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Analytica Chimica Acta (v.720, #)

Editorial Board (pp. iii).

Hierarchical dendritic gold microstructure-based aptasensor for ultrasensitive electrochemical detection of thrombin using functionalized mesoporous silica nanospheres as signal tags by Juan Tang; Dianping Tang; Reinhard Niessner; Dietmar Knopp; Guonan Chen (pp. 1-8).

Display Omitted► We designed a simple and facile electrochemical aptasensor for ultrasensitive detection of thrombin. ► A new signal tag with nanogold-thionine-functionalized mesoporous silica nanospheres. ► Densely packed hierarchical dendritic gold microstructures (HDGMs) with secondary and tertiary branches as matrices.A sensitive electrochemical approach for the detection of thrombin was designed by using densely packed hierarchical dendritic gold microstructures (HDGMs) with secondary and tertiary branches as matrices, and thionine-functionalized mesoporous silica nanospheres as signal tags. To prepare the signal tags, the positively charged thionine (as an indicator) was initially adsorbed onto the mesoporous silica nanoparticles (MSNs). Then [AuCl₄]⁻ ions were in situ reduced on the thionine-modified MSNs by ascorbic acid to construct nanogold-decorated MSNs (GMSNs). The formed GMSNs were employed as label of the aminated aptamers. The assay was carried out in PBS, pH 7.4 with a sandwich-type assay mode by using the assembled thionine in the GMSNs as indicators. Compared with the pure silica nanoparticles, mesoporous silica could provide a larger surface for the immobilization of biomolecules and improve the sensitivity of the aptasensor. Under optimal conditions, the electrochemical aptasensors exhibited a wide linear range from 0.001 to 600ngmL⁻¹ (i.e. 0.03pM to 0.018μM thrombin) with a low detection limit (LOD) of 0.5pgmL⁻¹ (≈15fM) thrombin at 3 σ. No obvious non-specific adsorption was observed during a series of analyses to detect target analyte. The precision, selectivity and stability of the aptasensors were acceptable. Importantly, the methodology was evaluated with thrombin spiked samples in blank fetal calf serum, and the recoveries were 94.2–112%, indicating an exciting potential for thrombin detection.

Keywords: Electrochemical aptasensor; Thrombin; Hierarchical dendritic gold microstructures; Nanolabels; Mesoporous silica nanostructures

Certified reference materials for analytical mercury speciation in biological and environmental matrices: Do they meet user needs?; a review by Carmen Ibáñez-Palomino; José Fermín López-Sánchez; Angels Sahuquillo (pp. 9-15).

Display Omitted► We review the application and usefulness of current CRMs for analytical mercury speciation. ► Similarity of CRMs with field samples assures valuable information. ► There is a lack of CRMs for Hg speciation in soils and waters. ► Spiking/fortification procedures must be carefully designed to simulate the behavior of Hg species naturally occurring.The usefulness of a certified reference material (CRM) for analytical method validation and quality control purposes is attributed mainly to its key properties, namely homogeneity and stability. However, it is also advisable to select suitable CRMs in terms of representativeness. To assess the representativeness of a CRM for analytical mercury speciation, a number of aspects must be considered in regard to the routine samples analyzed: the origin of the matrix, the type of mercury species and the level of concentration.This review critically analyzes the availability of current CRMs for mercury speciation analysis in environmental and biological fields. The characteristics of the CRMs are compared with the matrices and samples covered in papers published in the last five years on mercury speciation, mainly in water, soils, sediments, sewage sludge, seafood, blood, urine and hair.

Keywords: Abbreviations; AAS; atomic absorption spectroscopy; AFS; atomic fluorescence spectroscopy; CV; cold vapor; CRM; certified reference material; EtHg; ⁺; ethylmercury; HPLC; high performance liquid chromatography; ICP-MS; inductively coupled plasma mass spectrometry; MeHg; ⁺; methylmercury; PhHg; ⁺; phenylmercury; SRM; standard reference materialReference materials; Certified reference materials; Mercury speciation; Methylmercury; Environmental matrices; Biological matrices

Neutral losses: A type of important variables in prediction of branching degree for acyclic alkenes from mass spectra by Liangxiao Zhang; Wei Fan; Dongsheng Cao; Maomao Zeng; Hongbin Xiao; Yizeng Liang (pp. 16-21).

Display Omitted► The neutral loss was extracted and creatively employed to predict branching degree. ► Dissimilarity analysis was used as tool to extract information from unknown spectra. ► An effective branching degree predictor was built by using only ONE variable.Neutral losses are a type of important variables in mass spectral interpretation. Since it is hard to calculate or extract neutral losses from mass spectra, they are usually discarded. In this study, dissimilarity analysis was employed to extract mass spectral characteristics for predicting branching degree of acyclic alkenes. The relationships between branching degree and neutral loss were constructed under direction of experimental observation and mass spectral fragmentations. A branching degree predictor of acyclic alkenes was subsequently built based on the above relationships. After tested by the experimental data in previous studies, the predictor could correctly provide the branching degree from abundant ions of mass spectra. More importantly, this predictor was able to point out which acyclic alkenes could be predicted correctly or not.

