| 1. |
- Abbas, Aamer, 1973, et al.
(author)
-
Chemical images of marine bio-active compounds by surface enhanced Raman spectroscopy and transposed orthogonal partial least squares (T-OPLS)
- 2012
-
In: Analytica Chimica Acta. - : Elsevier BV. - 0003-2670 .- 1873-4324. ; 737, s. 37-44
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Journal article (peer-reviewed)abstract
- Surface enhanced Raman spectroscopy combined with transposed Orthogonal Partial Least Squares (T-OPLS) was shown to produce chemical images of the natural antibacterial surface-active compound 1,1,3,3-tetrabromo-2-heptanone (TBH) on Bonnemaisonia hamifera. The use of gold colloids function-alised with the internal standard 4-mercapto-benzonitrile (MBN) made it possible to create images of the relative concentration of TBH over the surfaces. A gradient of TBH could be mapped over and in the close vicinity of the B. hamifera algal vesicles at the attomol/pixel level. T-OPLS produced a measure of the spectral correlation for each pixel of the hyperspectral images whilst not including spectral variation that was linearly independent of the target spectrum. In this paper we show the possibility to retrieve specific spectral information with a low magnitude in a complex matrix.
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| 2. |
- Abdel-Rehim, Mohamed
(author)
-
Microextraction by packed sorbent (MEPS) : A tutorial
- 2011
-
In: Analytica Chimica Acta. - : Elsevier BV. - 0003-2670 .- 1873-4324. ; 701:2, s. 119-128
-
Journal article (peer-reviewed)abstract
- This tutorial provides an overview on a new technique for sample preparation, microextraction by packed sorbent (MEPS). Not only the automation process by MEPS is the advantage but also the much smaller volumes of the samples, solvents and dead volumes in the system. Other significant advantages such as the speed and the simplicity of the sample preparation process are provided. In this tutorial the main concepts of MEPS will be elucidated. Different practical aspects in MEPS are addressed. The factors affecting MEPS performance will be discussed. The application of MEPS in clinical and pre-clinical studies for quantification of drugs and metabolites in blood, plasma and urine will be provided. A comparison between MEPS and other extraction techniques such as SPE, LLE, SPME and SBSE will be discussed. (C) 2011 Elsevier B.V. All rights reserved.
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| 3. |
- Ahmad Tajudin, Asilah, et al.
(author)
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MALDI-target integrated platform for affinity-captured protein digestion.
- 2014
-
In: Analytica Chimica Acta. - : Elsevier BV. - 1873-4324 .- 0003-2670. ; 807:Jan 7, s. 1-8
-
Journal article (peer-reviewed)abstract
- To address immunocapture of proteins in large cohorts of clinical samples high throughput sample processing is required. Here a method using the proteomic sample platform, ISET (integrated selective enrichment target) that integrates highly specific immunoaffinity capture of protein biomarker, digestion and sample cleanup with a direct interface to mass spectrometry is presented. The robustness of the on-ISET protein digestion protocol was validated by MALDI MS analysis of model proteins, ranging from 40fmol to 1pmol per nanovial. On-ISET digestion and MALDI MS/MS analysis of immunoaffinity captured disease-associated biomarker PSA (prostate specific antigen) from human seminal plasma are presented.
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| 4. |
- Azenha, Manuel, et al.
(author)
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Vapor-phase testing of the memory-effects in benzene- and toluene-imprinted polymers conditioned at elevated temperature
- 2013
-
In: Analytica Chimica Acta. - : Elsevier. - 0003-2670 .- 1873-4324. ; 802, s. 40-45
-
Journal article (peer-reviewed)abstract
- The preparation of polymers imprinted with common aromatic solvents such as benzene and toluene is an under-exploited subject of research. The present study was aimed at the understanding of whether true solvent memory effects can be achieved by molecular imprinting, as well as if they are stable at elevated temperature. A set of copolymers, comprising low and high cross-linking levels, was prepared from four different combinations of functional monomer and cross-linker, namely methacrylic acid (MAA)/ethylene glycol dimethacrylate (EGDMA), methyl methacrylate (MMA)/EGDMA, MAA/divinyl benzene (DVB) and MMA/DVB. Each possible combination was prepared separately in benzene, toluene and acetonitrile. The obtained materials were applied as coatings onto nickel-titanium (Ni-Ti) alloy wires which were incorporated into solid-phase microextraction devices and finally tested for their ability to competitively adsorb vapors from the headspace of an aqueous solution containing a few volatile organic compounds. Porosity analysis showed that, regardless of the solvent used, only a high cross-linking level permitted the preparation of mesoporous copolymers (BJH radius typically in the range 13-15nm), a requirement for providing accessibility to the targeted nanoscale-imprinted cavities. A noticeable exception was, however, observed for the MMA/DVB copolymers which exhibited much diminished BJH radius. The porosity data correlated well with the extraction profiles found, which suggested the presence of benzene-imprinted sites in all the highly cross-linked copolymers prepared in benzene, except for the MMA/DVB copolymers. Concerning the effect of an elevated conditioning temperature on the memory-effects created by the imprinting process, the results were clearly indicative that the tested copolymers, including the more robust highly cross-linked ones, are not suitable for high temperature applications such as solid-phase microextraction coupled to gas chromatography.
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| 5. |
- Badia, J. D., et al.
(author)
-
A statistical design of experiments for optimizing the MALDI-TOF-MS sample preparation of polymers. An application in the assessment of the thermo-mechanical degradation mechanisms of poly (ethylene terephthalate)
- 2011
-
In: Analytica Chimica Acta. - : Elsevier BV. - 0003-2670 .- 1873-4324. ; 692:1-2, s. 85-95
-
Journal article (peer-reviewed)abstract
- The sample preparation procedure for MALDI-TOF MS of polymers is addressed in this study by the application of a statistical Design of Experiments (DoE). Industrial poly (ethylene terephthalate) (PET) was chosen as model polymer. Different experimental settings (levels) for matrixes, analyte/matrix proportions and concentrations of cationization agent were considered. The quality parameters used for the analysis were signal-to-noise ratio and resolution. A closer inspection of the statistical results provided the study not only with the best combination of factors for the MALDI sample preparation, but also with a better understanding of the influence of the different factors, individually or in combination, to the signal. The application of DoE for the improvement of the MALDI measure of PET stated that the best combination of factors and levels was the following: matrix (dithranol), proportion analyte/matrix/cationization agent (1/15/1, V/V/V), and concentration of cationization agent (2 g L-1). In a second part, multiple processing by means of successive injection cycles was used to simulate the thermo-mechanical degradation effects on the oligomeric distribution of PET under mechanical recycling. The application of MALDI-TOF-MS showed that thermo-mechanical degradation primarily affected initially predominant cyclic species. Several degradation mechanisms were proposed, remarking intramolecular transesterification and hydrolysis. The ether links of the glycol unit in PET were shown to act as potential reaction sites, driving the main reactions of degradation.
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| 6. |
- Bagan, Hector, et al.
