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Analytica Chimica Acta (v.701, #1)

Editorial Board (pp. iii).

Anodized aluminum wire as a solid-phase microextraction fiber for rapid determination of volatile constituents in medicinal plant by Mohammad Bagher Gholivand; Marzieh Piryaei; Mir Mahdi Abolghasemi (pp. 1-5).

Display Omitted► The aluminum wire was anodized on 16% (w/v) sulfuric acid solution. ► The fiber was evaluated for the extraction of essential oil of plant. ► Different parameters affecting the extraction efficiency were optimized.Headspace solid phase microextraction using anodized aluminum fiber in combination with capillary GC–MS was utilized as monitoring technique for the collection and detection of the volatile compounds of Echinophora platyloba DC. Experimental parameters, including the sample weight, extraction temperature, extraction time and humidity effect, desorption time and desorption temperature were examined and optimized. Using HS-SPME followed by GC–MS, 53 compounds were separated and identified in E. platyloba DC, which mainly included E-β ocimene (47.63%), R-D-decalactone (13.28%), α-pinene (7.43%) and nonane (6.71%). Compared with hydrodistillation (HD), HS-SPME, provides the advantages of a small amount of sample, timesaving, simplicity and cheapness. To the best of our knowledge, this is the first report on using anodized aluminum fiber in solid-phase microextraction coupled to headspace for the investigation of volatile fraction of medicinal plant.

Keywords: Solid phase microextraction; Anodized aluminum; Echinophora platyloba; DC; Gas chromatography–mass spectrometry

Effect of fluidic transport on the reaction kinetics in lectin microarrays by Bibhas Roy; Tamal Das; Tapas K. Maiti; Suman Chakraborty (pp. 6-14).

Display Omitted► For microfluidics based DNA-microarray systems, reaction rate constants are considered to be independent of hydrodynamic parameters. ► We have investigated whether this assumption remains valid for structurally complex protein molecules such as lectins. ► We show that both association and dissociation constants of inter-lectin binding depend on the imposed wall shear rate.Lectins are the proteins which can distinguish glycosylation patterns. They are frequently used as biomarkers for progressions of several diseases including cancer. As the lectin microarray based prognosis devices miniaturize the process of glycoprofiling, it is anticipated that their performance can be augmented by integration with microfluidic framework. This is analogous to microfluidics based DNA arrays. However, unlike small oligonucleotide microarrays, it remains uncertain whether the binding reaction-kinetic parameters can be considered invariant of imposed hydrodynamics, for relatively larger and structure sensitive molecules such as lectins. Here we show, using two standard lectins namely Concanavalin A and Abrus Agglutinin, that the steady state binding efficiency unexpectedly declines beyond a critical shear rate magnitude. This observation can be explained only if the associated reaction constants are presumed to be functions of hydrodynamic parameters. We methodically deduce the shear rate dependence of association and dissociation constants from the comparison of experimental and model-simulation trends. The aforementioned phenomena are perceived to be the consequences of strong hydrodynamic perturbations, culminating into molecular structural distortion. The exploration, therefore, reveals a unique coupling between reaction kinetics and hydrodynamics for biomacromolecules and provides a generic scheme towards futuristic microfluidics-coupled biomedical assays.

Keywords: Lectin microarray; Microfluidics; Glycomics; Concanavalin A; Abrus; Agglutinin; Reaction kinetics

Development of a flow method for the determination of phosphate in estuarine and freshwaters—Comparison of flow cells in spectrophotometric sequential injection analysis by Raquel B.R. Mesquita; M. Teresa S.O.B. Ferreira; Ildikó V. Tóth; Adriano A. Bordalo; Ian D. McKelvie; António O.S.S. Rangel (pp. 15-22).

