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Analytica Chimica Acta (v.716, #)

Editorial Board (pp. iii).

ExTech2010. Poznań, Poland, September 20–22, 2010 by Henryk Jeleń (pp. 1-1).

Simultaneous sampling and analysis of indoor air infested with Cimex lectularius L. (Hemiptera: Cimicidae) by solid phase microextraction, thin film microextraction and needle trap device by In-Yong Eom; Sanja Risticevic; Janusz Pawliszyn (pp. 2-10).

Display Omitted► Air in a room infested by Cimex lectularius L. was sampled by SPME, TFME and NTDs. ► Characterization of indoor air and C. lectularius pheromone was performed with use of different SPME formats. ► The performance characteristics of three different SPME formats were compared for wide range of analytes. ► NTD devices captured ( E)-2-hexenal and ( E)-2-octenal, compounds previously identified as alarm pheromones of bedbugs.Air in a room infested by Cimex lectularius L. (Hemiptera: Cimicidae) was sampled simultaneously by three different sampling devices including solid phase microextraction (SPME) fiber coatings, thin film microextraction (TFME) devices, and needle trap devices (NTDs) and then analyzed by gas chromatography–mass spectrometry (GC–MS). The main focus of this study was to fully characterize indoor air by identifying compounds extracted by three different microextraction formats and, therefore, perform both the device comparison and more complete characterization of C. lectularius pheromone. The NTD technique was capable of extracting both ( E)-2-hexenal and ( E)-2-octenal, which were previously identified as alarm pheromones of bedbugs, and superior NTD recoveries for these two components allowed reliable identification based on mass spectral library searching and linear temperature programmed retention index (LTPRI) technique. While the use of DVB/CAR/PDMS SPME fiber coatings provided complementary sample fingerprinting and profiling results, TFME sampling devices provided discriminative extraction coverage toward highly volatile analytes. In addition to two alarm pheromones, relative abundances of all other analytes were recorded for all three devices and aligned across all examined samples, namely, highly infested area, less infested area, and control samples which were characterized by different bedbug populations. The results presented in the current study illustrate comprehensive characterization of infested indoor air samples through the use of three different non-invasive SPME formats and identification of novel components comprising C. lectularius pheromone, therefore, promising future alternatives for use of potential synthetic pheromones for detection of infestations.

Keywords: Cimex lectularius; Pheromone; Indoor air; Solid phase microextraction; Thin film microextraction; Needle trap device

Influence of magnetic field on aqueous two-phase extraction of horse ferritin in the polyethylene glycol/hydroxyethyl starch system by Magdalena Zielińska-Dawidziak; Roman Błaszak; Dorota Piasecka-Kwiatkowska (pp. 11-15).

The presented experiments show the model of expectation of equine spleen ferritin extraction in a new aqueous two-phase system which was formed by mixing polyethylene glycol (PEG) and hydroxyethyl starch (HES). The tendency of the protein to migrate in the analyzed systems was dependent on the concentrations of HES and PEG as well as PEG molecular weight. The highest concentration of ferritin in the top phase (rich in PEG) was recorded in the system composed of 6% PEG 3000 and 3% HES. The obtained concentration was 0.88mgmL⁻¹. The lowest concentration was 0.42mgmL⁻¹ in the system composed of 5% PEG 6000 and 1% HES.Next the influence of the magnetic field on ferritin accumulation was analyzed. Selected samples were placed between homogeneous (S/S) or heterogeneous magnetic poles (N/S and S/N). It was observed that after the application of the magnetic field the extraction of ferritin into the PEG rich phase increased in every examined system. That increase was as high as 1.67-fold ferritin concentration in the PEG phase as compared with the total concentration of ferritin in the system before separation. Introduction of the magnetic field to two-phase extraction systems is shown as an effective method of changing the partition coefficient of ferritin.

Keywords: Equine spleen ferritin; Aqueous two-phase extraction; Magnetic field

Fast, selective, and sensitive analysis of low-abundance peptides in human plasma by electromembrane extraction by Marte Balchen; Hanne Lund; Léon Reubsaet; Stig Pedersen-Bjergaard (pp. 16-23).

