for simulated and real data sets. Completely general and thoroughly investigated results are presented for the three component cases. Secondly, the effects of selective regions in the profiles on the resolution of systems that suffered from the rank deficiency problem, due to rank overlap, are emphasized. In the case of two-way data sets the effect of selectivity constraint on the unique recovery of profiles was investigated and applied. However, to our knowledge, in this report, for the first time, the effect of the presence of selective windows in the profiles, on the unique resolution of three-way data sets has been systematically investigated.

Graphical abstract

Elucidating the sorption mechanism of “mixed-mode” SPME using the basic drug amphetamine as a model compound

28 May 2013, 09:59:13

Publication date: 11 June 2013
Source:Analytica Chimica Acta, Volume 782
Author(s): Hester Peltenburg , Floris A. Groothuis , Steven T.J. Droge , Ingrid J. Bosman , Joop L.M. Hermens
We studied the sorption of amphetamine as a model drug to represent small, polar organic cations to a new SPME coating combining C18 and propylsulfonic acid. This combination of hydrophobic and strong cation exchange (SCX) groups was compared to conventional SPME fibers with polyacrylate (PA) or C18 coating. The affinity of amphetamine at physiological pH (PBS) was 20 to 180 times greater for the new C18/SCX coating than for C18 alone and PA of different coating thickness. As amphetamine is a base and >99% protonated at physiological pH, this enhanced affinity is attributed to the ion-exchange phase in the coating. Tests at pH above the pK a of amphetamine show that, when normalized to the coating volume, neutral amphetamine also has a higher affinity compared to PA. As ion-exchange groups are not unlimitedly present in the coating, amphetamine isotherms level off to a saturation concentration on the C18/SCX fiber at the highest tested aqueous concentrations. Also, other cations (Na⁺, K⁺, Ca²⁺) compete for the SCX sites and decrease the sorption coefficients, e.g. by 1.7log units when comparing Milli-Q water with PBS. The C18/SCX fiber provides improved sensitivity over some of the classic SPME fibers. However, care should be taken near the cation exchange capacity of the fiber and the fiber should be calibrated in an appropriate matrix so as to eliminate competition effects.

Graphical abstract

Determination of naphthalene-derived compounds in apples by ultra-high performance liquid chromatography-tandem mass spectrometry

28 May 2013, 09:59:13

Publication date: 11 June 2013
Source:Analytica Chimica Acta, Volume 782
Author(s): X. Esparza , E. Moyano , J.R. Cosialls , M.T. Galceran
Naphthylacetic acid, naphthyloxy acetic acid and naphthylacetamide belong to a group of synthetic substances known as “auxin-like” compounds which are used as growth regulators in vegetables and fruits due to their structure similarities with the indoleacetic acid, the most important plant auxin. This paper reports a selective, sensitive and fast ultra-high performance liquid chromatography-tandem mass spectrometry (UHPLC–MS/MS) method for the determination of naphthylacetamide (NAD) and the isomers (α and β) of naphthylacetic acid (NAA) and naphthyloxy acetic (NOA) acid in apple samples. A baseline separation between the respective isomers was achieved using an RP-Amide column with gradient elution. The UHPLC-MS/MS method developed, using electrospray and selected reaction monitoring (SRM) acquisition mode led to a reliable determination of these family of compounds in apple samples at low quantitation levels, down to 1.0μgkg⁻¹ and 0.25μgkg⁻¹ respectively. For confirmation of NAA accurate mass measurement is proposed giving at these conditions quantitation limits of 10μgkg⁻¹ for this compound. The UHPLC-MS/MS method developed was used for the analysis of apple samples harvested in three different apple fields from Lleida (Spain) during the blooming period. NAD and NAA were found in samples collected during 4–5 weeks after application at concentrations between the quantification limits and 43μgkg⁻¹ and 24μgkg⁻¹, respectively.

Graphical abstract

Second-order advantage with excitation–emission photoinduced fluorimetry for the determination of the antiepileptic carbamazepine in environmental waters

28 May 2013, 09:59:13

Publication date: 11 June 2013
Source:Analytica Chimica Acta, Volume 782
Author(s): Valeria A. Lozano , Graciela M. Escandar
A photochemically induced fluorescence system combined with second-order chemometric analysis for the determination of the anticonvulsant carbamazepine (CBZ) is presented. CBZ is a widely used drug for the treatment of epilepsy and is included in the group of emerging contaminant present in the aquatic environment. CBZ is not fluorescent in solution but can be converted into a fluorescent compound through a photochemical reaction in a strong acid medium. The determination is carried out by measuring excitation–emission photoinduced fluorescence matrices of the products formed upon ultraviolet light irradiation in a laboratory-constructed reactor constituted by two simple 4W germicidal tubes. Working conditions related to both the reaction medium and the photoreactor geometry are optimized by an experimental design. The developed approach enabled the determination of CBZ at trace levels without the necessity of applying separation steps, and in the presence of uncalibrated interferences which also display photoinduced fluorescence and may be potentially present in the investigated samples. Different second-order algorithms were tested and successful resolution was achieved using multivariate curve resolution-alternating least-squares (MCR-ALS). The study is employed for the discussion of the scopes and yields of each of the applied second-order chemometric tools. The quality of the proposed method is probed through the determination of the studied emerging pollutant in both environmental and drinking water samples. After a pre-concentration step on a C18 membrane using 50.0mL of real water samples, a prediction relative error of 2% and limits of detection and quantification of 0.2 and 0.6ngmL⁻¹ were respectively obtained.