Display Omitted► Sequential injection determination of phosphate in estuarine and freshwaters. ► Alternative spectrophotometric flow cells are compared. ► Minimization of schlieren effect was assessed. ► Proposed method can cope with wide salinity ranges. ► Multi-reflective cell shows clear advantages.A sequential injection system with dual analytical line was developed and applied in the comparison of two different detection systems viz; a conventional spectrophotometer with a commercial flow cell, and a multi-reflective flow cell coupled with a photometric detector under the same experimental conditions. The study was based on the spectrophotometric determination of phosphate using the molybdenum-blue chemistry. The two alternative flow cells were compared in terms of their response to variation of sample salinity, susceptibility to interferences and to refractive index changes. The developed method was applied to the determination of phosphate in natural waters (estuarine, river, well and ground waters). The achieved detection limit (0.007μM PO₄³⁻) is consistent with the requirement of the target water samples, and a wide quantification range (0.024–9.5μM) was achieved using both detection systems.

Keywords: Sequential injection; Phosphate determination; Estuarine and river water; Spectrophotometry; Multi-reflective flow cell

Microfluidic worm-chip for in vivo analysis of neuronal activity upon dynamic chemical stimulations by Jingjing Wang; Xiaojun Feng; Wei Du; Bi-Feng Liu (pp. 23-28).

Display Omitted• A microfluidic device was developed integrating multiple stimuli delivery for in vivo neuronal analysis of immobilized Caenorhabditis elegans. • ASH neuronal responses to various stimuli were quantitatively evaluated. • Rapid identification of mutant animals was realized by comparing responses to those of the wild type. • ASH sensory adaptations upon repetitive stimuli of various durations were investigated.Conventional neuronal analysis at the single neuron level usually involves culturing of neurons in vitro and analysis of neuronal activities by electrophysiological or pharmacological methods. However, the extracellular environments of in vitro neuronal analysis cannot mimic the exact surroundings of the neurons. Here, we report a microfluidic worm-chip for in vivo analysis of neuronal activities upon dynamic chemical stimulations. A comb-shaped microvalve was developed to immobilize whole animal for high-resolution imaging of neuronal activities. Using a sequential sample introduction system, multiple chemical stimuli were delivered to an individual Caenorhabditis elegans nose tip based on programmed interface shifting of laminar flows. ASH sensory neuron responses to various stimuli in individual C. elegans were quantitatively evaluated, and mutants were significantly defective in neuronal responses to certain stimulus in comparison to others. Sensory reduction in the magnitude of the response to repetitive chemical stimulation with different durations was also found. Our study explored the possibility of real-time detection of neuronal activities in individual animals upon multiple stimulations.

Keywords: Microfluidic chip; C. elegans; In vivo; Neuronal analysis; Chemical stimulation

Solid-phase microextraction–gas chromatography–mass spectrometry method validation for the determination of endogenous substances: Urinary hexanal and heptanal as lung tumor biomarkers by Rossella Guadagni; Nadia Miraglia; Angela Simonelli; Angela Silvestre; Monica Lamberti; Daniela Feola; Antonio Acampora; Nicola Sannolo (pp. 29-36).

Display Omitted► The study reports an analytical method for hexanal and heptanal quantification. ► Analytes were quantified in urinary matrix by HS-SPME/GC/MS. ► Validation experiments were performed and FDA requirements were satisfied. ► Higher analytes levels were found in lung cancer patients with respect to controls. ► Urinary hexanal and heptanal are suggested as lung tumor biomarkers.Hexanal and heptanal are endogenous aldehydes coming from membrane lipid oxidation, found in lung cancer patients’ blood, and suggested as lung tumor biomarkers. Here the urinary matrix was investigated instead of blood and the difficulties related to the determination of endogenous substances in biological matrices were faced by developing an external calibration HS-SPME/GC/MS method. The methodology was validated according to international validation procedures and it was verified analyzing unknown biological samples from cancer patients and healthy subjects. Percentage accuracy and precision, ranging from −11.25 to 10.85% and from 0.45 to 4.46%, respectively, were obtained, together with limits of detection (LODs) and lower limits of quantification (LLOQs) of 0.11 and 0.23pgμL⁻¹ for hexanal and of 0.10 and 0.21pgμL⁻¹ for heptanal. Analytes percentage recoveries (66.3%, hexanal and 70.5%, heptanal) and stability were evaluated. No analytes degradation was found at room temperature, while the remarkable analytes loss found after 1 month storage suggests analyzing biological samples within a week from storage. Results coming from the analysis of unknown biological samples showed no evident differences of heptanal urinary excretion between lung cancer patients and healthy subjects (0.22–0.95 and 0.21–0.69pgμL⁻¹, respectively), while hexanal urinary concentrations in cancer patients (0.24–4.36pgμL⁻¹) were slightly higher than those found in control group ones (0.23–1.26pgμL⁻¹). The obtained results highly suggest to do further investigations in order to collect statistically significant biological data to discriminate between the pathological state of lung cancer patients and physiological conditions of healthy subjects, using the simple, rapid and cheap method here reported for the quantification of urinary aldehydes.