(author)
-
Crosslinked plastic scintillators: A new detection system for radioactivity measurement in organic and aggressive media
- 2014
-
In: Analytica Chimica Acta. - : Elsevier BV. - 1873-4324 .- 0003-2670. ; 852, s. 13-19
-
Journal article (peer-reviewed)abstract
- The measurement of radioactive solutions containing organic or aggressive media may cause stability problems in liquid and plastic scintillation (PS) techniques. In the case of PS, this can be overcome by adding a crosslinker to the polymer structure. The objectives of this study are to synthesise a suitable crosslinked plastic scintillator (C-PS) for radioactivity determination in organic and aggressive media. The results indicated that an increase in the crosslinker content reduces the detection efficiency and a more flexible crosslinker yields higher detection efficiency. For the polymer composition studied, 2,5-diphenyloxazole (PPO) is the most adequate fluorescent solute and an increase in its concentration causes little change in the detection efficiency. The inclusion of a secondary fluorescent solute 1,4-bis-2-(5-phenyloxazolyl) benzene (POPOP) improves the C-PS radiometrical characteristics. For the final composition chosen, the synthesis of the C-PS exhibits good reproducibility with elevated yield. The obtained C-PS also displays high stability in different organic (toluene, hydrotreated vegetable oil (HVO) and methanol) and aggressive media (hydrochloric acid, nitric acid and hydrogen peroxide). Finally, the C-PS exhibits high detection efficiency both in water and in aggressive media and can also be applied in organic media showing similar or even higher detection efficiency values. (C) 2014 Elsevier B.V. All rights reserved.
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| 7. |
- Baxter, Douglas, et al.
(author)
-
Serum/plasma methylmercury determination by isotope dilution gas chromatography : inductively coupled plasma mass spectrometry
- 2011
-
In: Analytica Chimica Acta. - : Elsevier BV. - 0003-2670 .- 1873-4324. ; 701:2, s. 134-138
-
Journal article (peer-reviewed)abstract
- A method for the determination of methylmercury in plasma and serum samples was developed. The method uses isotope dilution with 198Hg-labelled methylmercury, extraction into dichloromethane, back-extraction into water, aqueous-phase ethylation, purge and trap collection, thermal desorption, separation by gas chromatography, and mercury isotope specific detection by inductively coupled plasma mass spectrometry. By spiking 2 mL sample with 1.2 ng tracer, measurements in a concentration interval of (0.007–2.9) μg L−1 could be performed with uncertainty amplification factors <2. A limit of quantification of 0.03 μg L−1 was estimated at 10 times the standard deviation of concentrations measured in preparation blanks. Within- and between-run relative standard deviations were <10% at added concentration levels of 0.14 μg L−1, 0.35 μg L−1 and 2.8 μg L−1, with recoveries in the range 82% to 110%. Application of the method to 50 plasma/serum samples yielded a median (mean; range) concentration of methylmercury of 0.081 (0.091; <0.03–0.19) μg L−1. This is the first time methylmercury has been directly measured in this kind of specimen, and is therefore the first estimate of a reference range.
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| 8. |
- Beni, Valerio, et al.
(author)
-
Investigation into the voltammetric behaviour and detection of selenium(IV) at metal electrodes in diverse electrolyte media
- 2011
-
In: Analytica Chimica Acta. - : Elsevier. - 0003-2670 .- 1873-4324. ; 699:2, s. 127-133
-
Journal article (peer-reviewed)abstract
- The voltammetric behaviour of selenium(IV) was studied at platinum and gold electrodes in sulphuricacid, perchloric acid and potassium chloride media as a basis for its voltammetric detection. The bestvoltammetric behaviour was recorded at gold electrodes with perchloric acid as the supporting electrolyte.The concomitant presence of metals, such as copper or lead, and of model biomolecules, suchas bovine serum albumin, in the solution resulted in a deterioration of the electrochemical response forselenium(IV). Quantitative detection of selenium(IV) by square wave anodic stripping voltammetry atboth a millimetre-sized gold disc electrode and a microband electrode array revealed linear responsesto selenium concentration in the ranges 5–15 M and 0.1–10 M, respectively, with 60 s preconcentration.The sensitivities were 6.4 A M−1 cm−2 and 100 A M−1 cm−2 at the disc and the microband array,respectively. The detection limit at the microband electrode array was 25 nM, illustrating the potentialityof such microelectrodes for the development of mercury-free analytical methods for the trace detectionof selenium(IV).
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| 9. |
- Bhand, Sunil, et al.
(author)
-
Fructose-selective calorimetric biosensor in flow injection analysis.
- 2010
-
In: Analytica Chimica Acta. - : Elsevier BV. - 1873-4324 .- 0003-2670. ; 668:1, s. 13-18
-
Journal article (peer-reviewed)abstract
- A highly selective, interference free biosensor for the measurement of fructose in real syrup samples was developed. The assay is based on the phosphorylation of D(-)fructose to fructose-6-phosphate by hexokinase and subsequent conversion of fructose-6-phosphate to fructose-1,6-biphosphate by fructose-6-phosphate-kinase. The heat liberated in the second reaction is monitored using an enzyme thermistor. The major advantages of this biosensor are rapid and selective measurement of fructose without the need to eliminate glucose and inexpensive FIA-based, mediator-free calorimetric measurement suitable for regular fructose analysis. This method was optimised for parameters, such as pH, ionic strength, interference, operational stability and shelf life. Good and reproducible linearity (0.5-6.0 mM) with a detection limit of 0.12 mM was obtained. Fructose determination in commercial syrup samples and spiked samples confirmed the reliability of this set-up and technique. The biosensor gave reproducible results with good overall stability for continuous measurements over a period of three months besides a useful shelf life of six months. The method could be used for routine fructose monitoring in food samples.
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| 10. |
- Chaintreau, Alain, et al.
(author)
-
Site-specific C-13 content by quantitative isotopic C-13 nuclear magnetic resonance spectrometry : a pilot inter-laboratory study
- 2013
-
In: Analytica Chimica Acta. - : Elsevier BV. - 0003-2670 .- 1873-4324. ; 788, s. 108-113
-
Journal article (peer-reviewed)abstract
- Isotopic C-13 NMR spectrometry, which is able to measure intra-molecular C-13 composition, is of emerging demand because of the new information provided by the C-13 site-specific content of a given molecule. A systematic evaluation of instrumental behaviour is of importance to envisage isotopic C-13 NMR as a routine tool. This paper describes the first collaborative study of intra-molecular C-13 composition by NMR. The main goals of the ring test were to establish intra-and inter-variability of the spectrometer response. Eight instruments with different configuration were retained for the exercise on the basis of a qualification test. Reproducibility at the natural abundance of isotopic C-13 NMR was then assessed on vanillin from three different origins associated with specific delta C-13(i) profiles. The standard deviation was, on average, between 0.9 and 1.2 parts per thousand for intra-variability. The highest standard deviation for inter-variability was 2.1%. This is significantly higher than the internal precision but could be considered good in respect of a first ring test on a new analytical method. The standard deviation of delta C-13(i) in vanillin was not homogeneous over the eight carbons, with no trend either for the carbon position or for the configuration of the spectrometer. However, since the repeatability for each instrument was satisfactory, correction factors for each carbon in vanillin could be calculated to harmonize the results.(C) 2013 Elsevier B.V. All rights reserved.
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| 11. |
- Co, Michelle, 1975-, et al.
(author)
-
Degradation effects in the extraction of antioxidants from birch bark using water at elevated temperature and pressure
- 2012
-
In: Analytica Chimica Acta. - : Elsevier BV. - 0003-2670 .- 1873-4324. ; 716, s. 40-48
-
Journal article (peer-reviewed)abstract
- 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 El 80, contained birch bark extracts obtained after extraction at 80 and 180 degrees C for up to 45 min, respectively. Two other samples, P80 and P180, were only extracted for 5 min at the two temperatures and were thereafter filtered and hydrothermally treated at 80 and 180 degrees 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 degrees C showed that the extraction reached a steady-state already after 5 min, and that the extracted compounds were stable throughout the entire extraction process. Processing at 180 degrees 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 degrees 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.
