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  • 351.
    Wärmländer, Sebastian K. T. S.
    et al.
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Sholts, Sabrina B.
    Erlandson, Jon M.
    Gjerdrum, Thor
    Westerholm, Roger
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Could the Health Decline of Prehistoric California Indians be Related to Exposure to Polycyclic Aromatic Hydrocarbons (PAHs) from Natural Bitumen?2011In: Journal of Environmental Health Perspectives, ISSN 0091-6765, E-ISSN 1552-9924, Vol. 119, no 9, p. 1203-1207Article in journal (Refereed)
    Abstract [en]

    BACKGROUND: The negative health effects of polycyclic aromatic hydrocarbons (PAHs) are well established for modern human populations but have so far not been studied in prehistoric contexts. PAHs are the main component of fossil bitumen, a naturally occurring material used by past societies such as the Chumash Indians in California as an adhesive, as a waterproofing agent, and for medicinal purposes. The rich archaeological and ethnohistoric record of the coastal Chumash suggests that they were exposed to multiple uptake pathways of bituminous PAHs, including direct contact, fume inhalation, and oral uptake from contaminated water and seafood. OBJECTIVES: We investigated the possibility that PAHs from natural bitumen compromised the health of the prehistoric Chumash Indians in California. CONCLUSIONS: Exposure of the ancient Chumash Indians to toxic PAHs appears to have gradually increased across a period of 7,500 years because of an increased use of bitumen in the Chumash technology, together with a dietary shift toward PAH-contaminated marine food. Skeletal analysis indicates a concurrent population health decline that may be related to PAH uptake. However, establishing such a connection is virtually impossible without knowing the actual exposure levels experienced by these populations. Future methodological research may provide techniques for determining PAH levels in ancient skeletal material, which would open new avenues for research on the health of prehistoric populations and on the long-term effects of human PAH exposure.

  • 352. Yang, Liu
    et al.
    Said, Rana
    Abdel-Rehim, Mohamed
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Sorbent, device, matrix and application in microextraction by packed sorbent (MEPS): A review2017In: Journal of chromatography. B, ISSN 1570-0232, E-ISSN 1873-376X, Vol. 1043, p. 33-43Article, review/survey (Refereed)
    Abstract [en]

    Microextraction by packed sorbent (MEPS) is a new miniaturized form of solid-phase extraction and it is a green sample pretreatment technology. MEPS has been widely accepted and used by several research groups online or offline as a sample preparation technique before instrument analysis. MEPS reduces the sample handling time and organic solvent consumption. MEPS is suitable for small sample volumes and can easily be connected with different chromatographic techniques without modification. The sorbent bed in MEPS is integrated into a liquid handling syringe that allows for low void volume sample manipulations either manually or in combination with laboratory robotics. MEPS is a simple, fast and robust sample preparation technique with several advantages, miniaturization, automation, fast operation course, on-line coupling with analytical instruments and low-cost operation with less solvent and low sample consumption. Sorbent type, device, and matrix are important factors in MEPS research and applications. The performance of MEPS has recently been illustrated by online with liquid chromatography-mass spectrometry and gas chromatography-mass spectrometry assays for pharmaceutical, environmental, and food analyses. This paper deals with MEPS device-optimized sorbent, sample matrix, and application. The progress and potential development of the technique are also discussed.

  • 353. 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%).

  • 354.
    Zamani, L
    et al.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Andersson, F O
    Edebrink, P
    Yang, Y
    Jacobsson, S P
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Conformational studies of a monoclonal antibody, IgG1, by chemical oxidation: Structural analysis by ultrahigh-pressure LC-electrospray ionization time-of-flight MS and multivariate data analysis2008In: Analytical Biochemistry, Vol. 380, p. 155-163Article in journal (Refereed)
  • 355.
    Zamani, Leila
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Extracellular metabolite fingerprinting of spent mammalian cell culture medium in relation to the quality of an expressed recombinant proteinManuscript (preprint) (Other academic)
    Abstract [en]

    This study demonstrates methodology for predicting the quality (in terms, for instance, of specific activities) of recombinant proteins expressed by mammalian cell cultures, at upstream process stages, using metabolic fingerprint analysis. Metabolites extracted from samples taken from a culture of a transfected Chinese Hamster Ovary (CHO) cell line expressing a recombinant protein in a bioreactor at various days of the cell culture process were analyzed by ultra high-pressure liquid chromatography-electrospray ionization-time of flight mass spectrometry (UHPLC-ESI-TOFMS). The LC-MS data were processed and the extracted information was correlated with the concentration of the active protein by partial least squares (PLS) regression, which revealed strong correlations between the LC-MS results and the concentration of active protein (R

    2 = 0.99). The correlations between the LC-MS data and other parameters (glucose concentration, lactate concentration and the number of viable cells) were also studied. To obtain an overview of the data, Principal Component Analysis (PCA) was applied to the LC-MS data obtained from the samples to observe clustering or separation in the sample set. The PCA indicated that the LC-MS data obtained from samples from different days were significantly separated in temporal order from day 7 to day 28, according to the first Principal Component.

