Analytica Chimica Acta (v.770, #C)

Multiple headspace-solid-phase microextraction: An application to quantification of mushroom volatiles by Rosaria Costa; Laura Tedone; Selenia De Grazia; Paola Dugo; Luigi Mondello (1-6).
Display Omitted► Multiple headspace extraction-solid phase microextraction (MHS-SPME) has been applied to the analysis of Agaricus bisporus. ► Mushroom flavor is characterized by the presence of compounds with a 8-carbon atoms skeleton. ► Formation of 8-carbon compounds involves a unique fungal biochemical pathway. ► The MHS-SPME allowed to determine quantitatively 5 target analytes of A. bisporus for the first time.Multiple headspace-solid phase microextraction (MHS-SPME) followed by gas chromatography/mass spectrometry (GC–MS) and flame ionization detection (GC–FID) was applied to the identification and quantification of volatiles released by the mushroom Agaricus bisporus, also known as champignon. MHS-SPME allows to perform quantitative analysis of volatiles from solid matrices, free of matrix interferences. Samples analyzed were fresh mushrooms (chopped and homogenized) and mushroom-containing food dressings. 1-Octen-3-ol, 3-octanol, 3-octanone, 1-octen-3-one and benzaldehyde were common constituents of the samples analyzed. Method performance has been tested through the evaluation of limit of detection (LoD, range 0.033–0.078 ng), limit of quantification (LoQ, range 0.111–0.259 ng) and analyte recovery (92.3–108.5%). The results obtained showed quantitative differences among the samples, which can be attributed to critical factors, such as the degree of cell damage upon sample preparation, that are here discussed. Considerations on the mushrooms biochemistry and on the basic principles of MHS analysis are also presented.
Keywords: Multiple headspace extraction; Solid phase microextraction; Mushroom flavor; Agaricus bisporus; Quantitative analysis;

Display Omitted► Continuous flow hydride generation technique for LIBS detection of As, Sb, Pb and Ge. ► Optimization of chemical and instrumental parameters in HG-LIBS. ► Quantitative determination of As, Sb, Pb and Ge in aqueous samples. ► Enhancements in LOD values compared to direct liquids analysis by LIBS. ► Investigation of the effect of carrier gas on LIBS signal strength.A laser induced breakdown spectrometry hyphenated with on-line continuous flow hydride generation sample introduction system, HG-LIBS, has been used for the determination of arsenic, antimony, lead and germanium in aqueous environments. Optimum chemical and instrumental parameters governing chemical hydride generation, laser plasma formation and detection were investigated for each element under argon and nitrogen atmosphere. Arsenic, antimony and germanium have presented strong enhancement in signal strength under argon atmosphere while lead has shown no sensitivity to ambient gas type. Detection limits of 1.1 mg L−1, 1.0 mg L−1, 1.3 mg L−1 and 0.2 mg L−1 were obtained for As, Sb, Pb and Ge, respectively. Up to 77 times enhancement in detection limit of Pb were obtained, compared to the result obtained from the direct analysis of liquids by LIBS. Applicability of the technique to real water samples was tested through spiking experiments and recoveries higher than 80% were obtained. Results demonstrate that, HG-LIBS approach is suitable for quantitative analysis of toxic elements and sufficiently fast for real time continuous monitoring in aqueous environments.
Keywords: Laser-induced breakdown spectroscopy; Hydride generation; Toxic elements; Detection limit;

SI and FR plots for LC × LC-DAD chromatograms of geographically different wine samples.Display Omitted► We compare two chemometric techniques for rapid screening of LC × LC-DAD. ► The Fisher ratio and similarity index methods were compared. ► Significant concentration differences of peaks between sample types were determined. ► Various chromatographic conditions were found to have an effect on both methods.Two chemometric methods are compared for the rapid screening of comprehensive two-dimensional liquid chromatographic (LC × LC) analysis of wine. The similarity index and Fisher ratio methods were both found to be able to distinguish geographical variability and to determine potentially significant peaks for further quantitative and qualitative study. An experimental data set consisting of five different wine samples and multiple simulated data sets were analyzed in the investigation of the screening methods. Several statistical analyses are employed in the understanding and verification of the results from the similarity index and Fisher ratio methods. The sum rank difference (SRD) method was used to compare the rankings of the two different methods as applied to the different data sets and to determine the amount of variability associated with the ranking of the peak differences. The major advantage the similarity index method offers is that it is an unsupervised method; no a priori knowledge of the samples (i.e., class identification) is required, while the Fisher ratio method is supervised. Both methods are rapid and require little user intervention other than the determination of a threshold for inclusion/exclusion of compounds from further analysis.
Keywords: Multiway data; Fisher ratio; Similarity index; Multivariate curve resolution; Honestly significant difference; Equivalence test;

