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.717, #)
A simple method using on-line continuous leaching and ion exchange chromatography coupled to inductively coupled plasma mass spectrometry for the speciation analysis of bio-accessible arsenic in rice by Nolan S. Horner; Diane Beauchemin (pp. 1-6).
Display Omitted► Simplifying the mini-column packing procedure significantly improves reproducibility. ► Measuring bio-accessibility on-line gives the same results as batch methods. ► Results are obtained within minutes instead of the hours required by batch methods. ► Cooking rice affects the bio-accessibility of arsenic as well as its speciation analysis. ► The method can easily be used for risk assessment of arsenic in rice.A simple method for the speciation analysis of bio-accessible arsenic (As) in rice was developed using a continuous on-line leaching method to release the bio-accessible fraction. The continuous on-line leaching method has several advantages over commonly used batch methods including quicker and easier sample preparation, reduced risk of contamination and access to real time leaching data. The bio-accessibility of As in the samples was monitored using inductively coupled plasma mass spectrometry (ICP-MS). Results from a certified reference material as well as cooked and uncooked white rice showed that the majority of As was leached by saliva. Results obtained using the continuous on-line leaching method were comparable to those obtained using a batch method. Speciation analysis of the saliva leachate was performed using ion exchange chromatography coupled to ICP-MS. The four most toxic forms of As (As(III), monomethylarsonic acid (MMA), dimethylarsinic acid (DMA) and As(V)) were clearly separated within 5min in a single chromatographic run. Over 92% of bio-accessible As in the certified reference material and uncooked white rice sample was in the form of DMA and As(V), whereas it was present as DMA and As(III) in the cooked white rice.
Keywords: Bio-accessibility; Inductively coupled plasma mass spectrometry; Speciation analysis; Arsenic
Photopolymerization and photostructuring of molecularly imprinted polymers for sensor applications—A review by Yannick Fuchs; Olivier Soppera; Karsten Haupt (pp. 7-20).
Display Omitted► Molecularly imprinted polymers (MIPs) are synthetic receptors for sensors and biochips. ► The photopolymerization of MIPs allows for the spatially resolved synthesis of micro and nanostructures. ► Using photopolymerization MIPs can be easily patterned at transducer surfaces.Biosensors are already well established in modern analytical chemistry, and have become important tools for clinical diagnostics, environmental analysis, production monitoring, drug detection or screening. They are based on the specific molecular recognition of a target molecule by a biological receptor such as an antibody or an enzyme. Synthetic biomimetic receptors like molecularly imprinted polymers (MIPs) have been shown to be a potential alternative to biomolecules as recognition element for biosensing. Produced by a templating process at the molecular level, MIPs are capable of recognizing and binding target molecules with similar specificity and selectivity to their natural analogues. One of the main challenges in MIP sensor development is the miniaturization of MIP structures and their interfacing with the transducer or with a microchip. Photostructuring appears thereby as one of the most suitable methods for patterning MIPs at the micro and nano scale, directly on the transducer surface. In the present review, a general overview on MIPs in biosensing applications is given, and the photopolymerization and photopatterning of MIPs are particularly described.
Keywords: Molecularly imprinted polymers; Biomimetic sensors; Microchips; Photopolymerization; Photostructuring
The use of electrothermal vaporizer coupled to the inductively coupled plasma mass spectrometry for the determination of arsenic, selenium and transition metals in biological samples treated with formic acid by Luciano Tormen; Raul A. Gil; Vera L.A. Frescura; Luis Dante Martinez; Adilson J. Curtius (pp. 21-27).