A totally new concept based on electrokinetic migration was evaluated for the extraction of three biologically active peptides from human plasma. Angiotensin 2, leu-enkephalin, and endomorphin 1 migrated from a diluted human plasma sample (2mL, positive electrode), through a supported liquid membrane (SLM) of 1-octanol, di-isobutylketon, and di-(2-ethylhexyl) phosphate (DEHP) (55:35:10, w/w/w), and into an acidified acceptor solution (25μL 50mM HCl, negative electrode) by the application of an electrical potential (20V) across the SLM. After only five min of extraction, the acceptor solution was injected and analyzed directly by liquid chromatography. The three peptides were quantified by tandem mass spectrometry, with acceptable linearity ranging from 100.0 to 1000.0pgmL⁻¹ ( r² in the range 0.9736–0.9988), and repeatability (RSD) ranging between 15% and 24% ( n=5), using plasma spiked with the three peptides in 100pgmL⁻¹ concentration. The estimated detection limits (S/N ratio of 3:1) for angiotensin 2, leu-enkephalin, and endomorphin 1, were 60, 24, and 24pgmL⁻¹, respectively. With this novel approach based on electromembrane extraction (EME) coupled to LC–MS/MS, endogenous concentrations of the peptides were detected in non-spiked human plasma samples, with a total analysis time less than 50min. These experimental findings were highly interesting, and showed the opportunities for EME with regard to future peptide extractions.

Keywords: Electromembrane extraction (EME); Peptides; Sample preparation; Supported liquid membrane (SLM); Biological samples; MS/MS

Determination of SCFAs in water using GC-FID. Selection of the separation system by Anna Banel; Anna Jakimska; Marta Wasielewska; Lidia Wolska; Bogdan Zygmunt (pp. 24-27).

In the present study, an analytical procedure was developed for the determination of short-chain fatty acids (SCFAs) in landfill leachate and municipal wastewater employing injection of aqueous samples to gas chromatograph with flame ionization detector (GC-FID). Chromatographic conditions such as a separation system, injection volume, oven temperature program were investigated and selected. With two columns, one with a polar (polyethylene glycol) and one with a non-polar (dimethylpolisiloxane) stationary phase, good separation of SCFAs, containing from 2 to 8 carbon atoms, was achieved. The sample volume was 2μL and the temperature program 80°C (30s) then 7°Cmin⁻¹ to 220°C (2min). LOQs values were below 0.25mgL⁻¹. The concentrations of the acids in the landfill leachate studied ranged from 0.45±0,059 (average±extended uncertainty) mgL⁻¹ for pentanoic acid to 15.2±0.73mgL⁻¹ for ethanoic acid. Concentrations of SCFAs in the municipal wastewater were lower than LOQs.

Keywords: Short-chain fatty acids (SCFAs); Chromatographic columns; Gas chromatography; Wastewater; Landfill leachate

Ionic liquids based simultaneous ultrasonic and microwave assisted extraction of phenolic compounds from burdock leaves by Zaixiang Lou; Hongxin Wang; Song Zhu; Shangwei Chen; Ming Zhang; Zhouping Wang (pp. 28-33).

The ionic liquids based simultaneous ultrasonic and microwave assisted extraction (IL-UMAE) technique was first proposed and applied to isolate compounds. The ionic liquids comprising a range of four anions, five 1-alkyl-3-methylimidazolium derivatives were designed and prepared. The results suggested that varying the anion and cation both had apparent effects on the extraction of phenolics. The results also showed that irradiation power, time and solid–liquid ratio significantly affected the yields. The yields of caffeic acid and quercetin obtained by IL-UMAE were higher than those by regular UMAE. Compared with conventional heat-reflux extraction (HRE), the proposed approach exhibited higher efficiency (8–17% enhanced) and shorter extraction time (from 5h to 30s). The results indicated ILUMAE to be a fast and efficient extraction technique. Moreover, the proposed method was validated by the reproducibility and recovery experiments. The ILUMAE method provided good recoveries (from 96.1% to 105.3%) with RSD lower than 5.2%, which indicated that the proposed method was credible. Based on the designable nature of ionic liquids, and the rapid and highly efficient performance of the proposed approach, ILUMAE provided a new alternative for preparation of various useful substances from solid samples.

Keywords: Ionic liquids; Simultaneous ultrasonic and microwave assisted extraction technique; Burdock leaves; Phenolic compounds

Novel polyamide-based nanofibers prepared by electrospinning technique for headspace solid-phase microextraction of phenol and chlorophenols from environmental samples by Habib Bagheri; Ali Aghakhani; Masoud Baghernejad; Alireza Akbarinejad (pp. 34-39).