Keywords: Dissimilarity analysis; Acyclic alkene; Neutral loss; Mass spectra; Branching degree predictor

NIR analysis for batch process of ethanol precipitation coupled with a new calibration model updating strategy by Bing Xu; Zhisheng Wu; Zhaozhou Lin; Chenglin Sui; Xinyuan Shi; Yanjiang Qiao (pp. 22-28).

Display Omitted► NIR analysis for low content of API in ethanol precipitation process is verified. ► A dynamic PLS model updating strategy is brought forward. ► Simple interval calculation (SIC) theory is coupled into the updating strategy. ► Effectiveness of model updating is visualized by object status plot (OSP).Ethanol precipitation plays a major role in the pretreatment of Flos Lonicerae Japonicae of Qingkailing injection, and is also one of the most popular purification techniques in Chinese herbal medicines. In order to monitor and have a better understanding of the ethanol precipitation process, a PLS model was built based on NIR spectroscopy and HPLC analysis of chlorogenic acid content within the framework of FDA's PAT initiative. Nevertheless, due to the complex mechanism of and the raw materials’ natural variability introduced into the ethanol precipitation process, it was unable to foresee the variations in new batches which may jeopardize the robustness of the established model. Therefore, based on the simple interval calculation (SIC) theory, a new model expansion updating strategy which could continuously expand the variation coverage of the calibration model along with the batch proceeding of ethanol precipitation process was proposed. Effects of model updating were validated by an individual batch with 60 samples. After two times of updating, the root mean squared error of prediction (RMSEP) decreased from 0.268mgmL⁻¹ to 0.199mgmL⁻¹, while the insiders in the object status plot (OSP) increased from 44 to 58, demonstrating the good performance of the proposed approach.

Keywords: Ethanol precipitation; Near infrared spectroscopy; Calibration model updating; Simple interval calculation; Flos Lonicerae Japonicae; Process analytical technology

Electropolymerized surface ion imprinting films on a gold nanoparticles/single-wall carbon nanotube nanohybrids modified glassy carbon electrode for electrochemical detection of trace mercury(II) in water by Xu-Cheng Fu; Ju Wu; Li Nie; Cheng-Gen Xie; Jin-Huai Liu; Xing-Jiu Huang (pp. 29-37).

Display Omitted► Ion imprinting films on AuNPs/SWCNTs/GCE. ► High sensitivity and selectivity for Hg(II) detection. ► Regeneration easily. ► Good repeatability and stability. ► Could be exploited for on-line detection of Hg(II).Electrochemical detection of Hg(II) using a electropolymerized ion imprinting poly(2-mercaptobenzothiazole) films at the surface of gold nanoparticles/single-walled carbon nanotube nanohybrids modified glassy carbon electrode (PMBT/AuNPs/SWCNTs/GCE) is described for the first time. The Hg(II)-imprinted PMBT/AuNPs/SWCNTs/GCE sensor exhibits larger binding to functionalized capacity, larger affinity, faster binding kinetics and higher selectivity to template Hg(II). The differential pulse anodic stripping voltammetry (DPASV) response of the Hg(II)-imprinted PMBT/AuNPs/SWCNTs/GCE sensor to Hg(II) is ca. 3.7- and 10.5-fold higher than that at the non-imprinted PMBT/AuNPs/SWCNTs/GCE and the imprinted PMBT/AuNPs/GCE, respectively, and the detection limit for Hg(II) is 0.08nM (S/N=3, which is well below the guideline value given by the World Health Organization) and a sensitivity of 0.749μAnM⁻¹ was obtained. Excellent wide linear range (0.4–96.0nM) and good repeatability (relative standard deviation of 2.6%) were obtained for Hg(II). The interference experiments show that Ag(I), Pb(II), Cd(II), Zn(II) and Cu(II) had little or no influence on the Hg(II) signal. These values, particularly the high sensitivity and excellent selectivity in contrast to the values reported previously in the area of electrochemical Hg(II) detection, demonstrate the analytical performance of the Hg(II)-imprinted PMBT/AuNPs/SWCNTs/GCE toward Hg(II) is superior to the existing electrodes and could be used for efficient determination of Hg(II) in natural water samples.

Keywords: Ion imprinting; Single-walled carbon nanotubes; Electrochemical sensor; Poly(2-mercaptobenzothiazole) film; Mercury(II) detection

Immobilization of tris(1,10-phenanthroline)ruthenium with graphene oxide for electrochemiluminescent analysis by Yali Yuan; Haijuan Li; Shuang Han; Lianzhe Hu; Saima Parveen; Haoran Cai; Guobao Xu (pp. 38-42).