Display Omitted► Simple sample treatment of biologic samples with formic acid is proposed. ► The treatment with formic acid is easy, rapid, less expensive and environmental friendly allowing a high sample throughput. ► External calibration with aqueous standard allows the simultaneous determination of As, Co, Cu, Fe, Mn, Ni, Se and V. ► The use of ETV avoids plasma instability, carbon deposit on the cones and does not require sample digestion.A fast method for the determination of As, Co, Cu, Fe, Mn, Ni, Se and V in biological samples by ETV-ICP-MS, after a simple sample treatment with formic acid, is proposed. Approximately 75mg of each sample is mixed with 5mL of formic acid, kept at 90°C for 1h and then diluted with nitric acid aqueous solution to a 5% (v/v) formic acid and 1% (v/v) nitric acid final concentrations. A palladium solution was used as a chemical modifier. The instrumental conditions, such as carrier gas flow rate, RF power, pyrolysis and vaporization temperatures and argon internal flow rate during vaporization were optimized. The formic acid causes a slight decrease of the analytes signal intensities, but does not increase the signal of the mainly polyatomic ions (14N35Cl+,14N12C+,40Ar12C+,13C37Cl+,40Ar36Ar+,40Ar35Cl+,35Cl16O+,40Ar18O+) that affect the analytes signals. The effect of charge transfer reactions, that could increase the ionization efficiency of some elements with high ionization potentials was not observed due to the elimination of most of the organic compounds during the pyrolysis step. External calibration with aqueous standard solutions containing 5% (v/v) formic acid allows the simultaneous determination of all analytes with high accuracy. The detection limits in the samples were between 0.01 (Co) and 850μgkg−1 (Fe and Se) and the precision expressed by the relative standard deviations (RSD) were between 0.1% (Mn) and 10% (Ni). Accuracy was validated by the analysis of four certified reference biological materials of animal tissues (lobster hepatopancreas, dogfish muscle, oyster tissue and bovine liver). The recommended procedure avoids plasma instability, carbon deposit on the cones and does not require sample digestion.
Keywords: ICP-MS; Biological samples; Formic acid solubilization; Trace elements; Electrothermal vaporizer
Online characterization of regulated and unregulated gaseous and particulate exhaust emissions from two-stroke mopeds: A chemometric approach by M. Clairotte; T.W. Adam; R. Chirico; B. Giechaskiel; U. Manfredi; M. Elsasser; M. Sklorz; P.F. DeCarlo; M.F. Heringa; R. Zimmermann; G. Martini; A. Krasenbrink; A. Vicet; E. Tournié; A.S.H. Prévôt; C. Astorga (pp. 28-38).
Display Omitted► We monitor on real-time basis gas and particulate phases of moped exhaust. ► Two mopeds complying with EURO-1 and EURO-2 emission standards are studied. ► Multivariate data analysis highlighted the effect of temperature on the particles and heavy PAH emissions. ► The more recent after-treatment device may generate potentially harmful particles.Two-stroke mopeds are a popular and convenient mean of transport in particular in the highly populated cities. These vehicles can emit potentially toxic gaseous and aerosol pollutants due to their engine technology. The legislative measurements of moped emissions are based on offline methods; however, the online characterization of gas and particulate phases offers great possibilities to understand aerosol formation mechanism and to adapt future emission standards. The purpose of this work was to study the emission behavior of two mopeds complying with different European emission standards (EURO-1 and EURO-2). A sophisticated set of online analyzers was applied to simultaneously monitor the gas phase and particulate phase of exhaust on a real time basis. The gaseous emission was analyzed with a high resolution Fourier transform infrared spectrometer (FTIR; nitrogen species) and a resonance-enhanced multiphoton ionization time-of-flight mass spectrometer (REMPI-ToF-MS; polycyclic aromatic hydrocarbons: PAH), whereas the particulate phase was chemically characterized by a high-resolution time-of-flight aerosol mass spectrometer (HR-ToF-AMS; organic, nitrate and chloride aerosol) and a multiangle absorption photometer (MAAP; black carbon). The physical characterization of the aerosol was carried out with a condensation particle counter (CPC; particle number concentration) and a fast mobility particle sizer (FMPS; size distribution in real time). In order to extract underlying correlation between gas and solid emissions, principal component analysis was applied to the comprehensive online dataset. Multivariate analysis highlighted the considerable effect of the exhaust temperature on the particles and heavy PAH emissions. The results showed that the after-treatment used to comply with the latest EURO-2 emission standard may be responsible for the production of more potentially harmful particles compared to the EURO-1 moped emissions.
Keywords: Aerosol mass spectrometer; Black carbon; 2-Stroke engine; Online measurement; Polycyclic aromatic hydrocarbons; Multivariate analysis
Tracing the origin of extra virgin olive oils by infrared spectroscopy and chemometrics: A case study by Marta Bevilacqua; Remo Bucci; Andrea D. Magrì; Antonio L. Magrì; Federico Marini (pp. 39-51).
