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Analytica Chimica Acta (v.746, #)

Editorial Board (pp. iii).

Introducing nonlinear, multivariate ‘Predictor Surfaces’ for quantitative modeling of chemical systems with higher-order, coupled predictor variables by Rebecca B. Horton; Morgan McConico; Currie Landry; Tho Tran; Frank Vogt (pp. 1-14).

This Prediction SurfaceYβˆ(x) describes how the FT-IR spectrum of the microalgae species Dunaliella parva changes as a function of the carbon concentration x= c_C in the culturing medium. The black spectrum was obtained from a D. parva sample grown under an unknown carbon concentration which is determined by that concentration for which the spectrum fits closest onto the Predictor Surface.Display Omitted► Novel nonlinear chemometric calibration incorporates higher-order and coupled predictor terms. ► Predictor Surfaces visualize nonlinearities and coupling among chemical parameters. ► Microalgae cells act as in situ bioprobes for quantifying environmental parameters. ► Novel monitoring method for shifts in marine ecosystems and resulting ecological consequences.Innovations in chemometrics are required for studies of chemical systems which are governed by nonlinear responses to chemical parameters and/or interdependencies (coupling) among these parameters. Conventional and linear multivariate models have limited use for quantitative and qualitative investigations of such systems because they are based on the assumption that the measured data are simple superpositions of several input parameters. ‘ Predictor Surfaces’ were developed for studies of more chemically complex systems such as biological materials in order to ensure accurate quantitative analyses and proper chemical modeling for in-depth studies of such systems. Predictor Surfaces are based on approximating nonlinear multivariate model functions by multivariate Taylor expansions which inherently introduce the required coupled and higher-order predictor variables.As proof-of-principle for the Predictor Surfaces’ capabilities, an application from environmental analytical chemistry was chosen. Microalgae cells are known to sensitively adapt to changes in environmental parameters such as pollution and/or nutrient availability and thus have potential as novel in situ sensors for environmental monitoring. These adaptations of the microalgae cells are reflected in their chemical signatures which were then acquired by means of FT-IR spectroscopy. In this study, the concentrations of three nutrients, namely inorganic carbon and two nitrogen containing ions, were chosen. Biological considerations predict that changes in nutrient availability produce a nonlinear response in the cells’ biomass composition; it is also known that microalgae need certain nutrient mixes to thrive. The nonlinear Predictor Surfaces were demonstrated to be more accurate in predicting the values of these nutrients’ concentrations than principal component regression. For qualitative chemical studies of biological systems, the Predictor Surfaces themselves are a novel tool as they visualize nonlinearities and more importantly the coupling among predictor variables. Thus, they can serve as a novel tool for studies in bioanalytical chemistry, biology, and ecology.

Keywords: Nonlinear chemometrics; Multivariate polynomial Predictor Surfaces; In situ environmental sensing; Fourier transform infrared; Microalgae

Sample preparation methods for subsequent determination of metals and non-metals in crude oil—A review by Paola A. Mello; Juliana S.F. Pereira; Marcia F. Mesko; Juliano S. Barin; Erico M.M. Flores (pp. 15-36).

Display Omitted► Sample preparation strategies used for crude oil in last ten years are discussed. ► Methods related to wet digestion with concentrated acids or combustion are covered. ► Trends in sample preparation are discussed, as well as speciation analysis. ► Methods focusing on further metals and non-metals determination are discussed. ► Official methods are covered and certified reference materials are summarized.In this review sample preparation strategies used for crude oil digestion in last ten years are discussed focusing on further metals and non-metals determination. One of the main challenges of proposed methods has been to overcome the difficulty to bring crude oil samples into solution, which should be compatible with analytical techniques used for element determination. On this aspect, this review summarizes the sample preparation methods for metals and non metals determination in crude oil including those based on wet digestion, combustion, emulsification, extraction, sample dilution with organic solvents, among others. Conventional methods related to wet digestion with concentrated acids or combustion are also covered, with special emphasis to closed systems. Trends in sample digestion, such as microwave-assisted digestion using diluted acids combined with high-efficiency decomposition systems are discussed. On the other hand, strategies based on sample dilution in organic solvents and procedures recommended for speciation analysis are reported as well as the use of direct analysis in view of the recent importance for crude oil field. A compilation concerning sample preparation for crude oil provided by official methods as well as certified reference materials available for accuracy evaluation is also presented and discussed.