Hasse diagram technique as a tool for water quality assessment by Tsvetomil Voyslavov; Stefan Tsakovski; Vasil Simeonov (29-35).
Display Omitted► Pre-selection procedure by self-organizing maps technique to reduce irrelevant information. ► Supervised pattern recognition to reveal specific patterns of pollutions along the river flow using Hasse diagram technique. ► Risk assessment combining chemometric techniques and local ecological legislation.The management of the quality large water catchments is a complex problem which requires intelligent data analysis on various levels – analytical, spatial, and temporal. Recently, a successful approach is developed combining advanced multivariate data treatment approaches like self-organizing maps of Kohonen (SOM) and Hasse diagram technique (HDT). In the first step of the environmetric analysis the monitoring data were subject to pre-processing using SOMs to reduce the number of objects and/or water quality parameters. In the next step HDT for partial ranking (both in spatial and temporal aspect) was applied according to the pre-selected set of the water quality parameters. The use of the water quality norms issued by the Bulgarian environmental authorities revealed important details in assessing the Maritsa River water quality. Thus, the relations between different water quality patterns and sampling stations could be used by water management authorities during the period of observation.
Keywords: Surface water; Quality assessment; Self-organizing maps; Hasse diagram technique;

Prediction of intracellular storage polymers using quantitative image analysis in enhanced biological phosphorus removal systems by Daniela P. Mesquita; Cristiano Leal; Jorge R. Cunha; Adrian Oehmen; A. Luís Amaral; Maria A.M. Reis; Eugénio C. Ferreira (36-44).
Display Omitted► Fluorescence staining and image analysis were used to monitor an EBPR system. ► Intracellular storage polymers were measured in anaerobic and aerobic stages. ► Partial least squares (PLS) were used to model the polymers concentrations. ► Previous stage identification improved the assessment of the polymer concentrations. ► A novel method for intracellular storage polymers assessment was established.The present study focuses on predicting the concentration of intracellular storage polymers in enhanced biological phosphorus removal (EBPR) systems. For that purpose, quantitative image analysis techniques were developed for determining the intracellular concentrations of PHA (PHB and PHV) with Nile blue and glycogen with aniline blue staining. Partial least squares (PLS) were used to predict the standard analytical values of these polymers by the proposed methodology. Identification of the aerobic and anaerobic stages proved to be crucial for improving the assessment of PHA, PHB and PHV intracellular concentrations. Current Nile blue based methodology can be seen as a feasible starting point for further enhancement. Glycogen detection based on the developed aniline blue staining methodology combined with the image analysis data proved to be a promising technique, toward the elimination of the need for analytical off-line measurements.
Keywords: Partial least squares; EBPR wastewater treatment systems; Image analysis; Intracellular polymers; Polyhydroxyalkanoates; Glycogen;

Assessment of bitter taste of pharmaceuticals with multisensor system employing 3 way PLS regression by Alisa Rudnitskaya; Dmitry Kirsanov; Yulia Blinova; Evgeny Legin; Boris Seleznev; David Clapham; Robert S. Ives; Kenneth A. Saunders; Andrey Legin (45-52).
Display Omitted► Chemically diverse APIs are studied with potentiometric “electronic tongue”. ► Bitter taste of APIs can be predicted with 3wayPLS regression from ET data. ► High correlation of ET assessment with human panel and rat in vivo model.The application of the potentiometric multisensor system (electronic tongue, ET) for quantification of the bitter taste of structurally diverse active pharmaceutical ingredients (API) is reported. The measurements were performed using a set of bitter substances that had been assessed by a professional human sensory panel and the in vivo rat brief access taste aversion (BATA) model to produce bitterness intensity scores for each substance at different concentrations. The set consisted of eight substances, both inorganic and organic – azelastine, caffeine, chlorhexidine, potassium nitrate, naratriptan, paracetamol, quinine, and sumatriptan. With the aim of enhancing the response of the sensors to the studied APIs, measurements were carried out at different pH levels ranging from 2 to 10, thus promoting ionization of the compounds. This experiment yielded a 3 way data array (samples × sensors × pH levels) from which 3wayPLS regression models were constructed with both human panel and rat model reference data. These models revealed that artificial assessment of bitter taste with ET in the chosen set of API's is possible with average relative errors of 16% in terms of human panel bitterness score and 25% in terms of inhibition values from in vivo rat model data. Furthermore, these 3wayPLS models were applied for prediction of the bitterness in blind test samples of a further set of API's. The results of the prediction were compared with the inhibition values obtained from the in vivo rat model.
Keywords: Electronic tongue; Potentiometric chemical sensors; Bitterness; API; n-Way PLS regression;