In this paper, the potential of coupling mid- and near-infrared spectroscopic fingerprinting techniques and chemometric classification methods for the traceability of extra virgin olive oil samples from the PDO Sabina was investigated. To this purpose, two different pattern recognition algorithm representative of the discriminant (PLS-DA) and modeling (SIMCA) approach to classification were employed. Results obtained after processing the spectroscopic data by PLS-DA evidenced a rather high classification accuracy, NIR providing better predictions than MIR (as evaluated both in cross-validation and on an external test set). SIMCA confirmed these results and showed how the category models for the class Sabina can be rather sensitive and highly specific. Lastly, as samples from two harvesting years (2009 and 2010) were investigated, it was possible to evidence that the different production year can have a relevant effect on the spectroscopic fingerprint. Notwithstanding this, it was still possible to build models that are transferable from one year to another with good accuracy.Display Omitted► Traceability models built using fast, cheap and non destructive techniques. ► Classification accuracy was higher on NIR than on MIR data. ► SIMCA models rather sensitive and highly specific. ► Verified effect of harvest year on the spectroscopic signals. ► Possibility of building models transferable from one production year to another.In this paper, the potential of coupling mid- and near-infrared spectroscopic fingerprinting techniques and chemometric classification methods for the traceability of extra virgin olive oil samples from the PDO Sabina was investigated. To this purpose, two different pattern recognition algorithm representative of the discriminant (PLS-DA) and modeling (SIMCA) approach to classification were employed. Results obtained after processing the spectroscopic data by PLS-DA evidenced a rather high classification accuracy, NIR providing better predictions than MIR (as evaluated both in cross-validation and on an external test set). SIMCA confirmed these results and showed how the category models for the class Sabina can be rather sensitive and highly specific. Lastly, as samples from two harvesting years (2009 and 2010) were investigated, it was possible to evidence that the different production year can have a relevant effect on the spectroscopic fingerprint. Notwithstanding this, it was still possible to build models that are transferable from one year to another with good accuracy.
Keywords: Extra virgin olive oil; Chemometrics; Partial least squares discriminant analysis (PLS-DA); SIMCA; Food traceability; Infrared spectroscopy
Cross-column retention prediction in reversed-phase high-performance liquid chromatography by artificial neural network modelling by Angelo Antonio D’Archivio; Andrea Giannitto; Maria Anna Maggi; Fabrizio Ruggieri (pp. 52-60).
Display Omitted► Cross-column retention prediction is attempted by artificial neural network regression. ► Observed retentions of representative solutes are adopted as column descriptors. ► Solute and column descriptors are combined in a comprehensive predictive model. ► Model predictive performance is severely evaluated on unknown solutes and columns.Linear solvation energy relationships (LSERs) are commonly applied to model the effect of solute structure on the retention of analytes in reversed-phase high-performance liquid chromatography (RP-HPLC). Standard LSER approaches can be used, in principle, to predict RP-HPLC behaviour of unknown analytes under fixed separation condition. However, as solute structure is the only source of variability described by the model, a LSER established for a given column/eluent pair cannot be transferred to external separation conditions. In the present investigation, we attempt cross-column prediction by combining in the same model usual LSER molecular descriptors with observed retentions of selected solutes within the calibration set, adopted to represent the stationary phase features. A multi-layer artificial neural network (ANN) is used as regression tool to model the combined effect of solute structure and column on retention. This model is generated and validated using literature retention data of 34 solutes collected on 15 different RP-HPLC columns at a fixed eluent composition (acetonitrile–water 30:70, v/v). The calibration set is designed by selecting 25 solutes and 11 columns able to represent the variability of the chemical structure of the investigated compounds and dissimilarity of the stationary phases of the data set, respectively. The final predictive performance of the optimised ANN model is tested on the four columns excluded from calibration. Retention of the 25 solutes used to train the network and that of the nine unknown molecules on the external stationary phases is comparably well predicted.
Keywords: Retention modelling; Artificial neural network; Reversed-phase high-performance liquid chromatography; Cross-column prediction; Solvatochromic descriptors
A superoxide anion biosensor based on direct electron transfer of superoxide dismutase on sodium alginate sol–gel film and its application to monitoring of living cells by Xiuhua Wang; Min Han; Jianchun Bao; Wenwen Tu; Zhihui Dai (pp. 61-66).
