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  • 1.
    Alm, Erik
    et al.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Bro, Rasmus
    Engelsen, Sören B.
    Karlberg, Bo
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Torgrip, Ralf J. O.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Vibrational overtone combination spectroscopy (VOCSY)—a new way of using IR and NIR data2007In: Analytical and Bioanalytical Chemistry, ISSN 1618-2642, E-ISSN 1618-2650, Vol. 388, no 1, p. 179-188Article in journal (Refereed)
    Abstract [en]

    This work explores a novel method for rearranging 1st order (one-way) infra-red (IR) and/or near infra-red (NIR) ordinary spectra into a representation suitable for multi-way modelling and analysis. The method is based on the fact that the fundamental IR absorption and the first, second, and consecutive overtones of NIR absorptions represent identical chemical information. It is therefore possible to rearrange these overtone regions of the vectors comprising an IR and NIR spectrum into a matrix where the fundamental, 1st, 2nd, and consecutive overtones of the spectrum are arranged as either rows or columns in a matrix, resulting in a true three-way tensor of data for several samples. This tensorization facilitates explorative analysis and modelling with multi-way methods, for example parallel factor analysis (PARAFAC), N-way partial least squares (N-PLS), and Tucker models. The vibrational overtone combination spectroscopy (VOCSY) arrangement is shown to benefit from the “order advantage”, producing more robust, stable, and interpretable models than, for example, the traditional PLS modelling method. The proposed method also opens the field of NIR for true peak decomposition—a feature unique to the method because the latent factors acquired using PARAFAC can represent pure spectral components whereas latent factors in principal component analysis (PCA) and PLS usually do not.

  • 2.
    Claeson Bohnstedt, Kristina
    et al.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Karlberg, Bo
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Basun, Hans
    Schmidt, Staffan
    Porous graphitic carbon chromatography-tandem mass spectrometry for the detection of isoprostanes in human cerebrospinal fluid2005In: Journal of chromatography. B, ISSN 1570-0232, E-ISSN 1873-376X, Vol. 827, no 1, p. 39-43Article in journal (Refereed)
    Abstract [en]

    F2-isoprostanes are produced by the non-enzymatic peroxidation of arachidonic acid in membrane phospholipids. This paper describes a new method for the determination of all four classes of F2-isoprostanes in human cerebrospinal fluid (CSF) involving separation on a 1 mm × 150 mm porous graphitic carbon (PGC) column and detection by triple quadrupole mass spectrometry in negative-ion electrospray mode. The sample pre-treatment consisted of an ultrafiltration step, following which 300 μl of CSF sample could be injected directly onto a 1 mm × 10 mm PGC guard column functioning as a trap for the analytes. The loading solvent was Milli-Q water at 125 μl/min. After 3 min, the sample was switched into the separation column. The F2-isoprostanes were separated in 20 min using a linear solvent gradient comprising water, methanol, acetonitrile and ammonium hydroxide at a pH of 9.5 and a flow of 50 μl/min The limit of detection (calculated as 3S/N) was approximately 40 pM (14 pg/ml). The assay was linear within the examined range (18–450 pg/ml), using CSF spiked with iPF2α-III standard (r2 > 0.995). Repeatability data were calculated for CSF spiked to 90 pg/ml and the relative standard deviation (RSD) obtained was 3% (n = 6).

  • 3.
    Hansson, Helena
    et al.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Karlberg, Bo
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Nilsson, Ulrika
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Dynamic hollow-fibre liquid phase microextraction for human plasma samples automated by sequential injection analysisManuscript (preprint) (Other academic)
    Abstract [en]

    This paper presents an easily handled, hollow-fibre liquid phase microextraction (HF-LPME) sample clean-up method, automated by the use of a programmable sequential injection analysis (SIA) system. Use of a SIA system significantly reduces the need for manual sample handling. This new type of clean-up system was assessed and compared with manual HF-LPME for the extraction of acidic compounds (dinitrophenols) from human plasma, in terms of human intervention requirements, efficiency, repeatability and carry-over. Its application to a SIA system for basic compounds (b-blockers) is also presented. The sample aliquots collected off-line from the SIA system were subsequently subjected to separation with LC and the various analytes were detected with ESI-MS.

    Extraction efficiency values between 28 and 56% (RSD 5-10%, n = 7) were achieved for the dinitrophenol compounds after an extraction cycle of 58 min including a 30 min washing step. According to the MS analysis the SIA/HF-LPME method yielded clean chromatograms with no detectable interfering peaks. Ion suppression in positive ESI-MS was between 4 and 21% when tested on extracts with b-blockers.

