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Analytica Chimica Acta (v.734, #)

Editorial Board (pp. iii).

Carbon nanotubes applications in separation science: A review by Antonio V. Herrera-Herrera; Miguel Ángel González-Curbelo; Javier Hernández-Borges; Miguel Ángel Rodríguez-Delgado (pp. 1-30).
Display Omitted► The use of CNTs in Separation Science in the period 2009–2011 is reviewed. ► CNTs as stationary phases in LC, CE and GC. ► CNTs as pseudostationary phases in EKC. ► CNTs as sorbents in SPE and SPME. ► Other uses of CNTs in separation science, as LDI substrates or in membranes.Due to the intensive and multidisciplinary research carried out during the last two decades on carbon nanotubes (CNTs), the scientific community understands nowadays much better the chemistry, structure and properties of these interesting materials. In fact, they have found their particular place in a wide number of application fields (nanotechnology, electronics, optics, medicine, etc.) among which Analytical Chemistry is becoming more and more important. The aim of this review is to provide an updated report of the most recent manuscripts (years 2009–2011) regarding the use of CNTs in Separation Science. In particular, the use of CNTs as solid-phase extraction and microextraction sorbents, as part of membranes as well as their use in chromatography and electrophoresis will be discussed and commented. Besides, although not as fully related to Separation Science as the previous techniques, the use of CNTs as laser desorption/ionization substrates has also been considered because of its importance in the field.

Keywords: Abbreviations; ABTZ; 2-aminobenzothiazole; APDC; ammonium pyrrolidine dithiocarbamate; BGE; background electrolyte; BMA; butylmethacrylate; BMImBF; 4; 1-butyl-3-methylimidazolium tetrafluoroborate; BMImPF; 6; 1-butyl-3-methylimidazolium hexafluorophosphate; BSA; bovine serum albumin; ButOH; butanol; C; 12; MImCl; 1-dodecyl-3-methylimidazolium chloride; C; 12; MImHSO; 3; 1-dodecyl-3-methylimidazolium hydrogen sulfate; C; 12; MImCH; 3; SO; 3; 1-dodecyl-3-methylimidazolium methanesulfonate; C; 12; MIm-NO; 3; 1-dodecyl-3-methylimidazolium nitrate; CAR–PDMS; carboxen–poly(dimethylsiloxane); CNTs; carbon nanotubes; CTAC; cetyltrimethylammonium chloride; CVD; chemical vapor deposition; CW–DVB; carbowax–divinylbenzene; D2EHPA; di-(2-ethyl hexyl phosphoric acid); DMF; dimethylformamide; dSPE; dispersive SPE; DWCNTs; double walled carbon nanotubes; EDA; ethylenediamine; EDMA; ethylene dimethacrylate; EtOH; ethanol; FI; flow injection; FT-IR; Fourier transform infrared spectroscopy; GMA; glycidyl methacrylate; HF; hollow fiber; IDA; iminodiacetic acid; IL; ionic liquid; m-CNTs; magnetic carbon nanotubes; MES; mono-(2-(methacryloyloxy)ethyl) succinate; MIP-CNTs; molecularly imprinted polymer-carbon nanotubes; MMA; methacrylamide; MMMs; mixed matrix membranes; MWCNTs; multi-walled carbon nanotubes; NaDDBS; sodium dodecylbenzenesulfonate; NBHAE; N,N′-bis(2-hydroxybenzylidene)-2,2′(aminophenylthio)ethane; NPs; nanoparticles; NTC; nontubular carbon; ODA; octadecylamine; ODS; octadecylsilyl; o-MWCNTs; oxidized multi-walled carbon nanotubes; OT; open-tubular; P2AT; poly(2-amino thiophenol); PA; polyacrylate; PAHs; Polycyclic aromatic hydrocarbons; PAN; 1-(2-pyridylazo)-2-naphthol; PANI; polyaniline; PBNPI; poly(bisphenol A-co-4-nitrophthalic anhydride-co-1,3-phenylene diamine); PCBs; polychlorinated biphenyls; PEDOT; poly (3,4-dixythiophene); PEG; polyethylene glycol; PES; polyethersulfone; PDDA; poly(diallyldimethylammonium chloride); PDMS; polydimethylsiloxane; PDMS–DVB; poly(dimethylsiloxane)–divinylbenzene; PIDA; phenyl-iminodiacetic acid; PPy; poly(pirrole); PrOH; propanol; PS–DVB; polystyrene–divinylbenzene; PSF; polysulfone; PSPs; pseudostationary phases; PVA; poly (vinyl alcohol); SDS; sodium dodecyl sulphate; SEM; scanning electron microscopy; SNs; silica nanoparticles; SWCNHs; single-walled carbon nanohorns; SWCNTs; single-walled carbon nanotubes; TAA; tris(2-aminoethyl)amine; TGA; thermal gravimetric analysis; TOPO; tri-n-octyl phosphine oxide; VOCs; volatile organic compoundsCarbon nanotubes; Review; Analytical chemistry; Separation science