Keywords: Abbreviations; API; American Petroleum Institute gravity; ASTM; American Society for Testing and Materials; CCC; counter-current chromatography; CRMs; certified reference materials; DIHEN; direct injection high-efficiency nebulizer; DS-GF AAS; direct sampling graphite furnace atomic absorption spectrometry; ETV; electrothermal vaporization; FF AAS; filter furnace atomic absorption spectrometry; FMIC; focused microwave-induced combustion; FT-ICR-MS; Fourier transform ion cyclotron resonance mass spectrometry; GC-FID; gas chromatography with a flame ionization detector; GC-ICP-MS; gas chromatography coupled to inductively coupled plasma mass spectrometry; GC–MS; gas chromatography–mass spectrometry; GF AAS; graphite furnace atomic absorption spectrometry; GPC; gel permeation chromatography; HPA; High Pressure Asher™; HPLC; high performance liquid chromatography; HR-CS GF AAS; high-resolution continuum-source graphite furnace atomic absorption spectrometry; IC; ion chromatography; ICP-MS; inductively coupled plasma mass spectrometry; ICP-OES; inductively coupled plasma optical emission spectrometry; ID; isotope dilution; IP; Institute of Petroleum; ISO; International Organization for Standards; LA; laser ablation; LA-ICP-IDMS; laser ablation inductively coupled plasma isotope dilution mass spectrometry; LA-ICP-MS; laser ablation inductively coupled plasma mass spectrometry; LC–MS; liquid chromatography–mass spectrometry; LODs; limits of detection; LOQs; limits of quantification; MIC; microwave-induced combustion; NAA; neutron activation analysis; NIST; National Institute for Standards and Technology; O/W emulsion; oil-in-water emulsion; PTFE; polytetrafluoroethylene; RCC; residual carbon content; REEs; rare earth elements; RMs; reference materials; RSD; relative standard deviation; SARA; saturates, aromatics, resins and asphaltenes; SEC; size exclusion chromatography; μSEC; size exclusion microchromatography; SEC-HPLC-ICP-MS; size exclusion chromatography with high-performance liquid chromatography coupled to inductively coupled plasma mass spectrometry; SPE; solid phase extraction; SPME; solid phase microextraction; TXRF; total reflection X-ray fluorescence; USN; ultrasonic nebulizer; UV; ultraviolet radiation; W/O emulsion; water-in-oil emulsionSample digestion; Petroleum; Trace elements determination; ICP-OES; ICP-MS; Direct analysis

Insights into information contained in multiplicative scatter correction parameters and the potential for estimating particle size from these parameters by Yi-Chieh Chen; Suresh N. Thennadil (pp. 37-46).

Display Omitted► Indepth analysis of information contained in MSC parameters. ► MSC parameters vary systematically with particle size and concentration. ► A novel method to extract the mean particle diameter from the MSC parameters.This paper investigates the nature of information contained in scatter correction parameters. The study had two objectives. The first objective was to examine the nature and extent of information contained in scatter correction parameters. The second objective is to examine whether this information can be effectively extracted by proposing a method to obtain particularly the mean particle diameter from the scatter correction parameters. By using a combination of experimental data and simulated data generated using fundamental light propagation theory, a deeper and more fundamental insight of what information is removed by the multiplicative scatter correction (MSC) method is obtained. It was found that the MSC parameters are strongly influenced not only by particle size but also by particle concentration as well as refractive index of the medium. The possibility of extracting particle size information in addition to particle concentration was considered by proposing a two-step method which was tested using a 2-component and 4-component data set. This method can in principle, be used in conjunction with any scatter correction technique provided that the scatter correction parameters exhibit a systematic dependence with respect to particle size and concentration. It was found that the approach which uses the MSC parameters gave a better estimate of the particle diameter compared to using partial least squares (PLS) regression for the 2-component data. For the 4 component data it was found that PLS regression gave better results but further examination indicated this was due to chance correlations of the particle diameter with the two of the absorbing species in the mixture.

