Forgot your password?
New user?
New Window Opens on the Secret Life of Microbes: Scientists Develop First Microbial Profiles of Ecosystems
CAS announces the release of SciFinder Scholar for Mac OS X
Press Releases
Press Releases
| Check out our New Publishers' Select for Free Articles |
Analytica Chimica Acta (v.753, #)
Preparation and evaluation of mesoporous cellular foams coating of solid-phase microextraction fibers by determination of tetrabromobisphenol A, tetrabromobisphenol S and related compounds by Xuemei Wang; Jiyan Liu; Aifeng Liu; Qian Liu; Xinzhen Du; Guibin Jiang (pp. 1-7).
Display Omitted► Two novel mesoporous cellular foams were synthesized and used as SPME coating. ► Four SPME fibers were prepared by sol–gel technology and immobilized resin method. ► New coating had excellent extraction ability to seven brominated flame retardants.Two kinds of mesoporous cellular foams (MCFs), including mesoporous silica materials (MCF-1) and phenyl modified mesoporous materials (Ph-MCF-1), were synthesized and for the first time used as fiber-coating materials for solid-phase microextraction (SPME). By using stainless steel wire as the supporting core, four types of fibers were prepared by sol–gel method and immobilized by epoxy-resin method. To evaluate the performance of the home-made fibers for SPME, seven brominated flame retardants (BFRs), including tetrabromobisphenol A (TBBPA), tetrabromobisphenol S (TBBPS) and related compounds were selected as analytes. The main parameters that affect the extraction and desorption efficiencies, such as extraction temperature, extraction time, desorption time, stirring rate and ionic strength of samples were investigated and optimized. The optimized SPME coupled with high performance liquid chromatography (HPLC) was successfully applied to the determination of the seven BFRs in water samples. The linearity range was from 5.0 to 1000μgL−1 for each compound except TBBPS (from 1.0 to 1000μgL−1), with the correlation coefficients ( r2) ranging from 0.9993 to 0.9999. The limits of detection of the method were 0.4–0.9μgL−1. The relative standard deviations varied from 1.2 to 5.1% ( n=5). The repeatability of fiber-to-fiber and batch-to-batch was 2.5–6.5% and 3.2–6.7%. The recoveries of the BFRs from aqueous samples were in the range between 86.5 and 103.6%. Compared with three commercial fibers (100μm PDMS, 85μm PA and 65μm PDMS/DVB), the MCFs-coated fiber showed about 3.5-fold higher extraction efficiency.
Keywords: Solid-phase microextraction; Fiber coating; Mesoporous cellular foams material; Brominated flame retardants
Review on recent advances in the analysis of isolated organelles by Chad P. Satori; Vratislav Kostal; Edgar A. Arriaga (pp. 8-18).
Display Omitted► Advancements in organelle release. ► New approaches to fractionate organelles. ► Updates on new techniques to characterize isolated organelles.The analysis of isolated organelles is one of the pillars of modern bioanalytical chemistry. This review describes recent developments on the isolation and characterization of isolated organelles both from living organisms and cell cultures. Salient reports on methods to release organelles focused on reproducibility and yield, membrane isolation, and integrated devices for organelle release. New developments on organelle fractionation after their isolation were on the topics of centrifugation, immunocapture, free flow electrophoresis, flow field-flow fractionation, fluorescence activated organelle sorting, laser capture microdissection, and dielectrophoresis. New concepts on characterization of isolated organelles included atomic force microscopy, optical tweezers combined with Raman spectroscopy, organelle sensors, flow cytometry, capillary electrophoresis, and microfluidic devices.
Keywords: Organelle isolation; Organelle purification; Subcellular; Centrifugation; Electrophoresis; Dielectrophoresis; Fluorescence; Atomic force microscopy; Microfluidics
Discriminant analysis in the presence of interferences: Combined application of target factor analysis and a Bayesian soft-classifier by Caitlin N. Rinke; Mary R. Williams; Christopher Brown; Matthieu Baudelet; Martin Richardson; Michael E. Sigman (pp. 19-26).