A novel solid phase microextraction (SPME) fiber was fabricated by electrospinning method in which a polymeric solution was converted to nanofibers using high voltages. A thin stainless steel wire was coated by the network of polymeric nanofibers. The polymeric nanofiber coating on the wire was mechanically stable due to the fine and continuous nanofibers formation around the wire with a three dimensional structure. Polyamide (nylon 6), due to its suitable characteristics was used to prepare the unbreakable SPME nanofiber. The scanning electron microscopy (SEM) images of this new coating showed a diameter range of 100–200nm for polyamide nanofibers with a homogeneous and porous surface structure. The extraction efficiency of new coating was investigated for headspace solid-phase microextraction (HS-SPME) of some environmentally important chlorophenols from aqueous samples followed by gas chromatography–mass spectrometry (GC–MS) analysis. Effect of different parameters influencing the extraction efficiency including extraction temperature, extraction time, ionic strength and polyamide amount were investigated and optimized. In order to improve the chromatographic behavior of phenolic compounds, all the analytes were derivatized prior to the extraction process using basic acetic anhydride. The detection limits of the method under optimized conditions were in the range of 2–10ngL⁻¹. The relative standard deviations (RSD) ( n= 3) at the concentration level of 1.7–6.7ngmL⁻¹ were obtained between 1 and 7.4%. The calibration curves of chlorophenols showed linearity in the range of 27–1330ngL⁻¹ for phenol and monochlorophenols and 7–1000ngL⁻¹ for dichloro and trichlorophenols. Also, the proposed method was successfully applied to the extraction of phenol and chlorophenols from real water samples and relative recoveries were between 84 and 98% for all the selected analytes except for 2,4,6 tricholophenol which was between 72 and 74%.

Keywords: Electrospinning; Polyamide nanofiber; Solid phase microextraction; Gas chromatography–mass spectrometry; Chlorophenols

Degradation effects in the extraction of antioxidants from birch bark using water at elevated temperature and pressure by Michelle Co; Camilla Zettersten; Leif Nyholm; Per J.R. Sjöberg; Charlotta Turner (pp. 40-48).

Display Omitted► Degradation of antioxidants was studied at elevated temperature and pressure. ► Extraction with and without hydrothermal treatments of birch bark was conducted. ► Online HPLC-DAD-ECD-MS/MS facilitates molecular elucidation of the extracted antioxidants.Experiments with birch bark samples have been carried to enable a distinction between extraction and degradation effects during pressurised hot water extraction. Two samples, E80 and E180, contained birch bark extracts obtained after extraction at 80 and 180°C for up to 45min, respectively. Two other samples, P80 and P180, were only extracted for 5min at the two temperatures and were thereafter filtered and hydrothermally treated at 80 and 180°C, respectively. During the latter treatment, samples were collected at different times to assess the stability of the extracted compounds. An offline DPPH (2,2-diphenyl-1-picrylhydrazyl) assay, as well as a high performance liquid chromatographic separation coupled to an electrochemical detector, were used to determine the antioxidant capacity of the processed samples. The results obtained with the different techniques were compared to assess the yield of the extraction and degradation processes. In addition, an online hyphenated system comprising high performance liquid chromatography coupled to diode-array; electrochemical; and tandem mass spectrometric detection (HPLC-DAD-ECD-MS/MS) was used to study the compositions of the extracts in more detail. The results for the samples processed at 80°C showed that the extraction reached a steady-state already after 5min, and that the extracted compounds were stable throughout the entire extraction process. Processing at 180°C, on the other hand, gave rise to partly degraded extracts with a multitude of peaks in both the diode array and electrochemical detectors, and a higher antioxidant capacity compared to for the extracts obtained at 80°C. It is concluded that HPLC-DAD-ECD is a more appropriate technique for the determination of antioxidants than the DPPH assay. The mass spectrometric results indicate that one of the extracted antioxidants, catechin, was isomerised to its diastereoisomers; (+)-catechin, (−)-catechin, (+)-epicatechin, and (−)-epicatechin.

Keywords: Degradation; Pressurised fluid extraction; Antioxidants; DPPH assay; Electrochemical detection; Diode-array detection; Tandem mass spectrometry; Elevated temperature; Birch bark

Removal of caffeine from green tea by microwave-enhanced vacuum ice water extraction by Zaixiang Lou; Chaojuan Er; Jing Li; Hongxin Wang; Song Zhu; Juntao Sun (pp. 49-53).

It indicated that the vacuum ice water extraction is an effective method for the removal of caffeine from green tea. By the proposed method, the removal yield of caffeine was higher than 87%, while the content of total phenolics in decaffeination green tea was still higher than 170.35mgg⁻¹. The vacuum ice water extraction was selective and efficient in removing caffeine.Display Omitted► Opposite to the present methods, we try to remove caffeine in low temperature (0°C). ► A microwave-enhanced vacuum ice water extraction (MVIE) method was first proposed. ► MVIE removed 87.6% of caffeine from green tea with little loss of total phenolics. ► MVIE was selective and efficient for the removal of caffeine from green tea. ► The contents several catechins in green tea were almost not changed in MVIE. ► MVIE is a new and good alternative for the removal of caffeine from green tea.In order to selectively remove caffeine from green tea, a microwave-enhanced vacuum ice water extraction (MVIE) method was proposed. The effects of MVIE variables including extraction time, microwave power, and solvent to solid radio on the removal yield of caffeine and the loss of total phenolics (TP) from green tea were investigated. The optimized conditions were as follows: solvent (mL) to solid (g) ratio was 10:1, microwave extraction time was 6min, microwave power was 350W and 2.5h of vacuum ice water extraction. The removal yield of caffeine by MVIE was 87.6%, which was significantly higher than that by hot water extraction, indicating a significant improvement of removal efficiency. Moreover, the loss of TP of green tea in the proposed method was much lower than that in the hot water extraction. After decaffeination by MVIE, the removal yield of TP tea was 36.2%, and the content of TP in green tea was still higher than 170mgg⁻¹. Therefore, the proposed microwave-enhanced vacuum ice water extraction was selective, more efficient for the removal of caffeine. The main phenolic compounds of green tea were also determined, and the results indicated that the contents of several catechins were almost not changed in MVIE. This study suggests that MVIE is a new and good alternative for the removal of caffeine from green tea, with a great potential for industrial application.

