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  • 1. Badia, J. D.
    et al.
    Strömberg, E.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Ribes-Greus, A.
    Karlsson, S.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    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)2011In: Analytica Chimica Acta, ISSN 0003-2670, E-ISSN 1873-4324, Vol. 692, no 1-2, p. 85-95Article in journal (Refereed)
    Abstract [en]

    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.

  • 2. Crespo, Gaston A.
    et al.
    Andrade, F J
    Inon, F A
    Tudino, M B
    Kinetic method for the determination of trace amounts of copper(II) in water matrices by its catalytic effect on the oxidation of 1,5-diphenylcarbazide2005In: Analytica Chimica Acta, ISSN 0003-2670, E-ISSN 1873-4324, Vol. 539, no 1-2, p. 317-325Article in journal (Refereed)
  • 3. Degueldre, C.
    et al.
    Favarger, P. Y.
    Wold, Susanna
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Nuclear Chemistry.
    Gold colloid analysis by inductively coupled plasma-mass spectrometry in a single particle mode2006In: Analytica Chimica Acta, ISSN 0003-2670, E-ISSN 1873-4324, Vol. 555, no 2, p. 263-268Article in journal (Refereed)
    Abstract [en]

    Analysis in a single particle mode of gold colloids in water has been performed by inductively coupled plasma-mass spectrometry (ICP-MS). The signal induced by the flash of ions due to the ionization of a colloid in the plasma torch can be measured for the ions (197)An(+) by the mass spectrometer without interferences. The intensity of the MS signal is recorded in time scan. The recorded peak distributions were analysed as a function of the colloid size for five monodisperse colloids (80-250 nm). This study describes the experimental conditions to analyse gold colloids in a single particle mode. The size detection limit is around 25 nm corresponding to 0.15 fg colloids and one particle per ml may be detected during a 1 min time scan within standard procedure.

  • 4.
    Emmer, Åsa
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Analytical Chemistry.
    Roeraade, Johan
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Analytical Chemistry.
    Enzymatic protein digest in chip-based nanovials with immobilized proteolytic enzymes2005In: Analytica Chimica Acta, ISSN 0003-2670, E-ISSN 1873-4324, Vol. 542, no 2, p. 137-143Article in journal (Refereed)
    Abstract [en]

    In the present work, protein digest reactions in silicon-based microchips, coated with immobilized proteolytic enzymes, have been carried out. The performance of such vials, modified with trypsin or chymotrypsin, was tested with myoglobin as a substrate. Capillary electrophoresis and matrix-assisted laser desorption/ionization mass spectrometry were utilized for analysis of the digests, and the influence of different instrumentation setups. immobilization procedures and reaction conditions are discussed.

  • 5. Gao, Qiuju
    et al.
    Araia, Musie
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Analytical Chemistry.
    Leck, Caroline
    Emmer, Åsa
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Analytical Chemistry.
    Characterization of exopolysaccharides in marine colloids by capillary electrophoresis with indirect UV detection2010In: Analytica Chimica Acta, ISSN 0003-2670, E-ISSN 1873-4324, Vol. 662, no 2, p. 193-199Article in journal (Refereed)
    Abstract [en]

    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.

  • 6. Guinovart, Tomas
    et al.
    Crespo, Gaston A.
    Xavier Rius, F.
    Andrade, Francisco J.
    A reference electrode based on polyvinyl butyral (PVB) polymer for decentralized chemical measurements2014In: Analytica Chimica Acta, ISSN 0003-2670, E-ISSN 1873-4324, Vol. 821, p. 72-80Article in journal (Refereed)
    Abstract [en]

    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.

  • 7.
    Hartmann, Michael
    et al.
    NMI Natural and Medical Sciences Institute at the University of Tuebingen.
    Toegl, A.
    Kirchner, R.
    Templin, M. F.
    NMI Natural and Medical Sciences Institute at the University of Tuebingen.
    Joos, T. O.
    NMI Natural and Medical Sciences Institute at the University of Tuebingen.
    Increasing robustness and sensitivity of protein microarrays through microagitation and automation2006In: Analytica Chimica Acta, ISSN 0003-2670, E-ISSN 1873-4324, Vol. 564, no 1, p. 66-73Article in journal (Refereed)
    Abstract [en]

    Assay systems that employ protein microarrays for the analysis of complex samples are powerful tools to generate a high amount of data from a limiting amount of sample. Due to miniaturization, these systems are susceptible to fluctuations during signal generation and the use of uniform conditions for sample incubation and during the assay procedure is required to get reproducible results. Diffusion limits may prevent constant conditions on all parts of the array and can lead to the decease of the sensitivity of the array. Therefore, we set-up an automated assay system integrating a novel microagitation device using surface acoustic wave (SAW) technology. Multiplexed assays for the detection of autoantibodies from human serum and sandwich immunoassay for the detection of matrix metalloproteases (MMPs) were used to evaluate the system. Diffusion-rate limited solid phase reactions were enhanced by microagitation using the SAW technology resulting in up to three-fold higher signals.