Display Omitted► A novel background-independent soft classification method is described. ► Target factor analysis is combined with Bayesian decision theory. ► Target factors are taken from a library of target analytes. ► Trace metal transfers to complex backgrounds are analyzed by LIBS. ► The method is shown to be both conservative and accurate.A method is described for performing discriminant analysis in the presence of interfering background signal. The method is based on performing target factor analysis on a data set comprised of contributions from analyte(s) and interfering components. A library of data from representative analyte classes is tested for possible contributing factors by performing oblique rotations of the principal factors to obtain the best match, in a least-squares sense, between test and predicted vectors. The degree of match between the test and predicted vectors is measured by the Pearson correlation coefficient, r, and the distribution of r for each class is determined. A Bayesian soft classifier is used to calculate the posterior probability based on the distributions of r for each class, which assist the analyst in assessing the presence of one or more analytes. The method is demonstrated by analyses performed on spectra obtained by laser induced breakdown spectroscopy (LIBS). Single and multiple bullet jacketing transfers to steel and porcelain substrates were analyzed to identify the jacketing materials. Additionally, the metal surrounding bullet holes was analyzed to identify the class of bullet jacketing that passed through a stainless steel plate. Of 36 single sample transfers, the copper jacketed (CJ) and non-jacketed (NJ) class on porcelain had an average posterior probability of the metal deposited on the substrate of 1.0. Metal jacketed (MJ) bullet transfers to steel and porcelain were not detected as successfully. Multiple transfers of CJ/NJ and CJ/MJ on the two substrates resulted in posterior probabilities that reflected the presence of both jacketing materials. The MJ/NJ transfers gave posterior probabilities that reflected the presence of the NJ material, but the MJ component was mistaken for CJ on steel, while non-zero probabilities were obtained for both CJ and MJ on porcelain. Jacketing transfer from a bullet to steel as the projectile passed through the steel also proved difficult to analyze. Over 50% of the samples left insufficient transfer to be identified. Transfer from NJ and CJ jacketing was successfully identified by posterior probabilities greater than 0.8.
Keywords: Target factor analysis; Discriminant analysis; Bayesian classifier; Laser-induced breakdown spectroscopy
Ultrasensitive one-step rapid detection of ochratoxin A by the folding-based electrochemical aptasensor by Jingjing Wu; Huaqin Chu; Zhanlong Mei; Yi Deng; Feng Xue; Lei Zheng; Wei Chen (pp. 27-31).
Display Omitted► One-step electrochemical aptasensor for OTA detection. ► Rapid and ultrasensitive OTA detection with LOD of 0.095pgmL−1 in less than 15min. ► Successful application of the electrochemical aptasensor in OTA spiked samples. ► Providing a potential tool for on-site quality control of OTA related pollutions.A one-step electrochemical aptasensor using the thiol- and methylene blue- (MB-) dual-labeled aptamer modified gold electrode for determination of ochratoxin A (OTA) was presented in this research. The aptamer against OTA was covalently immobilized on the surface of the electrode by the self-assembly effect and used as recognition probes for OTA detection by the binding induced folding of the aptamer. Under the optimal conditions, the developed electrochemical aptasensor demonstrated a wide linear range from 0.1pgmL−1 to 1000pgmL−1 with the limit of detection (LOD) of 0.095pgmL−1, which was an extraordinary sensitivity compared with other common methods for OTA detection. Moreover, as a practical application, this proposed electrochemical aptasensor was used to monitor the OTA level in red wine samples without any special pretreatment and with satisfactory results obtained. Study results showed that this electrochemical aptasensor could be a potential useful platform for on-site OTA measurement in real complex samples.
Keywords: Ochratoxin A detection; Aptamer; Electrochemical aptasensor; Ultrasensitive; One-step detection
Layer by layer assembly of catalase and amine-terminated ionic liquid onto titanium nitride nanoparticles modified glassy carbon electrode: Study of direct voltammetry and bioelectrocatalytic activity by Shagayegh Saadati; Abdollah Salimi; Rahman Hallaj; Amin Rostami (pp. 32-41).
Display Omitted► Catalase and amine-terminated ionic liquid were immobilized to GC/TiNnp with LBL assembly method. ► First a thin layer of NH2-IL is covalently attached to GC/TiNnp electrode using electro-oxidation. ► With alternative assemble of IL and catalase with positive and negative charged, multilayer was formed. ► Immobilized catalase shows excellent electrocatalytic activity toward H2O2 reduction. ► Biosensor response is directly correlated to the number of bilayers.A novel, simple and facile layer by layer (LBL) approach is used for modification of glassy carbon (GC) electrode with multilayer of catalase and nanocomposite containing 1-(3-Aminopropyl)-3-methylimidazolium bromide (amine terminated ionic liquid (NH2-IL)) and titanium nitride nanoparticles (TiNnp). First a thin layer of NH2-IL is covalently attached to GC/TiNnp electrode using electro-oxidation method. Then, with alternative self assemble positively charged NH2-IL and negatively charged catalase a sensitive H2O2 biosensor is constructed, whose response is directly correlated to the number of bilayers. The surface coverage of active catalase per bilayer, heterogeneous electron transfer rate constant ( ks) and Michaelis–Menten constant ( KM) of immobilized catalase were 3.32×10−12molcm−2, 5.28s−1 and 1.1mM, respectively. The biosensor shows good stability, high reproducibility, long life-time, and fast amperometric response with the high sensitivity of 380μAmM−1cm−2 and low detection limit of 100nM at concentration range up to 2.1mM.