Keywords: Bioanalytical method validation; Urine; Hexanal; Heptanal; Lung tumor biomarkers; Endogenous substances

Determination of the total and extractable mass fractions of cadmium and lead in mineral feed by using isotope dilution inductively coupled plasma mass spectrometry by Emilia Vassileva; Michel Hoenig (pp. 37-44).

Display Omitted► The protocol for the total and extractable mass fractions of Pb and Cd in mineral feed sample based on isotope dilution inductively coupled plasma mass spectrometry is developed. ► The ID ICP-MS method for the total and extractable mass fractions of Cd and Pb in feed sample is used for the validation of external calibration method for both elements in feed matrix. ► Two methods for the determination of Cd were developed: matrix separation of Cd followed by standard ICP-MS measurement in CRI mode without preliminary matrix separation.This paper describes the determination of the total and extractable mass fractions of Cd and Pb in mineral feed test sample distributed by the Community Reference Laboratory for Heavy Metals in Feed and Food (CRL-HM), in the frame of the fifth interlaboratory comparison for the European Union National Reference Laboratories (NRL).The developed in this study protocol for the total and extractable mass fractions of Pb and Cd in mineral feed sample is based on isotope dilution inductively coupled plasma mass spectrometry (ID ICP-MS). The applied dual spiking approach reduced by 50% the number of analytical steps. The addition of hydrofluoric acid in the digestion step was found necessary to ensure a full decomposition and complete isotope equilibration. Quadrupole inductively coupled plasma mass spectrometer equipped with collision reaction interface (CRI) was employed for the measurements of Cd and Pb. Two methods for the determination of Cd were applied and compared. In the first one the high molybdenum content was reduced by introduction of matrix separation step followed by standard ICP-MS mode measurement, whereas in the second one CRI mode was used for the determination of Cd without preliminary matrix separation. The estimation of the combined uncertainty was performed according to the ISO guidelines. Uncertainty propagation was used as a tool for validation of proposed analytical procedure. Contributions from the correction for moisture content, sample homogeneity, procedural blank, instrumental background and dead time effects were evaluated in both cases. The largest uncertainty contributors for Cd and Pb is due to the within bottle homogeneity of the mineral feed sample – 50.3% and 90% respectively. The IUPAC data for isotope composition are the second major contributor to the combined uncertainty of the result for the total mass fraction of Cd in mineral feed – 43.3%. However, the ID ICP-MS results achieved from the two series of samples (partial and total extraction) were in excellent agreement within uncertainty, irrespective of the method used for extraction.The ID ICP-MS results for the total and extractable mass fractions of Cd and Pb in feed sample were compared with the results obtained with external calibration approach and routinely applied in the daily analytical practice of the Belgium National Reference Laboratory for trace elements in food and feed.

Keywords: Isotope dilution inductively coupled plasma mass spectrometry; External calibration; Cadmium; Lead; Mineral feed; Total mass fractions; Extractable fractions; Method validation

Isoliquiritigenin (4,2′,4′-trihydroxychalcone): A new matrix-assisted laser desorption/ionization matrix with outstanding properties for the analysis of neutral oligosaccharides by Hongmei Yang; Jianwei Wang; Fengrui Song; Yihan Zhou; Shuying Liu (pp. 45-51).