Keywords: Vacuum ice water extraction; Microwave; Caffeine; Green tea; Catechins

Reprint of: Application of micro-thin-layer chromatography as a simple fractionation tool for fast screening of raw extracts derived from complex biological, pharmaceutical and environmental samples by Paweł K. Zarzycki; Magdalena M. Ślączka; Magdalena B. Zarzycka; Elżbieta Włodarczyk; Michał J. Baran (pp. 54-60).

The main goal of present paper is to demonstrate the separation and detection capability of micro-TLC technique involving simple one step liquid extraction protocols of complex materials without multi-steps sample pre-purification. In the present studies target components (cyanobacteria pigments, lipids and fullerenes) were isolated from heavy loading complex matrices including spirulina dried cells, birds’ feathers and fatty oils as well as soot samples derived from biomass fuel and fossils-fired home heating systems. In each case isocratic separation protocol involving less that 1mL of one component or binary mixture mobile phases can be completed within time of 5–8min. Sensitive detection of components of interest was performed via fluorescence or staining techniques using iodine or phosphomolybdic acid. Described methodology can be applied for fast fractionation or screening of whole range of target substances as well as chemo-taxonomic studies and fingerprinting of complex mixtures, which are present in raw biological or environmental samples.

Keywords: Micro-TLC; Spirulina; Birds’ feathers; Soot; Fullerenes; Biomass fuel

Reprint of: Extraction of fluoxetine from aquatic and urine samples using sodium dodecyl sulfate-coated iron oxide magnetic nanoparticles followed by spectrofluorimetric determination by Habib Bagheri; Omid Zandi; Ali Aghakhani (pp. 61-65).

A new method based on the combination of magnetic solid phase extraction (MSPE) and spectrofluorimetric determination was developed for isolation and preconcentration of fluoxetine form aquatic and biological samples using sodium dodecyl sulfate (SDS) coated Fe₃O₄ nanoparticles (NPs) as a sorbent. The unique properties of Fe₃O₄ NPs including high surface area and strong magnetism were utilized effectively in the MSPE process. Effect of different parameters influencing the extraction efficiency of fluoxetine including the amount of Fe₃O₄ and SDS, pH value, sample volume, extraction time, desorption solvent and time were optimized. Under optimized condition, the method was successfully applied to the extraction of fluoxetine from water and urine samples and absolute recovery amount of 85%, detection limit of 20μgL⁻¹ and a relative standard deviation (RSD) of 1.4% were obtained. The method linear response was over a range of 50–1000μgL⁻¹ with R²=0.9968. The relative recovery in different aquatic and urine matrices were investigated and values of 80% to 104% were obtained. The whole procedure showed to be conveniently fast, efficient and economical for extraction of fluoxetine from environmental and biological samples.

Keywords: Magnetic solid phase extraction; Fe; ₃; O; ₄; Fluoxetine; Spectrofluorimetry; Water analysis; Urine analysis

Heart-cutting multidimensional gas chromatography: A review of recent evolution, applications, and future prospects by Peter Q. Tranchida; Danilo Sciarrone; Paola Dugo; Luigi Mondello (pp. 66-75).

Display Omitted► The review describes main recent advances made in the field of heart-cutting multidimensional GC. ► The history of classical MDGC is also briefly described. ► Applications carried out with modern-day instrumentation are shown. ► The future prospects of heart-cutting multidimensional GC are discussed.The present contribution is focused on the main advances made in the field of heart-cutting multidimensional gas chromatography (MDGC), over approximately the last decade. Brief details on the history of classical MDGC are also given. A series of applications, carried out with modern-day commercially available instrumentation are shown, demonstrating the usefulness of the bidimensional methodology in specific analytical situations. Finally, the future prospects of MDGC are considered, within the shadow projected by a very powerful GC technique, namely comprehensive two-dimensional gas chromatography.

Keywords: Multidimensional gas chromatography; Heart-cutting; Deans switch; Valve switching

Synthesis and bioanalytical applications of specific-shaped metallic nanostructures: A review by Shiho Tokonami; Yojiro Yamamoto; Hiroshi Shiigi; Tsutomu Nagaoka (pp. 76-91).