Display Omitted► Ru(phen)₃²⁺-based regenerable ECL sensor has been demonstrated for the first time. ► Ru(phen)₃²⁺ has better adsorbability than Ru(bpy)₃²⁺. ► Ru(phen)₃²⁺ is readily and strongly immobilized on graphene oxide by adsorption. ► Ru(phen)₃²⁺/GO regenerable sensor has excellent long-term stability. ► Ru(phen)₃²⁺ is an attractive alternative to Ru(bpy)₃²⁺ for regenerable ECL sensors.Electrochemiluminescence (ECL) of ruthenium complexes has broad applications and the immobilization of Ru(bpy)₃²⁺ has received extensive attention. In comparison with Ru(bpy)₃²⁺, Ru(phen)₃²⁺ can be immobilized more easily because of its better adsorbability. In this study, immobilization of Ru(phen)₃²⁺ for ECL analysis has been demonstrated for the first time by using graphene oxide (GO) as an immobilization matrix. The immobilization of Ru(phen)₃²⁺ is achieved easily by mixing Ru(phen)₃²⁺ with GO without using any ion exchange polymer or covalent method. The strong binding of Ru(phen)₃²⁺ with GO is attributed to both the π–π stacking interaction and the electrostatic interaction. The Ru(phen)₃²⁺/GO modified electrode was characterized by using tripropylamine (TPA) as the coreactant. The linear range of TPA is from 3×10⁻⁷ to 3×10⁻²molL⁻¹ with the detection limit of 3×10⁻⁷molL⁻¹. The ECL sensor demonstrates outstanding long-term stability. After the storage in the ambient environment for 90 days, the ECL response remains comparable with its original signal.

Keywords: Tris(1,10-phenanthroline)ruthenium; Electrochemiluminescence; Graphene oxide; Tris(bipyridyl) ruthenium; Tripropylamine

Impedimetric immunosensor for human serum albumin detection on a direct aldehyde-functionalized silicon nitride surface by David Caballero; Elena Martinez; Joan Bausells; Abdelhamid Errachid; Josep Samitier (pp. 43-48).

Display Omitted► An impedimetric label-free immunosensor was developed for the specific detection of human serum albumin proteins. ► Anti-HSA antibodies were covalently immobilized on silicon nitride surfaces using a direct functionalization methodology. ► Silicon nitride offers multiple advantages compared to other common materials. ► The proposed sensor has high sensitivity and good selectivity for the detection of HSA proteins.In this work we report the fabrication and characterization of a label-free impedimetric immunosensor based on a silicon nitride (Si₃N₄) surface for the specific detection of human serum albumin (HSA) proteins. Silicon nitride provides several advantages compared with other materials commonly used, such as gold, and in particular in solid-state physics for electronic-based biosensors. However, few Si₃N₄-based biosensors have been developed; the lack of an efficient and direct protocol for the integration of biological elements with silicon-based substrates is still one of its the main drawbacks. Here, we use a direct functionalization method for the direct covalent binding of monoclonal anti-HSA antibodies on an aldehyde-functionalized Si-p/SiO₂/Si₃N₄ structure. This methodology, in contrast with most of the protocols reported in literature, requires less chemical reagents, it is less time-consuming and it does not need any chemical activation. The detection capability of the immunosensor was tested by performing non-faradaic electrochemical impedance spectroscopy (EIS) measurements for the specific detection of HSA proteins. Protein concentrations within the linear range of 10⁻¹³–10⁻⁷M were detected, showing a sensitivity of 0.128ΩμM⁻¹ and a limit of detection of 10⁻¹⁴M. The specificity of the sensor was also addressed by studying the interferences with a similar protein, bovine serum albumin. The results obtained show that the antibodies were efficiently immobilized and the proteins detected specifically, thus, establishing the basis and the potential applicability of the developed silicon nitride-based immunosensor for the detection of proteins in real and more complex samples.

Keywords: Immunosensor; Silicon nitride; Aldehyde; Electrochemical impedance spectroscopy; Human serum albumin

Amperometric enzyme electrodes of glucose and lactate based on poly(diallyldimethylammonium)-alginate-metal ion-enzyme biocomposites by Cong Qin; Chao Chen; Qingji Xie; Lihua Wang; Xiuhui He; Yi Huang; Yaping Zhou; Fangyun Xie; Dawei Yang; Shouzhuo Yao (pp. 49-56).

Display Omitted► Poly(diallyldimethylammonium)-alginate-metal ion-enzyme biocomposites are prepared. ► The biocomposites are studied by microscopic/electrochemical methods. ► Amperometric enzyme electrodes of glucose and lactate are thus developed. ► The enzyme electrodes work well for biosensing of glucose and lactate. ► The enzyme electrodes work well as bioanodes for biofuel cells of glucose and lactate.Sodium alginate (AlgNa) and poly(diallyldimethylammonium chloride) (PDDA) were mixed to obtain an interpenetrating polymer composite via electrostatic interaction and then cast on an Au electrode surface, followed by incorporation of metal ions (e.g. Fe³⁺ or Ca²⁺, to form AlgFe or AlgCa hydrogel) and glucose oxidase (GOx) (or lactate oxidase (LOx)), to prepare amperometric enzyme electrodes. The interactions of PDDA, Alg, and Fe³⁺ are studied by visual inspection as well as microscopic and electrochemical methods. Under optimized conditions, the PDDA-AlgFe-enzyme/Au and PDDA-AlgCa-enzyme/Au electrodes can give good analytical performance (e.g. nM-scale limit of detection of glucose or lactate, and sensitivities>50μAcm⁻²mM⁻¹) in the first-generation biosensing mode, which are better than the reported analogs using typical polysaccharide biopolymers as enzyme-immobilization matrices. The enzyme electrodes also worked well in the second-generation biosensing mode in the coexistence of p-benzoquione or ferrocene monocarboxylic acid artificial mediator. Biofuel cells (BFCs) with the enzyme electrodes as the bioanodes and glucose (or lactate) as the biofuel were also fabricated with satisfactory results. The proposed protocols for preparation of high performance Alg-based biocomposites may find wide applications in bioanalysis.