Display Omitted► The novel matrix isoliquiritigenin exhibited outstanding properties in the analysis of oligosaccharides by MALDI-TOF MS. ► Adequate signal for an analyte can be obtained in much lower matrix concentrations and laser intensity. ► Higher homogeneity of crystallization, higher sensitivity, as well as better resolution, SN⁻¹, and salt tolerance. ► Enough fragmentation yield to get richer structural information and reliable quantitative analysis of oligosaccharides.A novel matrix of isoliquiritigenin (ISL), a flavonoid with a chalcone structure (4,2′,4′-trihydroxychalcone), was demonstrated to be advantageous in the analysis of neutral oligosaccharides by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS). With ISL as a matrix, adequate signal for an analyte can be obtained in much lower matrix concentrations and laser intensity compared to commonly used MALDI matrices. Four different sample preparation methods were tested, and the dried droplet method exhibited the best performance on MALDI-TOF-MS analysis of oligosaccharides with ISL as a matrix. For the analysis of carbohydrates, compared with popular matrices such as 2,5-dihydroxybenzoic acid (DHB) and 2,4,6-trihydroxyacetophenone (THAP), ISL exhibited outstanding matrix properties as follows: (1) higher homogeneity of crystallization thus allowing automatic data acquisition, (2) better spectral quality in terms of resolution and signal to noise ratio (SN⁻¹), (3) better salt tolerance, (4) higher sensitivity, and (5) enough fragmentation yield to use LIFT-TOF/TOF MS to get richer structural information. In addition, reliable quantitative analysis of oligosaccharides with a good linearity over two concentration orders (1–100pmolμL⁻¹) and good reproducibility of the signal intensity (RSD less than 15%) were achieved using this matrix. These results give a new outlook on high-speed analysis of neutral carbohydrates by MALDI-TOF MS.

Keywords: Abbreviations; ACN; acetonitrile; 3-AQ; 3-aminoquinoline; α-CD; α-cyclodextrin; β-CD; cyclomaltoheptaose; DHB; 2,5-dihydroxybenzoic acid; ESI; electrospray ionization; ISL; isoliquiritigenin; MALDI-TOF MS; matrix-assisted laser desorption/ionization time-of-flight mass spectrometry; S; N; ⁻¹; signal to noise ratio; THAP; 2,4,6-trihydroxyacetophenoneNovel matrix; Isoliquiritigenin; Neutral oligosaccharides; Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry; Outstanding matrix properties

Analysis of pesticides by gas chromatography/multiphoton ionization/mass spectrometry using a femtosecond laser by Adan Li; Tomoko Imasaka; Tomohiro Uchimura; Totaro Imasaka (pp. 52-59).

Display Omitted► Gas chromatography/multiphoton ionization/time-of-flight mass spectrometry was utilized for analysis. ► A standard mixture sample containing 49 pesticides and 4 real samples were measured. ► Third-harmonic emission of a Ti:sapphire laser (100fs) was employed as an ionization source. ► Most of the pesticides were softly ionized by the femtosecond laser. ► Three pesticides were found, although some of them were not detected by GC/EI/MS–MS.Gas chromatography/multiphoton ionization/time-of-flight mass spectrometry (GC/MPI/TOFMS) was utilized for analysis of a standard mixture sample containing 49 pesticides and 4 real samples using the third-harmonic emission (267nm) of a femtosecond Ti:sapphire laser (100fs) as the ionization source. A sample of a standard mixture of n-alkane was also measured for calibration of the retention time indices of the pesticides. Two photons are required for the excitation of n-alkane due to an absorption band located in the far ultraviolet region (140nm). The n-alkane molecule in the excited state was subsequently ionized either directly or by absorbing another photon because of a high ionization potential. Due to a large excess of energy, the molecular ion was decomposed and formed many fragment ions. Compared to n-alkanes, most of the pesticides were softly ionized by the femtosecond laser; one photon was used for excitation and another was used for the subsequent ionization. The pesticides with no conjugated double bond had a lower ionization efficiency. The present analytical instrument was applied to several samples prepared from a variety of vegetables and a single fruit after pretreatment with solid-phase extraction. Three pesticides were found in these samples, although some of them were not detected by conventional GC/EI/MS–MS due to insufficient sensitivity and selectivity.

Keywords: Femtosecond laser; Gas chromatography; Multiphoton ionization; Time-of-flight mass spectrometry; Pesticides; Density functional theory

Synchronous determination of mercury (II) and copper (II) based on quantum dots-multilayer film by Qiang Ma; Enna Ha; Fengping Yang; Xingguang Su (pp. 60-65).