Recent developments and applications of screen-printed electrodes in environmental assays—A review by Meng Li; Yuan-Ting Li; Da-Wei Li; Yi-Tao Long (pp. 31-44).
The configuration designs and printing materials of screen-printed electrodes (SPEs) are developed over the past decades and the applications of SPEs in environmental analysis are reviewed in this article.Display Omitted► Screen-printed electrodes (SPEs) are economical substrates that attract interests. ► SPEs have been utilised for the rapid in situ analysis of environmental pollutants. ► The configuration designs and printing materials of SPEs are developed a lot. ► Some pretreatment techniques of surfaces are especially addressed.Screen-printed electrodes (SPEs), which are used as economical electrochemical substrates, have gone through significant improvements over the past few decades with respect to both their format and their printing materials. Because of their advantageous material properties, such as disposability, simplicity, and rapid responses, SPEs have been successfully utilised for the rapid in situ analysis of environmental pollutants. This critical review describes the basic fabrication principles, the configuration designs of SPEs and the hybrid analytical techniques based on SPEs. We mainly overview the electrochemical applications of SPEs in environmental analysis over the past 3 years, including the determination of organic compounds, heavy metals and gas pollutants.

Keywords: Abbreviations; AChE; acetylcholinesterase; AuNPs; gold nanoparticles; ASV; anodic stripping voltammetry; BChE; butyrylcholinesterase; BOD; biochemical oxygen demand; BiSPEs; bismuth-modified SPEs; μBSPEs; screen-printed microband electrodes; CB; carbon black; CC; catechol; CNTs; carbon nanotubes; CO; carbon monoxide; COD; chemical oxygen demand; CoPC; cobalt-phthalocyanine; CTAB; cetyltrimethylammonium bromide; CTS; Chitosan, poly-[β-1-4]-2-amino-2-deoxy-; d; -glucopyranose; CV; cyclic voltammetry; DAB; 1,2-diaminobenzene; DPV; differential pulse voltammetry; ECL; electrochemiluminescence; FIA; flow injection analysis; Fe; 3; O; 4; /Au; Au-colloid-coated Fe; 3; O; 4; GCE; glassy carbon electrode; GO; graphene oxide; HQ; hydroquinone; HRP; horseradish peroxidase; ISEs; ion-selective electrodes; ITO; tin-doped indium oxide; Lac; laccase; LPG; liquefied petroleum gas; LSM; strontium-doped lanthanum manganite; MnO; x; manganese oxide; MWCNTs; multi-walled carbon nanotubes; NO; x; nitrogen oxide; 1-OHP; 1-hydroxypyrene; Ops; organophosphate pesticides; OPH; OP hydrolase; PAHs; polyaromatic hydrocarbons; PANI; polyaniline; PANI-MB; plyaniline-methylene blue; PANI-PDTDA; plyaniline-poly(2,2′-dithiodianiline); PAP; polyazetidineprepolymer; PASE; 1-pyrenebutanoic acid, succinimidyl ester; PPO; polyphenol oxidase enzyme; SAMs; self-assembled monolayers; SERS; surface-enhanced Raman scattering; SPBE; screen-printed bismuth electrode; SPCE; screen-printed carbon electrode; SPEs; screen-printed electrodes; SPUMEs; screen-printed edge band ultramicroelectrodes; Tyr; tyrosinase; VOCs; volatile organic compounds; YSZ; yttria-stabilised zirconiaScreen-printed electrodes; Electrochemistry; Environmental analysis; Recent developments