Display Omitted► The direct electron transfer of SOD was facilitated on SA sol–gel film. ► O2− sensor has high selectivity, stability and sensitivity. ► The proposed measurement for O2− can be applied in living cells.The direct electron transfer of superoxide dismutase (SOD) was greatly facilitated by sodium alginate (SA) sol–gel film with the formal potential of 0.14V, which was just located between O2−/O2 and O2−/H2O2. The preparation of the SOD/SA modified electrode was simple without any mediators or promoters. Based on bimolecular recognition for specific reactivity of SOD/SA toward O2−, the SOD modified electrode was utilized to measure O2− with good analytical performance, such as low applied potential (0V), high selectivity (no obvious interference), wide linear range (0.44–229.88μM) and low detection limit (0.23μM) in pH 7.0 phosphate buffer solution. Furthermore, it could be successfully exploited for the determination of O2− released from living cells directly adhered on the modified electrode surface. Thus, the proposed O2− biosensor, combining with the properties of SA sol–gel film, provided a novel approach for protein immobilization, direct electron transfer study of the immobilized protein and real-time determination of O2− released from living cells.
Keywords: Abbreviations; SOD; superoxide dismutase; SA; sodium alginate; ROS; reactive oxygen species; O; 2; −; superoxide anion; RNS; reactive nitrogen species; H; 2; O; 2; hydrogen peroxide; NO; nitric oxide; DA; dopamine; AA; ascorbic acid; ONOO; −; peroxynitrite; PBS; phosphate butter solution; SCE; saturated calomel electrode; FESEM; field emission scanning electron microscopy; FTIR; Fourier transform infrared; i; pa; anodic peak current; i; pc; cathodic peak current; E; o; ′; formal potentialSuperoxide dismutase; Sodium alginate sol–gel film; Living cells; Superoxide sensor; Direct electron transfer
Development of a multiplex UPLC-MRM MS method for quantification of human membrane transport proteins OATP1B1, OATP1B3 and OATP2B1 in in vitro systems and tissues by Chengjie Ji; William R. Tschantz; Nathan D. Pfeifer; Mohammed Ullah; Nalini Sadagopan (pp. 67-76).
.Display Omitted► We present a novel UPLC-MRM MS method for quantification of three OATP isoforms. ► The specificity, accuracy and reproducibility of our method were characterized. ► Purified membrane protein standards are required to achieve absolute quantification. ► OATP2B1 was first quantified in human brain capillary endothelial cells using MS.OATP1B1, OATP1B3 and OATP2B1 are important members of the organic anion transporting polypeptides (OATP) family and are implicated in the hepatic disposition of endobiotics and xenobiotics. Quantitating the expression levels of human OATP1B1, OATP1B3 and OATP2B1 in in vitro systems and tissue samples could significantly improve attempts to scale up in vitro data and result in more effective in vitro– in vivo correlation of transporter-mediated effects on drug disposition, such as hepatic clearance. In the present study, a quantification method was developed, characterized, and implemented for simultaneous determination of human OATP1B1, OATP1B3 and OATP2B1 in HEK cells transfected with OATP-expressing plasmid vectors ( SLCO1B1, SLCO1B3, and SLCO2B1, respectively), human hepatocytes, human brain capillary endothelial cells, and humanized mouse liver tissue using UPLC-MRM MS. Purified membrane protein standards prepared and characterized as previously reported (Protein Expr. Purif. 2008, 57, 163-71) were first used as standards for absolute quantification of the expression levels of the three human OATP membrane proteins. The specificity of the optimized MRM transitions were characterized by analyzing the tryptic digests of the membrane protein fraction of wild type HEK cells and control mouse liver tissue using the herein reported UPLC-MRM MS method. The linearity of the calibration curve spanned from 0.2μgmL−1 (0.040μgmg−1) to 20μgmL−1 (4.0μgmg−1), with accuracy (% RE) within 15% at all concentrations examined for all three OATPs of interest in this study. The intra- and inter-day assay accuracy (% RE) and coefficient of variations (% CV) of triplicates are all within 15% for all levels of quality control samples prepared by mixing the membrane fraction of control mouse liver tissue with the required amount of purified human OATP1B1, OATP1B3 and OATP2B1.
Keywords: Organic anion transporting polypeptides (OATP1B1, OATP1B3 and OATP2B1); Purified membrane protein standards; UPLC-MRM MS; Quantification
Natural dissolved organic matter affects electrospray ionization during analysis of emerging contaminants by mass spectrometry by Samanthi Wickramasekara; Selene Hernández-Ruiz; Leif Abrell; Robert Arnold; Jon Chorover (pp. 77-84).