We developed a sensitive sensor for synchronous detection of Hg (II) and Cu (II) based on the quenchedand recovered PL intensity of QDs-multilayer films. Solutions containing Hg (II) or Cu (II) were used to quench the fluorescence of the QDs-multilayer films firstly. Then, glutathione (GSH) was used to remove Hg (II) or Cu (II) from the QDs-multilayer films due to stronger affinity of GSH-metal ions than that of QDs metal ions. Thus, the fluorescence of QDs-multilayer films was recovered.Display Omitted► QDs-multilayer films were developed for synchronous detection of Hg (II) and Cu (II). ► Hg (II) and Cu (II) could quench the photoluminescence of the QDs-multilayer films. ► Glutathione was used to remove metal ions and recovery photoluminescence of QDs-multilayer films.A sensitive sensor for mercury (II) and copper (II) synchronous detection was established via the changed photoluminescence of CdTe quantum dots (QDs) multilayer films in this work. QDs were deposited on the quartz slides to form QDs-multilayer films by electrostatic interactions with poly(dimethyldiallyl ammonium chloride) (PDDA). Hg²⁺ or Cu²⁺ could quench the photoluminescence of the QDs-multilayer films, and glutathione (GSH) was used to remove Hg²⁺ or Cu²⁺ from QDs-multilayer films due to strong affinity of GSH-metal ions, which resulted in the recovered photoluminescence of QDs-multilayer films. There are good linear relationships between the metal ions concentration and the photoluminescence intensity of QDs in the quenched and recovered process. It was found that the Stern–Volmer constants for Hg²⁺ are higher than that for Cu²⁺. Based on different quenching and recovery constant between Hg²⁺ and Cu²⁺, the synchronous detection of Hg²⁺ and Cu²⁺ can be achieved. The linear ranges of this assay were obtained from 0.005 to 0.5μM for Hg²⁺ and from 0.01 to 1μM for Cu²⁺, respectively. And the artificial water samples were determined by this method with satisfactory results, the recoveries for Hg²⁺ and Cu²⁺ ions were found in the range of 90.4–106.4%. To the best of our knowledge, it is the first report about the synchronous detection of Hg²⁺ and Cu²⁺ by using quenched and recovered photoluminescence of quantum dots multilayer films.

Keywords: Quantum dots; Synchronous detection; Multilayer films; Ion sensor

An amperometric biosensor based on acetylcholinesterase immobilized onto iron oxide nanoparticles/multi-walled carbon nanotubes modified gold electrode for measurement of organophosphorus insecticides by Nidhi Chauhan; Chandra Shekhar Pundir (pp. 66-74).

The stepwise amperometric biosensor fabrication process and immobilized acetylcholinesterase inhibition in pesticide solution.Display Omitted• Constructed a novel composite material using Fe₃O₄NP and c-MWCNT at Au electrode for electrocatalysis. • The properties of nanoparticles modified electrodes were studied by SEM, FTIR, CVs and EIS. • The biosensor exhibited good sensitivity (0.475mAμM⁻¹) • The half life of electrode was 2 months. • The sensor was suitable for trace detection of OP pesticide residues in milk and water.An acetylcholinesterase (AChE) purified from maize seedlings was immobilized covalently onto iron oxide nanoparticles (Fe₃O₄NP) and carboxylated multi walled carbon nanotubes (c-MWCNT) modified Au electrode. An organophosphorus (OP) biosensor was fabricated using this AChE/Fe₃O₄/c-MWCNT/Au electrode as a working electrode, Ag/AgCl as standard and Pt wire as an auxiliary electrode connected through a potentiostat. The biosensor was based on inhibition of AChE by OP compounds/insecticides. The properties of nanoparticles modified electrodes were studied by scanning electron microscopy (SEM), Fourier transform infrared (FTIR), cyclic voltammograms (CVs) and electrochemical impedance spectroscopy (EIS). The synergistic action of Fe₃O₄NP and c-MWCNT showed excellent electrocatalytic activity at low potential (+0.4V). The optimum working conditions for the sensor were pH 7.5, 35°C, 600μM substrate concentration and 10min for inhibition by pesticide. Under optimum conditions, the inhibition rates of OP pesticides were proportional to their concentrations in the range of 0.1–40nM, 0.1–50nM, 1–50nM and 10–100nM for malathion, chlorpyrifos, monocrotophos and endosulfan respectively. The detection limits were 0.1nM for malathion and chlorpyrifos, 1nM for monocrotophos and 10nM for endosulfan. The biosensor exhibited good sensitivity (0.475mAμM⁻¹), reusability (more than 50 times) and stability (2 months). The sensor was suitable for trace detection of OP pesticide residues in milk and water.