The inner cavities of β-CD could restrain fluoroquinolones to form stable host–guest inclusion complexes, and the guanidyl group of l-arg could enable l-arg to form electrostatic interactions with negatively charged groups ―COO of fluoroquinolones.Display Omitted► Electropolymerization of β-cyclodextrin and l-arginine on carbon paste electrode. ► The electrooxidation and reaction of FQs on the modified CPE were surmised. ► The sensor is used to detect ciprofloxacin, ofloxacin, norfloxacin and gatifloxacin. ► Determine FQs drugs in pharmaceutical formulations and human serum samples. ► It showed high stability, repeatability, reproducibility, good sensitivity.An electrochemical sensor for fluoroquinolones (FQs) based on polymerization of β-cyclodextrin (β-CD) and l-arginine (l-arg) modified carbon paste electrode (CPE) (P-β-CD-l-arg/CPE) was built for the first time. Synergistic effect of l-arg and β-CD was used to construct this sensor for quantification of these important antibiotics. Scanning electron microscope (SEM) image shows that polymer of β-CD and l-arg has been successfully modified on electrode. Electrochemical impedance spectroscopy (EIS) and cyclic voltammograms (CV) further indicate that polymer of β-CD and l-arg efficiently decreased the charge transfer resistance value of electrode and improved the electron transfer kinetic between analyte and electrode. Under the optimized conditions, this modified electrode was utilized to determine the concentrations of ciprofloxacin, ofloxacin, norfloxacin and gatifloxacin. The differential pulse voltammogram (DPV) exhibits the oxidation peak currents were linearly proportional to their concentration in the range of 0.05–100 μM for ciprofloxacin, 0.1–100 μM for ofloxacin, 0.1–40 μM for norfloxacin and 0.06–100 μM for gatifloxacin, respectively. This method was also successfully used to detect the concentrations of each drug in pharmaceutical formulations and human serum samples. In addition, this proposed fluoroquinolones sensor exhibited good reproducibility, long-term stability and fast current response.
Keywords: l-Arginine; β-Cyclodextrin; Fluoroquinolones; Cyclic voltammetry; Differential pulse voltammetry;

Construction of label-free electrochemical immunosensor on mesoporous carbon nanospheres for breast cancer susceptibility gene by Haixia Fan; Yong Zhang; Dan Wu; Hongmin Ma; Xiaojing Li; Yan Li; Huan Wang; He Li; Bin Du; Qin Wei (62-67).
Display Omitted► The immunosensor is designed to determine breast cancer susceptibility gene. ► Mesoporous carbon nanospheres (MCN) have great adsorption capacity. ► MCN could enhance the electroactivity of toluidine blue. ► Room temperature ionic liquid should increase the electrochemical signal.In this contribution, mesoporous carbon nanospheres (MCN) were used to fabricate a label-free electrochemical immunosensor for breast cancer susceptibility gene (BRCAl). The detection platform was constructed by conjugation of anti-BRCA1 on glassy carbon electrodes which were modified by mesoporous carbon nanospheres–toluidine blue nanocomposite (MCN–TB)/room temperature ionic-liquid (RTIL) composited film. TB was adsorbed onto MCN and acted as a redox probe. The electroactivity of TB was greatly enhanced in the presence of MCN. The good conductivity of MCN and BMIM·BF4 could promote the electron transfer and thus enhance the detection sensitivity. Moreover, the large surface area of MCN and the protein-binding properties of BMIM·BF4 could greatly increase the antibody loading. The specific antibody–antigen immunoreaction on the electrode surface resulted in a decrease of amperometric signal of the electrode. Under optimized conditions, the amperometric signal decreased linearly with BRCAl concentration in the range of 0.01–15 ng mL−1 with a low detection limit of 3.97 pg mL−1. The immunosensor exhibits high sensitivity, good selectivity and stability.
Keywords: Mesoporous carbon nanospheres; Electrochemical immunosensor; Ionic liquid; Breast cancer susceptibility gene;

In the present work, polythiophene-coated Fe3O4 nanoparticles (Fe3O4@PTh NPs) have been successfully synthesized. The synthesized Fe3O4@PTh NPs were applied as an efficient sorbent for extraction and pre-concentration of several typical plasticizer compounds from environmental water samples.Display Omitted► A novel polythiophene-coated Fe3O4 nanoparticles (Fe3O4@PTh NPs) was synthesized. ► The synthesized Fe3O4@PTh NPs were characterized by using different instruments. ► The Fe3O4@PTh NPs were applied as a sorbent for extraction of several plasticizers. ► After extraction, separation of NPs from solution was achieved by a magnetic field. ► The proposed procedure was applied to analysis of the analytes in real water samples.In the present work, a novel type of superparamagnetic nanosorbent, polythiophene-coated Fe3O4 nanoparticles (Fe3O4@PTh NPs), have been successfully synthesized. The synthesized NPs were characterized by scanning electron microscopy (SEM), Fourier transform-infrared (FT-IR) spectroscopy, and thermal gravimetric analysis (TGA). The synthesized Fe3O4@PTh NPs were applied as an efficient sorbent for extraction and preconcentration of several typical plasticizer compounds (di-n-butyl phthalate (DBP), di-(2-ethylhexyl) phthalate (DEHP), and dioctyl adipate (DOA)) from environmental water samples. Separation of Fe3O4@PTh NPs from the aqueous solution was simply achieved by applying external magnetic field. Separation and determination of the extracted plasticizers was performed by gas chromatography–flame ionization detection (GC–FID). Several variables affecting the extraction efficiency of the analytes i.e., amount of NPs sorbent, salt concentration, extraction time, and desorption conditions were investigated and optimized. The best working conditions were as follows: amount of sorbent, 100 mg; NaCl concentration, 30% (w/v); sample volume, 45 mL; extraction time, 10 min; and 100 μL of ethyl acetate for desorption of the analytes within 2 min. Under optimized conditions, preconcentration factors for DBP, DEHP, and DOA were obtained as 86, 194, and 213, respectively. The calibration curves were linear (R 2  > 0.998) in the concentration range of 0.4–100 μg L−1 for both DEHP and DOA and 0.7–100 μg L−1 for DBP. The limits of detection (LODs) were obtained in the range of 0.2–0.4 μg L−1. The intra-day relative standard deviations (RSDs%) based on four replicates were obtained in the range of 4.0–12.3%. The proposed procedure was applied to analysis of water samples including river water, bottled mineral water, and boiling water exposed to polyethylene container (after cooling) and recoveries between 85 and 99% and RSDs lower than 12.8% were obtained.
Keywords: Polythiophene-coated Fe3O4 magnetic nanoparticles; Magnetic separation; Phthalates; Gas chromatography–flame ionization detector; Solid-phase extraction;