Display Omitted► Matrix effects on EDC/PPCPs analysis were quantified by post column DOM infusion. ► Matrix effects were distinguished between Suwannee River DOM and its fractions. ► A supramolecular association of DOM is interpreted with matrix effects measurements. ► The greatest interferences were produced by fractionated DOM.Dissolved organic matter (DOM), present in many forms in water, can interfere with analysis of organic contaminants by atmospheric pressure ionization–mass spectrometry. A quantitative analysis of this interference, or matrix effect, on organic contaminant target analyte measurements was carried out using un-fractionated and fractionated dissolved natural organic matter from the Suwannee River, GA (SROM), a standard reference material, that was directly infused into the tandem mass spectrometer during multiple reaction monitoring (MRM) of a suite of endocrine disrupting compounds–pharmaceuticals and personal care products (EDC/PPCPs). Most target analytes suffered signal suppression in the presence of both fractionated and un-fractionated SROM, however greater interferences were measured with fractionated relative to bulk SROM. This finding is consistent with the view of organic matter as a supramolecular association of low molecular mass components having separate charged and structural features revealed only after dissociation.
Keywords: Abbreviations; SROM; Suwannee River organic matter; DOM; dissolved organic matter; DOC; dissolved organic carbon; HoA; hydrophobic acid; HoB; hydrophobic base; HoN; hydrophobic neutral; HiA; hydrophilic acid; HiB; hydrophilic base; HiN; hydrophilic neutralMatrix effect; Dissolved organic matter; Electrospray ionization; Ultra high pressure liquid chromatography-tandem mass spectrometry (UHPLC–MSMS); Endocrine disrupting chemicals (EDCs); Pharmaceuticals and personal care products (PPCPs)
Endogenous and synthetic steroids in bovine urine – Preparation of in-house reference material, stability studies and results of a proficiency test by K.S. Schmidt; R. Hackenberg; C.S. Stachel; P. Gowik (pp. 85-91).
Display Omitted► The production of well-characterised in-house reference material is described. ► Homogeneity and stability studies were carried out. ► The realisation of a proficiency test for steroids in bovine urine is described. ► Both GC–MS and LC–MS/MS methods were successfully applied.Within the framework of the German National Residue Control Plan a specific number of samples of animal origin have to be analysed for natural and synthetic steroids each year. As a measure of external quality control of the methods applied in routine analysis a proficiency test was carried out. To this end, in-house reference material containing incurred residues of 17α- and 17β-nortestosterone and 17α- and 17β-estradiol as well as fortified residues of 17α-methyltestosterone and 17α-trenbolone in bovine urine were produced. Before sending the proficiency test material to the participants, the homogeneity of all samples was tested and confirmed. Furthermore extensive short- and long-term stability studies were carried out.The statistical evaluation of the proficiency test was performed by applying robust statistics as described in standard DIN 38402. Based on the target value and standard deviation z-scores were calculated as standardised measure of the laboratory performance. The evaluation of the proficiency test showed that nine laboratories submitted quantitative results within the tolerance limits for all analytes. Taking into account the individual decision limits, there were no false negative results. In overall evaluation, 11 of 12 laboratories participated successfully.
Keywords: Anabolic steroids; Bovine urine; Residue control; Proficiency test; Homogeneity test; Stability studies; In-house reference material
Comparative analysis of smokeless gunpowders by Fourier transform infrared and Raman spectroscopy by María López-López; Jose Luis Ferrando; Carmen García-Ruiz (pp. 92-99).