Keywords: Multiplicative scatter correction; Light scattering; Particle size estimation; Extended multiplicative scatter correction; Near infrared spectroscopy; Preprocessing

Electroanalytical and isothermal calorimetric study of As(III) complexation by the metal poisoning remediators, 2,3-dimercapto-1-propanesulfonate and meso-2,3-dimercaptosuccinic acid by Santiago Cavanillas; Elena Chekmeneva; Cristina Ariño; José Manuel Díaz-Cruz; Miquel Esteban (pp. 47-52).

Display Omitted► A voltammetric approach is applied to the study of As(III) complexation by poisoning remediators. ► Voltammetry measurements are complemented with Isothermal Titration Calorimetry (ITC) and Electrospray Ionization Mass Spectrometry (ESI-MS). ► Voltammetric data are analyzed by Gaussian Peak Adjustment (GPA) method.A recently developed methodology, which combines voltammetry, ITC, ESI-MS and several chemometric tools, has been applied for the first time to the study of As(III) complexes. The ligands considered, DMSA and DMPS, are commonly used to treat heavy metal poisoning. The study yields a reliable and consistent picture of the binding of As(III) by the chelating therapy agents DMSA and DMPS providing an unambiguous description of the stoichiometries of the complexes (ML₂, with the occasional appearance of ML in the case of DMSA), both ligands have stability constants of the same order, with a log β₂ of 9.2 and 9.8, respectively. These values confirm the potential efficiency of both ligands in the treatment of As(III) poisoning.

Keywords: 2,3-Dimercapto-1-propanesulfonate; Meso-2,3-dimercaptosuccinic acid; Arsenic; Voltammetry; Isothermal Titration Calorimetry; Multivariate Curve Resolution

Determination of arsenic and antimony in seawater by voltammetric and chronopotentiometric stripping using a vibrated gold microwire electrode by Pascal Salaün; Kristopher B. Gibbon-Walsh; Georgina M.S. Alves; Helena M.V.M. Soares; Constant M.G. van den Berg (pp. 53-62).

Display Omitted► Inorganic speciation of arsenic and antimony in seawater at a gold electrode. ► Sensitive methods both in relatively low acidic and in neutral conditions of pH. ► New experimental approaches to decrease detection limits and avoid interferences. ► As^III remains adsorbed on the gold surface after stripping during a short time. ► On-board analysis of As(III) at sub nanomolar levels.The oxidation potentials of As⁰/As^III and Sb⁰/Sb^III on the gold electrode are very close to each other due to their similar chemistry. Arsenic concentration in seawater is low (10–20nM), Sb occurring at ∼0.1 time that of As. Methods are shown here for the electroanalytical speciation of inorganic arsenic and inorganic antimony in seawater using a solid gold microwire electrode. Anodic stripping voltammetry (ASV) and chronopotentiometry (ASC) are used at pH≤2 and pH 8, using a vibrating gold microwire electrode. Under vibrations, the diffusion layer size at a 5μm diameter wire is 0.7μm. The detection limits for the As^III and Sb^III are below 0.1nM using 2min and 10min deposition times respectively. As^III and Sb^III can be determined in acidic conditions (after addition of hydrazine) or at neutral pH. In the latter case, oxidation of As⁰ to As^III was found to proceed through a transient As^III species. Adsorption of this species on the gold electrode at potentials where Sb^III diffused away is used for selective deposition of As^III. Addition of EDTA removes the interfering effect of manganese when analysing As^III. Imposition of a desorption step for Sb^III analysis is required. Total inorganic arsenic (iAs=As^V+As^III) can be determined without interference from Sb nor mono-methyl arsenious acid (MMA) at 1.6E_dep=−1V. Total inorganic antimony (iSb=Sb^V+Sb^III) is determined at pH 1 using E_dep=−1.8V without interference by As.The methods were tested in samples from the Irish Sea (Liverpool Bay). As^III was determined on-board ship immediately after sampling. As^III concentrations were found to range from 0.44 to 1.56nM and were higher near the coast. Sb^III was below the detection limit (<0.1nM Sb^III), iAs was comprised between 8 and 25nM while iSb varied from 0.5 to 1.7nM.