Keywords: Layer by layer; Catalase; IL; Titanium nitride nanoparticle; H; 2; O; 2; Biosensor
Sulfide determination in hydrothermal seawater samples using a vibrating gold micro-wire electrode in conjunction with stripping chronopotentiometry by Virginie Aumond; Matthieu Waeles; Pascal Salaün; Kristoff Gibbon-Walsh; Constant M.G. van den Berg; Pierre-Marie Sarradin; Ricardo D. Riso (pp. 42-47).
A rapid electrochemical stripping chronopotentiometric procedure to determined sulfide in unaltered hydrothermal seawater samples is presented. Sulfide is deposited at −0.25V (vs Ag/AgCl, KCl 3M) at a vibrating gold microwire and then stripped through the application of a reductive constant current (typically −2μA). The hydrodynamic conditions are modulated by vibration allowing a short deposition step, which is shown here to be necessary to minimize H2S volatilization. The limit of detection (LOD) is 30nM after a deposition step of 7s. This LOD is in the same range as the most sensitive cathodic voltammetric technique using a mercury drop electrode and is well below those reported previously for other electrodes capable of being implemented in situ.
Keywords: Sulfide; Stripping chronopotentiometry; Vibrating electrode; Gold; Seawater; Hydrothermal
Halogen bonding: A new retention mechanism for the solid phase extraction of perfluorinated iodoalkanes by Xiao Qing Yan; Qian Jin Shen; Xiao Ran Zhao; Hai Yue Gao; Xue Pang; Wei Jun Jin (pp. 48-56).
Display Omitted► Halogen bonding (XB) is firstly utilised in solid phase extraction. ► The perfluorinated iodine alkanes can be extracted by CI⋯Cl− halogen bonding. ► The CI⋯Cl− halogen bond is well characterised by spectroscopy methods. ► The analytes with strong halogen-bonding abilities can be selectively extracted.For the first time, halogen-bonding interaction is utilised in the solid phase extraction of perfluorinated iodoalkane (PFI). Nine PFIs, as model analytes, were tested, and analyses by UV,19F NMR and Raman spectroscopies demonstrate that the PFIs are extracted by a strong anion exchange (SAX) sorbent from n-hexane due to the CI⋯Cl− halogen-bonding interactions. The results also show that the adsorptivities of SAX for the diiodoperfluoro-alkanes (diiodo-PFIs) were much stronger than those for the perfluoroalkyl iodides (monoiodo-PFIs). Specifically, the recoveries for 1,6-diiodoperfluorohexane and 1,8-diiodoperfluorooctane were higher than 80% when 100mL of sample spiked with a 5ngmL−1 analyte mixture was extracted. Interestingly, SAX had no adsorption for hexafluorobenzene at all, which is known to be unable to form a halogen bond with Cl−. The analytical performance of the halogen bond-based SPE-GC–MS method for the diiodo-PFIs was also examined in soil samples. The sorbent SAX enabled the selective extraction of four diiodo-PFIs successfully from soil samples. The recoveries of the diiodo-PFIs extracted from 5g soil sample at the 100ngg−1 spike level were in the range of 73.2–93.8% except 26.8% for 1,2-diiodoperfluoroethane. The limit of detection varied from 0.02 to 0.04ngg−1 in soil samples. Overall, this work reveals the great application potential of halogen bonding in the field of solid phase extraction to selectively extract compounds with strong halogen-bonding abilities.
Keywords: Halogen bonding; Solid phase extraction; Perfluorinated iodine alkanes; Strong anion exchange sorbent
Determination of hydroxylated metabolites of polycyclic aromatic hydrocarbons in sediment samples by combining subcritical water extraction and dispersive liquid–liquid microextraction with derivatization by Xiaowei Wang; Li Lin; Tiangang Luan; Lihua Yang; Nora F.Y. Tam (pp. 57-63).