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| 12. |
- Fredriksson, Mattias, et al.
(author)
-
Combined use of algorithms for peak picking, peak tracking and retention modelling to optimize the chromatographic conditions for liquid chromatography-mass spectrometry analysis of fluocinolone acetonide and its degradation products
- 2011
-
In: Analytica Chimica Acta. - : Elsevier BV. - 0003-2670 .- 1873-4324. ; 704:1-2, s. 180-188
-
Journal article (peer-reviewed)abstract
- A strategy for rapid optimization of liquid chromatography column temperature and gradient shape is presented. The optimization as such is based on the well established retention and peak width models implemented in software like e.g. DryLab and LC simulator. The novel part of the strategy is a highly automated processing algorithm for detection and tracking of chromatographic peaks in noisy liquid chromatography-mass spectrometry (LC-MS) data. The strategy is presented and visualized by the optimization of the separation of two degradants present in ultraviolet (UV) exposed fluocinolone acetonide. It should be stressed, however, that it can be utilized for LC-MS analysis of any sample and application where several runs are conducted on the same sample. In the application presented, 30 components that were difficult or impossible to detect in the UV data could be automatically detected and tracked in the MS data by using the proposed strategy. The number of correctly tracked components was above 95%. Using the parameters from the reconstructed data sets to the model gave good agreement between predicted and observed retention times at optimal conditions. The area of the smallest tracked component was estimated to 0.08% compared to the main component, a level relevant for the characterization of impurities in the pharmaceutical industry.
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| 13. |
- Gao, Qiuju, et al.
(author)
-
Characterization of exopolysaccharides in marine colloids by capillary electrophoresis with indirect UV detection
- 2010
-
In: Analytica Chimica Acta. - : Elsevier BV. - 0003-2670 .- 1873-4324. ; 662:2, s. 193-199
-
Journal article (peer-reviewed)abstract
- A method was established using capillary electrophoresis with indirect UV detection for analysis of monosaccharides liberated from exopolysaccharides by acidic hydrolysis. Tangential flow filtration was used to isolate high molecular weight polysaccharides from seawater. The capillary electrophoresis method included the use of a background electrolyte consisting of 2,6-dimethoxyphenol and cetyltrimethylammonium bromide. Several neutral sugars commonly existing in marine polysaccharides were separated under optimized conditions. The relative standard deviations were between 1.3% and 2.3% for relative migration time and 1.3-2.5% for peak height. Detection limits (at S/N 3) were in the range of 27.2-47.8 mu M. The proposed approach was applied to the analysis of hydrolyzed colloidal polysaccharides in seawater collected from the Baltic Sea. Nanomolar levels of liberated monosaccharides in seawater samples can be detected by preconcentration up to 30,000 times.
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| 14. |
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| 15. |
- Guinovart, Tomas, et al.
(author)
-
A reference electrode based on polyvinyl butyral (PVB) polymer for decentralized chemical measurements
- 2014
-
In: Analytica Chimica Acta. - : Elsevier. - 0003-2670 .- 1873-4324. ; 821, s. 72-80
-
Journal article (peer-reviewed)abstract
- A new solid-state reference electrode using a polymeric membrane of polyvinyl butyral (PVB), Ag/AgCl and NaCl to be used in decentralized chemical measurements is presented. The electrode is made by drop-casting the membrane cocktail onto a glassy carbon (GC) substrate. A stable potential (less than 1 mV dec−1) over a wide range of concentrations for the several chemical species tested is obtained. No significant influence to changes in redox potential, light and pH are observed. The response of this novel electrode shows good correlation when compared with a conventional double-junction reference electrode. Also good long-term stability (90 ± 33 μV/h) and a lifetime of approximately 4 months are obtained. Aspects related to the working mechanisms are discussed. Atomic Force Microscopy (AFM) studies reveal the presence of nanopores and channels on the surface, and electrochemical impedance spectroscopy (EIS) of optimized electrodes show low bulk resistances, usually in the kΩ range, suggesting that a nanoporous polymeric structure is formed in the interface with the solution. Future applications of this electrode as a disposable device for decentralized measurements are discussed. Examples of the utilization on wearable substrates (tattoos, fabrics, etc) are provided.
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| 16. |
- Hakonen, Aron, 1970, et al.
(author)
-
A potential tool for high-resolution monitoring of ocean acidification.
- 2013
-
In: Analytica Chimica Acta. - : Elsevier BV. - 0003-2670 .- 1873-4324. ; 786, s. 1-7
-
Journal article (peer-reviewed)abstract
- Current anthropogenic carbon dioxide emissions generate besides global warming unprecedented acid-ification rates of the oceans. Recent evidence indicates the possibility that ocean acidification and lowoceanic pH may be a major reason for several mass extinctions in the past. However, a major bottleneck forresearch on ocean acidification is long-term monitoring and the collection of consistent high-resolutionpH measurements. This study presents a low-power (<1 W) small sample volume (25l) semiconductor based fluorescence method for real-time ship-board pH measurements at high temporal and spatialresolution (approximately 15 s and 100 m between samples). A 405 nm light emitting diode and the blueand green channels from a digital camera was used for swift detection of fluorescence from the pH sen-sitive dye 6,8-Dihydroxypyrene-1,3-disulfonic acid in real-time. Main principles were demonstrated byautomated continuous measurements of pH in the surface water across the Baltic Sea and the Kattegatregion with a large range in salinity (∼3–30) and temperature (∼0–25◦C). Ship-board precision of salinityand temperature adjusted pH measurements were estimated as low as 0.0001 pH units.
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| 17. |
- Herzog, Gregoire, et al.
(author)
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Stripping voltammetry at micro-interface arrays: A review
- 2013
-
In: Analytica Chimica Acta. - : Elsevier. - 0003-2670 .- 1873-4324. ; 769, s. 10-21
-
Research review (peer-reviewed)abstract
- In this article, a comprehensive overview of the most recent developments in the field of stripping voltammetryat regular micro-interfaces (both solid–liquid and liquid–liquid interfaces) is presented. Thisreview will report on the most conventional arrays of metallic micro-electrodes but also on the rapidlygrowing field of electrochemistry at arrays of micro-interfaces between two immiscible electrolyte solutions(ITIES). The main fabrication methods, together with some design considerations and diffusionphenomena at such interfaces are discussed. Main applications of micro-interface arrays are presentedincluding heavy metals detection at micro-electrode arrays and detection of organic molecules (aminoacids, vitamins, peptides and drugs) at the ITIES. Stripping analysis at micro-interface arrays is suitablefor the detection of analytes in several real media including water, soil extracts and biological fluids(blood and saliva) with high specificity, sensitivity (detection limits of nM, ppb level) and reliability.Stripping analysis at ITIES and micro-electrode arrays are two complementary approaches that havethe advantages of being cost effective, simple to use and easily adaptable to field measurement.
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| 18. |
- Huang, Hui, et al.