Keywords: Metalloids; Speciation; Seawater; Stripping; Vibrated gold microwire electrode; Monitoring

Functionalized polypyrrole nanotube arrays as electrochemical biosensor for the determination of copper ions by Meng Lin; Xiaoke Hu; Zhaohu Ma; Lingxin Chen (pp. 63-69).

Display Omitted► PPy nanotube arrays were electropolymerized using ZnO nanowire arrays as templates. ► PPy nanotube arrays were anchored onto ITO glass without any chemical linker. ► Using SWV, the biosensor was found to be highly sensitive and selective to Cu²⁺. ► The biosensor was successfully applied for the determination of Cu²⁺ in drinking water.A novel electrochemical biosensor based on functionalized polypyrrole (PPy) nanotube arrays modified with a tripeptide (Gly-Gly-His) proved to be highly effective for electrochemical analysis of copper ions (Cu²⁺). The vertically oriented PPy nanotube arrays were electropolymerized by using modified zinc oxide (ZnO) nanowire arrays as templates which were electrodeposited on indium–tin oxide (ITO) coated glass substrates. The electrodes were functionalized by appending pyrrole-α-carboxylic acid onto the surface of polypyrrole nanotube arrays by electrochemical polymerization. The carboxylic groups of the polymer were covalently coupled with the amine groups of the tripeptide, and its structural features were confirmed by attenuated total reflection infrared (ATR-IR) spectroscopy. The tripeptide modified PPy nanotube arrays electrode was used for the electrochemical analysis of various trace copper ions by square wave voltammetry. The electrode was found to be highly sensitive and selective to Cu²⁺ in the range of 0.1–30μM. Furthermore, the developed biosensor exhibited a high stability and reproducibility, despite the repeated use of the biosensor electrode.

Keywords: Electrochemical biosensor; Conducting polymer; Polypyrrole nanotube arrays; Zinc oxide nanowire arrays; Copper ions

Simultaneous electrochemical detection of multiple tumor markers based on dual catalysis amplification of multi-functionalized onion-like mesoporous graphene sheets by Jing Han; Ying Zhuo; Yaqin Chai; Ruo Yuan; Wen Zhang; Qiang Zhu (pp. 70-76).