Graphical abstract

Detection of Panton-Valentine Leukocidin DNA from methicillin-resistant Staphylococcus aureus by resistive pulse sensing and loop-mediated isothermal amplification with gold nanoparticles

28 May 2013, 09:59:13

Publication date: 11 June 2013
Source:Analytica Chimica Acta, Volume 782
Author(s): Alice Kar Lai Yang , Haifei Lu , Shu Yuen Wu , Ho Chin Kwok , Ho Pui Ho , Samuel Yu , Anthony Ka Lun Cheung , Siu Kai Kong
This report describes a novel diagnostic assay for rapid detection of the Panton-Valentine Leukocidin (PVL) toxin of methicillin-resistant Staphylococcus aureus (MRSA) utilizing resistive pulse sensing (RPS), loop-mediated isothermal DNA amplification (LAMP) in combination with gold nanoparticles (AuNPs). The PVL DNA from MRSA was specifically amplified by LAMP using four primers at one temperature (65°C). The DNA products with biotin were then conjugated to a first AuNP1 (55±2nm) through biotin–avidin binding. A second AuNP2 (30±1.5nm) coated with a specific DNA probe hybridized with the LAMP DNA products at the loop region to enhance assay sensitivity and specificity, to generate supra-AuNP1-DNA-AuNP2 assemblies. Scanning electron microscopy confirmed the presence of these supra-assemblies. Using RPS, detection and quantitation of the agglomerated AuNPs were performed by a tunable fluidic nanopore sensor. The results demonstrate that the LAMP-based RPS sensor is sensitive and rapid for detecting the PVL DNA. This technique could achieve a limit of detection (LOD) up to about 500 copies of genomic DNA from the bacteria MRSA MW2 and the detection can be completed within two hours with a straightforward signal-to-readout setup. It is anticipated that this LAMP-based AuNP RPS may become an effective tool for MRSA detection and a potential platform in clinical laboratory to report the presence or absence of other types of infectious agents.

Graphical abstract

Gold immunochromatographic strips for enhanced detection of Avian influenza and Newcastle disease viruses

28 May 2013, 09:59:13

Publication date: 11 June 2013
Source:Analytica Chimica Acta, Volume 782
Author(s): Jinfeng Li , Mingqiang Zou , Yan Chen , Qiang Xue , Fan Zhang , Beibei Li , Yanfei Wang , Xiaohua Qi , Yi Yang
A new technique that uses gold immunochromatographic strips enhances the detection sensitivity by inducing the clustering of additional gold nanoparticles (AuNPs) around the immunogold particles immobilized on nitrocellulose strips. The additional AuNPs provide an intense signal that can be detected by the naked eye. The AuNPs were synthesized and conjugated to monoclonal antibodies using self-assembly. Other antibodies were immobilized in a defined detection zone on the nitrocellulose membrane. The detection principle is based on a “sandwich” immunoreaction, where gold-labeled antibodies serve as signal vehicles. To improve the sensitivity of the strips, we use a mixture of 1% HAuCl4 and 10mmolL⁻¹ NH2OH·HCl to “enlarge” the gold nanoparticles. The detecting limits of Avian influenza virus (AIV) and Newcastle disease virus (NDV) are significantly increased. Compared with commercial test strips, this method is 100-fold more sensitive. This method is easy to perform and can be carried out on-site in test laboratories.

Graphical abstract

A highly sensitive fluorescence resonance energy transfer aptasensor for staphylococcal enterotoxin B detection based on exonuclease-catalyzed target recycling strategy