In-sample derivatization-solid-phase microextraction of amphetamines and ecstasy related stimulants from water and urine by Inés Racamonde; Rosario Rodil; José Benito Quintana; Rafael Cela (75-84).
Display Omitted► First SPME method for determination of amphetamines and ecstasy in (waste)water. ► In-sample simultaneous derivatization and extraction with iso-butyl chloroformate. ► Wastewater (100 mL): LODs: 0.4–2 ng L−1, RSD < 15%; recoveries: 84–114%. ► Urine (1 mL): LODs:<1 μg L−1, RSD < 11%; recoveries: 98–110%. ► Solvent-free and fully automatable method.A solid-phase microextraction (SPME) method for the determination of five amphetamine type stimulants (ATSs) in water and urine samples is presented. Analytes were simultaneously derivatized with iso-butyl chloroformate (iBCF) in the aqueous sample while being extracted, improving in this way the extractability of ATSs and permitting their determination by gas chromatography–mass spectrometry (GC–MS). The SPME procedure was carefully optimized in order to achieve adequate limits of detection (LODs) for environmental concentrations. Hence, different operational parameters were considered: type of SPME coating, ionic strength, basic catalyzer and derivatizing agent amount, extraction time and temperature. The final SPME procedure consists into the extraction of 100 mL of sample containing 2 g of dipotassium monohydrogen phosphate trihydrate and 100 μL of iBCF (1:1 in acetonitrile), for 40 min at 60 °C with a polydimethylsiloxane-divinylbenzene (PDMS-DVB) fiber. Under these conditions, LODs in wastewater ranged from 0.4 to 2 ng L−1, relative recoveries in the 84–114% range and relative standard deviations (RSD) lower than 15% were obtained. The application of the method to wastewater and river water samples showed the ecstasy ATS, 3,4-methylenedioxymethamphetamine (MDMA), as the most frequently detected, followed by methamphetamine, in concentrations around 20 ng L−1. Finally, the method was downscaled and also validated with urine samples, proving its good performance with this matrix too: RSD < 11%, recoveries in the 98–110% range and LODs lower than 0.1 μg L−1.
Keywords: Illicit drugs; Amphetamines; Ecstasy; 3,4-Methylenedioxymethamphetamine; Derivatization; Solid-phase microextraction;

Application of polydimethylsiloxane rod extraction to the determination of sixteen halogenated flame retardants in water samples by Carme Valls-Cantenys; Eugenia Villaverde-de-Sáa; Rosario Rodil; José Benito Quintana; Mònica Iglesias; Victòria Salvadó; Rafael Cela (85-93).
Display Omitted► Simultaneous determination of nine BDEs and seven non-BDE flame retardants. ► Disposable polydimethylsiloxane (PDMS) is an efficient tool for flame retardants extraction. ► Enrichment factors between 108 and 840 were obtained. ► Detection limits obtained were in the range from 0.4 to 10 ng L−1. ► The method has been successfully applied in the analysis of complex matrix waters.An extraction and preconcentration procedure for the determination in water samples of several halogenated flame retardants (FRs), nine brominated diphenyls ethers (BDEs) and seven non-BDE FRs, was developed and validated. The optimised procedure is based on polydimethylsiloxane (PDMS) rods as sorptive extraction material, followed by liquid desorption and gas chromatography coupled to negative chemical ionisation–mass spectrometry (GC–NCI–MS) determination, rendering an efficient and inexpensive method. The final optimised protocol consists of overnight extraction of 100 mL of sample solutions containing 40% MeOH and 4% NaCl, followed by a 15-min sonication-assisted desorption with 300 μL of ethyl acetate, solvent evaporation and GC–NCI–MS analysis. Under these conditions, extraction efficiencies in the 9 to 70% range were obtained, leading to enrichment factors between 108 and 840, detection limits in the range from 0.4 to 10 ng L−1and RSD values in the 2–23% range. After method validation, different real water samples, including river, ria, sea, landfill leachate, influent and effluent wastewater from an urban sewage treatment plant (STP) and effluent wastewater from a textile industry, were analysed. BDE-47, BDE-99, BDE-100 and BDE-197 were detected in wastewater and landfill leachate samples at concentration levels up to 2887 ng L−1. Among the non-BDE FRs, bis (2-ethylhexyl)-3,4,5,6-tetrabromo-phthalate (DEHTBP) was detected in surface water samples (sea, river and ria) between 1.3 and 2.2 ng L−1 and 1,2-bis(2,4,6-tribromophenoxy)ethane (BTBPE) in the landfill leachate (64 ng L−1).
Keywords: Halogenated flame retardants; Brominated diphenylethers (BDEs); Polydimethylsiloxane (PDMS); Gas chromatography–negative chemical ionisation–mass spectrometry (GC–NCI–MS); Water;