  • 4. Horvai, G.
    et al.
    Worsfold, P.
    Karlberg, Bo
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Andersen, J. E. T.
    Analytical chemistry and bioanalytical chemistry - A yet unshaped social relationship2011In: TrAC. Trends in analytical chemistry, ISSN 0165-9936, E-ISSN 1879-3142, Vol. 30, no 3, p. 422-424Article in journal (Refereed)
  • 5. Horvai, George
    et al.
    Worsfold, Paul
    Karlberg, Bo
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Andersen, Jens E. T.
    European analytical column no. 392011In: Analytical and Bioanalytical Chemistry, ISSN 1618-2642, E-ISSN 1618-2650, Vol. 400, no 6, p. 1539-1541Article in journal (Refereed)
  • 6. Horvai, George
    et al.
    Worsfold, Paul
    Karlberg, Bo
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Andersen, Jens E. T.
    European Analytical Column No. 39 Analytical chemistry and = oanalytical chemistry - an unshaped social relationship2011In: Journal of the Serbian Chemical Society, ISSN 0352-5139, E-ISSN 1820-7421, Vol. 76, no 4, p. 643-646Article in journal (Refereed)
  • 7. Horvai, George
    et al.
    Worsfold, Paul
    Karlberg, Bo
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Andersen, Jens E. T.
    European analytical column no. 39. Analytical chemistry and bioanalytical chemistry: a yet unshaped social relationship2011In: Accreditation and Quality Assurance, ISSN 0949-1775, E-ISSN 1432-0517, Vol. 16, no 4-5, p. 267-269Article in journal (Refereed)
  • 8.
    Karlberg, B
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Publication of chemical research: do we need ethical standards?2007In: Accreditation and Quality Assurance, Vol. 12, p. 49-50Article in journal (Refereed)
  • 9.
    Karlberg, B
    et al.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Andersen, J E T
    Emons, H
    DAC tries a new format, TrAC2008In: Trends in Analytical Chemistry, Vol. 27, p. 97-100Article in journal (Refereed)
  • 10.
    Karlberg, Bo
    et al.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Emons, H.
    Andersen, J. E. T.
    European analytical column no. 36 (January 2008)2009In: Journal of Analytical Chemistry, ISSN 1061-9348, E-ISSN 1608-3199, Vol. 64, no 3, p. 319-321Article in journal (Refereed)
  • 11.
    Karlberg, Bo
    et al.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Emons, Hendrik
    Andersen, Jens E. T.
    European analytical column No. 36 (January 2008)2008In: Analytical and Bioanalytical Chemistry, ISSN 1618-2642, E-ISSN 1618-2650, Vol. 391, no 4, p. 1109-1112Article in journal (Refereed)
  • 12.
    Karlberg, Bo
    et al.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Grasserbauer, Manfred
    Andersen, Jens E. T.
    European Analytical Column: Analytical chemistry faces challenges2009In: TrAC. Trends in analytical chemistry, ISSN 0165-9936, E-ISSN 1879-3142, Vol. 28, no 5, p. 515-518Article in journal (Refereed)
  • 13.
    Karlberg, Bo
    et al.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Korte, Ernst-Heiner
    European Analytical Column No. 35 (January 2007)2007In: Analytical and Bioanalytical Chemistry, ISSN 1618-2642, E-ISSN 1618-2650, Vol. 388, no 3, p. 513-515Article in journal (Refereed)
  • 14. Kubán, P
    et al.
    Karlberg, B
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Flow/sequential injection sample treatment coupled to capillary electrophoresis. A review2009In: Analytica Chimica Acta, ISSN 0003-2670, E-ISSN 1873-4324, Vol. 648, p. 129-145Article in journal (Refereed)
    Abstract [en]

    Various flow sample handling approaches coupled to capillary electrophoresis (CE) are reviewed, covering the research in this field in the 12 years since the milestone year of 1997, when practical interfaces to on-line couple flow injection (FI) and capillary electrophoresis were first developed independently by two research groups. Some previous attempts are also presented. Since 1997 a plethora of ingenious coupled systems have been developed. Although several reviews are available on various aspects of the topic, we have opted for a comprehensive overview of all FI-CE systems, as well as related and similar systems. This coupling has thus also led to the development of systems based on hybrids between the classical and microchip approaches. Truly microchip FI-CE systems are also included in this review. The developed systems have been used for various sample treatments, including on-line membrane-assisted sample treatment, column-based preconcentration, on-line derivatization and monitoring, to name just a few. The utility of coupling flow sampling to CE has been demonstrated in various practical applications that are discussed in detail. The current state-of-the-art and foreseeable future developments are also discussed.

  • 15. Tzanavaras, P D
    et al.
    Themelis, D G
    Zotou, A
    Stratis, J
    Karlberg, B
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Optimization and validation of a dissolution test for selegiline hydrochloride tablets by a novel rapid HPLC assay using a monolithic stationary phase2008In: Journal of Pharmaceutical and Biomedical Analysis, Vol. 46, p. 670-675Article in journal (Refereed)
  • 16. Zacharisa, Constantinos K.
    et al.
    Tzanavaras, Paraskevas D.
    Voulgaropoulosa, Anastasios N.
    Karlberg, Bo
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Amperometric determination of cyanides at the low ppb level by automated preconcentration based on gas diffusion coupled to sequential injection analysis2009In: Talanta: The International Journal of Pure and Applied Analytical Chemistry, ISSN 0039-9140, E-ISSN 1873-3573, Vol. 77, p. 1620-1626Article in journal (Refereed)
    Abstract [en]

     

     

     

    A simple, sensitive method for determining free cyanides is described. The assay is based on automated gas diffusion of the analyte using sequential injection analysis (SIA) coupled to amperometric detection on a silverworking electrode. The effects of varying several parameters affecting the analytical procedure (including the flow rates of the donor and acceptor streams, the concentrations of the reagents and the sample volumes)were studied. The validity and quality of themethodwere also assessed, by examining its linearity, limits of detection and quantitation, precision, selectivity to potentially interfering substances. Its sensitivity can be enhanced by applying a simple preconcentration step, following which limits of detection were found to be 0.05–0.12gL−1.

     Application of the proposed assay to the analysis of tap, mineral and tablewater samples spiked at concentrations ranging from1 to 10gL−1 CN−, yielded satisfactory recoveries (88–112%).

1 - 16 of 16
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