Keywords: Alginate; Poly(diallyldimethylammonium); Glucose oxidase; Lactate oxidase; Amperometric enzyme biosensors; Biofuel cells

Facile synthesis of magnetic one-dimensional polyaniline and its application in magnetic solid phase extraction for fluoroquinolones in honey samples by Qiang Gao; Hao-Bo Zheng; Dan Luo; Jun Ding; Yu-Qi Feng (pp. 57-62).

By mixing magnetic nanoparticles (MNPs) and one-dimensional polyanilines (1D-PANIs) in a solvent, magnetic one-dimensional polyanilines (1D-PANIs/MNPs) were formed facilely due to the encapsulation of magnetic nanoparticles into the interconnected network of 1D-PANIs. The 1D-PANIs/MNPs have been demonstrated to be applicable for magnetic solid-phase extraction.Display Omitted► Magnetic 1D polyaniline (1D-PANIs/MNPs) was prepared by a simple co-mixing method. ► Efficacy of 1D-PANIs/MNPs for isolating four fluoroquinolones (FQs) from honey was tested. ► The optimized conditions were established for 1D-PANIs/MNPs-based magnetic solid-phase extraction (MSPE). ► π–π and hydrophobic interactions played a dominant role to the retention between the FQs and 1D-PANIs/MNPs. ► A simple, rapid, and effective MSPE-HPLC analysis method for FQs in honey samples was developed.In this work, we proposed a simple co-mixing method to fabricate magnetic one-dimensional polyaniline (denoted as 1D-PANIs/MNPs). One-dimensional polyanilines (1D-PANIs) and magnetic nanoparticles (MNPs) were prepared by chemical oxidation and solvothermal methods, respectively. When MNPs and 1D-PANIs (with mass ratio 4:1) were co-mixed and vortexed evenly in a solvent (e.g., ethanol, water, acetonitrile), they could assemble into 1D-PANIs/MNPs spontaneously and thus be magnetically separable. To testify the feasibility of 1D-PANIs/MNPs in sample preparation, it was applied as the sorbent for magnetic solid phase extraction (MSPE) of fluoroquinolones (FQs) in honey samples. Under optimized conditions, a rapid, convenient, and efficient method for the determination of four FQs in honey samples by 1D-PANIs/MNPs-based MSPE coupling with high performance liquid chromatography with fluorescence detection (HPLC-FLD) was established. The limits of detection (LODs) for four FQs ranged from 0.4 to 1.4ngg⁻¹. The intra- and interday relative standard deviations (RSDs) were less than 17.6%. The recoveries of FQs for three spiked honey samples ranged from 86.3 to 121.3%, with RSDs of less than 16.3%.

Keywords: Magnetic one-dimensional polyaniline; Magnetic solid phase extraction; Honey samples; Fluoroquinolones; High performance liquid chromatography with fluorescence detection

Hydrophobic polymer monoliths as novel phase separators: Application in continuous liquid–liquid extraction systems by Daniela Peroni; Dominique Vanhoutte; Francisco Vilaplana; Peter Schoenmakers; Sjaak de Koning; Hans-Gerd Janssen (pp. 63-70).

Display Omitted► Hydrophobic PS-DVB monoliths as “selective solvent gates” for new phase separators. ► Polymer monoliths’ wettability is modulated tuning surface chemistry and porosity. ► New separators coupled to segmented-flow-based chips for liquid–liquid extraction. ► Efficient separation of organic solvents from water at different flow rates/ratios. ► Good performance for continuous liquid extraction prior to gas-chromatography.Hydrophobic macroporous polymer monoliths are shown to be interesting materials for the construction of “selective solvent gates”. With the appropriate surface chemistry and porous properties the monoliths can be made permeable only for apolar organic solvents and not for water. Different poly(butyl methacrylate- co-ethylene dimethacrylate) (BMA-EDMA) and poly(styrene- co-divinylbenzene) (PS-DVB) monoliths prepared with tailored chemistries and porosities were evaluated for this purpose. After extensive characterization, the PS-DVB monoliths were selected due to their higher hydrophobicity and their more suitable flow characteristics. BMA-EDMA monoliths are preferred for mid-polarity solvents such as ethyl acetate, for which they provide efficient separation from water. Breakthrough experiments confirmed that the pressures necessary to generate flow of organic solvents through PS-DVB monoliths were substantially lower than for water. A phase separator was constructed using the monoliths as the flow selector. This device was successfully coupled on-line with a chip-based continuous liquid–liquid-extraction (LLE) system with segmented flow. Efficient separation of different solvents was obtained across a wide range of flow rates (0.5–4.0mLmin⁻¹) and aqueous-to-organic flow ratios ( β=1–10). Good robustness and long life-time were also confirmed. The suitability of the device to perform simple, cheap, and reliable phase separation in a continuous LLE system prior to gas-chromatographic analysis was proven for some selected real-life applications.