Display Omitted► SPE of aminopolycarboxylic acids without preparing iron complexes is studied. ► Adjusting water sample conditions the retention on activated charcoal is feasible. ► There is not any significant matrix-effect in the quantification by GC/MS. ► Method performance characteristics are given. Robustness and uncertainty are evaluated.A new sample preparation procedure to determine aminopolycarboxylic acids (ethylenediaminetetraacetic acid, EDTA, nitrilotriacetic acid, NTA, diethylenetriaminepentaacetic acid, DTPA, and cyclohexanediaminetetraacetic acid, CDTA) in river water is described. The procedure consists of the solid-phase extraction of the aminopolycaroxyllic acids on activated charcoal cartridges after increasing the ionic strength and acidifying the sample. The extract was eluted with methanol and the analytes were methylated in presence of BF3/methanol to determine them by GC with mass spectrometric detection. Recoveries were higher than 90% with good repeatabilities and inter-day precision for concentrations close to quantification limits (about 10 μg L−1) and higher. It has been verified that the proposed method is robust according to the Youden and Steiner test and free of matrix effects arisen from the presence of organic matter and iron(III) as deduced from statistical tests. A bottom-up approach was followed to estimate the uncertainty of the measured concentration. At concentrations close to 10 μg L−1 the most relevant step of the method is the calculus of the interpolated concentration which has a high value of relative standard uncertainty.
Keywords: Aminopolycarboxylic acids; Activated charcoal; Water; Gas chromatography; Uncertainty;

Influence of material transition and interfacial area changes on flow and concentration in electro-osmotic flows by Sudheer D. Rani; Byoung-Hee You; Steve A. Soper; Michael C. Murphy; Dimitris E. Nikitopoulos (103-110).
Display Omitted► Combined material and geometrical transition in electrokinetic flows was studied. ► Material and geometrical transition resulted in dispersion and reduced flow rates. ► Effect of only geometrical transition on species was less compared to material transition. ► Sample dispersion was quantified with standard metrics. ► Correlations were developed to estimate the reduction in flow rates.This paper presents a numerical study to investigate the effect of geometrical and material transition on the flow and progression of a sample plug in electrokinetic flows. Three cases were investigated: (a) effect of sudden cross-sectional area change (geometrical transition or mismatch) at the interface, (b) effect of only material transition (i.e. varying ζ-potential), and (c) effect of combined material transition and cross-sectional area change at the interface. The geometric transition was quantified based on the ratio of reduced flow area A 2 at the mismatch plane to the original cross-sectional area A 1. Multiple simulations were performed for varying degrees of area reduction i.e. 0–75% reduction in the available flow area, and the effect of dispersion on the sample plug was quantified by standard metrics. Simulations showed that a 13% combined material and geometrical transition can be tolerated without significant loss of sample resolution. A 6.54% reduction in the flow rates was found between 0% and 75% combined material and geometrical transition.
Keywords: Electrokinetic flows; Material transition; Geometrical transition; Concentration; Zeta potential; Microfluidics;