Display Omitted► Spectra of different smokeless gunpowders were compared by FTIR and Raman spectroscopy. ► Gunpowders containing dinitrotoluene (>10%, m/m) and triple-base gunpowders were identified by both techniques. ► Identification of gunpowders stabilized with diphenylamine was also accomplished by Raman spectroscopy. ► Discriminant analysis applied to FTIR and Raman gunpowder spectra is a useful tool for the identification of gunpowders.Fourier Transform Infrared (FTIR) and Raman spectroscopic techniques were used to perform a comparative study of the spectral profiles of single-base, double-base and triple-base smokeless gunpowders. Preliminary results based on visual comparison of the spectra point out that spectra obtained by both vibrational techniques were useful for a rapid identification of gunpowders containing dinitrotoluene as one of the major components and triple-base gunpowders. Additionally, the Raman spectra of gunpowders with diphenylamine in its primary composition showed a characteristic band, assigned to 2-nitro-diphenylamine, allowing the identification of this type of gunpowders.Further differentiation among the spectra of different types of smokeless gunpowders obtained by both vibrational spectroscopic techniques was investigated by discriminant analysis. Different analyses were applied to spectral data considering the different composition of gunpowders. The presence or absence of different compounds (such as dinitrotoluene, diphenylamine or dibutyl phthalate) or the type of gunpowder according to the number of active components (single-base or double-base gunpowder) has been taken into account. FTIR and Raman spectroscopy in combination with discriminant analyses were successful tools of forensic interest for the classification of gunpowders and the possible identification of unknown samples of gunpowders.
Keywords: Fourier transform infrared spectroscopy; Raman spectroscopy; Smokeless gunpowders; Discriminant analysis
Multi-way partial least-squares and residual bi-linearization for the direct determination of monohydroxy-polycyclic aromatic hydrocarbons on octadecyl membranes via room-temperature fluorescence excitation emission matrices by Hector C. Goicoechea; Korina Calimag-Williams; Andres D. Campiglia (pp. 100-109).
Display Omitted► We apply N-PLS/RBL to the analysis of metabolites of polycyclic aromatic hydrocarbons in urine. ► C18 membranes are used for sample extraction and solid substrates for spectroscopic measurements. ► Quantification is made via room-temperature fluorescence excitation emission matrices. ► N-PLS/RBL and RTF-EEM successfully address the issue of spectral overlapping on solid substrates.Multi-way partial least-squares (N-PLS) is combined to the residual bi-linearization procedure (RBL) for the direct analysis of metabolites of polycyclic aromatic hydrocarbons in urine samples. Metabolite analysis is carried out via a two-step experimental procedure based on solid-phase extraction and room temperature fluorescence spectroscopy. Excitation-emission matrices are recorded from octadecyl (C18) membranes that serve as solid substrates for sample extraction and spectroscopic measurements. Excellent metabolite recoveries were obtained in all cases, which varied from 96.2±1.35% (9-hydroxyphenanthrene) to 99.7±0.49% (3-hydroxybenzo[ a]pyrene). Background correction of extraction membranes is carried out with a new alternating least-squares (ALS) procedure adapted to second order data. The performance of N-PLS/RBL is compared to the well-established multivariate curve resolution-alternating least-squares (MCR-ALS) algorithm. Both algorithms provided similar analytical figures of merit, including their ability to handle unknown interference in urine samples. With only 10mL of sample, the limits of detection varied between 0.06–0.08ngmL−1 (1-hydroxypyrene) and 0.016–0.018ngmL−1 (2-hydroxyfluorene). When compared to previously reported univariate calibration data, the limits of detection via N-PLS/RBL and MCR-ALS are approximately one order of magnitude higher. This was somehow expected due to the effect of unexpected components in multivariate figures of merit, i.e. a more realistic approach to the analysis of metabolites in human urine samples.
Keywords: Second-order multivariate calibration; Solid-phase extraction; Room-temperature fluorescence; Excitation-emission matrices; Urine analysis
Investigation of gamma radiation effect on the anion exchange resin Amberlite IRA-400 in hydroxide form by Fourier transformed infrared and13C nuclear magnetic resonance spectroscopies by A. Traboulsi; N. Dupuy; C. Rebufa; M. Sergent; V. Labed (pp. 110-121).
Display Omitted► Our works complete the existing studies on the γ-radiation impact on the Amberlite IR400 in OH form. ► The irradiation effect under different conditions was determined from an experimental design. ► Its structure was characterized by resolving FTIR and13C NMR concatenated data from chemometric tools. ► Principal components analysis discriminated influencing factors as doses and conditions. ► SIMPLISMA allowed to identify the new chemical functional groups and their relative proportion.Radiation-induced decomposition of the anion exchange resin Amberlite IRA-400 in hydroxide form by gamma radiolysis has been studied under different irradiation doses and irradiation atmospheres. In this work, we focused on the degradation of the solid part of the resin by Fourier transformed infrared (FTIR) and13C nuclear magnetic resonance (NMR) spectroscopies associated with chemometric treatments. FTIR and13C NMR techniques showed that onlyCH2N+(CH3)3 groups were detached from the resin whereas the polystyrene divinylbenzene backbone remains intact. The quaternary ammonium groups were replaced by amine or carbonyl groups according to the irradiation atmosphere (with or without water or oxygen). Principal components analysis (PCA) was used to classify the degraded resins according to their irradiation conditions by separating the effect of the dose or the environment. The PCA loadings have shown spectral regions which discriminate the irradiated resins whereas SIMPLe-to-use Interactive Self-modeling Mixture Analysis (SIMPLISMA) allows to identify families of component characterizing the chemical structure of resins and estimate their relative contributions according to the irradiation atmospheres.