Keywords: Gas chromatography; Chip-based liquid–liquid extraction; Phase separation; Monoliths

A novel superparamagnetic surface molecularly imprinted nanoparticle adopting dummy template: An efficient solid-phase extraction adsorbent for bisphenol A by Zhenkun Lin; Wenjing Cheng; Yanyan Li; Zhiren Liu; Xiangping Chen; Changjiang Huang (pp. 71-76).

BPF was adopted as a dummy template to prepare BPA-MIP with a superparamagnetic core–shell nanoparticle as the supporter, which was approved to be an efficient SPE adsorbent.Display Omitted► BPF was used as a dummy template to prepare BPA-MIP. ► A superparamagnetic core–shell nanoparticle was designed as MIP supporter. ► A method for BPA extraction from water sample was provided. ► MIP bead was proved to be an efficient SPE adsorbent.Leakage of the residual template molecules is one of the biggest challenges for application of molecularly imprinted polymer (MIP) in solid-phase extraction (SPE). In this study, bisphenol F (BPF) was adopted as a dummy template to prepare MIP of bisphenol A (BPA) with a superparamagnetic core–shell nanoparticle as the supporter, aiming to avoid residual template leakage and to increase the efficiency of SPE. Characterization and test of the obtained products (called mag-DMIP beads) revealed that these novel nanoparticles not only had excellent magnetic property but also displayed high selectivity to the target molecule BPA. As mag-DMIP beads were adopted as the adsorbents of solid-phase extraction for detecting BPA in real water samples, the recoveries of spiked samples ranged from 84.7% to 93.8% with the limit of detection of 2.50pgmL⁻¹, revealing that mag-DMIP beads were efficient SPE adsorbents.

Keywords: Molecularly imprinted polymer; Superparamagnetic; Dummy template; Solid-phase extraction; Bisphenol A

Advances in humeomics: Enhanced structural identification of humic molecules after size fractionation of a soil humic acid by Antonio Nebbioso; Alessandro Piccolo (pp. 77-90).

Display Omitted► Humeomics applied to size-fractions of a humic material separated by HPSEC. ► Enhanced analytical yield and detection of single humic molecules. ► Humeomics increased for weaker conformational stability of humic associations. ► Role played by single molecules in stabilizing humic supramolecular associations. ► Realistic structure–activity relationship.We size fractionated a soil humic acid (HA) by preparative high performance size exclusion chromatography (HPSEC) and evaluated the analytical capacity of humeomics to isolate and identify humic molecular components in the separated size-fractions. HA and its three size-fractions were chemically fractionated to extract non-covalently bound organosoluble compounds (ORG1), weakly ester-bound organosoluble (ORG2) and hydrosoluble constituents (AQU2), strongly ester-bound organosoluble components (ORG3), and final unextractable residues (RES4). According to their solubility, the extracts were characterized by either GC–MS or on-line thermochemolysis/GC–MS techniques. The humeomic sequence showed that the analytical yields of identified compounds in either ORG or AQU extracts of size-fractions were invariably larger than for the unfractionated HA. This was attributed to a weaker conformational stability of humic suprastructures obtained by HPSEC fractionation, thereby enabling an improved separation and identification of single humic molecules. In line with the supramolecular understanding of humic substances, we found that hydrophobic compounds were mainly distributed in the largest size-fraction, while hydrophilic components were eluted in the smallest size-fraction. Furthermore, compounds with linear chains or stackable aromatic rings associated in regular structures were more abundant in the former fraction, whereas irregularly shaped compounds, that hindered association in larger size, were mostly found in the latter fraction. Thus the structural characteristics of single humic molecules determined their mutual association in humic suprastructures, as well as their conformational strength and shape. The lack of de novo synthesized macropolymers in the unfractionated soil humic matter was confirmed by the absence of RES4 fractions in the separated size-fractions. Our results indicate that humeomics capacity to reveal the complex molecular composition of humic suprastructures was significantly improved by subjecting humic matter to a preliminary HPSEC fractionation.

Keywords: Humic substances; Soil organic matter; Humeomics; Molecular characterization; GC–MS; Thermochemolysis

Optimisation of beryllium-7 gamma analysis following BCR sequential extraction by A. Taylor; W.H. Blake; M.J. Keith-Roach (pp. 91-96).