Display Omitted► We combine subcritical water extraction (SWE) with dispersive liquid–liquid microextraction (DLLME). ► Subcritical water is used as the extraction solvent for SWE and the sample solution for the following DLLME. ► Acetonitrile is used as the organic modifier for SWE and disperser solvent for DLLME in succession. ► We examine changes of OH-PAHs during the degradation by microorganism.A sample preparation method for the determination of hydroxylated polycyclic aromatic hydrocarbons (OH-PAHs) in sediment samples was developed using gas chromatography–mass spectrometry (GC–MS). Dispersive liquid–liquid microextraction (DLLME) with derivatization was performed following the subcritical water extraction (SWE) that provided which was provided by accelerated solvent extraction (ASE). Several important parameters that affected both SWE extraction and DLLME, such as the selection of organic modifier, its volume, extraction temperature, extraction pressure and extraction time were also investigated. High sensitivity of the hydroxylated PAHs derivatives by N-( tert-butyldimethylsilyl)- N-methyl-trifluoroacetamide (MTBSTFA) could be achieved with the limits of detection (LODs) ranging from 0.0139 (2-OH-nap) to 0.2334μgkg−1 (3-OH-fluo) and the relative standard deviations (RSDs) between 2.81% (2-OH-phe) and 11.07% (1-OH-pyr). Moreover, the proposed method was compared with SWE coupled with solid phase extraction (SPE), and the results showed that ASE–DLLME was more promising with recoveries ranging from 57.63% to 91.07%. The proposed method was then applied to determine the hydroxylated metabolites of phenanthrene in contaminated sediments produced during the degradation by two PAH-degraders isolated from mangrove sediments.
Keywords: Hydroxylated polycyclic aromatic hydrocarbons; Accelerated solvent extraction; Subcritical water extraction; Dispersive liquid–liquid microextraction; Sediment
Highly specific revelation of rat serum glycopeptidome by boronic acid-functionalized mesoporous silica by Liting Liu; Ying Zhang; Lei Zhang; Guoquan Yan; Jun Yao; Pengyuan Yang; Haojie Lu (pp. 64-72).
A highly ordered boronic acid-functionalized mesoporous silica was synthesized and applied for the revelation of rat serum glycopeptidome for the first time.Display Omitted► A highly ordered boronic acid-functionalized mesoporous silica was synthesized. ► The as-prepared material possessed both glycopeptide-suitable pore size and glycopeptide-specific selectivity. ► The as-prepared material showed highly efficient ability for enrichment of endogenous glycopeptides from serum. ► Rat serum glycopeptidome was reveled for the first time.Although the specific profiling of endogenous glycopeptides in serum is highly inclined towards the discovery of disease biomarkers, studies on the endogenous glycopeptides (glycopeptidome) have never been conducted because of several factors. These factors include the high dynamic range of serum proteins, the inadequacy of traditional sample preparation techniques in proteomics for low-molecular-weight (LMW) proteins, and the relatively low abundances of glycopeptides. Boronic acid-functionalized mesoporous silica was synthesized in this study to overcome the limitations of the state-of-the-art methods for glycopeptidome research. The boronic acid-functionalized mesoporous silica exhibited excellent selectivity by analyzing glycopeptides in the mixture of glycopeptides/non-glycopeptides at molar ratio of 1:100, extreme sensitivity (the limit of detection was at the fmol level), good binding capacity (40mgg−1), as well as the high post-enrichment recovery of glycopeptides (up to 88.10%). The as-prepared material possessing both glycopeptide-suitable pore size and glycopeptide-specific selectivity has shown special capability for enriching the endogenous glycopeptides. Fifteen unique glycosylation sites mapped to 15 different endogenous glycopeptides were identified in rat serum. The established protocol revealed for the first time the rat serum glycopeptidome.
Keywords: Serum glycopeptidome; Mesoporous materials; Size exclusion; Enrichment; Mass spectrometry
Rapid differentiation of Panax ginseng and Panax quinquefolius by matrix-assisted laser desorption/ionization mass spectrometry by Ying-Han Lai; Pui-Kin So; Samual Chun-Lap Lo; Eddy Wing Yin Ng; Terence Chuen Wai Poon; Zhong-Ping Yao (pp. 73-81).
Display Omitted► Rapid differentiation of Panax ginseng and Panax quinquefolius by MALDI-MS. ► Direct analysis of raw herbal samples by MALDI-MS. ► Identification of adulterated Panax quinquefolius. ► Quantitative measurements of ginsenosides and compositions of Panax ginseng and Panax quinquefolius mixtures.A matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS)-based method has been developed for rapid differentiation between Panax ginseng and Panax quinquefolius, two herbal medicines with similar chemical and physical properties but different therapeutic effects. This method required only a small quantity of samples, and the herbal medicines were analyzed by MALDI-MS either after a brief extraction step, or directly on the powder form or small pieces of raw samples. The acquired MALDI-MS spectra showed different patterns of ginsenosides and small chemical molecules between P. ginseng and P. quinquefolius, thus allowing unambiguous differentiation between the two Panax species based on the specific ions, intensity ratios of characteristic ions or principal component analysis. The approach could also be used to differentiate red ginseng or P. quinquefolius adulterated with P. ginseng from pure P. ginseng and pure Panax quinquefolium. The intensity ratios of characteristic ions in the MALDI-MS spectra showed high reproducibility and enabled quantitative determination of ginsenosides in the herbal samples and percentage of P. quinquefolius in the adulterated binary mixture. The method is simple, rapid, robust, and can be extended for analysis of other herbal medicines.