Keywords: Ion exchange resin; Fourier transformed infrared (FTIR); 13; C nuclear magnetic resonance; Gamma irradiation; Chemometric
A fluorescent chemosensor for Hg2+ based on naphthalimide derivative by fluorescence enhancement in aqueous solution by Chun-Yan Li; Fen Xu; Yong-Fei Li; Kai Zhou; Yu Zhou (pp. 122-126).
Display Omitted► Naphthalimide was synthesized and used to recognize Hg2+ in aqueous solution. ► The chemosensor can be applied to the quantification of Hg2+ with wide linear range. ► The chemosensor has been used for determination of Hg2+ in real samples successfully.Naphthalimide derivative (compound1) containing hydrophilic hexanoic acid group was synthesized and used to recognize Hg2+ in aqueous solution. The fluorescence enhancement of1 is attributed to the formation of a complex between1 and Hg2+ by 1:1 complex ratio ( K=2.08×105), which has been utilized as the basis of fabrication of the Hg2+-sensitive fluorescent chemosensor. The comparison of this method with some other fluorescence methods for the determination of Hg2+ indicated that the method can be applied in aqueous solution rather than organic solution. The analytical performance characteristics of the proposed Hg2+-sensitive chemosensor were investigated. The chemosensor can be applied to the quantification of Hg2+ with a linear range covering from 2.57×10−7 to 9.27×10−5M and a detection limit of 4.93×10−8M. The experiment results show that the response behavior of1 toward Hg2+ is pH independent in medium condition (pH 4.0–8.0). Most importantly, the fluorescence changes of the chemosensor are remarkably specific for Hg2+ in the presence of other metal ions, which meet the selective requirements for practical application. Moreover, the response of the chemosensor toward Hg2+ is fast (response time less than 1min). In addition, the chemosensor has been used for determination of Hg2+ in hair samples with satisfactory results, which further demonstrates its value of practical applications.
Keywords: Fluorescence; Chemosensor; Hg; 2+; Naphthalimide
Label-free colorimetric sensing of ascorbic acid based on Fenton reaction with unmodified gold nanoparticle probes and multiple molecular logic gates by Li-Pei Zhang; Bo Hu; Jian-Hua Wang (pp. 127-133).
Ascorbic acid is detected based on its prevention on the color change of ssDNA–AuNPs system, by using both naked eye visualization and visible absorption spectroscopy.Display Omitted► Ascorbic acid (AA) prevents ssDNA cleavage and prohibits color change of ssDNA–AuNPs system, deriving a novel approach for AA detection. ► Ascorbic acid is assayed by visible spectroscopy and naked eye visualization, facilitating fast detection of AA in biological samples. ► A multiple logic gate system is designed with small molecules as inputs and the colorimetric changes in the AuNPs solution as outputs.A label-free strategy based on Fenton reaction with unmodified gold nanoparticles (AuNPs) as probe is demonstrated for ascorbic acid (AA) sensing. AuNPs is stable in the presence of single stranded DNA (ssDNA) which prevents salt-induced aggregation of AuNPs in solution. The hydroxyl free radicals generated by Fenton reaction lead to ssDNA cleavage into different sequence fragments which induce aggregation of AuNPs to produce a red-to-blue color change. As an efficient biological antioxidant, AA could effectively scavenge free radicals to avoid the cleavage of ssDNA, so that it prevents color change of the AuNPs solution. Thus, the color change of AuNPs in the presence and absence of AA provides a new approach for the detection of AA. The absorbance ratio at two wavelengths, A670/A520, decreases linearly with AA content within 1–15μM, giving rise to a detection limit of 0.3μM and a RSD of 2.8% (10μM). The color display of AuNPs solution makes it feasible for the estimation of AA content by naked eye visualization. Moreover, based on Fenton reaction and unmodified gold nanoparticles, a multiple logic gate system includes two logic operations, i.e., INHIBIT and NOR, has been designed with small molecules (AA,l-cysteine, glutathione) as inputs and the colorimetric changes of AuNPs solution as outputs.