Showing decrease in analytical uncertainty using the optimal (combined preconcentrated sample extract) method. nv (no value) where extract activities were 7Be geochemical behaviour is required to support tracer studies. ► Sequential extraction with natural⁷Be returns high analytical uncertainties. ► Preconcentrating extracts from a large sample mass improved analytical uncertainty. ► This optimised method can be readily employed in studies using low activity samples.The application of cosmogenic⁷Be as a sediment tracer at the catchment-scale requires an understanding of its geochemical associations in soil to underpin the assumption of irreversible adsorption. Sequential extractions offer a readily accessible means of determining the associations of⁷Be with operationally defined soil phases. However, the subdivision of the low activity concentrations of fallout⁷Be in soils into geochemical fractions can introduce high gamma counting uncertainties. Extending analysis time significantly is not always an option for batches of samples, owing to the on-going decay of⁷Be ( t_1/2=53.3 days).Here, three different methods of preparing and quantifying⁷Be extracted using the optimised BCR three-step scheme have been evaluated and compared with a focus on reducing analytical uncertainties. The optimal method involved carrying out the BCR extraction in triplicate, sub-sampling each set of triplicates for stable Be analysis before combining each set and coprecipitating the⁷Be with metal oxyhydroxides to produce a thin source for gamma analysis. This method was applied to BCR extractions of natural⁷Be in four agricultural soils. The approach gave good counting statistics from a 24h analysis period (∼10% (2 σ) where extract activity >40% of total activity) and generated statistically useful sequential extraction profiles. Total recoveries of⁷Be fell between 84 and 112%. The stable Be data demonstrated that the extraction procedure had a high reproducibility (<1% RSD), thus gamma counting uncertainties dominated the overall uncertainty.In addition, extractions of soil equilibrated with stable Be at a concentration below the Cation Exchange Capacity (CEC) of the soil demonstrated that doubling the soil:solution ratio to enhance the mass of soil used in a sequential extraction scheme affects the apparent distribution of approximately 10% of the total Be. At high concentration, stable Be was found to be a poor proxy for⁷Be fallout in sequential extractions.

Keywords: Beryllium-7; Sequential extraction; Preconcentration; Gamma spectrometry; Analytical uncertainty

Analysis of antibiotics from liquid sample using electrospray ionization-ion mobility spectrometry by Shu Li; Jian Jia; Xiaoguang Gao; Xiuli He; Jianping Li (pp. 97-103).

Display Omitted► The reduced mobilities of 18 antibiotics are determined. ► Establishing antibiotic mass-mobility correlation using (12,4) potential model. ► Multi-component characteristics of antibiotics can be revealed using ESI-IMS. ► Most mixtures of antibiotics can be analyzed using ESI-IMS. ► The detection limit of amoxicillin is 70pg.The recent findings of antibiotic residues in aquatic environment at trace level have gained much concern for the detrimental effect on ecological and human health due to bacterial resistance. Here, the feasibility of using electrospray ionization ion mobility spectrometry (ESI-IMS) for analysis antibiotics in liquid sample is demonstrated. Reduced mobilities and collision cross sections of 18 antibiotics are experimentally measured and compared with theoretical values according to mass-mobility correlation. Gentamicin is used as an example to investigate the capability of ESI-IMS for multi-component analysis of antibiotics. Mixtures of antibiotics at different concentrations are analyzed. The estimated detection limit for amoxicillin is 0.7mgL⁻¹ (70pg) and the linear range of response maintains over two orders. This method will be a potential technique for the analysis of antibiotics in aquatic environment.

Keywords: Abbreviations; β-las; β-lactams; amis; aminoglycosides; macs; macrolides; quis; quinolones; suls; sulphanilamides; tets; tetracyclines; chls; chloramphenicols; amo; amoxicillin; amp; ampicillin; ben; benzylpenicillin; gen; gentamicin; neo; neomycin; str; streptomycin; ery; erythromycin; kit; kitasamycin; tyl; tylosin; lom; lomefloxacin; ofl; ofloxacin; pef; pefloxacin; sde; sulfadimethoxine; sdi; sulfadimidine; sul; sulfanilamide; dox; doxycycline; oxy; oxytetracycline; chl; chloramphenicolElectrospray ionization; Ion mobility spectrometry; Antibiotics; Collision cross section; (12,4) hard core potential model; Multi-component analysis

Volatile composition and sensory properties of Vitis vinifera red cultivars from North West Spain: Correlation between sensory and instrumental analysis by M. Vilanova; E. Campo; A. Escudero; M. Graña; A. Masa; J. Cacho (pp. 104-111).

Partial least squares regression (PLSR1) product space volatile compounds with OAV>0.2 and significant aroma descriptors: (a) aroma intensity, (b) aroma quality, (c) herbaceous and (d) red fruit.Display Omitted► Aroma of Vitis vinifera red cultivars from NW Spain was studied by GC–MS and sensory analysis. ► PLSR was a satisfactory model for prediction aroma descriptors from instrumental data. ► This work contributes to gain knowledge about sensory and volatile composition of minority grape cultivars.The aroma and volatile composition of wines from five red cultivars from NW Spain ( Brancellao, Mencía, Merenzao, Mouratón and Sousón) have been studied by gas chromatography–mass spectrometry (GC–MS) and sensory descriptive analysis (SDA) during three consecutive vintages (2007–2009) in order to characterize these wines. In addition, relationships between the instrumental (volatile) and sensory variables were analyzed through the application of partial least squares regression (PLSR). Results revealed that the effect of “cultivar” was very important as a third of compounds (16 in total) varied significantly ( P≤0.05) among varieties. Mencía wines presented the highest concentrations of γ-nonalactone, whereas Sousón wines were the richest in monoterpene compounds. On the contrary, no significant difference was observed with respect to the esters content, probably as a consequence of using the same yeast for all vinifications. Twenty out of 51 quantified volatile compounds were present in some samples at concentrations higher than their corresponding odor thresholds (OAV>1), thus contributing to the final wine aroma. Partial least square (PLS) regression was applied to volatile compounds with OAV>0.2 and aroma descriptors with %GM>10. PLSR yielded a satisfactory model for the prediction of four important aroma descriptors in this set of wines – aroma quality, aroma intensity, herbaceous and red fruit – from instrumental analysis data. This work contributes to gaining knowledge about the sensory profiles and its relation to the volatile composition of minority Galician red grape cultivars.