Application of direct calibration in multivariate image analysis of heterogeneous materials by Benoît Jaillais; Jean-Claude Boulet; Jean-Michel Roger; François Balfourier; Pierre Berbezy; Dominique Bertrand (pp. 45-53).
Display Omitted► Screening of wheat accessions based on multivariate images. ► Processing of multivariate images by Direct Calibration. ► Useful and harmful spaces determination and choice of dimensions in PCA improved. ► Possible application to very large images, such as hyperspectral images. ► False RGB images in which an RGB channel corresponds to a specific tissue.Many scientific instruments produce multivariate images characterized by three-way tables, an element of which represents the intensity value at a spatial location for a given spectral channel. A problem frequently encountered is to attempt estimating the contributions of some compounds at each location of these images. Usual regression methods of calibration, such as PLS, require having a matrix of calibration X ( n× p) and the corresponding vector y of the dependent variable ( n×1). X can be built up by sampling pixel-vectors in the images, but y is sometimes difficult to obtain, if the surface of the samples is formed by chemically heterogeneous regions. In this case, the quantitative analyses related to y may be difficult, if the pixels represent very small areas (for example on microscopic images) or very large ones (satellite images). This is for example the case when dealing with biological solid samples representing different tissues. Direct Calibration (DC), sometimes referred to as “spectral unmixing”, do not require having such a calibration set. However, it is indeed needed to have both a matrix of “perturbing” pixel-vectors (noted K) and a vector of the “pure” component spectrum to be analyzed ( p), which are more easily obtainable. For estimating the contribution, the unknown pixel vectorx and the pure spectrum p are first projected orthogonally onto K giving the vectors x⊥ onto p⊥, respectively. The contribution is then estimated by a second projection of x⊥ onto p⊥. A method, based on principal component analysis, for determining the optimal dimensions of K is proposed. DC was applied on a collection of multivariate images of kernel of wheat to estimate the proportion of three tissues, namely out-layers, “ waxy” endosperm and normal endosperm. The eventual results are presented as images of wheat kernels in false colors associated to the estimated proportions of the tissues. It is shown that DC is appropriate for estimating contributions in situations in which the more usual methods of calibration cannot be applied.

Keywords: Direct Calibration; Multivariate imaging; Orthogonal subspace projection; Wheat; Endosperm


Absolute quantitative analysis for sorbic acid in processed foods using proton nuclear magnetic resonance spectroscopy by Takashi Ohtsuki; Kyoko Sato; Naoki Sugimoto; Hiroshi Akiyama; Yoko Kawamura (pp. 54-61).
Display Omitted► A method using qHNMR was applied and validated to determine SA in processed foods. ► This method has good accuracy, precision, selectiveness, and linearity. ► The proposed method is more rapid and simple than the conventional method. ► We found that the proposed method is reliable for the accurate determination of SA. ► This method can be used for the monitoring of SA in processed foods.An analytical method using solvent extraction and quantitative proton nuclear magnetic resonance (qHNMR) spectroscopy was applied and validated for the absolute quantification of sorbic acid (SA) in processed foods. The proposed method showed good linearity. The recoveries for samples spiked at the maximum usage level specified for food in Japan and at 0.13gkg−1 (beverage: 0.013gkg−1) were larger than 80%, whereas those for samples spiked at 0.063gkg−1 (beverage: 0.0063gkg−1) were between 56.9 and 83.5%. The limit of quantification was 0.063gkg−1 for foods (and 0.0063gkg−1 for beverages containing Lactobacillus species). Analysis of the SA content of commercial processed foods revealed quantities equal to or greater than those measured using conventional steam-distillation extraction and high-performance liquid chromatography quantification. The proposed method was rapid, simple, accurate, and precise, and provided International System of Units traceability without the need for authentic analyte standards. It could therefore be used as an alternative to the quantification of SA in processed foods using conventional method.