(author)
-
Ultrasensitive and simultaneous detection of heavy metal ions based on three-dimensional graphene-carbon nanotubes hybrid electrode materials
- 2014
-
In: Analytica Chimica Acta. - : Elsevier. - 0003-2670 .- 1873-4324. ; 852, s. 45-54
-
Journal article (peer-reviewed)abstract
- A green and facile method was developed to prepare a novel hybrid nanocomposite that consisted of one-dimensional multi-walled carbon nanotubes (MWCNTs) and two-dimensional graphene oxide (GO) sheets. The as-prepared three-dimensional GO-MWCNTs hybrid nanocomposites exhibit excellent water-solubility owing to the high hydrophilicity of GO components; meanwhile, a certain amount of MWCNTs loaded on the surface of GO sheets through p-p interaction seem to be "dissolved" in water. Moreover, the graphene(G)-MWCNTs nanocomposites with excellent conductivity were obtained conveniently by the direct electrochemical reduction of GO-MWCNTs nanocomposites. Seeing that there is a good synergistic effect between MWCNTs and graphene components in enhancing preconcentration efficiency of metal ions and accelerating electron transfer rate at G-MWCNTs/electrolyte interface, the G-MWCNTs nanocomposites possess fast, simultaneous and sensitive detection performance for trace amounts of heavy metal ions. The electrochemical results demonstrate that the G-MWCNTs nanocomposites can act as a kind of practical sensing material to simultaneously determine Pb2+ and Cd2+ ions in terms of anodic stripping voltammetry (ASV). The linear calibration plots for Pb2+ and Cd2+ ranged from 0.5 mg L-1 to 30 mg L-1. The detection limits were determined to be 0.2 mg L-1 (S/N = 3) for Pb2+ and 0.1 mg L-1 (S/N = 3) for Cd2+ in the case of a deposition time of 180 s. It is worth mentioning that the G-MWCNTs modified electrodes were successfully applied to the simultaneous detection of Cd2+ and Pb2+ ions in real electroplating effluent samples containing lots of surface active impurities, showing a good application prospect in the determination of trace amounts of heavy metals.
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| 19. |
- Hyder, Murtaza, et al.
(author)
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Application of hollow fiber liquid phase microextraction for pinic acid and pinonic acid analysis from organic aerosols.
- 2012
-
In: Analytica Chimica Acta. - : Elsevier BV. - 1873-4324 .- 0003-2670. ; 713:3, s. 79-85
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Journal article (peer-reviewed)abstract
- A method based on hollow fiber liquid phase microextraction (HF-LPME) for analysis of pinic acid and pinonic acid was developed and for the first time successfully applied to ambient aerosol samples. In this method, the aerosol samples were dissolved in 0.05M H(2)SO(4) and the solution was extracted using three-phase HF-LPME where donor phase was 0.1M (NH(4))(2)CO(3). Different parameters like type of organic solvent for membrane phase, extraction time and stirring speed etc. were optimized. Optimum extraction time was 4.5h and optimum-stirring speed was found to be 900rpm. We used 6-undecanone as organic phase along with tri-n-octylphosphine oxide (optimum TOPO contents was 15% w/v), which gave an enormous enrichment for both pinic and pinonic acid. Enrichment factors of 28,050 and 27,400 times were obtained for pinonic acid and pinic acid, respectively, that are the highest ever published. The extraction efficiency for pinic acid and pinonic acid were 68.5% and 70.1%, respectively. Very low limits of detection were obtained. Values of 1.0ngL(-1) and 0.5ngL(-1) in aqueous solutions, corresponding to 24pgm(-3) and 12pgm(-3) in aerosol samples were the limits of detections for pinonic acid and pinic acid, respectively. Both pinonic acid and pinic acid were found in all aerosol samples analyzed.
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| 20. |
- Jäntti, Sirkku E., et al.
(author)
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Steroid and steroid glucuronide profiles in urine during pregnancy determined by liquid chromatography-electrospray ionization-tandem mass spectrometry
- 2013
-
In: Analytica Chimica Acta. - : Elsevier. - 0003-2670 .- 1873-4324. ; 802, s. 56-66
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Journal article (peer-reviewed)abstract
- An ultra performance liquid chromatography-electrospray ionization-tandem mass spectrometry (UPLC-MS/MS) method was developed for the analysis of steroids and their glucuronides in urine samples. The method provides high sensitivity and fast analysis, as both steroids and their glucuronides can be analyzed directly without hydrolysis or complex sample preparation. The method was applied in profiling of targeted and nontargeted steroids and steroid glucuronides during pregnancy. The concentrations of 11 of 27 targeted steroids and steroid glucuronides and the concentrations of 25 nontargeted steroid glucuronides increased about 10-400 fold during the pregnancy. The concentrations of most of these 36 compounds began to increase in the first days of the pregnancy, increased gradually during the pregnancy, achieved a maximum in late pregnancy, and decreased sharply after delivery. Exceptionally, the concentrations of allopregnanolone and 17-hydroxypregnenolone started to increase later than those of the other steroids. Moreover, the concentrations of E2 glucuronides began to decrease one week before the delivery, in contrast to most of the steroids and steroid glucuronides, whose concentrations dropped sharply during the delivery. Concentrations of 34 compounds decreased noticeably when the subject was on sick leave owing a series of painful contractions. The results suggest that steroids and especially steroid glucuronides may provide a valuable diagnostic tool to follow the course of pregnancy.
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| 21. |
- Kondo, Elsuida, et al.
(author)
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Metabolic profiling of yeast culture using gas chromatography coupled with orthogonal acceleration accurate mass time-of-flight mass spectrometry : Application to biomarker discovery
- 2014
-
In: Analytica Chimica Acta. - : Elsevier. - 0003-2670 .- 1873-4324. ; 807, s. 135-142
-
Journal article (peer-reviewed)abstract
- Yeast and yeast cultures are frequently used as additives in diets of dairy cows. Beneficial effects from the inclusion of yeast culture in diets for dairy mammals have been reported, and the aim of this study was to develop a comprehensive analytical method for the accurate mass identification of the 'global' metabolites in order to differentiate a variety of yeasts at varying growth stages (Diamond V XP, Yea-Sacc and Levucell). Microwave-assisted derivatization for metabolic profiling is demonstrated through the analysis of differing yeast samples developed for cattle feed, which include a wide range of metabolites of interest covering a large range of compound classes. Accurate identification of the components was undertaken using GC-oa-ToFMS (gas chromatography-orthogonal acceleration-time-of-flight mass spectrometry), followed by principal component analysis (PCA) and orthogonal partial least squares discriminant analysis (OPLS-DA) for data reduction and biomarker discovery. Semi-quantification (fold changes in relative peak areas) was reported for metabolites identified as possible discriminative biomarkers (p-value <0.05, fold change >2), including d-ribose (four fold decrease), myo-inositol (five fold increase), l-phenylalanine (three fold increase), glucopyranoside (two fold increase), fructose (three fold increase) and threitol (three fold increase) respectively. (C) 2013 Elsevier B. V. All rights reserved.
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| 22. |
- Labib, Mahmoud, et al.
(author)
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A novel competitive capacitive glucose biosensor based on concanavalin A-labeled nanogold colloids assembled on a polytyramine-modified gold electrode.