Keywords: Colorimetric sensor; Gold nanoparticles; Fenton reaction; Ascorbic acid; Logic gates
Preparation and evaluation of an immunoaffinity sorbent for the analysis of opioid peptides by on-line immunoaffinity solid-phase extraction capillary electrophoresis–mass spectrometry by Silvia Medina-Casanellas; Fernando Benavente; José Barbosa; Victoria Sanz-Nebot (pp. 134-142).
Display Omitted► We prepared an IA sorbent for the analysis of opioid peptides by IA-SPE-CE–MS. ► We followed a site-specific antibody immobilization approach. ► The main features of the IA sorbent were studied. ► Endomorphins 1 and 2 were analyzed in standards and plasma samples to achieve the best LODs.In this study, we explored a procedure for the preparation of an immunoaffinity (IA) sorbent for the analysis of opioid peptides by on-line immunoaffinity solid-phase extraction capillary electrophoresis–mass spectrometry (IA-SPE-CE–MS). We followed a site-specific antibody immobilization approach based on the covalent attachment of the oxidized antibodies through their carbohydrate moieties to hydrazide silica particles, using a polyclonal antibody against Endomorphin 1 and 2 (End1 and End2). The main features of the IA sorbent were studied, such as the amount of hydrazide groups and antibodies attached onto oxidized diol silica particles. Once the procedure was optimized, standard solutions of End1 and End2 were used in order to establish the IA-SPE-CE–MS methodology. Acceptable repeatability, reproducibility and linearity range values were obtained for the proposed methodology. The limits of detection (LODs) of 1ngmL−1 were approximately 100-fold better than those obtained by CE–MS. Selectivity of the IA sorbent was good but some cross-reactivity against Dynorphin A (1–7) was observed when a mixture of several opioid peptides was analyzed. Human plasma samples spiked with End1 and End2 were also analyzed and both peptides could be detected down to 100ngmL−1.
Keywords: Capillary electrophoresis; Endomorphin; Immunoaffinity; Neuropeptide; On-line preconcentration; Time-of-flight mass spectrometry
Assessment of trace metal binding kinetics in the resin phase of diffusive gradients in thin films by Jacqueline L. Levy; Hao Zhang; William Davison; Jaume Puy; Josep Galceran (pp. 143-150).
Display Omitted► Method developed to assess the kinetics of metal binding to DGT binding phase. ► Multiple resin layer DGT devices were used to simulate different resin depths. ► Minimal penetration of metals at pH 7 verified their accurate measurement using DGT. ► At lower pH up to 42% of an individual metal accumulated in the back resin layer. ► Mn measurements were most affected by slow binding kinetics.The dynamic technique of diffusive gradients in thin films (DGT), that measures metal speciation in situ, has found wide environmental application. Simple interpretation of the metal accumulation in terms of a solution concentration has assumed that trace metals do not penetrate beyond the surface of the binding layer, but penetration, although theoretically discussed has not yet been directly measured. Multiple binding layers were used to enable analysis of different depths of a DGT binding phase (Chelex-100 or iminodiacetate resins). In simple metal solution (no ligand) at pH 7, metal penetration to the back layer was low and similar for all metals. However, at lower pH up to 42% of an individual metal accumulated in the back resin layer. This was most noticeable for Mn at pH 4 and 5, but Cd and Co were also affected at pH 4. These results were consistent with rate limited binding, particularly for Mn. A kinetic model successfully fitted the data and allowed derivation of a binding rate constant and the mean distance that metals penetrate into a resin gel ( λM). Only for Mn, Co and Cd were experimentally derived λM values greater than the diameter of a Chelex-100 resin bead. For most situations, then, the penetration into the binding layer is negligible and binding of trace metal ions can be regarded as instantaneous, validating the simple use and interpretation of DGT. For weakly binding metals at low pH the slower binding allows penetration, which may affect the DGT measurement.
Keywords: Diffusive gradients in thin films; Binding; Resin; Trace metals; Kinetics