Keywords: Absolute quantification; Food analysis; Processed food; Quantitative proton nuclear magnetic resonance spectroscopy; Sorbic acid


Determination of beta-conglycinin in soybean and soybean products using a sandwich enzyme-linked immunosorbent assay by Wenjing Hei; Zhen Li; Xi Ma; Pingli He (pp. 62-68).
Display Omitted► A double antibody sandwich ELISA was developed to measure β-conglycinin in soybean and soybean products. ► The assay had a practical working range between 3 and 100ngmL−1, and showed no cross-reactivity with other proteins. ► The assay was used to analyze 469 soybean seeds and five soybean products treated with different processing techniques.Soybean protein has long been recognized as a source of dietary allergens for humans and animals with β-conglycinin being the major allergen. This paper presents a sandwich enzyme-linked immunosorbent assay (ELISA) that allows for the detection of trace amount of β-conglycinin in soybean and soybean products. In the sandwich ELISA, mouse anti-β-conglycinin monoclonal antibody (Mab 5C5) was used as coating antibody, and rabbit anti-β-conglycinin polyclonal antibody (Pab) was used as secondary antibody. The assay showed high specificity for β-conglycinin with minimum cross-reactions with other soy proteins. The practical working range for the determination of β-conglycinin using the developed assay was 3–100ngmL−1 and the limit of determination (LOD) was 1.63ngmL−1. The recoveries of β-conglycinin in spiked soybean samples were between 88.1% and 106.6% with relative standard deviation less than 8.9% (intra-day) and 13.1% (inter-day). The developed method was used to analyze 469 soybean seed samples from different sources as well as five soybean products treated with different processing techniques. The data showed that the concentration of β-conglycinin decreased significantly after processing, especially for soybean protein isolation, where the concentration of β-conglycinin dropped to nearly zero. The assay provides a specific and sensitive method for the screening of β-conglycinin and allows for further investigation into hypersensitive mechanisms of soybean proteins and development of soybean processing techniques to reduce their negative effects.

Keywords: Soybean; Beta-conglycinin; Polyclonal antibody; Monoclonal antibody; Enzyme-linked immunosorbent assay


A nanoparticle-supported fluorescence resonance energy transfer system formed via layer-by-layer approach as a ratiometric sensor for mercury ions in water by Chao Ma; Fang Zeng; Guangfei Wu; Shuizhu Wu (pp. 69-78).
Display Omitted► A FRET-based ratiometric sensor for Hg2+ in water was developed. ► The donors and acceptors were confined in specific sites of the polymer nanoparticles. ► The layer-by-layer approach ensures tunable energy transfer efficiency.This article describes the design and preparation of a novel fluorescence resonance energy transfer (FRET)-based ratiometric sensor with the polymer nanoparticle as scaffold for detecting Hg2+ in aqueous media. In this study, a fluorescent dye fluorescein isothiocyanate (FITC, served as the donor) and a spirolactam rhodamine derivative (SRHB, served as mercury ion probe) were covalently attached onto polyethylenimine (PEI) and polyacrylic acid (PAA) respectively; and a ratiometric sensing system was then formed through the deposition of the donor- and probe-containing polyelectrolytes onto the negatively charged polymer particles via the layer-by-layer approach. The ratiometric fluorescent signal change of the system is based on the intra-particle fluorescence resonance energy transfer (FRET) process modulated by mercury ions. Under optimized structural and experimental conditions, the particle-based detection system exhibits stable response for Hg2+ in aqueous media. More importantly, in this newly developed particle-based detection system formed by LBL approach, varied numbers of the PAA/PEI layers which served as the spacer could be placed between the donor-containing layer and the probe-containing layer, hence the donor–acceptor distance and energy transfer efficiency could be effectively tuned (from ca. 25% to 76%), this approach has well solved the problem for many particle-based FRET systems that the donor–acceptor distance cannot be precisely controlled. Also, it is found that the ratiometric sensor is applicable in a pH range of 4.6–7.3 in water with the detection limit of 200nM. This approach may provide a new strategy for ratiometric detection of analytes in some environmental and biological applications.