- 2010
-
In: Analytica Chimica Acta. - : Elsevier BV. - 1873-4324 .- 0003-2670. ; 659:1-2, s. 194-200
-
Journal article (peer-reviewed)abstract
- A highly sensitive competitive capacitive glucose biosensor was constructed based on gold nanoparticles, which were employed as a platform to immobilize concanavalin A (Con A). Gold nanoparticles were fixed on a gold electrode, on which a layer of polytyramine was preformed via electrochemical polymerization. The sensing mechanism is based on the competitive dissociation of a glucose polymer or a glycoconjugate from the glycoligand binding sites of immobilized Con A by the added glucose. To further improve the sensor response, several glucose polymers as well as a synthesized glycoconjugate using the periodate method, were screened. Consequently, dextran (MW 39 kDa) was selected and the feasibility of the proposed biosensor was evaluated for a competitive assay of glucose. Experimental results show that the biosensor responded linearly to glucose in the range from 1.0 x 10(-6) to 1.0 x 10(-2) M, corresponding to 0.18 microg mL(-1) to 1.8 mg mL(-1) of glucose with a detection limit of 1.0 x 10(-6) M under optimized conditions. The studied biosensor exhibited a response time of about 15 min and a neglectable loss in sensitivity after 10 repeated analytical cycles.
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| 23. |
- Lebogang, Lesedi, et al.
(author)
-
Development of a real-time capacitive biosensor for cyclic cyanotoxic peptides based on Adda-specific antibodies.
- 2014
-
In: Analytica Chimica Acta. - : Elsevier BV. - 1873-4324 .- 0003-2670. ; 826, s. 69-76
-
Journal article (peer-reviewed)abstract
- The harmful effects of cyanotoxins in surface waters have led to increasing demands for accurate early warning methods. This study proposes a capacitive immunosensor for broad-spectrum detection of the group of toxic cyclic peptides called microcystins (∼80 congeners) at very low concentration levels. The novel analytical platform offers significant advances compared to the existing methods. Monoclonal antibodies (mAbs, clone AD4G2) that recognize a common element of microcystins were used to construct the biosensing layer. Initially, a stable insulating anchor layer for the mAbs was made by electropolymerization of tyramine onto a gold electrode surface, with subsequent incorporation of gold nanoparticles (AuNPs) on the glutaraldehyde (5%) activated polytyramine surface. The biosensor responded linearly to microcystin concentrations from 1×10(-13)M to 1×10(-10)M MC-LR standard with a limit of detection of 2.1×10(-14)M. The stability of the biosensor was evaluated by repeated measurements of the antigen and by determining the capacitance change relative to the original response, which decreased below 90% after the 30th cycle.
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| 24. |
- Lee, SangWook, et al.
(author)
-
Improved porous silicon microarray based prostate specific antigen immunoassay by optimized surface density of the capture antibody
- 2013
-
In: Analytica Chimica Acta. - : Elsevier BV. - 1873-4324 .- 0003-2670. ; 796, s. 108-114
-
Journal article (peer-reviewed)abstract
- Enriching the surface density of immobilized capture antibodies enhances the detection signal of antibody sandwich microarrays. In this study, we improved the detection sensitivity of our previously developed P-Si (porous silicon) antibody microarray by optimizing concentrations of the capturing antibody. We investigated immunoassays using a P-Si microarray at three different capture antibody (PSA - prostate specific antigen) concentrations, analyzing the influence of the antibody density on the assay detection sensitivity. The LOD (limit of detection) for PSA was 2.5 ng mL(-1), 80 pg mL(1), and 800 fg mL(-1) when arraying the PSA antibody, H117 at the concentration 15 mu g mL(-1), 35 mu g mL(-1), and 154 mu g mL(-1), respectively. We further investigated PSA spiked into human female serum in the range of 800 fg mL(-1) to 500 ng mL(-1). The microarray showed a LOD of 800 fg mL(-1) and a dynamic range of 800 fg mL(-1) to 80 ng mL(-1) in serum spiked samples. (C) 2013 Elsevier B.V. All rights reserved.
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| 25. |
- Li, Zhe, 1987-, et al.
(author)
-
Screening for pharmaceutical transformation products formed in river sediment by combining ultrahigh performance liquid chromatography/high resolution mass spectrometry with a rapid data-processing method
- 2014
-
In: Analytica Chimica Acta. - : Elsevier BV. - 0003-2670 .- 1873-4324. ; 810, s. 61-70
-
Journal article (peer-reviewed)abstract
- While the occurrence of pharmaceuticals in the aquatic environment has been extensively investigated, their environmental fate is less thoroughly explored. Scarce information on their transformation pathways and transformation products (TPs) limits conventional target analytical approaches. In this study, samples from water/sediment tests were analyzed by ultrahigh performance liquid chromatography interfaced with quadrupole time-of-flight mass spectrometry (UHPLC/QToF-MS). A data processing method based on peak detection, time-trend filtration and structure assignment was established to provide an efficient way for identifying the key TPs in terms of persistence; all software used for the individual steps of this method is freely available. The accurate mass and meaningful time-trends were major contributors in facilitating the isolation of plausible TP peaks. In total, 16 TPs from 9 parent pharmaceuticals were identified. Eleven out of the 16 TPs were confirmed by corresponding reference standards; no standards were available for the remaining TPs. For additional 6 potential TPs, a molecular formula was suggested but no additional structural information could be generated. Among the TPs identified in the water/sediment tests, carbamazepine-10,11-epoxide (parent: carbamazepine), saluamine (parent: furosemide), chlorothiazide and 4-amino-6-chloro-1,3-benzenedisulfonamide (parent of both: hydrochlorothiazide), and 1-naphthol (parent: propranolol) accumulated over the entire incubation period of 35 days.
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| 26. |
- Lindahl, Sofia, et al.
(author)
-
An on-line method for pressurized hot water extraction and enzymatic hydrolysis of quercetin glucosides from onions.
- 2013
-
In: Analytica Chimica Acta. - : Elsevier BV. - 1873-4324 .- 0003-2670. ; 785, s. 50-59
-
Journal article (peer-reviewed)abstract
- A novel environmentally sound continuous-flow hot water extraction and enzymatic hydrolysis method for determination of quercetin in onion raw materials was successfully constructed using a stepwise optimization approach. In the first step, enzymatic hydrolysis of quercetin-3,4'-diglucoside to quercetin was optimized using a three level central composite design considering temperature (75-95°C), pH (3-6) and volume concentration of ethanol (5-15%). The enzyme used was a thermostable β-glucosidase variant (termed TnBgl1A_N221S/P342L) covalently immobilized on either of two acrylic support-materials (Eupergit(®) C 250L or monolithic cryogel). Optimal reaction conditions were irrespective of support 84°C, 5% ethanol and pH 5.5, and at these conditions, no significant loss of enzyme activity was observed during 72h of use. In a second step, hot water extractions from chopped yellow onions, run at the optimal temperature for hydrolysis, were optimized in a two level design with respect to pH (2.6 and 5.5), ethanol concentration (0 and 5%) and flow rate (1 and 3mLmin(-1)) Obtained results showed that the total quercetin extraction yield was 1.7 times higher using a flow rate of 3mLmin(-1) (extraction time 90min), compared to a flow rate of 1mLmin(-1) (extraction time 240min). Presence of 5% ethanol was favorable for the extraction yield, while a further decrease in pH was not, not even for the extraction step alone. Finally, the complete continuous flow method (84°C, 5% ethanol, pH 5.5, 3mLmin(-1)) was used to extract quercetin from yellow, red and shallot onions and resulted in higher or similar yield (e.g. 8.4±0.7μmolg(-1) fresh weight yellow onion) compared to a conventional batch extraction method using methanol as extraction solvent.
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| 27. |
- Liu, Qian, et al.