Keywords: Sensory analysis; GC–MS; PCA; PLS regression

Preparation of strongly fluorescent silica nanoparticles of polyelectrolyte-protected cadmium telluride quantum dots and their application to cell toxicity and imaging by Jian-hua Tang; Lian Xie; Bin Zhang; Ting Qiu; Bin Qi; Hong-ping Xie (pp. 112-117).

The staining effect of the control group (a), QDs@SiO₂ (b) and QDs-PDADMAC@SiO₂(c).Display Omitted► The fluorescence intensity of QDs-PDADMAC@SiO₂ is stronger than that of QDs@SiO₂. ► The fluorescence stability of QDs-PDADMAC@SiO₂ is better than that of QDs@SiO₂. ► The cytotoxicity of QDs-PDADMAC@SiO₂ was lower than that of QDs@SiO₂ ► The staining effect of QDs-PDADMAC@SiO₂ was much better than that of QDs@SiO₂.Based on the polyelectrolyte-protected CdTe quantum dots (QDs), which were prepared by self-assembling of QDs and poly-diallyldimethylammonium chloride (PDADMAC) in the help of electrostatic attraction, the strong fluorescence silica nanoparticles (QDs-PDADMAC@SiO₂) have been prepared via a water-in-oil reverse microemulsion method. Transmission electron microscopy and Zeta potential analysis were used to characterize the as-prepared nanoparticles. All of the particles were almost spherical and there is a uniform distribution of the particle size with the average diameter about 25nm. There is a large Zeta potential of −35.07mV which is necessary for good monodispersity of nanoparticles solution. As compared with the QDs coated by SiO₂ (QDs@SiO₂), the QDs-PDADMAC@SiO₂ nanoparticles have much stronger fluorescence, and their fluorescence stability could be obviously improved. Moreover, QDs-PDADMAC@SiO₂ exhibits good biological compatibility which promotes their application in cellular imaging.

Keywords: Polyelectrolyte-protected CdTe quantum dots; Strong fluorescence silica nanoparticles; Reverse microemulsion method; Cellular toxicity; Cellular imaging

A dendrimer-based immunosensor for improved capture and detection of tumor necrosis factor-α cytokine by Admira Bosnjakovic; Manoj K. Mishra; Hye Jung Han; Roberto Romero; Rangaramanujam M. Kannan (pp. 118-125).

Display Omitted► Sensitive, early detection of cytokines can help in identifying perinatal diseases. ► Appropriately grafted dendrimer on the biosensor leads to better antibody orientation. ► Significantly improved detection limit and sensitivity has been shown for TNF-α. ► Platform approach is adaptable to both capture and detection, and for a wide variety of cytokines.A dendrimer-based sandwich type enzyme-linked immunosorbent assay (ELISA) was developed for the improved detection of recombinant human tumor necrosis factor-alpha (TNF-α) for early diagnosis of perinatal diseases. Hydroxyl-terminated generation four poly(amidoamine) dendrimer (G4-OH) was used for the development of a solid phase bio-sensing platform. The surface of the ELISA plate was modified with polyethylene-glycol (PEG) and thiol-functionalized G4-OH was immobilized on the PEG-functionalized plate. A capture antibody was oxidized and covalently immobilized onto the dendrimer-modified ELISA plate, which provides favorable orientation for the antigen binding sites toward the analyte. The dendrimer-modified plate showed enhanced sensitivity, and the detection limit for TNF-α was found to be 0.48pgmL⁻¹, which is significantly better than the commercially available ELISA kit. The selectivity of the dendrimer-modified ELISA plate was further evaluated with a mixture of cytokines, which showed results for similar to that of TNF-α alone. The modified plate provides a greater opportunity for the detection of a wide range of cytokines and biomarkers.

Keywords: PAMAM dendrimer; TNF-α; ELISA; Dendrimer biosensor

Chromogenic platform based on recombinant Drosophila melanogaster acetylcholinesterase for visible unidirectional assay of organophosphate and carbamate insecticide residues by Zheng Han; Chensen Chi; Bing Bai; Gang Liu; Qinxiong Rao; Shaojie Peng; Hong Liu; Zhihui Zhao; Dabing Zhang; Aibo Wu (pp. 126-133).