Inter-laboratory trials for analysis of perfluorooctanesulfonate and perfluorooctanoate in water samples: Performance and recommendations by Sachi Taniyasu; Kurunthachalam Kannan; Qian Wu; Karen Y. Kwok; Leo W.Y. Yeung; Paul K.S. Lam; Brock Chittim; Takafumi Kida; Takumi Takasuga; Yoshiteru Tsuchiya; Nobuyoshi Yamashita (111-120).
Display Omitted► Three inter-laboratory trials were conducted to validate perfluorochemical analysis in water samples. ► Provision of SOPs and standards improved the precision and accuracy of analysis. ► The repeatability and reproducibility coefficients of variation were below 35%. ► Accuracy was improved with the use of appropriate labeled internal standards.The ISO 25101 (International Organization for Standardization, Geneva) describes a new international standard method for the determination of perfluorooctanesulfonate (PFOS) and perfluorooctanoate (PFOA) in unfiltered samples of drinking and surface waters. The method is based on the extraction of target analytes by solid phase extraction, solvent elution, and determination by high performance liquid chromatography–tandem mass spectrometry (HPLC–MS/MS). For the determination of the performance of this method, more than 20 laboratories from 9 different countries participated in an inter-laboratory trial in 2006. In addition, inter-laboratory trials were conducted in 2008 and 2009 for the analysis of perfluoroalkylsubstances (PFASs), including PFOS and PFOA, in water samples by following the protocols of Japanese Industrial Standard (JIS). Overall, the repeatability coefficients of variation (i.e., within-laboratory precision) for PFOS and PFOA in all water samples were between 3 and 11%, showing a adequate precision of the ISO and JIS methods. The reproducibility coefficients of variation (i.e., between-laboratory precision) were found to vary within a range of 7–31% for surface water and 20–40% for wastewater. The recoveries of PFOS and PFOA, as a measure of accuracy, varied from 84 to 100% for surface water and from 84 to 100% for wastewater among the samples with acceptable criteria for internal standards recovery. The determined concentrations of PFASs in samples compared well with the “true” values. The results of the inter-laboratory trial confirmed that the analytical methods are robust and reliable and can be used as a standard method for the analysis of target compounds in water samples.
Keywords: Inter-laboratory trial; PFOS; Perfluoroalkyl substances; Water; HPLC–MS/MS, ISO;

Display Omitted► Untargeted LC/MS/MS screening for drug identification in blood, plasma and urine. ► The assay shares the sample preparation workflow with established GC/MS screening. ► Compound identification with the “Wiley Registry of Tandem Mass Spectral Data”. ► Selectivity, detection capability and reliability of identification are discussed. ► Parallel screening with LC/MS/MS and GC/MS offers utmost reliability.Systematic toxicological analysis (STA) is aimed at detecting and identifying all substances of toxicological relevance (i.e. drugs, drugs of abuse, poisons and/or their metabolites) in biological material. Particularly, gas chromatography–mass spectrometry (GC/MS) represents a competent and commonly applied screening and confirmation tool. Herein, we present an untargeted liquid chromatography–tandem mass spectrometry (LC/MS/MS) assay aimed to complement existing GC/MS screening for the detection and identification of drugs in blood, plasma and urine samples. Solid-phase extraction was accomplished on mixed-mode cartridges. LC was based on gradient elution in a miniaturized C18 column. High resolution electrospray ionization-MS/MS in positive ion mode with data-dependent acquisition control was used to generate tandem mass spectral information that enabled compound identification via automated library search in the “Wiley Registry of Tandem Mass Spectral Data, MSforID”. Fitness of the developed LC/MS/MS method for application in STA in terms of selectivity, detection capability and reliability of identification (sensitivity/specificity) was demonstrated with blank samples, certified reference materials, proficiency test samples, and authentic casework samples.
Keywords: Liquid chromatography; Mass spectrometry; Electrospray ionization; Tandem mass spectral library; Systematic toxicological analysis; Forensic analysis;

Core–shell Fe3O4–Au magnetic nanoparticles and P-GS@QDs were prepared to immobilize Ab1 and Ab2 respectively and combined to fabricate a novel sandwich-type ECL immunosensor for detecting CA125 at low concentration.Display Omitted► ECL immunosensor for CA125 based on a microfluidic strategy with a homemade ECL cell was proposed. ► Core–shell Fe3O4–Au magnetic nanoparticles were employed as the carriers of the primary antibodies. ► CdTe quantum dots functionalized graphene sheet were used for signal amplification.In this paper, a novel, low-cost electrochemiluminescence (ECL) immunosensor using core–shell Fe3O4–Au magnetic nanoparticles (AuMNPs) as the carriers of the primary antibody of carbohydrate antigen 125 (CA125) was designed. Graphene sheet (GS) with property of good conductivity and large surface area was a captivating candidate to amplify ECL signal. We successively synthesized functionalized GS by loading large amounts of quantum dots (QDs) onto the poly (diallyldimethyl-ammonium chloride) (PDDA) coated graphene sheet (P-GS@QDs) via self-assembly electrostatic reactions, which were used to label secondary antibodies. The ECL immunosensors coupled with a microfluidic strategy exhibited a wide detection range (0.005–50 U mL−1) and a low detection limit (1.2 mU mL−1) with the help of an external magnetic field to gather immunosensors. The method was evaluated with clinical serum sample, receiving good correlation with results from commercially available analytical procedure.
Keywords: Core–shell Fe3O4–Au; CdTe quantum dots; Graphene; Electrochemiluminescence; Immunosensor;