  • 8.
    Horvath, Daniel G.
    et al.
    Santa Clara Univ, Dept Chem & Biochem, Santa Clara, CA 95053 USA..
    Braza, Samuel
    Santa Clara Univ, Dept Chem & Biochem, Santa Clara, CA 95053 USA..
    Moore, Trevor
    Santa Clara Univ, Dept Chem & Biochem, Santa Clara, CA 95053 USA..
    Pan, Ching W.
    Santa Clara Univ, Dept Chem & Biochem, Santa Clara, CA 95053 USA..
    Zhu, Lailai
    KTH, School of Engineering Sciences (SCI), Mechanics, Fluid Physics. Princeton Univ, Dept Mech & Aerosp Engn, Princeton, NJ 08544 USA..
    Pak, On Shun
    Santa Clara Univ, Dept Mech Engn, Santa Clara, CA 95053 USA..
    Abbyad, Paul
    Santa Clara Univ, Dept Chem & Biochem, Santa Clara, CA 95053 USA..
    Sorting by interfacial tension (SIFT): Label-free enzyme sorting using droplet microfluidics2019In: Analytica Chimica Acta, ISSN 0003-2670, E-ISSN 1873-4324, Vol. 1089, p. 108-114Article in journal (Refereed)
    Abstract [en]

    Droplet microfluidics has the ability to greatly increase the throughput of screening and sorting of enzymes by carrying reagents in picoliter droplets flowing in inert oils. It was found with the use of a specific surfactant, the interfacial tension of droplets can be very sensitive to droplet pH. This enables the sorting of droplets of different pH when confined droplets encounter a microfabricated trench. The device can be extended to sort enzymes, as a large number of enzymatic reactions lead to the production of an acidic or basic product and a concurrent change in solution pH. The progress of an enzymatic reaction is tracked from the position of a flowing train of droplets. We demonstrate the sorting of esterase isoenzymes based on their enzymatic activity. This label-free technology, that we dub droplet sorting by interfacial tension (SIFT), requires no active components and would have applications for enzyme sorting in high-throughput applications that include enzyme screening and directed evolution of enzymes.

  • 9.
    Huang, Hui
    et al.
    Shandong University, Peoples R China.
    Chen, Ting
    Liu, Xiuyu
    Ma, Houyi
    Ultrasensitive and simultaneous detection of heavy metal ions based on three-dimensional graphene-carbon nanotubes hybrid electrode materials2014In: Analytica Chimica Acta, ISSN 0003-2670, E-ISSN 1873-4324, Vol. 852, p. 45-54Article in journal (Refereed)
    Abstract [en]

    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.

  • 10.
    Huang, Hui
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science. Shandong Univ, Peoples R China.
    Zhu, Wencai
    Gao, Xiaochun
    Liu, Xiuyu
    Ma, Houyi
    Synthesis of a novel electrode material containing phytic acid-polyaniline nanofibers for simultaneous determination of cadmium and lead ions2016In: Analytica Chimica Acta, ISSN 0003-2670, E-ISSN 1873-4324, Vol. 947, p. 32-41Article in journal (Refereed)
    Abstract [en]

    The development of nanostructured conducting polymers based materials for electrochemical applications has attracted intense attention due to their environmental stability, unique reversible redox properties, abundant electron active sites, rapid electron transfer and tunable conductivity. Here, a phytic acid doped polyaniline nanofibers based nanocomposite was synthesized using a simple and green method, the properties of the resulting nanomaterial was characterized by electrochemical impedance spectroscopy (EIS), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), and energy dispersive spectroscopy (EDS). A glassy carbon electrode modified by the nanocomposite was evaluated as a new platform for the simultaneous detection of trace amounts of Cd2+ and Pb2+ using differential pulse anodic stripping voltammetry (DPASV). The synergistic contribution from PANI nanofibers and phytic acid enhances the accumulation efficiency and the charge transfer rate of metal ions during the DPASV analysis. Under the optimal conditions, good linear relationships were obtained for Cd2+ in a range of 0.05–60 μg L−1, with the detection limit (S/N = 3) of 0.02 μg L−1, and for Pb2+ in a range of 0.1–60 μg L−1, with the detection limit (S/N = 3) of 0.05 μg L−1. The new electrode was successfully applied to real water samples for simultaneous detection of Cd2+ and Pb2+ with good recovery rates. Therefore, the new electrode material may be a capable candidate for the detection of trace levels of heavy metal ions.