Display Omitted► Bio-applications and sensors using metal nanoparticles (NPs). ► Basic characteristics of metal NPs with various shapes, and their synthesis methods. ► Optical applications by using hollow nanoparticles. ► Photothermal therapy by using gold nanorods. ► Electrical sensors by using gold nanoparticle array.Many successful synthesis routes for producing different shapes of metallic nanostructures, including sphere, rod, cube, and hollow shapes, have been developed in the past few decades. Many applications using these nanostructures have been studied because the outstanding properties of the nanostructures are not exhibited by their bulk-state counterparts. This review paper reports some recent developments in clinical and biosensor applications. The first part focused on the synthesis methods of metallic nanostructures having various shapes along with their optical properties. The second and third part is an introduction of the gold nanoparticle assemblies and arrays, explaining the conjugation methods of metallic nanostructures with biological entities. The final part reviews on the recent bioanalytical applications using various shapes of metallic nanostructures.

Keywords: Metal nanoparticle; Nanostructure; Nanoparticle array; Detection; Biosensor

Ranking and similarity for quantitative structure–retention relationship models in predicting Lee retention indices of polycyclic aromatic hydrocarbons by Károly Héberger; Biljana Škrbić (pp. 92-100).

Cross-validation of sum of ranking differences (SRDs emphasizes the pattern in the data (Box and Whisker plot of SRD values (Y axis) for different models (M1–M24) and experimental values I_exp). The average was used as benchmark.Display Omitted► Sum of ranking differences (SRD) ranks and groups seemingly equivalent models. ► Generalized pair correlation method (GPCM) also works as pattern recognition method. ► Best and worst models can be selected unambiguously. ► SRD and GPCM are ordering techniques and similarity measures. ► Principal Component and Cluster Analysis reveal very similar groupings. ► Validation by comparison of correlation measures and randomization test.Quantitative structure–(chromatographic) retention relationship (QSRR) models for prediction of Lee retention indices for polycyclic aromatic hydrocarbons (PAHs) were gathered from the literature and the predictive performances of models were compared. Numerous Lee retention indices (46) were served as a reliable basis for ranking by a recently developed novel method of ordering based on the sum of ranking differences (SRD) [TrAC, Trends Anal. Chem. 29 (2010) 101–109], by which the best model can be selected easily. Two kinds of references for ranking were accepted, average (consensus) and the experimental retention indices. Leave-many-out cross validation of the SRD procedure provides an easy way to group similar models. Significant differences among models can be revealed by using Wilcoxon's matched pair test.Principal component analysis (PCA) and cluster analysis (CA) arranged the models in three groups, i.e. similarities among models are manifested. The classical exploratory techniques and cross-validation (CV) justified the findings based on SRD ranking, i.e. the seven fold CV can be applied for pattern recognition. Generalized pair correlation method (GCPM) provided very similar grouping pattern to the procedures based of sum of ranking differences. The two methods (SRD and GPCM) exert astonishingly similar grouping (pattern recognition) though their background philosophy and way of calculation are totally different.

Keywords: Prediction; Model comparison; Ranking; Quantitative structure–retention relationships; Polycyclic aromatic hydrocarbons

Using near-infrared overtone regions to determine biodiesel content and adulteration of diesel/biodiesel blends with vegetable oils by Fernanda Vera Cruz de Vasconcelos; Paulo Fernandes Barbosa de Souza Jr.; Maria Fernanda Pimentel; Márcio José Coelho Pontes; Claudete Fernandes Pereira (pp. 101-107).

Display Omitted► We describe a systematic study of NIR overtone regions to determine biodiesel. ► Potential adulteration with vegetable oil in diesel blends was also investigated. ► Strategies of regression with variable selection were evaluated: PLS/JK and MLR/SPA. ► Performance of the models was compared with usual NIR/MIR spectral regions. ► Overtones can be useful to develop low cost instruments to monitor diesel blends.This work evaluates the use of near-infrared (NIR) overtone regions to determine biodiesel content, as well potential adulteration with vegetable oil, in diesel/biodiesel blends. For this purpose, NIR spectra (12,000–6300cm⁻¹) were obtained using three different optical path lengths: 10mm, 20mm and 50mm. Two strategies of regression with variable selection were evaluated: partial least squares (PLS) with significant regression coefficients selected by Jack-Knife algorithm (PLS/JK) and multiple linear regression (MLR) with wavenumber selection by successive projections algorithm (MLR/SPA). For comparison, the results obtained by using PLS full-spectrum models are also presented. In addition, the performance of models using NIR (1.0mm optical path length, 9000–4000cm⁻¹) and MIR (UATR – universal attenuated total reflectance, 4000–650cm⁻¹) spectral regions was also investigated. The results demonstrated the potential of overtone regions with MLR/SPA regression strategy to determine biodiesel content in diesel/biodiesel blends, considering the possible presence of raw oil as a contaminant. This strategy is simple, fast and uses a fewer number of spectral variables. Considering this, the overtone regions can be useful to develop low cost instruments for quality control of diesel/biodiesel blends, considering the lower cost of optical components for this spectral region.