In this work, we developed a novel multiple-label method and dual catalysis amplification for simultaneous detection of multiple tumor markers. Firstly, AuNPs modified Prussian blue nanoparticles and AuNPs modified nickel hexacyanoferrates nanoparticles decorated onion-like mesoporous graphene sheets, respectively (denoted as Au@PBNPs/O-GS and Au@NiNPs/O-GS) as distinguishable signal tags were utilized to label different detection antibodies. Subsequently, streptavidin and biotinylated alkaline phosphatase (bio-AP) were employed to block the possible remaining active sites. With the bio-AP, the amplification signals could be achieved by catalysis of the ascorbic acid 2-phosphate to in situ produce AA. Then, AA was further catalyzed by Au@PBNPs/O-GS and Au@NiNPs/O-GS nanocomposites, respectively, to obtain the higher signal responses. (A) Preparation procedure of Ab2 bioconjucates (bio-AP/SA/ anti-fPSA/Au@PBNPs/O-GS and bio-AP/SA/ anti-PSA/Au@NiNPs/O-GS). (B) Fabrication process of the immunosensor and the dual catalysis amplification mechanism.Display Omitted► A novel strategy for simultaneous determination of fPSA and PSA has been constructed. ► The Au@PBNPs/O-GS and Au@NiNPs/O-GS hybrids were employed as distinguishable signal tags. ► With the SA and bio-AP, the dual signal amplifications could be achieved. ► The proposed method offers promise for rapid and simple analysis of biological samples.In this work, a sandwich-type electrochemical immunosensor for simultaneous sensitive detection of prostate specific antigen (PSA) and free prostate specific antigen (fPSA) is fabricated. Gold nanoparticles (AuNPs) modified Prussian blue and nickel hexacyanoferrates nanoparticles were firstly prepared, respectively, and then decorated onion-like mesoporous graphene sheets (denoted as Au@PBNPs/O-GS and Au@NiNPs/O-GS) as distinguishable signal tags to label different detection antibodies. Subsequently, streptavidin and biotinylated alkaline phosphatase (bio-AP) were employed to block the possible remaining active sites. With the employment of the as prepared nanohybrids, the dual catalysis amplification can be achieved by catalysis of the ascorbic acid 2-phosphate to in situ produce AA in the presence of bio-AP, and then AA was further catalyzed by Au@PBNPs/O-GS and Au@NiNPs/O-GS nanohybrids, respectively, to obtain the higher signal responses. The experiment results show that the linear range of the proposed immunosensor for simultaneous determination of fPSA is from 0.02 to 10ngmL⁻¹ with a detection limit of 6.7pgmL⁻¹ and PSA is from 0.01 to 50ngmL⁻¹ with a detection limit of 3.4pgmL⁻¹ (S/N=3). Importantly, the proposed method offers promise for rapid, simple and cost-effective analysis of biological samples.

Keywords: Electrochemical immunosensor; Simultaneous detection; Dual catalysis amplification; Onion-like mesoporous graphene sheets; Gold nanoparticles modified Prussian blue nanoparticles; Gold nanoparticles modified nickel hexacyanoferrates nanoparticles

Novel sample preparation technique with needle-type micro-extraction device for volatile organic compounds in indoor air samples by Ikuo Ueta; Ayako Mizuguchi; Koji Fujimura; Susumu Kawakubo; Yoshihiro Saito (pp. 77-83).

Display Omitted► A novel needle-type particle-packed extraction device was developed. ► The extraction needle was designed for preconcentration of indoor air VOCs prior to GC–MS analysis. ► The needle showed excellent extraction and desorption performances for several VOCs. ► Sufficient storage performance of the extracted VOCs in the needle was also demonstrated. ► The results of the real indoor air samples obtained by the needle have a good agreement with the results by a conventional method.A novel needle-type sample preparation device was developed for the effective preconcentration of volatile organic compounds (VOCs) in indoor air before gas chromatography–mass spectrometry (GC–MS) analysis. To develop a device for extracting a wide range of VOCs typically found in indoor air, several types of particulate sorbents were tested as the extraction medium in the needle-type extraction device. To determine the content of these VOCs, air samples were collected for 30min with the packed sorbent(s) in the extraction needle, and the extracted VOCs were thermally desorbed in a GC injection port by the direct insertion of the needle. A double-bed sorbent consisting of a needle packed with divinylbenzene and activated carbon particles exhibited excellent extraction and desorption performance and adequate extraction capacity for all the investigated VOCs. The results also clearly demonstrated that the proposed sample preparation method is a more rapid, simpler extraction/desorption technique than traditional sample preparation methods.