28 May 2013, 09:59:13

Publication date: 11 June 2013
Source:Analytica Chimica Acta, Volume 782
Author(s): Shijia Wu , Nuo Duan , Xiaoyuan Ma , Yu Xia , Hongxin Wang , Zhouping Wang
An ultrasensitive fluorescence resonance energy transfer (FRET) bioassay was developed to detect staphylococcal enterotoxin B (SEB), a low molecular exotoxin, using an aptamer-affinity method coupled with upconversion nanoparticles (UCNPs)-sensing, and the fluorescence intensity was prominently enhanced using an exonuclease-catalyzed target recycling strategy. To construct this aptasensor, both fluorescence donor probes (complementary DNA1–UCNPs) and fluorescence quencher probes (complementary DNA2–Black Hole Quencher3 (BHQ3)) were hybridized to an SEB aptamer, and double-strand oligonucleotides were fabricated, which quenched the fluorescence of the UCNPs via FRET. The formation of an aptamer–SEB complex in the presence of the SEB analyte resulted in not only the dissociation of aptamer from the double-strand DNA but also both the disruption of the FRET system and the restoration of the UCNPs fluorescence. In addition, the SEB was liberated from the aptamer–SEB complex using exonuclease I, an exonuclease specific to single-stranded DNA, for analyte recycling by selectively digesting a particular DNA (SEB aptamer). Based on this exonuclease-catalyzed target recycling strategy, an amplified fluorescence intensity could be produced using different SEB concentrations. Using optimized experimental conditions produced an ultrasensitive aptasensor for the detection of SEB, with a wide linear range of 0.001–1ngmL⁻¹ and a lower detection limit (LOD) of 0.3pgmL⁻¹ SEB (at 3σ). The fabricated aptasensor was used to measure SEB in a real milk samples and validated using the ELISA method. Furthermore, a novel aptasensor FRET assay was established for the first time using 30mol% Mn²⁺ ions doped NaYF4:Yb/Er (20/2mol%) UCNPs as the donor probes, which suggests that UCNPs are superior fluorescence labeling materials for food safety analysis.

Graphical abstract

Separation of phthalates by cyclodextrin modified micellar electrokinetic chromatography: Quantitation in perfumes

28 May 2013, 09:59:13

Publication date: 11 June 2013
Source:Analytica Chimica Acta, Volume 782
Author(s): Virginia Pérez-Fernández , Maria José González , Maria Ángeles García , Maria Luisa Marina
A new CE method has been developed for the simultaneous separation of a group of parent phthalates. Due to the neutral character of these compounds, the addition of several bile salts as surfactants (sodium cholate (SC), sodium deoxycholate (SDC), sodium taurodeoxycholate (STDC), sodium taurocholate (STC)) to the separation buffer was explored showing the high potential of SDC as pseudostationary phase. However, the resolution of all the phthalates was not achieved when employing only this bile salt as additive, being necessary the addition of neutral cyclodextrins (CD) and organic modifiers to the separation media. The optimized cyclodextrin modified micellar electrokinetic chromatography (CD-MEKC) method consisted of the employ of a background electrolyte (BGE) containing 25mM β-CD-100mM SDC in a 100mM borate buffer (pH 8.5) with a 10% (v/v) of acetonitrile, employing a voltage of 30kV and a temperature of 25°C. This separation medium enabled the total resolution of eight compounds and the partial resolution of two of the analytes, di-n-octyl phthalate (DNOP) and diethyl hexyl phthalate (DEHP) (Rs~0.8), in only 12min. The analytical characteristics of the developed method were studied showing their suitability for the determination of these compounds in commercial perfumes. In all the analyzed perfumes the most common phthalate was diethyl phthalate (DEP) that appeared in ten of the fifteen analyzed products. Also dimethyl phthalate (DMP), diallyl phthalate (DAP), dicyclohexyl phthalate (DCP), and di-n-pentyl phthalate (DNPP) were found in some of the analyzed samples.

Graphical abstract

Dimethyl(3,3,3-trifluoropropyl)silyldiethylamine—A new silylating agent for the derivatization of β-blockers and β-agonists in environmental samples

28 May 2013, 09:59:13

Publication date: 11 June 2013
Source:Analytica Chimica Acta, Volume 782
Author(s): Magda Caban , Katarzyna Mioduszewska , Piotr Stepnowski , Marek Kwiatkowski , Jolanta Kumirska
Research into alternative derivatizing agents remains a major task in the trace analysis of polar compounds using GC. DIMETRIS (dimethyl(3,3,3-trifluoropropyl)silyldiethylamine) is a new and interesting proposition in this field. This agent possesses strong nucleophilic properties and reacts selectively with hydroxyl groups. The derivatization reaction takes place in the absence of any catalysts. The derivatives possess good chromatographic properties and are easily detected by mass spectrometry. By introducing fluorine atoms into the structure of the derivatives, we were able to use an electron-capture detector for their GC determination. No degradation of new derivatives was observed after seven days of storage in a refrigerator or during the GC analyses. Unlike a number of acylation agents, DIMETRIS does not corrode the analytical equipment. In this work β-blockers and β-agonists were used for testing the derivatizing properties of DIMETRIS. Derivatization of these drugs was optimal at 30°C for 30min. The method quantification limits of the target compounds determined in tap water samples by SPE-GC–MS(SIM) ranged from 3 to 40ngL⁻¹ and resembled those obtained with samples derivatized using a mixture of N,O-bis(trimethylsilyl)trifluoroacetamide (BSTFA) and 1% chlorotrimethylsilane (TMCS) (hitherto regarded as optimal). This work confirmed that DIMETRIS is suitable for the trace analysis of pharmaceuticals in natural samples and provides an interesting alternative to silylating and acylating agents.

Graphical abstract