Keywords: Diesel/biodiesel blends; Near-infrared (NIR) spectrometry; Multivariate calibration; Variable selection; Successive projections algorithm (SPA); Jack-Knife algorithm (JK)

Comparison of quantification strategies for one-point standard addition calibration: The homoscedastic case by Richard J.C. Brown; Thomas P.S. Gillam (pp. 108-111).

The precision characteristics of two quantification methods for one point standard addition calibration have been quantified and compared.Display Omitted► When using one-point standard addition calibration two quantification strategies are possible. ► This work has compared the precision characteristics of these two methods: extrapolation and use of analytical intensities. ► It has been determined that the precision ratio of the two strategies is dependent on surprisingly simple parameters. ► For conventional standard addition the relevant parameter is the sample to standard mass ratio. ► For sequential standard addition the relevant parameter is the sample to standard analyte content ratio.Two quantification strategies for one-point standard addition calibration have been compared mathematically. One strategy involved the extrapolation of measurement points to their intercept with the x-axis to determine the analyte content in the unknown sample, and the other strategy is based upon direct calculation of the analyte content in the unknown sample using the instrumental responses obtained during measurement. The cases of both conventional standard addition calibration (C-SAC) and sequential standard addition calibration (S-SAC) have been considered. The homoscedastic situation has been considered, where the absolute precision of the instrumental response is constant. It has been determined that the precision ratio of the two strategies is dependent on surprisingly simple parameters: such as the sample to standard mass ratio (for C-SAC) and the analyte content ratio (for S-SAC).

Keywords: Standard addition; Calibration; Precision; Extrapolation; Comparison

Graphene-based solid-phase extraction combined with flame atomic absorption spectrometry for a sensitive determination of trace amounts of lead in environmental water and vegetable samples by Yukun Wang; Shutao Gao; Xiaohuan Zang; Jingci Li; Jingjun Ma (pp. 112-118).

Display Omitted► Graphene as a novel sorbent material in a column for solid-phase extraction (SPE). ► SPE for the determination of lead (Pb) in environment water samples and vegetable samples. ► The system can be reused for many times. ► The adsorption capacity of graphene over many other adsorbents. ► Graphene has great potentials as an excellent sorbent material.Graphene, a novel class of carbon nanostructures, has great promise for use as sorbent materials because of its ultrahigh specific surface area. A new method using a column packed with graphene as sorbent was developed for the preconcentration of trace amounts of lead (Pb) using dithizone as chelating reagent prior to its determination by flame atomic absorption spectrometry. Some effective parameters on the extraction and complex formation were selected and optimized. Under optimum conditions, the calibration graph was linear in the concentration range of 10.0–600.0μgL⁻¹ with a detection limit of 0.61μgL⁻¹. The relative standard deviation for ten replicate measurements of 20.0 and 400.0μgL⁻¹ of Pb were 3.56 and 3.25%, respectively. Comparative studies showed that graphene is superior to other adsorbents including C18 silica, graphitic carbon, and single- and multi-walled carbon nanotubes for the extraction of Pb. The proposed method was successfully applied in the analysis of environmental water and vegetable samples. Good spiked recoveries over the range of 95.3–100.4% were obtained. This work not only proposes a useful method for sample preconcentration, but also reveals the great potential of graphene as an excellent sorbent material in analytical processes.

Keywords: Graphene; Solid-phase extraction; Preconcentration; Flame atomic absorption spectrometry; Dithizone; Lead

Evaluation of low-cost disposable polymeric materials for sorptive extraction of organic pollutants in water samples by Ailette Prieto; Rosario Rodil; José Benito Quintana; Isaac Rodríguez; Rafael Cela; Monika Möder (pp. 119-127).