Keywords: Acetylcholinesterase; Iron oxide nanoparticles; Multi walled carbon nanotubes; Organophosphorus pesticides; Amperometric biosensor

An ultrasensitive hydrogen peroxide biosensor based on electrocatalytic synergy of graphene–gold nanocomposite, CdTe–CdS core–shell quantum dots and gold nanoparticles by Gu Zhiguo; Yang Shuping; Li Zaijun; Sun Xiulan; Wang Guangli; Fang Yinjun; Liu Junkang (pp. 75-80).

We first reported an ultrasensitive hydrogen peroxide biosensor in this work, which was fabricated by coating graphene–gold nanocomposite, CdTe–CdS core–shell quantum dots, gold nanoparticles and horseradish peroxidase in sequence on the surface of gold electrode. Since a promising their electrocatalytic synergy towards hydrogen peroxide was achieved, the biosensor displayed very high sensitivity, low detection limit ( S/ N=3) (3.2×10⁻¹¹M) and good long-term stability (20 weeks).Display Omitted• We for the first time integrated novel hydrogen peroxide biosensor based on G–AuNP, CdTe–CdS and AuNPs. • Three nanomaterials show remarkable synergistic electrocatalysis towards hydrogen peroxide. • The biosensor provides the best sensitivity in all biosensors based on graphene for detection of glucose up to now.We first reported an ultrasensitive hydrogen peroxide biosensor in this work. The biosensor was fabricated by coating graphene–gold nanocomposite (G–AuNP), CdTe–CdS core–shell quantum dots (CdTe–CdS), gold nanoparticles (AuNPs) and horseradish peroxidase (HRP) in sequence on the surface of gold electrode (GE). Cyclic voltammetry and differential pulse voltammetry were used to investigate electrochemical performances of the biosensor. Since promising electrocatalytic synergy of G–AuNP, CdTe–CdS and AuNPs towards hydrogen peroxide was achieved, the biosensor displayed a high sensitivity, low detection limit ( S/ N=3) (3.2×10⁻¹¹M), wide calibration range (from 1×10⁻¹⁰M to 1.2×10⁻⁸M) and good long-term stability (20 weeks). Moreover, the effects of omitting G–AuNP, CdTe–CdS and AuNP were also examined. It was found that sensitivity of the biosensor is more 11-fold better if G–AuNP, CdTe–CdS and AuNPs are used. This could be ascribed to improvement of the conductivity between graphene nanosheets in the G–AuNP due to introduction of the AuNPs, ultrafast charge transfer from CdTe–CdS to the graphene sheets and AuNP due to unique electrochemical properties of the CdTe–CdS, and good biocompatibility of the AuNPs for horseradish peroxidase. The biosensor is of best sensitivity in all hydrogen peroxide biosensors based on graphene and its composites up to now.

Keywords: Graphene–gold nanocomposite; CdTe–CdS core–shell quantum dots; Gold nanoparticles; Biosensor; Hydrogen peroxide

Determination of cobalamins (hydroxo-, cyano-, adenosyl- and methyl-cobalamins) in seawater using reversed-phase liquid chromatography with diode-array detection by Ana Suárez-Suárez; Antonio Tovar-Sánchez; Ramón Rosselló-Mora (pp. 81-85).