(author)
-
Graphene-assisted matrix solid-phase dispersion for extraction of polybrominated diphenyl ethers and their methoxylated and hydroxylated analogs from environmental samples
- 2011
-
In: Analytica Chimica Acta. - : Elsevier. - 0003-2670 .- 1873-4324. ; 708:1-2, s. 61-68
-
Journal article (peer-reviewed)abstract
- In this work, we developed a novel graphene-assisted matrix solid-phase dispersion (GA-MSPD) method for extraction of polybrominated diphenyl ethers (PBDEs) and their methoxylated (MeO-) and hydroxylated (OH-) analogs from environmental samples. We found that grinding the solid sample with chemically converted graphene (CCG) powder yielded a tight contact and sufficient dispersion of the sample matrix due to the large surface area and flexible nanosheet morphology of CCG. The resultant blend was eluted using a two-step elution strategy: PBDEs and MeO-PBDEs were eluted firstly by hexane/dichloromethane and analyzed by GC-ECD, and then OH-PBDEs were eluted by acetone and determined by LC-ESI-MS/MS. The GA-MSPD conditions were optimized in detail. Better recoveries were obtained with GA-MSPD than with other sorbents (C18 silica, Florisil and carbon nanotubes) and other extraction techniques (Soxhlet and accelerated solvent extraction). Other advantages of GA-MSPD, including reduced consumption of sorbent and solvent, good selectivity and short extraction time, were also demonstrated. In analysis of soil samples, the method detection limits of five PBDEs, ten MeO-PBDEs and ten OH-PBDEs were in the range of 5.9-28.7, 14.3-46.6, and 5.3-212.6 pg g(-1) dry weight, respectively. The proposed method was successfully applied to the extraction of PBDEs, MeO-PBDEs and OH-PBDEs from different kinds of spiked environmental samples, including soil, tree bark and fish.
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| 28. |
- Liu, Tao, et al.
(author)
-
Comparison of theoretical and experimental models for characterizing solvent properties using reversed phase liquid chromatography
- 2011
-
In: Analytica Chimica Acta. - : Elsevier BV. - 0003-2670 .- 1873-4324. ; 702:1, s. 37-44
-
Journal article (peer-reviewed)abstract
- Theoretical and experimental quantitative structure-retention relationships (QSRR) models are useful for characterizing solvent properties and column selectivity in reversed phase liquid chromatography (RPLC). The chromatographic behavior of a model analyte. the herbicide atrazine, in a system derived from nine organic solvents and three chromatographic columns was used for developing QSRR models. Multiple linear regression (MLR) and partial least squares regression (PLSR) were used as statistical approaches. The similarities and differences between linear solvation energy relationships (LSER), and semi-empirical and theoretical molecular models were demonstrated. QSRR models show high predictive power, and can successfully predict retention factor (log k) for new solvents. The models are useful for solvent optimization and reducing time for method development in RPLC. The herbicide atrazine can be readily analyzed at a low level, and all three columns provided good resolution, high-performance and symmetrical peaks. The method is suitable for analysis of atrazine in water samples.
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| 29. |
- Löfstedt, Tommy, 1982-, et al.
(author)
-
Global, local and unique decompositions in OnPLS for multiblock data analysis
- 2013
-
In: Analytica Chimica Acta. - : Elsevier BV. - 0003-2670 .- 1873-4324. ; 791, s. 13-24
-
Journal article (other academic/artistic)abstract
- Background OnPLS is an extension of O2PLS that decomposes a set of matrices, in either multiblock or path model analysis, such that each matrix consists of two parts: a globally joint part containing variation shared with all other connected matrices, and another containing unique or locally joint variation, i.e. variation that is specific to a particular matrix or shared with some, but not all, other connected matrices.Results A further extension of OnPLS suggested here decomposes the non-globally joint parts into locally joint and unique parts, using the OnPLS method to first find and extract a globally joint model, and then applying OnPLS recursively to subsets of matrices containing the non-globally joint variation remaining after the globally joint variation has been extracted. This results in a set of locally joint models. The variation that is left after the globally joint and locally joint variation has been extracted is not related (by definition) to the other matrices and thus represents the strictly unique variation specific to each matrix. The method's utility is demonstrated by its application to both a simulated data set and a real data set acquired from metabolomic, proteomic and transcriptomic profiling of three genotypes of hybrid aspen.Conclusions The results show that OnPLS can successfully decompose each matrix into global, local and unique models, resulting in lower numbers of globally joint components and higher intercorrelations of scores. OnPLS also increases the interpretability of models of connected matrices, because of the locally joint and unique models it generates.
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| 30. |
- Madsen, Rasmus, et al.
(author)
-
Chemometrics in metabolomics - a review in human disease diagnosis
- 2010
-
In: Analytica Chimica Acta. - : Elsevier BV. - 0003-2670 .- 1873-4324. ; 659:1-2, s. 23-33
-
Journal article (peer-reviewed)abstract
- Metabolomics is a post genomic research field concerned with developing methods for analysis of low molecular weight compounds in biological systems, such as cells, organs or organisms. Analyzing metabolic differences between unperturbed and perturbed systems, such as healthy volunteers and patients with a disease, can lead to insights into the underlying pathology. In metabolomics analysis, large amounts of data are routinely produced in order to characterize samples. The use of multivariate data analysis techniques and chemometrics is a commonly used strategy for obtaining reliable results. Metabolomics have been applied in different fields such as disease diagnosis, toxicology, plant science and pharmaceutical and environmental research. In this review we take a closer look at the chemometric methods used and the available results within the field of disease diagnosis. We will first present some current strategies for performing metabolomics studies, especially regarding disease diagnosis. The main focus will be on data analysis strategies and validation of multivariate models, since there are many pitfalls in this regard. Further, we highlight the most interesting metabolomics publications and discuss these in detail; additional studies are mentioned as a reference for the interested reader. A general trend is an increased focus on biological interpretation rather than merely the ability to classify samples. In the conclusions, the general trends and some recommendations for improving metabolomics data analysis are provided.
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| 31. |
- Mustafa, Arwa, et al.
(author)
-
Pressurized liquid extraction as a green approach in food and herbal plants extraction: A review.
- 2011
-
In: Analytica Chimica Acta. - : Elsevier BV. - 1873-4324 .- 0003-2670. ; 703:1, s. 8-18
-
Journal article (peer-reviewed)abstract
- Pressurized liquid extraction is a "green" technology for the extraction of nutraceuticals from foods and herbal plants. This review discusses the extraction principles and the optimization of the extraction parameters that improves the extraction efficiency. The use of different solvent mixtures and other extraction additives to enhance the efficiency of the extraction are discussed. Dynamic mode of extraction in Pressurized liquid extraction, and the use of combined and hyphenated sample preparation and analytical techniques are presented. This work discusses how different studies used Pressurized liquid extraction to enrich phenolic compounds, lignans, carotenoids, oils and lipids, essential oils and other nutraceuticals from foods and herbal plants.
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| 32. |
- Petersson, Erik V., et al.
(author)
-
Pressurized Hot Water Extraction of anthocyanins from red onion : A study on extraction and degradation rates
- 2010
-
In: Analytica Chimica Acta. - : Elsevier BV. - 0003-2670 .- 1873-4324. ; 663:1, s. 27-32
-
Journal article (peer-reviewed)abstract
- Pressurized Hot Water Extraction (PHWE) is a quick, efficient and environmentally friendly technique for extractions. However, when using PHWE to extract thermally unstable analytes, extraction and degradation effects occur at the same time, and thereby compete. At first, the extraction effect dominates, but degradation effects soon take over. In this paper, extraction and degradation rates of anthocyanins from red onion were studied with experiments in a static batch reactor at 110 °C. A total extraction curve was calculated with data from the actual extraction and degradation curves, showing that more anthocyanins, 21–36% depending on the species, could be extracted if no degradation occurred, but then longer extraction times would be required than those needed to reach the peak level in the apparent extraction curves. The results give information about the different kinetic processes competing during an extraction procedure.