Keywords: Mercury; Fluorescence; Layer-by-layer; Energy transfer; Sensor


Study on low-cost calibration-free pH sensing with disposable optical sensors by Xudong Ge; Yordan Kostov; Leah Tolosa; Govind Rao (pp. 79-87).
Display Omitted► Development of disposable calibration-free optical pH sensor. ► Derivation of theoretical calibration model. ► Strategy to eliminate inter-coaster inconsistency.As labor costs become more expensive, less labor-intensive disposable devices have become more ubiquitous. Similarly, the disposable optical pH sensor developed in our lab could provide a convenient yet cost-effective way for pH sensing in processes that require stringent pH control. This optical pH sensor is prepared in uniform individual lots of 100–200 sensors per lot. Calibration is accomplished on a few randomly selected sensors out of each lot. We show that all others in the same lot can then be used directly without requiring individual calibration. In this paper, a calibration model is derived to include all the factors that affect the signal of the disposable sensor. Experimental results show that the derived calibration model fits the experimental data. The readings of 28 randomly selected disposable sensors with 4 sensors from each of the 7 lots show an error less than 0.1 pH units in the useful sensing range of the sensor. The calibration model indicates that if further improvement on precision is desired, more uniform porous material and more advanced coating techniques will be required. When it comes to the effects of the varying coasters, house-made low-cost fluorometers, the variability in the brightness ratio of the blue-to-violet LEDs is the primary reason for the lack of precision. Other factors like LED light intensity distribution, optical properties of the filters and electronics also contribute to the coaster-to-coaster difference, but to a lesser extent. Two different methods for correcting the instrument variations were introduced. After correction, the collective reading errors for all the tested instruments were reduced to less than 0.2 pH units within the sensor's useful sensing range. Based on this result, our lab is currently implementing further improvements in modifying the coasters to equalize the ratios of blue-to-violet LED brightness.

Keywords: Disposable; Calibration-free; Optical sensor; pH


Unraveling virus identity by detection of depleted probes with capillary electrophoresis by Chin-Yu Wang; Tzu-Hung Hsiao; Liang-Hui Chu; Yi-Ling Lin; Jau-Ling Huang; Chung-Hsuan Chen; Konan Peck (pp. 88-92).
Display Omitted► The probe depletion approach allowed discriminating from one base for virus identity. ► The probe depletion method abrogating the need for fluorophore labeled in capillary. ► The probe depletion approach is applicable to both RNA and DNA viruses. ► The working principle may be applied in miniaturized portable devices in the future.With the emergence of new viral infections and pandemics, there is a need to develop faster methods to unravel the virus identities in a large number of clinical samples. This report describes a virus identification method featuring high throughput, high resolution, and high sensitivity detection of viruses. Identification of virus is based on liquid hybridization of different lengths of virus-specific probes to their corresponding viruses. The probes bound to target sequences are removed by a biotin–streptavidin pull-down mechanism and the supernatant is analyzed by capillary electrophoresis. The probes depleted from the sample appear as diminished peaks in the electropherograms and the remaining probes serve as calibrators to align peaks in different capillaries. The virus identities are unraveled by a signal processing and peak detection algorithm developed in-house. Nine viruses were used in the study to demonstrate how the system works to unravel the virus identity in single and double virus infections. With properly designed probes, the system is able to distinguish closely related viruses. The system takes advantage of the high resolution feature of capillary electrophoresis to resolve probes that differ by length. The method may facilitate virus identity screen from more candidate viruses with an automated 4-color DNA sequencer.