Display Omitted► We optimized a HPLC method for the quantification of four cobalamins in seawater. ► The method was successfully applied to coastal seawater samples from Mallorca. ► Four cobalamins were separated and quantified simultaneously in a single injection. ► Cobalamin concentration ranged 44-99ngmL^-1 in the seawater samples.A high-performance liquid chromatography method was developed for the separation and determination of four cobalamins in seawater. Chromatographic separation was performed on a reversed-phase discovery RP-amide C₁₆ column with buffer potassium dihydrogenphosphate and acetonitrile as the mobile phases in linear gradients elution mode. Cobalamins were previously preconcentrated in C₁₈ resins cartridges. Detection was performed using UV-diode array detector in a range of λ of 200–400nm. The method showed to be linear over a range of 1–300ngmL⁻¹ with acceptable precision and accuracy. The detection limits ranged between 0.07pgmL⁻¹ for 5′-deoxyadenosylcobalamin and 0.5pgmL⁻¹ for hydroxocobalamin. The mean cobalamins recoveries for direct determination ranged between 76 and 93% for hydroxo-, cyano- and methylcobalamin, while the recovery for 5′-deoxyadenosylcobalamin was only 31% suggesting that the preconcentration method was not valid for this cobalamin. The method was successfully applied to coastal seawater where the concentrations ranged from 4.2 to 7.3ngL⁻¹ for hydroxo-, 1.4–3.9ngL⁻¹ for cyano-, 2.1–4.6ngL⁻¹ for 5′-deoxyadenosyl- and 33–83.5ngL⁻¹ for methylcobalamin.

Keywords: Vitamins; Cobalamins; Seawater; Solid-phase extraction; RP-HPLC

Application of an ultrasound-assisted surfactant-enhanced emulsification microextraction method for the analysis of diethofencarb and pyrimethanil fungicides in water and fruit juice samples by Jing Cheng; Yating Xia; Yiwen Zhou; Feng Guo; Gang Chen (pp. 86-91).

Display Omitted► A UASEME is used as a pre-treatment method of water and fruit juice samples. ► Diethofencarb and pyrimethanil fungicides are target analytes. ► HPLC–DAD/ESI-MS detection is used to detect and confirm the residual levels. ► The proposed method presents low LODs, good repeatability, good recoveries. ► The residues can be founded in some water samples.In this work, a simple, practical and environmentally friendly sample pre-treatment method, ultrasound-assisted surfactant-enhanced emulsification microextraction coupled with high performance liquid chromatography–diode array detector/electrospray ionisation mass spectrometry, was developed to determine diethofencarb and pyrimethanil residues in water and fruit juice samples. Tween 80 was used as an emulsifier and carbon tetrachloride was chosen as the extraction solvent, and no dispersive organic solvent was needed, which is typically required in common dispersive liquid–liquid microextraction methods. Several variables, such as the type and volume of extraction solvent and surfactant, extraction temperature and ultrasound extraction time were investigated and optimised. Under optimal conditions, the enrichment factors were 265 and 253 for diethofencarb and pyrimethanil, respectively. The limits of detection (LODs), calculated as three times the signal-to-noise ratio (S/N), were 0.01μgL⁻¹ for both diethofencarb and pyrimethanil. The linearity of the method was obtained in the range of 0.05–2000μgL⁻¹, with correlation coefficients of 0.9994–0.9998. The water (at fortified levels of 0.1 and 1.0μgL⁻¹) and fruit juice samples (at fortified levels of 0.1 and 1.0μgL⁻¹) were successfully analysed using the proposed method, and the relative recoveries were in the range of 88–114%, 93–111%, 86–117% and 94–101%, respectively.

Keywords: Ultrasound-assisted surfactant-enhanced emulsification microextraction; Diethofencarb; Pyrimethanil; Water and fruit juice analysis

Construction and initial evaluation of an apparatus for spatial comprehensive two-dimensional liquid-phase separations by Dominique J.D. Vanhoutte; Sebastiaan Eeltink; Wim Th. Kok; Peter J. Schoenmakers (pp. 92-97).

Display Omitted► A possible alternative to conventional column-based LC×LC is described and discussed. ► A prototype instrument was constructed in-house. ► Preparation of a monolithic separation body is described and its homogeneity evaluated. ► A valve configuration is described for manual sample injection. ► A mixture of dyes was separated in one dimension within 30s.Spatial comprehensive two-dimensional chromatography is discussed as a potentially alternative to the conventional column-based approach. In “spatial” separations each analyte ends up in a specific location, rather than being eluted at a specific time. Ultimately, higher peak-capacity-production rates (peak capacity per unit time) may be attained by spatial two- and three-dimensional separations. While low-pressure planar chromatography is well developed, the high-pressure equivalent is still in its infancy. We discuss the requirements for a device for high-pressure spatial two-dimensional chromatography and we describe a possible design. A prototype instrument has been constructed in-house. The preparation of a polymer monolithic separation body and a valve configuration that allows manual sample injection are described. Initial tests of this study included the investigation of the homogeneity of the monolith and the flow profile through the separation body. Furthermore, in order to evaluate the current chromatographic performance of the device, a mixture of dyes was separated in one dimension within 30s.