  • 11. Litborn, E
    et al.
    Emmer, Åsa
    Roeraade, J
    Chip-based nanovials for tryptic digest and capillary electrophoresis1999In: Analytica Chimica Acta, ISSN 0003-2670, E-ISSN 1873-4324, Vol. 401, no 1-2, p. 11-19Article in journal (Refereed)
  • 12. Pavankumar, A. R.
    et al.
    Zelenin, Sergey
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Protein Science. KTH, Centres, Science for Life Laboratory, SciLifeLab.
    Lundin, A.
    Schulte, T.
    Rajarathinam, K.
    Rebellato, P.
    Ardabili, Sahar
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Protein Science. KTH, Centres, Science for Life Laboratory, SciLifeLab.
    Salas, J.
    Achour, A.
    Russom, Aman
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Protein Science. KTH, Centres, Science for Life Laboratory, SciLifeLab.
    Bioanalytical advantages of a novel recombinant apyrase enzyme in ATP-based bioluminescence methods2018In: Analytica Chimica Acta, ISSN 0003-2670, E-ISSN 1873-4324, Vol. 1025, p. 118-123Article in journal (Refereed)
    Abstract [en]

    Ultrasensitive measurements of intracellular ATP (intATP) based on the firefly luciferase reactions are frequently used to enumerate bacterial or mammalian cells. During clinical applications, extracellular ATP (extATP) should be depleted in biological samples since it interferes with intATP and affects the quantification of bacteria. The extATP can be eliminated by ATP-degrading enzymes but complete hydrolysis of extATP remains a challenge for today's commercial enzymes. The catalytic efficiency of ATP-degrading enzymes depends on enzyme characteristics, sample composition and the ability to deplete diphosphates, triphosphates and their complexes generated during the reaction. This phenomenon restricts the usage of bioluminescence-based ATP methods in clinical diagnostics. In light of this, we have developed a recombinant Shigella flexneri apyrase (RSFA) enzyme and analysed its ATP depletion potential with five commercial biochemical sources including potato apyrase, acid phosphatase, alkaline phosphatase, hexokinase and glycerol kinase. The RSFA revealed superior activity by completely eliminating the extracellular ATP and ATP-complexes, even in biological samples like urine and serum. Therefore, our results can potentially unwrap the chemical and bio-analytical applications of ATP-based bioluminescence tests to develop highly sensitive point-of-care diagnostics.

  • 13.
    Vilaplana, Francisco
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Ribes-Greus, Amparo
    Instituto de Tecnología de Materiales (ITM), Universidad Politécnica de Valencia.
    Karlsson, Sigbritt
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Analytical strategies for the quality assessment of recycled high-impact polystyrene: A combination of thermal analysis, vibrational spectroscopy, and chromatography2007In: Analytica Chimica Acta, ISSN 0003-2670, E-ISSN 1873-4324, Vol. 604, no 1, p. 18-28Article in journal (Refereed)
    Abstract [en]

    Various analytical techniques (thermal analysis, vibrational spectroscopy, and chromatographic analysis) were used in order to monitor the changes in polymeric properties of recycled high-impact polystyrene (HIPS) throughout mechanical recycling processes. Three key quality properties were defined and analysed; these were the degree of mixing (composition), the degree of degradation, and the presence of low molecular weight compounds. Polymeric contaminations of polyethylene (PE) and polypropylene (PP) were detected in some samples using differential scanning calorimetry (DSC). Vibrational spectroscopy showed the presence of oxidised parts of the polymeric chain and gave also an assessment of the microstructure of the polybutadiene phase in HIPS. The presence of low molecular weight compounds in the HIPS samples was demonstrated using microwave assisted extraction followed by gas chromatography mass spectrometry (GC-MS). Several volatile organic compounds (VOCs), residues from the polymerisation, additives, and contaminations were detected in the polymeric materials. Styrene was identified already in virgin HIPS; in addition, benzaldehyde, alpha-methylbenzenaldehyde, and acetophenone were detected in recycled HIPS. The presence of oxygenated derivates of styrene may be attributed to the oxidation of polystyrene (PS). Several styrene dimers were found in virgin and recycled HIPS; these are produced during polymerisation of styrene and retained in the polymeric matrix as polymerisation residues. The amount of these dimers was highest in virgin HIPS, which indicated that emission of these compounds may have occurred during the first lifetime of the products. This paper demonstrates that a combination of different analytical strategies is necessary to obtain a detailed understanding of the quality of recycled HIPS.

  • 14.
    Zagorodni, Andrei
    KTH, Superseded Departments, Materials Science and Engineering.
    Evaluation of results obtained by analysis of fractions2004In: Analytica Chimica Acta, ISSN 0003-2670, E-ISSN 1873-4324, Vol. 512, no 2, p. 251-256Article in journal (Refereed)
    Abstract [en]

    The paper discusses treatment of experimental data obtained from the monitoring of continuous processes by a series of batch analyses (i.e. by analysis of fractions sequentially collected during the process). Common errors that are committed when graphically representing and fitting such data are shown. An approach for identification of such errors in published data is presented. One error results from the incorrect positioning of the analysis results along the X-axis when plotting data. In the case of equal fractions, this results in a systematic error along the X-axis. For non-equal fractions, the error in the coefficients of the fitting equation can be both systematic and random. A correct representation does not introduce any error if the actual function is linear in the region of the fraction collection. This plotting method is also a satisfactory procedure for low curvature functions. Another error originates because of the incorrect application of the least squares method. The reason lies in the fact that the analysis of each fraction does not represent an instant value of the measured parameter, but rather the averaged value over some period of time or over some volume. The actual error depends on the curvature of the fitting function. Furthermore, a reader encounters difficulties when evaluating published scientific information because many authors do not explain the methods by which their data were plotted and fit. The presented approach to the evaluation of graphical data makes it possible to identify the described errors.

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