Keywords: Virus identification; Capillary electrophoresis; Liquid hybridization; Signal processing


Development of an immunomagnetic bead-based time-resolved fluorescence immunoassay for rapid determination of levels of carcinoembryonic antigen in human serum by Jing-Yuan Hou; Tian-Cai Liu; Guan-Feng Lin; Zhi-Xiong Li; Li-Ping Zou; Ming Li; Ying-Song Wu (pp. 93-98).
Display Omitted► Magnetic beads was used as the solid phase for TRFIA. ► The linearity range was broadened greatly compared with conventional TRFIA method. ► The analysis time was significantly shorter compared with conventional TRFIA method. ► This method could be developed for practical clinical detections of tumor-associated antigens.A novel immunoassay for the determination of tumor markers in human serum was established by combining a time-resolved fluoroimmunoassay (TRFIA) and immunomagnetic separation. Based on a sandwich-type immunoassay format, analytes in samples were captured by magnetic beads coated with one monoclonal antibody and “sandwiched” by another monoclonal antibody labeled with europium chelates. The immunocomplex was separated and washed by exposure to a magnetic field and treatment with enhancement solution; fluorescence was then measured according to the number of europium ions dissociated. Levels of the model analyte, carcinoembryonic antigen (CEA), were determined in a linear range (1–1000ngmL−1) with a limit of detection of 0.5ngmL−1 under optimal conditions. The reproducibility, recovery, and specificity of the immunoassay were demonstrated to be acceptable. To evaluate this novel assay for clinical applications, 239 serum samples were evaluated. Compared with the conventional TRFIA and chemiluminescence immunoassay (CLIA), the correlation coefficients of the developed immunoassay were 0.985 and 0.975, respectively. These results showed good correlation and confirmed that our method is feasible and could be used for the clinical determination of CEA (or other tumor antigens) in human serum.

Keywords: Magnetic beads; Time-resolved fluoroimmunoassay; Carcinoembryonic antigen


Molecular imprinting solid phase extraction for selective detection of methidathion in olive oil by Idriss Bakas; Najwa Ben Oujji; Ewa Moczko; Georges Istamboulie; Sergey Piletsky; Elena Piletska; Ihya Ait-Ichou; Elhabib Ait-Addi; Thierry Noguer; Régis Rouillon (pp. 99-105).
Display Omitted► Development of a molecular imprinted polymer (MIP), based on molecular modelling for methidathion (organophosphorus insecticide). ► Optimisation of a protocol of extraction based on molecularly imprinted solid phase extraction (MISPE). ► Application of the optimised protocol for the extraction of methidathion from olive oil.A specific adsorbent for extraction of methidathion from olive oil was developed. The design of the molecularly imprinted polymer (MIP) was based on the results of the computational screening of the library of polymerisable functional monomers. MIP was prepared by thermal polymerisation using N,N’-methylene bisacrylamide (MBAA) as a functional monomer and ethylene glycol dimethacrylate (EGDMA) as a cross-linker. The polymers based on the itaconic acid (IA), methacrylic acid (MAA) and 2-(trifluoromethyl)acryl acid (TFMAA) functional monomers and one control polymer which was made without functional monomers with cross-linker EGDMA were also synthesised and tested. The performance of each polymer was compared using corresponding imprinting factor. As it was predicted by molecular modelling the best results were obtained for the MIP prepared with MBAA. The obtained MIP was optimised in solid-phase extraction coupled with high performance liquid chromatography (MISPE-HPLC-UV) and tested for the rapid screening of methidathion in olive oil. The proposed method allowed the efficient extraction of methidathion for concentrations ranging from 0.1 to 9mgL−1 ( r2=0.996). The limits of detection (LOD) and quantification (LOQ) in olive oil were 0.02mgL−1 and 0.1mgL−1, respectively. MIPs extraction was much more effective than traditional C18 reverse-phase solid phase extraction.

Keywords: Computational modelling; Methidathion; MIP; Olive oil
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