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| 33. |
- Riddar, Jakob Johnson, et al.
(author)
-
Determination of aromatic amines in aqueous extracts of polyurethane foam using hydrophilic interaction liquid chromatography and mass spectrometry
- 2010
-
In: Analytica Chimica Acta. - : Elsevier BV. - 0003-2670 .- 1873-4324. ; 678:1, s. 117-123
-
Journal article (peer-reviewed)abstract
- A method is presented for the determination of aromatic amines in aqueous extracts of polyurethane (PUR) foam. The method is based on the extraction of PUR foam using aqueous acetic acid (0.1%, w/v) followed by determination of extracted aromatic amines using hydrophilic interaction liquid chromatography (HILIC) and tandem mass spectrometry (MS/MS) with positive electrospray ionisation. The injections of volumes up to 5 mu L of aqueous solutions were made possible by on-column focusing with partially filled loop injections. The fragmentation patterns for 2,4- and 2,6-toluene diamine (TDA) and 4,4'-methylene dianiline (MDA) were clarified by performing a hydrogen-deuterium exchange study. TDA and MDA were determined using trideuterated 2,4- and 2,6-TDA and dideuterated 4,4'-MDA as internal standards. Linear calibration graphs were obtained over the range 0.025-0.5 mu g mL(-1) with correlation coefficients >0.996 and the instrumental detection limit for each compound was <50 fmol. The stability of the amines was influenced by the matrix, so their concentrations decreased over time. Agreement was observed between the results of analyses of PUR foam extracts by HILIC-MS/MS and results obtained by ethyl chloroformate derivatisation and reversed phase (RP) liquid chromatography-mass spectrometry (LC-MS/MS). TDA was observed to be unstable in extracts of foam but not in pure solutions.
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| 34. |
- Rui Climaco, Pinto, et al.
(author)
-
Design of experiments on 135 cloned poplar trees to map environmental influence in greenhouse
- 2011
-
In: Analytica Chimica Acta. - : Elsevier. - 0003-2670 .- 1873-4324. ; 685:2, s. 127-131
-
Journal article (peer-reviewed)abstract
- To find and ascertain phenotypic differences, minimal variation between biological replicates is always desired. Variation between the replicates can originate from genetic transformation but also from environmental effects in the greenhouse. Design of experiments (DoE) has been used in field trials for many years and proven its value but is underused within functional genomics including greenhouse experiments. We propose a strategy to estimate the effect of environmental factors with the ultimate goal of minimizing variation between biological replicates, based on DoE. DoE can be analyzed in many ways. We present a graphical solution together with solutions based on classical statistics as well as the newly developed OPLS methodology.In this study, we used DoE to evaluate the influence of plant specific factors (plant size, shoot type, plant quality, amount of fertilizer) and rotation of plant positions on height and section area of 135 cloned wild type poplar trees grown in the greenhouse. Statistical analysis revealed that plant position was the main contributor to variability among biological replicates and applying a plant rotation scheme could reduce this variation.
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| 35. |
- Safina, Gulnara, 1980
(author)
-
Application of surface plasmon resonance for the detection of carbohydrates, glycoconjugates, and measurement of the carbohydrate-specific interactions: A comparison with conventional analytical techniques. A critical review
- 2012
-
In: Analytica Chimica Acta. - : Elsevier BV. - 0003-2670 .- 1873-4324. ; 712:January, s. 9-29
-
Research review (peer-reviewed)abstract
- Carbohydrates (glycans) and their conjugates with proteins and lipids contribute significantly to many biological processes. That makes these compounds important targets to be detected, monitored and identified. The identification of the carbohydrate content in their conjugates with proteins and lipids (glycoforms) is often a challenging task. Most of the conventional instrumental analytical techniques are time-consuming and require tedious sample pretreatment and utilising various labeling agents. Surface plasmon resonance (SPR) has been intensively developed during last two decades and has received the increasing attention for different applications, from the real-time monitoring of affinity bindings to biosensors. SPR does not require any labels and is capable of direct measurement of biospecific interaction occurring on the sensing surface. This review provides a critical comparison of modern analytical instrumental techniques with SPR in terms of their analytical capabilities to detect carbohydrates, their conjugates with proteins and lipids and to study the carbohydrate-specific bindings. A few selected examples of the SPR approaches developed during 2004-2011 for the biosensing of glycoforms and for glycan-protein affinity studies are comprehensively discussed. © 2011 Elsevier B.V.
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| 36. |
- Schmekel, Birgitta, et al.
(author)
-
Analysis of breath samples for lung cancer survival
- 2014
-
In: Analytica Chimica Acta. - : Elsevier Masson. - 0003-2670 .- 1873-4324. ; 840, s. 82-86
-
Journal article (peer-reviewed)abstract
- Analyses of exhaled air by means of electronic noses offer a large diagnostic potential. Such analyses are non-invasive; samples can also be easily obtained from severely ill patients and repeated within short intervals. Lung cancer is the most deadly malignant tumor worldwide, and monitoring of lung cancer progression is of great importance and may help to decide best therapy. In this report, twenty-two patients with diagnosed lung cancer and ten healthy volunteers were studied using breath samples collected several times at certain intervals and analysed by an electronic nose. The samples were divided into three sub-groups; group d for survivor less than one year, group s for survivor more than a year and group h for the healthy volunteers. Prediction models based on partial least square and artificial neural nets could not classify the collected groups d, s and h, but separated well group d from group h. Using artificial neural net, group d could be separated from group s. Excellent predictions and stable models of survival day for group d were obtained, both based on partial least square and artificial neural nets, with correlation coefficients 0.981 and 0.985, respectively. Finally, the importance of consecutive measurements was shown.
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| 37. |
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| 38. |
- Taniyasu, Sachi, et al.
(author)
-
Inter-laboratory trials for analysis of perfluorooctanesulfonate and perfluorooctanoate in water samples : Performance and recommendations
- 2013
-
In: Analytica Chimica Acta. - : Elsevier. - 0003-2670 .- 1873-4324. ; 770, s. 111-120
-
Journal article (peer-reviewed)abstract
- 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.
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| 39. |
- Wang, Pu, et al.
(author)
-
Evaluation of Soxhlet extraction, accelerated solvent extraction and microwave-assisted extraction for the determination of polychlorinated biphenyls and polybrominated diphenyl ethers in soil and fish samples
- 2010
-
In: Analytica Chimica Acta. - : Elsevier. - 0003-2670 .- 1873-4324. ; 663:1, s. 43-48
-
Journal article (peer-reviewed)abstract
- Three commonly applied extraction techniques for persistent organic chemicals, Soxhlet extraction (SE), accelerated solvent extraction (ASE) and microwave-assisted extraction (MAE), were applied on soil and fish samples in order to evaluate their performances. For both PCBs and PBDEs, the two more recent developed techniques (ASE and MAE) were in general capable of producing comparable extraction results as the classical SE, and even higher extraction recoveries were obtained for some PCB congeners with large octanol-water partitioning coefficients (K(ow)). This relatively uniform extraction results from ASE and MAE indicated that elevated temperature and pressure are favorable to the efficient extraction of PCBs from the solid matrices. For PBDEs, difference between the results from MAE and ASE (or SE) suggests that the MAE extraction condition needs to be carefully optimized according to the characteristics of the matrix and analyte to avoid degradation of higher brominated BDE congeners and improve the extraction yields.