Keywords: Volatile organic compound; Extraction; Indoor air; Needle; Gas chromatography–mass spectrometry

Identification of photodegradation products of Allura Red AC (E129) in a beverage by ultra high performance liquid chromatography–quadrupole-time-of-flight mass spectrometry by Fabio Gosetti; Ugo Chiuminatto; Eleonora Mazzucco; Giorgio Calabrese; Maria Carla Gennaro; Emilio Marengo (pp. 84-89).

Display Omitted► Formation of degradation products by photoirradiation of a beverage with E129 dye. ► Non-target screening analysis by QqTOF. ► QqTOF high resolution MS/MS data for elucidation of the unknown species. ► Interaction among the ingredient of the beverage. ► Identification of aromatic amines and aromatic amides.The study deals with the identification of the degradation products formed by simulated sunlight photoirradiation in a beverage that contains Allura Red AC (E129) dye. An UHPLC–MS/MS method that makes use of high resolution quadrupole-time-of-flight mass spectrometer, was developed. For the identification of the degradation products the software tool Information Dependent Acquisition (IDA) was used to automatically obtain information about the high resolution MS and MS/MS spectra of the species present.Accurate mass data were essential for the identification of the appropriate elemental composition: the elucidation of unknown chemical structures was obtained by using powerful software to mine the recorded chromatogram.The identified degradation products are formed from side-reactions and/or from the interactions taking place among the dye and other ingredients present in the beverage (i.e. ascorbic acid, citric acid, sucrose, aromas, strawberry juice and extract of chamomile flowers). The presence of aromatic amine or amide groups in the chemical structures of the degradation products suggests the potential hazard for the consumer health.

Keywords: Ultra high performance liquid chromatography; High resolution mass spectrometry; Allura Red; Degradation products; Photodegradation; Non-target screening

Visual and trap emission spectrometric detections of Ag (I) ion with mesoporous ZnO/CdS@SiO₂ core/shell nanocomposites by Chuanxiao Yang; Xiangying Sun; Bin Liu (pp. 90-97).

A novel type of mesoporous ZnO/CdS@SiO₂ core/shell nanostructures was prepared with a simple method, which was successfully applied to the visual fluorescence detection of Ag⁺ in an aqueous medium based on the enhanced trap emission and the variations of dual-emission fluorescence features of ZnO/CdS QDs core.Display Omitted► A novel type of ZnO/CdS core/shell QDs was prepared. ► A simple method for encapsulating water-soluble ZnO/CdS QDs into mesoporous SiO₂ shell. ► The enhanced trap emission of ZnO QDs core greatly improves detection selectivity. ► High sensitivity and selectivity for visual fluorescence detection of Ag (I).A new method for the preparation of mesoporous ZnO/CdS@SiO₂ core/shell nanostructure (CSN) has been developed. The mesoporous silica shells allow Ag⁺ to enter into the interior of the nanostructures to contact with ZnO/CdS core, accordingly causes the quenching of its band edge emission (475nm) along with a simultaneous enhancement of red emission at around 595nm. So, a novel visual fluorescence detection strategy for Ag⁺ ion is proposed based on a common core/shell Quantum dots nanostructure. Under optimal conditions, the enhanced fluorescence intensity at 595nm increased linearly with the concentration of Ag⁺ ion ranging from 0.03μM to 0.24μM with a detection limit (3 σ) of 3.3nM.

Keywords: Visual fluorescence detection; Trap emission; Dual-emission fluorescence; Mesoporous ZnO/CdS@SiO; ₂; core/shell nanostructures; Ag; ⁺; ion

Simultaneous trace-levels determination of Hg(II) and Pb(II) ions in various samples using a modified carbon paste electrode based on multi-walled carbon nanotubes and a new synthesized Schiff base by Abbas Afkhami; Hasan Bagheri; Hosein Khoshsafar; Mohammad Saber-Tehrani; Masoumeh Tabatabaee; Ali Shirzadmehr (pp. 98-106).