Display Omitted► We developed and applied a new procedure using PES tube material in wastewater. ► PES showed best extraction results for both polar and non-polar compounds. ► The analytes were detected in the 0.03–25ngL⁻¹ range. ► The partition coefficients estimated for 13 of the compounds were higher for PES. ► The extraction of some analytes was only possible with PES.The capabilities of four commercially available and low cost polymeric materials for the extraction of polar and non-polar contaminants (log K_ow=−0.07–6.88, from caffeine to octocrylene, respectively) from water samples was compared. Tested sorbents were polyethersulphone, polypropylene and Kevlar, compared to polydimethylsiloxane as reference material. Parameters that affect the extraction process such as pH and ionic strength of the sample, extraction time and desorption conditions were thoroughly investigated. A set of experimental partition coefficients ( K_pw), at two different experimental conditions, was estimated for the best suited materials and compared with the theoretical octanol–water ( K_ow) partition coefficients of the analytes. Polyethersulphone displayed the largest extraction yields for both polar and non-polar analytes, with higher K_pw and lower matrix effects than polydimethylsiloxane and polypropylene. Thus, a sorptive microextraction method, followed by large volume injection (LVI) gas chromatography–tandem mass spectrometry (GC–MS/MS), was proposed using the former sorbent (2mg) for the simultaneous determination of model compounds in water samples. Good linearity (>0.99) was obtained for most of the analytes, except in the case of 4-nonylphenol (0.9466). Precision ( n=4) at 50 and 500ngL⁻¹ levels was in the 2–24% and limits of detection (LODs) were in the 0.6–25ngL⁻¹ range for all the analytes studied.

Keywords: Sorptive extraction; Polyethersulphone; Organic compounds; Water samples; Large volume injection-gas chromatography–mass spectrometry

Applicability of accelerated solvent extraction for synthetic colorants analysis in meat products with ultrahigh performance liquid chromatography–photodiode array detection by Qie Gen Liao; Wei Hong Li; Lin Guang Luo (pp. 128-132).

.Display Omitted► A method has been used for determination of synthetic colorants in meat products. ► Samples were extracted with ethanol–water–ammonia (75:24:1, v/v/v) using ASE at 85°C. ► Successful separation was obtained using gradient elution within 3.5min. ► Detection limits of synthetic colorants were in the ranges of 0.01–0.02mgkg⁻¹.Accelerated solvent extraction (ASE) coupled with ultrahigh performance liquid chromatography (UHPLC) with photodiode array detection (PDA) has been used for the quantitative determination of synthetic colorants in meat products. Samples were extracted with ethanol–water–ammonia with a ratio of 75:24:1 (v/v/v) using ASE instrument at 85°C. As a result, all the colorants in meat products were separated using an optimized gradient elution within 3.5min. Detection and quantification limits of synthetic colorants were in the ranges of 0.01–0.02mgkg⁻¹ and 0.05mgkg⁻¹, respectively. The intra-day and inter-day precision of the synthetic colorants were ranged between 1.7% (E123) to 5.2% (E124) and 3.2% (E124) to 6.0% (E129), respectively. The intra-day and inter-day recoveries of the synthetic colorants were ranged between 76.9% (E124) to 84.9% (E102) and 76.3% (E124) to 84.3% (E127), respectively. The method has been applied for the determination of seven synthetic colorants in meat products.

Keywords: Ultrahigh performance liquid chromatography (UHPLC); Photodiode array detection (PDA); Synthetic colorants; Accelerated solvent extraction (ASE); Meat products

Rapid identification and classification of Mycobacterium spp. using whole-cell protein barcodes with matrix assisted laser desorption ionization time of flight mass spectrometry in comparison with multigene phylogenetic analysis by Jun Wang; Wen Feng Chen; Qing X. Li (pp. 133-137).

Display Omitted► Identification of Mycobacterium spp. by whole-cell protein barcodes. ► The barcodes resolution is higher than concatenated 16S rDNA, rpoB and hsp65. ► Whole cell MALDI TOF aided with diagnostic proteins is robust for Mycobacterium spp. phenotypic characterization.The need of quick diagnostics and increasing number of bacterial species isolated necessitate development of a rapid and effective phenotypic identification method. Mass spectrometry (MS) profiling of whole cell proteins has potential to satisfy the requirements. The genus Mycobacterium contains more than 154 species that are taxonomically very close and require use of multiple genes including 16S rDNA for phylogenetic identification and classification. Six strains of five Mycobacterium species were selected as model bacteria in the present study because of their 16S rDNA similarity (98.4–99.8%) and the high similarity of the concatenated 16S rDNA, rpoB and hsp65 gene sequences (95.9–99.9%), requiring high identification resolution. The classification of the six strains by MALDI TOF MS protein barcodes was consistent with, but at much higher resolution than, that of the multi-locus sequence analysis of using 16S rDNA, rpoB and hsp65. The species were well differentiated using MALDI TOF MS and MALDI BioTyper™ software after quick preparation of whole-cell proteins. Several proteins were selected as diagnostic markers for species confirmation. An integration of MALDI TOF MS, MALDI BioTyper™ software and diagnostic protein fragments provides a robust phenotypic approach for bacterial identification and classification.

Keywords: Matrix assisted laser desorption ionization time of flight; Mycobacterium; Bacterial classification; Bacterial identification; Bacterial barcode; Whole-cell protein barcode

Effect of competitive cation binding on the measurement of Mn in marine waters and sediments by diffusive gradients in thin films by Sophie Tankéré-Muller; William Davison; Hao Zhang (pp. 138-144).