Display Omitted► A visible chromogenic platform for rapid analysis of OP and CM insecticide residues was developed. ► The assay has the capabilities of both qualitative measurement and quantitative analysis. ► The sensitivity, capabilities of resisting interferences and storage stability were desirable. ► Matrix effects were acceptable and detection performance was satisfactory in real application.In this study we propose a chromogenic platform for rapid analysis of organophosphate (OP) and carbamate (CM) insecticide residues, based on recombinant Drosophila melanogaster acetylcholinesterase (R- DmAChE) as enzyme and indoxyl acetate as substrate. The visible chromogenic strip had the advantages identical to those of commonly used lateral flow assays (LFAs) with utmost simplicity in sample loading and result observation. After optimization, depending on the color intensity (CI) values, the well-established assay has the capabilities of both qualitative measurement via naked eyes and quantitative analysis by colorimetric reader with the desirable IC₅₀ values against the tested six insecticides (0.06μgmL⁻¹ of carbofuran, 0.28μgmL⁻¹ of methomyl, 0.03μgmL⁻¹ of dichlorvos, 31.6μgmL⁻¹ of methamidophos, 2.0μgmL⁻¹ of monocrotophos, 6.3μgmL⁻¹ of omethoate). Acceptable matrix effects and satisfactory detection performance were confirmed by in-parallel LC–MS/MS analysis in different vegetable varieties at various spiked levels of 10⁻³ to 10¹μgg⁻¹. Overall, the testified suitability and applicability of this novel platform meet the requirements for practical use in food safety management and environmental monitoring, especially in the developing world.

Keywords: Chromogenic platform; Visible unidirectional assay; Insecticides; On-site analysis

Determination of non-steroidal anti-inflammatory drugs in water samples by solid-phase microextraction based sol–gel technique using poly(ethylene glycol) grafted multi-walled carbon nanotubes coated fiber by Ali Sarafraz-Yazdi; Amirhassan Amiri; Gholamhossein Rounaghi; Hossein Eshtiagh-Hosseini (pp. 134-141).

Display Omitted► A new, simple and sensitive method for determining NSAIDs was proposed. ► SPME based on sol–gel technology was proposed for the determination of NSAIDs. ► PEG-g-MWCNTs was used as stationary phase to prepare the sol–gel SPME fiber. ► This method has a considerably low LOD and a relatively wide linear rang.In this study, poly(ethylene glycol) (PEG) grafted multi-walled carbon nanotubes (PEG-g-MWCNTs) were synthesized by the covalent functionalization of MWCNTs with hydroxyl-terminated PEG chains. PEG-g-MWCNTs was used as a novel stationary phase to prepare the sol–gel solid-phase microextraction (SPME) fiber in combination with gas chromatography–flame ionization detector (GC–FID) for the determination of ibuprofen, naproxen and diclofenac in real water samples.Some parameters which influencing the extraction efficiency were such as desorption temperature and time, extraction temperature and time, pH, salt effect and stirring speed that were investigated and optimized. Under the optimal conditions, the method detection limits (S/N=3) were in the range of 0.007–0.03ngmL⁻¹ and the limits of quantification (S/N=10) between 0.05 and 0.07ngmL⁻¹. The relative standard deviations (RSDs) for one fiber (repeatability) ( n=5) were obtained from 5.9 up to 8.1% and between fibers or batch to batch ( n=3) (reproducibility) in the range of 7.2–9.1%. The developed method was successfully applied to real water samples while the relative recovery percentages obtained for the spiked water samples at 0.2ngmL⁻¹ were from 84 to 107%.

Keywords: Solid-phase microextraction; Multi-walled carbon nanotubes; Sol–gel technology; Non-steroidal anti-inflammatory drugs; Water samples

Prediction of liquid chromatographic retention for differentiation of structural isomers by Elli Tyrkkö; Anna Pelander; Ilkka Ojanperä (pp. 142-148).

Display Omitted► Structural isomers indistinguishable by accurate mass measurement techniques alone. ► Evaluation of a retention time prediction software for isomer differentiation. ► Software calculated correct elution order for 68% of isomer groups. ► Retention order predictions bring valuable data for isomer separation. ► Tentative compound identification possible without reference standard.A liquid chromatography (LC) retention time prediction software, ACD/ChromGenius, was employed to calculate retention times for structural isomers, which cannot be differentiated by accurate mass measurement techniques alone. For 486 drug compounds included in an in-house database for urine drug screening by liquid chromatography/quadrupole time-of-flight mass spectrometry (LC/Q-TOFMS), a retention time knowledge base was created with the software. ACD/ChromGenius calculated retention times for compounds based on the drawn molecular structure and given chromatographic parameters. The ability of the software for compound identification was evaluated by calculating the retention order of the 118 isomers, in 50 isomer groups of 2–5 compounds each, included in the database. ACD/ChromGenius predicted the correct elution order for 68% (34) of isomer groups. Of the 16 groups for which the isomer elution order was incorrectly calculated, two were diastereomer pairs and thus difficult to distinguish using the software. Correlation between the calculated and experimental retention times in the knowledge base tested was moderate, r²=0.8533. The mean and median absolute errors were 1.12min, and 0.84min, respectively, and the standard deviation was 1.04min. The information generated by ACD/ChromGenius, together with other in silico methods employing accurate mass data, makes the identification of substances more reliable. This study demonstrates an approach for tentatively identifying compounds in a large target database without a need for primary reference standards.

Keywords: Liquid chromatography; Retention time; Prediction; Elution order; Differentiation; Structural isomers

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Analytica Chimica Acta (v.720, #)

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Analytica Chimica Acta (v.720, #)