Display Omitted► A new chemically modified carbon paste electrode was constructed and used. ► A new Schiff base and multi-walled carbon nanotube was used as a modifier. ► The electrochemical properties of the modified electrode were studied. ► The electrode was used to the simultaneous determination of Pb²⁺ and Hg²⁺.A modified carbon paste electrode based on multi-walled carbon nanotubes (MWCNTs) and 3-(4-methoxybenzylideneamino)-2-thioxothiazolodin-4-one as a new synthesized Schiff base was constructed for the simultaneous determination of trace amounts of Hg(II) and Pb(II) by square wave anodic stripping voltammetry. The modified electrode showed an excellent selectivity and stability for Hg(II) and Pb(II) determinations and for accelerated electron transfer between the electrode and the analytes. The electrochemical properties and applications of the modified electrode were studied. Operational parameters such as pH, deposition potential and deposition time were optimized for the purpose of determination of traces of metal ions at pH 3.0. Under optimal conditions the limits of detection, based on three times the background noise, were 9.0×10⁻⁴ and 6.0×10⁻⁴μmolL⁻¹ for Hg(II) and Pb(II) with a 90s preconcentration, respectively. In addition, the modified electrode displayed a good reproducibility and selectivity, making it suitable for the simultaneous determination of Hg(II) and Pb(II) in real samples such as sea water, waste water, tobacco, marine and human teeth samples.

Keywords: Simultaneous determination; Square wave voltammetry; Modified carbon paste electrodes; Heavy metals

The sandwich-type electrochemiluminescence immunosensor for α-fetoprotein based on enrichment by Fe₃O₄-Au magnetic nano probes and signal amplification by CdS-Au composite nanoparticles labeled anti-AFP by Hankun Zhou; Ning Gan; Tianhua Li; Yuting Cao; Saolin Zeng; Lei Zheng; Zhiyong Guo (pp. 107-113).

Display Omitted► Sandwich immunoreaction, testing a large number of samples simultaneously. ► The magnetic separation and enrichment by Fe₃O₄-Au magnetic nano probes. ► The amplification of detection signal by CdS-Au composite nanoparticles labeled anti-AFP. ► Almost no background signal, which greatly improve the sensitivity of detection.A novel and sensitive sandwich-type electrochemiluminescence (ECL) immunosensor was fabricated on a glassy carbon electrode (GCE) for ultra trace levels of α-fetoprotein (AFP) based on sandwich immunoreaction strategy by enrichment using magnetic capture probes and quantum dots coated with Au shell (CdS-Au) as the signal tag. The capture probe was prepared by immobilizing the primary antibody of AFP (Ab1) on the core/shell Fe₃O₄-Au nanoparticles, which was first employed to capture AFP antigens to form Fe₃O₄-Au/Ab1/AFP complex from the serum after incubation. The product can be separated from the background solution through the magnetic separation. Then the CdS-Au labeled secondary antibody (Ab2) as signal tag (CdS-Au/Ab2) was conjugated successfully with Fe₃O₄-Au/Ab1/AFP complex to form a sandwich-type immunocomplex (Fe₃O₄-Au/Ab1/AFP/Ab2/CdS-Au), which can be further separated by an external magnetic field and produce ECL signals at a fixed voltage. The signal was proportional to a certain concentration range of AFP for quantification. Thus, an easy-to-use immunosensor with magnetic probes and a quantum dots signal tag was obtained. The immunosensor performed at a level of high sensitivity and a broad concentration range for AFP between 0.0005 and 5.0ngmL⁻¹ with a detection limit of 0.2pgmL⁻¹. The use of magnetic probes was combined with pre-concentration and separation for trace levels of tumor markers in the serum. Due to the amplification of the signal tag, the immunosensor is highly sensitive, which can offer great promise for rapid, simple, selective and cost-effective detection of effective biomonitoring for clinical application.