Display Omitted► Competition by cations affects measurement of Mn by DGT in seawater. ► Ca and Mg lower the DGT Mn response. ► Fe can displace Mn in sediments. ► Short deployment times overcome the Fe problem.The possible adverse effect of competitive binding on DGT (diffusive gradients in thin films) measurements of metals in marine situations was investigated. Of the divalent transition metals, manganese binds most weakly to Chelex resin and is most likely to be affected by competition. In media resembling seawater, the Chelex within DGT devices becomes saturated with Ca and Mg within 2h, and at pH 5–6 the sensitivity of the DGT measurement for Mn is substantially reduced, due to the appreciable concentration of Mn in contact with the resin. For media resembling freshwater DGT gives a near theoretical response for Mn. Iron was shown to be capable of displacing Mn and to a more limited extent Cd from the resin when its capacity for Fe is approached. Vertical profiles of Mn in a mesocosm sediment, obtained by deploying DGT for different times, could be explained by this displacement effect. The problem only occurs when Fe concentrations are exceptionally high and can be avoided by using short deployment times, typically less than 12h. Whilst most trace metals can be simply measured by deploying DGT in marine systems, for Mn consideration should be given to possible effects associated with the capacity of the Chelex binding layer being approached by accumulation of the other cations present.

Keywords: Diffusive gradients in thin films; Manganese; Seawater; Sediment; Chelex

Multi-criteria decision making development of ion chromatographic method for determination of inorganic anions in oilfield waters based on artificial neural networks retention model by Štefica Cerjan Stefanović; Tomislav Bolanča; Melita Luša; Šime Ukić; Marko Rogošić (pp. 145-154).

Display Omitted► Development of ad hoc methodology for anions determination in oilfield water. ► Artificial neural networks were used for modeling of anion retention in IC. ► Optimal networks were used for retention predictions in 47775 virtual experiments. ► Multi-criteria decision making was used for determination of optimal separation. ► Optimal method was finally validated and applied for real oilfield water sample.This paper describes the development of ad hoc methodology for determination of inorganic anions in oilfield water, since their composition often significantly differs from the average (concentration of components and/or matrix). Therefore, fast and reliable method development has to be performed in order to ensure the monitoring of desired properties under new conditions. The method development was based on computer assisted multi-criteria decision making strategy. The used criteria were: maximal value of objective functions used, maximal robustness of the separation method, minimal analysis time, and maximal retention distance between two nearest components. Artificial neural networks were used for modeling of anion retention. The reliability of developed method was extensively tested by the validation of performance characteristics. Based on validation results, the developed method shows satisfactory performance characteristics, proving the successful application of computer assisted methodology in the described case study.

Keywords: Ion chromatography; Artificial neural network; Multi-criteria decision making; Oilfield water

Capillary and gel electromigration techniques and MALDI-TOF MS – Suitable tools for identification of filamentous fungi by Marie Horká; Anna Kubesová; Jiří Šalplachta; Eva Zapletalová; Jaroslav Horký; Karel Šlais (pp. 155-162).

Display Omitted► We found methods for rapid identification of spores of filamentous fungi. ► Monilinia species were selected as model fungi. ► Optimization of electromigration and MALDI-TOF MS techniques. ► Methods were tested on real samples.Microbial strains are now spreading out of their original geographical areas of incidence and previously adequate morphological identification methods often must be accompanied by a phenotypic characterization for the successful microbial identification. The fungal genus Monilinia represents a suitable example. Monilinia species represent important fruit pathogens responsible for major losses in fruit production. Four closely related spp. of Monilinia: Monilinia laxa, Monilinia fructigena, Monilinia fructicola and Monilia polystroma have been yet identified. However, the classical characterization methods are not sufficient for current requirements, especially for phytosanitary purposes.In this study, rapid and reproducible methods have been developed for the characterization of Monilinia spp. based on the utilization of five well-established analytical techniques: CZE, CIEF, gel IEF, SDS-PAGE and MALDI-TOF MS, respectively. The applicability of these techniques for the identification of unknown spores of Monilinia spp. collected from infected fruits was also evaluated. It was found that isoelectric points, migration velocities or the protein patterns can be used as the identification markers in the case of cultivated filamentous fungi. Moreover, the results obtained by capillary electromigration techniques are independent on the host origin of the spores. On the other hand, the host origin of the fungi can play an important role in the precise fungi identification by the other techniques.

Keywords: CIEF and CZE; UV detection; Gel IEF; SDS-PAGE; MALDI-TOF MS; Monilinia; spp.

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Analytica Chimica Acta (v.716, #)

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Analytica Chimica Acta (v.716, #)