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| 40. |
- Winquist, Fredrik, et al.
(author)
-
Multicomponent analysis of drinking water by a voltammetric electronic tongue
- 2011
-
In: Analytica Chimica Acta. - : Elsevier. - 0003-2670 .- 1873-4324. ; 683:2, s. 192-197
-
Journal article (peer-reviewed)abstract
- A voltammetric electronic tongue is described that was used for multicomponent analysis of drinking water. Measurements were performed on drinking water from a tap and injections of the compounds NaCl, NaN3, NaHSO3, ascorbic acid, NaOCl and yeast suspensions could be identified. A PLS based model was developed for the simultaneously prediction of identification and concentration of the compounds NaCl, NaHSO3 and NaOCl .By utilizing this type of nonselective sensor technique for water quality surveillance, it will be feasible to detect a plurality of events without the need of a specific sensor for each type of event.
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| 41. |
- Yakovleva, Maria E, et al.
(author)
-
A study of glycoprotein-lectin interactions using quartz crystal microbalance.
- 2010
-
In: Analytica Chimica Acta. - : Elsevier BV. - 1873-4324 .- 0003-2670. ; 668:1, s. 80-85
-
Journal article (peer-reviewed)abstract
- A study of biospecific interactions between lectins and glycoproteins using a quartz crystal microbalance biosensor with dissipation monitoring (QCM-D) was reported. Four lectins were covalently immobilised on the thiol-modified gold electrode of the QCM chips in order to obtain sensing surfaces. The frequency shift served as analytical signal and the dissipation shift provided additional information about the viscoelastic properties of the glycoprotein-lectin complex formed on the surface of the QCM chip. The working conditions of the assay were optimised. The interaction between different lectins and glycoproteins was characterised by specific frequency shifts and each glycoprotein displayed its own unique lectin-binding pattern. This lectin pattern can serve as a finger print for the discrimination between various glycoproteins. The biosensor enabled quantitative determination of glycoproteins in the concentration range of 50 microg mL(-1) to 1 mg mL(-1) with good linearity and R.S.D. of less than 6.0%. An additional advantage of the proposed biosensor was the possibility to re-use the same lectin surfaces during a long period of time (2 month) without changes in analytical response. This was experimentally achieved by the application of a proper regeneration solution (10 mM glycine-HCl, pH 2.5). The lectin-based quartz crystal microbalance technique is suitable both for rapid screening and for quantitative assay of serum glycoproteins.
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| 42. |
- Yakovleva, ME, et al.
(author)
-
Lectin typing of Campylobacter jejuni using a novel quartz crystal microbalance technique
- 2011
-
In: ANALYTICA CHIMICA ACTA. - : Elsevier BV. - 0003-2670 .- 1873-4324. ; 694:1-2, s. 1-5
-
Journal article (peer-reviewed)abstract
- Abstract: Seven Campylobacter jejuni strains were characterised by a lectin typing assay. The typing system was based on a quartz crystal microbalance technique (QCM) with four commercially available lectins (wheat germ agglutinin, Maackia amurensis lectin, Lens culinaris agglutinin, and Concanavalin A), which were chosen for their differing carbohydrate specificities. Initially, the gold surfaces of the quartz crystals were modified with 11-mercaptoundecanoic acid followed by lectin immobilisation using a conventional amine-coupling technique. Bacterial cells were applied for lectin typing without preliminary treatment, and resonant frequency and dissipation responses were recorded. The adhesion of microorganisms on lectin surfaces was confirmed by atomic force microscopy. Scanning was performed in the tapping mode and the presence of bacteria on lectin-coated surfaces was successfully demonstrated. A significant difference in the dissipation response was observed for different C jejuni strains which made it possible to use this parameter for discriminating between bacterial strains. In summary, the QCM technique proved a powerful tool for the recognition and discrimination of C. jejuni strains. The approach may also prove applicable to strain discrimination of other bacterial species, particularly pathogens. (C) 2011 Elsevier B.V. All rights reserved.
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| 43. |
- Yakovleva, Maria, et al.
(author)
-
The enzyme thermistor-A realistic biosensor concept. A critical review.
- 2013
-
In: Analytica Chimica Acta. - : Elsevier BV. - 1873-4324 .- 0003-2670. ; 766, s. 1-12
-
Research review (peer-reviewed)abstract
- This review describes principles and features of thermal biosensors and microbiosensors in flow injection analysis. Examples are given that illustrate the great versatility and excellent operational stability offered by thermal biosensors. The examples are mostly from work with the original type of enzyme thermistor operating with an enzyme column, but there will also be work described involving miniaturised devices including thermal lab-on-chip constructions and other types of sensing materials, such as MIPs (molecularly imprinted polymers) for both affinity and catalytic reactions. Several recently presented thermal biosensor concepts are reviewed including a thermal-electrochemical hybrid sensor for lactose based on immobilised cellobiose dehydrogenase. Another recent method is the determination of fructose using a fructose-6-phosphate kinase column. Operation with complex sample matrices such as blood, plasma and milk and how to avoid non-specific temperature effects are considered.
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| 44. |
- Zhang, Haiyan, et al.
(author)
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Facile preparation of glutathione-stabilized gold nanoclusters for selective determination of chromium (III) and chromium (VI) in environmental water samples
- 2013
-
In: Analytica Chimica Acta. - : Elsevier BV. - 0003-2670 .- 1873-4324. ; 770, s. 140-146
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Journal article (peer-reviewed)abstract
- 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.
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| 45. |
- Österlund, Helene, et al.
(author)
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Simultaneous measurements of As, Mo, Sb, V and W using a ferrihydrite diffusive gradients in thin films (DGT) device
- 2010
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In: Analytica Chimica Acta. - : Elsevier BV. - 0003-2670 .- 1873-4324. ; 682:1-2, s. 59-65
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Journal article (peer-reviewed)abstract
- The ferrihydrite-backed DGT (diffusive gradients in thin films), recently developed for arsenic and phosphate measurements was, for the first time, characterized with respect to molybdate, antimonate, vanadate and tungstate determination. Arsenate was included in the characterization to allow comparison with literature data and thus provide quality control of the measurements. In addition to laboratory experiments, field measurements were carried out in a natural stream in northern Sweden affected by mine drainage. It was shown that ferrihydrite-DGT is suitable for simultaneous determination of labile arsenic, molybdate, antimonate, vanadate and tungstate over a wide pH range. Diffusion coefficients were estimated using two different methods; diffusion cell and direct uptake to DGT devices in synthetic solutions. Estimations of the coefficients using the direct uptake method were performed between pH 4 and 8. The results from the two methods agreed well irrespective of pH, except for molybdate and antimonate that showed decreased values at pH 8. Adsorption of the analytes to ferrihydrite gel discs was rapid at all pH values. However, there was a tendency toward lower adsorption affinity for antimonate compared to the other anions. 100% recovery of accumulated analytes was achieved through complete dissolution of the ferrihydrite adsorbent using 1.4 mol L-1 HNO3 with 0.1 mol L-1 HF. From field sampling it was concluded that the opportunities for accurate antimonate and molybdate determination decrease at pH ≥8.7. DGT labile concentrations were generally lower than dissolved concentrations. Relatively lower DGT concentrations, compared to dissolved (<0.45 μm), were observed under a period when ferric oxide precipitations were detected on the DGT protective filter.
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