Scheme for preparation of GSH-Au NCs (a) and application in selective determination of Cr(III) and Cr(VI) (b).Display Omitted► Facile and rapid preparation of fluorescent glutathione-stabilized gold nanoclusters. ► New method for selective determination of Cr(III) and Cr(VI) using GSH-Au NCs. ► The detection method possessed simplicity, high throughput, high selectivity and sensitivity.A novel method for selective determination of Cr(III) and Cr(VI) in environmental water samples was developed based on target-induced fluorescence quenching of glutathione-stabilized gold nanoclusters (GSH-Au NCs). Fluorescent GSH-Au NCs were synthesized by a one-step approach employing GSH as reducing/protecting reagent. It was found that Cr(III) and Cr(VI) showed pH-dependent fluorescence quenching capabilities for GSH-Au NCs, and thus selective determination of Cr(III) and Cr(VI) could be achieved at different pHs. Addition of EDTA was able to effectively eliminate the interferences from other metal ions, leading to a good selectivity for this method. Under optimized conditions, Cr(III) showed a linear range of 25–3800 μg L−1 and a limit of detection (LOD) of 2.5 μg L−1. The Cr(VI) ion demonstrated a linear range of 5–500 μg L−1 and LOD of 0.5 μg L−1. The run-to-run relative standard deviations (n  = 5) for Cr(III) and Cr(VI) were 3.9% and 2.8%, respectively. The recoveries of Cr(III) and Cr(VI) in environmental water samples were also satisfactory (76.3–116%). This method, with its simplicity, low cost, high selectivity and sensitivity, could be used as a promising tool for chromium analysis in environmental water samples.
Keywords: Glutathione; Gold nanoclusters; Chromium; Environmental sample; Fluorescence quenching;

The ATP recognition probe (S1) was immobilized on the surface of MB-AuNPs and hybridized with its partly complementary sequence (S2) to form a duplex. When the target ATP was introduced, S1 changed its conformation to combine with ATP (step Ia) and S2 was released (step Ib) to trigger the MB-assisted strand displacement amplification (step II). In cycle 1, S2 hybridized with the single-stranded toehold domain of S3 and the single-stranded DNA (S4) was dissociated from the MB-AuNPs by branch migration, enabling S3 to possess a newly exposed single-stranded toehold. Then the biotin-tagged single-stranded fuel (S6) was hybridized with the newly exposed toehold, releasing S5 and S2. At the same time, the double-stranded product and the biotin-tagged MB complexes were formed. The released S5 would further participate in the target recycling amplification reaction (cycle 2). S2 was used as catalyst to implement another circulation of the MB-assisted strand displacement amplification. In cycle 1, the released S4 could hybridize with the recognition probe (S1) by DNA displacement reaction, making more S2 to be dissociated to participate in cycle 1. The second amplification process (cycle 2) was initiated by S5, which could hybridize with the extension part in S1/ATP complex and be used as the primer of a polymerization reaction. In the presence of Klenow polymerase and dNTPs, the primer extended and formed a duplex with the ATP recognition probe. Thus the target ATP was displaced, which could bind with another recognition probe and trigger new amplification cycles. Finally, a large amount of biotin-tagged MB complexes were produced. As the fuel (S6) was modified with biotin, the S3/S6 double-stranded product on MB-AuNPs could incorporate with streptavidin-HRP to perform the enzyme-amplification CL detection.Display Omitted► An aptasensor is fabricated by strand displacement amplification and target recycling. ► The reaction efficiency is greatly improved by cross-circular amplification. ► Sensitive detection of other targets can be achieved by using different aptamers.A cross-circular amplification system for sensitive detection of adenosine triphosphate (ATP) in cancer cells was developed based on aptamer–target interaction, magnetic microbeads (MBs)-assisted strand displacement amplification and target recycling. Here we described a new recognition probe possessing two parts, the ATP aptamer and the extension part. The recognition probe was firstly immobilized on the surface of MBs and hybridized with its complementary sequence to form a duplex. When combined with ATP, the probe changed its conformation, revealing the extension part in single-strand form, which further served as a toehold for subsequent target recycling. The released complementary sequence of the probe acted as the catalyst of the MB-assisted strand displacement reaction. Incorporated with target recycling, a large amount of biotin-tagged MB complexes were formed to stimulate the generation of chemiluminescence (CL) signal in the presence of luminol and H2O2 by incorporating with streptavidin-HRP, reaching a detection limit of ATP as low as 6.1 × 10−10  M. Moreover, sample assays of ATP in Ramos Burkitt's lymphoma B cells were performed, which confirmed the reliability and practicality of the protocol.
Keywords: Adenosine triphosphate; Aptamer; Strand displacement amplification; Target recycling; Chemiluminescence;