Keywords: Monolithic media; Peak capacities; LC; ×; LC; Spatial chromatography

Solid phase extraction in combination with comprehensive two-dimensional gas chromatography coupled to time-of-flight mass spectrometry for the detailed investigation of volatiles in South African red wines by Berhane T. Weldegergis; Andrew M. Crouch; Tadeusz Górecki; André de Villiers (pp. 98-111).

.Display Omitted• A new SPE–GC×GC–TOFMS method for the analysis of wine volatiles is described. • A detailed comparison with HS-SPME–GC×GC–TOFMS is presented. • SPE–GC×GC–TOFMS beneficial for terpenes, volatile phenols and lactones. • Identification by TOFMS is improved by removal of most polar volatiles during SPE. • 276 compounds were identified, many for the first time in Pinotage wines.Comprehensive two-dimensional gas chromatography in combination with time-of-flight mass spectrometry (GC×GC–TOFMS) has been applied for the analysis of volatile compounds in three young South African red wines. In spite of the significant benefits offered by GC×GC–TOFMS for the separation and identification of volatiles in such a complex matrix, previous results utilizing headspace solid phase micro extraction (HS-SPME) demonstrated certain limitations. These were primarily associated with the choice of sample preparation technique, which failed to extract some influential semi-volatile wine constituents. Therefore, in the current report, we utilized solid phase extraction (SPE) in combination with GC×GC–TOFMS for the detailed investigation of particularly low-level semi-volatiles in South African wine. 214 compounds previously reported in grapes and related beverages were tentatively identified based on mass spectral data and retention indices, while 62 additional compounds were positively identified using authentic standards. The method proved particularly beneficial for the analysis of terpenes, lactones and volatile phenols, and allowed us to report the presence of numerous volatile compounds for the first time in Pinotage wines.

Keywords: Keyword; Comprehensive two-dimensional gas chromatography; Solid phase extraction; Time-of-flight mass spectrometry; Volatiles; Wine

Rapid radiochemical method for determination of actinides in emergency concrete and brick samples by Sherrod L. Maxwell; Brian K. Culligan; Angel Kelsey-Wall; Patrick J. Shaw (pp. 112-118).

Display Omitted► A rapid fusion method was tested on concrete and brick samples. ► Actinides were determined rapidly using the fusion plus extraction chromatography and alpha spectrometry. ► Stacked TEVA, TRU and DGA rein cartridges were used with rapid flow rates. ► High chemical yields, effective removal of interferences and very good results were obtained.A new rapid method for the determination of actinides in emergency concrete and brick samples has been developed at the Savannah River Site Environmental Lab (Aiken, SC, USA) that can be used in emergency response situations or for routine analysis. If a radiological dispersive device (RDD), Improvised Nuclear Device (IND) or nuclear accident occurs, there will be a urgent need for rapid analyses of many different environmental matrices, including building materials such as concrete and brick, to support dose mitigation and environmental clean-up. The new method for actinides in concrete and brick method utilizes a rapid sodium hydroxide fusion method, a lanthanum fluoride matrix removal step, and a column separation process with stacked TEVA, TRU and DGA Resin cartridges. Alpha emitters are prepared using rare earth microprecipitation for counting by alpha spectrometry. The method showed high chemical recoveries and effective removal of interferences. The determination of actinides in concrete and brick sample analysis can be performed in less than 8h with excellent quality for emergency samples. The rapid fusion technique is a rugged sample digestion method that ensures that any refractory actinide particles are effectively digested.

Keywords: Rapid; Plutonium; Actinides; Concrete; Brick; Emergency

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Analytica Chimica Acta (v.701, #1)