Keywords: MALDI-MS; Differentiation; Herbal medicine; Panax ginseng; Panax quinquefolius
Simple and label-free electrochemical assay for signal-on DNA hybridization directly at undecorated graphene oxide by Yuwei Hu; Fenghua Li; Dongxue Han; Tongshun Wu; Qixian Zhang; Li Niu; Yu Bao (pp. 82-89).
Display Omitted► A strategy developed for DNA detection with no need to decorate GO or label DNA. ► Specially designed ssDNA consists of immobilization part and probe part. ► Hybridization leads to ‘lying’ ssDNA to ‘standing’ dsDNA. ► Conformational and negative charge changes induce signal-on impedimetric result. ► Potential applications in DNA nanostructure frameworks and nanoelectronics.Exploring graphene oxide (GO), DNA hybridization detection usually relies on either GO decoration or DNA sequences labeling. The former endows GO with desired chemical, optical, and biological properties. The latter adopts labeled molecules to indicate hybridization. In the present work, we propose a simple, label-free DNA assay using undecorated GO directly as the sensing platform. GO is anchored on diazonium functionalized electrode through electrostatic attraction, hydrogen bonding or epoxy ring-opening. The π–π stacking interaction between hexagonal cells of GO and DNA base rings facilitates DNA immobilization. The adsorbed DNA sequence is specially designed with two parts, including immobilization sequence and probe sequence. In the absence of target, the two sequences lie nearly flat on GO platform. In the presence of target, probe hybridizes with it to form double helix DNA, which ‘stands’ on GO. While the immobilization sequence part remains ‘lying’ on GO surface. Hence, DNA hybridization induces GO interfacial property changes, including negative charge and conformational transition from ‘lying’ ssDNA to ‘standing’ dsDNA. These changes are monitored by electrochemical impedance spectroscopy and adopted as the analytical signal. This strategy eliminates the requirement for GO decoration or DNA labeling, representing a comparatively simple and effective way. Finally, the principle is applied to the detection of conserved sequence of the human immunodeficiency virus 1 pol gene fragment. The dynamic detection range is from 1.0×10−12 to 1.0×10−6M with detection limit of 1.1×10−13M with 3 σ. And the sequences with double- or four-base mismatched are readily distinguishable. In addition, this strategy may hold great promise for potential applications from DNA biosensing to nanostructure framework construction based on the versatile DNA self-assembly.
Keywords: Graphene oxide; DNA; Label-free; Impedimetric detection; Signal-on
Capillary electrophoresis of heparin and other glycosaminoglycans using a polyamine running electrolyte by Thomas N. Loegel; John D. Trombley; Richard T. Taylor; Neil D. Danielson (pp. 90-96).
Display Omitted► Ethylenediamine is likely acting as an ion-pairing agent. ► Oversulfated chondroitin sulfate is last peak instead of first peak. ► There is about a factor of five improved detectability with a 12.5min analysis time. ► Use of a 50μm ID capillary is possible.This study involves the use of polyamines as potential resolving agents for the capillary electrophoresis (CE) of glycosaminoglycans (GAGs), specifically heparin, dermatan sulfate, chondroitin sulfate, over-sulfated chondroitin sulfate (OSCS), and hyaluronan. All of the compounds can be separated from each other with the exception of chondroitin sulfate and hyaluronan. Using optimization software, the final run conditions are found to be 200mM ethylenediamine and 45.5mM phosphate as the electrolyte with −14V applied across a 50μm ID×24.5cm fused silica capillary at 15°C. The ion migration order, with OSCS as the last instead of the first peak, is in contrast to previous reports using either a high molarity TRIS or lithium phosphate run buffer with narrower bore capillaries. Total analysis time is 12. 5min and the relative standard deviation of the heparin migration time is about 2.5% ( n=5). The interaction mechanism between selected polyamines and heparin is explored using conductivity measurements in addition to CE experiments to show that an ion-pairing mechanism is likely.
Keywords: Capillary electrophoresis; Heparin; Polyamine electrolyte