Display Omitted► Cathodic ECL offers conventional and non-aggressive analysis conditions. ► The ECL hydrogen peroxide/ruthenium complex system for uric acid determination is novel. ► The ruthenium complex is electrochemically immobilized on graphite screen-printed electrodes. ► The quantification of the uric acid is based on a Stern–Volmer type equation. ► The use of the cathodic ECL working methodology reduces interferences during analysis.A new method for uric acid (UA) determination based on the quenching of the cathodic ECL of the tris(2,2-bipyridine)ruthenium(II)–uricase system is described. The biosensor is based on a double-layer design containing first tris(2,2-bipyridine)ruthenium(II) (Ru(bpy)3 2+) electrochemically immobilized on graphite screen-printed cells and uricase in chitosan as a second layer. The uric acid biosensing is based on the ECL quenching produced by uric acid over the cathodic ECL caused by immobilized Ru(bpy)3 2+ in the presence of uricase. The use of a −1.1 V pulse for 1 s with a dwelling time of 10 s makes it possible to estimate the initial enzymatic rate, which is used as the analytical signal. The Stern–Volmer type calibration function shows a dynamic range from 1.0 × 10−5 to 1.0 × 10−3  M with a limit of detection of 3.1 × 10−6  M and an accuracy of 13.6% (1.0 × 10−4  M, n  = 5) as relative standard deviation. Satisfactory results were obtained for urine samples, creating an affordable alternative for uric acid determination.
Keywords: Cathodic electrochemiluminescence; Disposable biosensor; Immobilized Ru(bpy)3 2+; Uric acid determination;

Colorimetric test-systems for creatinine detection based on composite molecularly imprinted polymer membranes by T.A. Sergeyeva; L.A. Gorbach; E.V. Piletska; S.A. Piletsky; O.O. Brovko; L.A. Honcharova; O.D. Lutsyk; L.M. Sergeeva; O.A. Zinchenko; A.V. El'skaya (161-168).
Display Omitted► A colorimetric test-system for the detection of creatinine in aqueous samples was developed. ► The test-system is based on composite molecularly imprinted polymer (MIP) membranes. ► The colorimetric test-system was characterized with 0.25 mM detection limit for creatinine. ► The linear dynamic range of the test-system for creatinine comprised 0.25–2.5 mM.An easy-to-use colorimetric test-system for the efficient detection of creatinine in aqueous samples was developed. The test-system is based on composite molecularly imprinted polymer (MIP) membranes with artificial receptor sites capable of creatinine recognition. A thin MIP layer was created on the surface of microfiltration polyvinylidene fluoride (PVDF) membranes using method of photo-initiated grafting polymerization. The MIP layer was obtained by co-polymerization of a functional monomer (e.g. 2-acrylamido-2-methyl-1-propanesulfonic acid, itaconic acid or methacrylic acid) with N, N′-methylenebisacrylamide as a cross-linker. The choice of the functional monomer was based on the results of computational modeling. The creatinine-selective composite MIP membranes were used for measuring creatinine in aqueous samples. Creatinine molecules were selectively adsorbed by the MIP membranes and quantified using color reaction with picrates. The intensity of MIP membranes staining was proportional to creatinine concentration in an analyzed sample. The colorimetric test-system based on the composite MIP membranes was characterized with 0.25 mM detection limit and 0.25–2.5 mM linear dynamic range. Storage stability of the MIP membranes was estimated as at least 1 year at room temperature. As compared to the traditional methods of creatinine detection the developed test-system is characterized by simplicity of operation, small size and low cost.
Keywords: Molecularly imprinted polymers; Molecularly imprinted polymer membranes; Grafting polymerization; Test-system; Creatinine;

Display Omitted► Development of “single specific primer-NASBA” method. ► Designing a highly specific NASBA primer for a segment of 16S rDNA variable region. ► Simultaneous detection of S. Enteritidis and S. Typhimurium. ► Achieving the low detection limit of less than 10 CFU mL−1. Salmonella Enteritidis and Salmonella Typhimurium are the most widespread causes of salmonellosis and gastrointestinal diseases worldwide. Thus, their simple and sensitive detection is significantly important in biosafety and point-of-care diagnostics. In that regard, although present nucleic acid-based attempts are mainly focused on the detection methods encompassing all Salmonella enterica members in a single reaction, serotypes other than S. Enteritidis and S. Typhimurium are clinically and epidemiologically rare to humans. Therefore, regarding high ribosomal RNA (rRNA) copy numbers in a cell, isothermal nucleic acid sequence-based amplification (NASBA) technique was employed for simple, sensitive and simultaneous detection of the bacteria. However, due to high sequence homology among 16S rRNA genes and consequently, very few specific regions, we developed a novel NASBA method called “single specific primer-NASBA or SSP-NASBA” in which the specificity of the antisense primer is sufficient to perform a specific NASBA reaction. Accordingly, we designed highly specific NASBA antisense and degenerate sense primers for a segment of 16S rRNA variable region by universal sequence alignment to simultaneously detect S. Enteritidis and S. Typhimurium. Meanwhile, the approach was successfully evaluated for various Salmonella as well as closely related non-Salmonella serovars. Specific and simultaneous detection of both bacteria was achieved with the designed primer set in a single reaction environment with a detection limit of less than 10 CFUs mL−1. The developed NASBA assay should facilitate the overall process and provide a simple, fast, specific and sensitive approach for molecular diagnostics of pathogens under various circumstances, e.g. outbreaks.
Keywords: Nucleic acid sequence-based amplification (NASBA); Simultaneous detection; 16S rRNA; Salmonella Enteritidis; Salmonella Typhimurium;