Keywords: Electrochemiluminescence; Sandwich immunoreaction; Magnetic capture probes; CdS-Au signal tag

Novel tandem column method for the rapid isolation of radiostrontium from human urine by Cory A. Hawkins; Ilya A. Shkrob; Carol J. Mertz; Mark L. Dietz; Michael D. Kaminski (pp. 114-122).

Display Omitted► Method for separation and preconcentration of radiostrontium from human urine. ► Recoveries >98%, concentration factor of ca. 50, processing time of nearly 1h. ► Retention model developed to assist optimization of separations on Diphonix^® column. ► Semi-automated sample preparation device developed.A method has been developed for the isolation of strontium from human urine for subsequent determination in sample volumes as low as 5–20mL. This method involves the acidification of the sample using methanesulfonic acid and its decolorization using charcoal, treatment of the filtrate with Diphonix^® resin, and subsequent concentration of strontium on Sr resin. Data from retention model simulations provided the initial conditions which were then optimized by actual column separations. Diphonix^® resin was shown to be effective at removing alkali metal ions from the urine matrix under conditions that retain higher valence ions. The suggested processing method provides 99% recovery of Sr²⁺, a concentration factor of 50, and an expected per sample processing time of less than 1h.

Keywords: Strontium; Human urine; Rapid; Method; Extraction chromatography

Ionic liquids as porogens in the microwave-assisted synthesis of methacrylate monoliths for chromatographic application by Brenda Singco; Chen-Lan Lin; Yi-Jie Cheng; Yung-Han Shih; Hsi-Ya Huang (pp. 123-133).

Display Omitted► An efficient and cleaner monoliths preparation utilizing ionic liquids in conjunction with microwave ► These ionic liquids with varied cation alkyl chain and anion type successfully tuned the morphology of different alkyl methacrylates ► Small molecules and peptide digests separated well in these monoliths.Several imidazolium-based ionic liquids (ILs) with varying cation alkyl chain length (C₄–C₁₀) and anion type (tetrafluoroborate ([BF₄]⁻), hexafluorophosphate ([PF₆]⁻) and bis(trifluoromethylsulfonyl)imide ([Tf₂N]⁻)) were used as reaction media in the microwave polymerization of methacrylate-based stationary phases. Scanning electron micrographs and backpressures of poly(butyl methacrylate-ethylene dimethacrylate) (poly(BMA-EDMA)) monoliths synthesized in the presence of these ionic liquids demonstrated that porosity and permeability decreased when cation alkyl chain length and anion hydrophobicity were increased. Performance of these monoliths was assessed for their ability to separate parabens by capillary electrochromatography (CEC). Intra-batch precision ( n=3 columns) for retention time and peak area ranged was 0.80–1.13% and 3.71–4.58%, respectively. In addition, a good repeatability of RSD_{Retention time}=<0.30% and ∼1.0%, RSD_{Peak area}=<1.30% and <4.3%, and RSD_Efficiency=<0.6% and <11.5% for intra-day and inter-day, respectively exemplify monolith performance reliability for poly(BMA-EDMA) fabricated using 1-hexyl-3-methylimidazolium tetrafluoroborate ([C₆mim][BF₄]) porogen. This monolith was also tested for its potential in nanoLC to separate protein digests in gradient mode. ILs as porogens also fabricated different alkyl methacrylate (AMA) (C4–C18) monoliths. Furthermore, employing binary IL porogen mixture such as 1-butyl-3-methylimidazolium tetrafluoroborate ([C₄mim][BF₄]) and 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([C₄mim][Tf₂N]) successfully decreased the denseness of the monolith, than when using [C₄mim][Tf₂N] IL alone, enabling a chromatographic run to be performed with 1:1 ratio produced baseline separation for the analytes. The combination of ILs and microwave irradiation made polymer synthesis very fast (∼10min), entirely green (organic solvent-free) and energy saving process.

Keywords: Ionic liquid; Chromatography; Methacrylate monolith; Microwave irradiation; Porogen

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Analytica Chimica Acta (v.746, #)