  • 356.
    Zamani, Leila
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Methods for structural studies of an antibody, screening metabolites in rat urine and analysis of spent cell cultivation media using LC/ESI-MS and chemometrics2009Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    This thesis describes bioanalytical methods for generating fingerprints of biological systems for extracting relevant information with (protein) drugs in focus. Similarities and differences between samples can reveal the hidden relevant information, which can be used to optimize the production and facilitate the quality control of such protein drugs during their development and manufacture. Metabolic fingerprinting and multivariate data analysis (MVDA) can also facilitate early diagnosis of diseases and the effects and toxicity of drugs.

    Currently, several protein drugs are available on the global market. Nevertheless, despite, the success of such biotherapeutics significant challenges remain to be overcome in maintaining their stability and efficacity throughout their production cycle and long-term storage. The native structure and functional activity of therapeutic proteins is affected by many variables from production to delivery, incl. variables assoc. with conditions in bioreactors, purification, storage and delivery. Thus, part of the work underlying this thesis focused on structural analysis of a protein drug using chemical labeling, peptide mapping, and evaluation of the charge state distributions of the whole protein generated by ESI. The other part focuses on non-targeted metabolomics with a view to optimizing the cell cultivation process and assessment of the drug’s toxicity. A combination of appropriate analytical methods and MVDA is needed to find markers that can facilitate optimization of the cultivation system and expression of the target proteins in early stages of process development. Rapid methods for characterizing the protein drugs in different stages of the process are also required for quality control.

    In order to obtain high quality fingerprints analytical separation techniques with high resolution (such as HPLC or UHPLC) and sensitive analytical detection techniques (such as ESI, quadrupole or TOF MS) have been used, singly or in combination.

  • 357.
    Zamani, Leila
    et al.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Andersson, Fredrik O.
    Edebrink, Per
    Yang, Yang
    Jacobsson, Sven P.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Conformational studies of a monoclonal antibody, IgG1, by chemical oxidation:Structural analysis by ultrahigh-pressure LC–electrospray ionizationtime-of-flight MS and multivariate data analysis2008In: Analytical Biochemistry, ISSN 0003-2697, E-ISSN 1096-0309, Vol. 380, no 2, p. 155-163Article in journal (Refereed)
    Abstract [en]

    We describe the development of a method in which protein oxidation by H2O2 followed by ultrahighpressure liquid chromatography (UHPLC) coupled with electrospray ionization time-of-flight mass spectrometry (ESI-ToFMS) and multivariate analysis are used to detect alterations in conformational states of proteins. In the study reported here, an IgG1 monoclonal antibody in native and denatured conformational states was oxidized by treatment with hydrogen peroxide. Peptide fragments generated by tryptic digestion were then analyzed by UHPLC-ESI-ToFMS. After reducing noise and extracting peaks from the LC–MS data using MzExplorer, software developed in-house and based on Matlab, we were able to distinguish peptides arising from the native and denatured states of the oxidized protein by principal component analysis. Peptides containing residues, which are inclined to undergo oxidation, such as methionine, are founded to be particularly important in this approach. We believe that the methodology could facilitate attempts to characterize the conformational states of recombinant monoclonal antibodies and other proteins.

  • 358.
    Zamani, Leila
    et al.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Lindholm, Jessica
    Ilag, Leopold L.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Jacobsson, Sven P.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Discrimination among IgG1-κ monoclonal antibodies produced by two cell lines using charge state distributions in nanoESI-TOF mass spectra2009In: Journal of the American Society for Mass Spectrometry, ISSN 1044-0305, E-ISSN 1879-1123, Vol. 20, no 6, p. 1030-1036Article in journal (Refereed)
    Abstract [en]

    Charge state distributions (CSDs) of proteins in nanoESI mass spectra are affected by the instrumental settings and experimental conditions, in addition to the conformations of the proteins in the analyzed solutions. In the presented study, instrumental and experimental parameters—the desolvation gas flow rate, temperature, pH, buffer (ammonium acetate), and organic modifier (methanol) concentrations—were optimized according to a reduced central composite face experimental design to maximize the separation of CSDs of monoclonal IgG1-antibodies produced by two production systems (CHO and GS-NS0 cell lines). Principal component analysis and Fisher linear discriminant analysis were then used to reduce the dimensions of the acquired dataset and quantify the separation of the protein classes, respectively. The results show that the IgG1-_ molecules produced by the two production systems can be clearly distinguished using the described approach, which could be readily applied to other proteins and production systems.

  • 359. Zazouli, Mohammad Ali
    et al.
    Akbari-adergani, Behrouz
    Javanbakht, Mehran
    Moein, Mohammad Mahdi
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    On-line extraction and determination of residual sulfathiazole in pharmaceutical wastewater with molecularly imprinted polymers in a packed cartridge coupled with high-performance liquid chromatography2017In: Analytical Methods, ISSN 1759-9660, E-ISSN 1759-9679, Vol. 9, no 20, p. 3019-3028Article in journal (Refereed)
    Abstract [en]

    A new, rapid and sensitive on-line extraction and determination technique was developed with molecularly imprinted polymers (MIPs) in a packed cartridge. An artificial selective polymeric sorbents packed in a polyethylene cartridge were employed for the separation of sulfathiazole residue. The packing particles were synthesized using methacrylic acid as a functional monomer, ethylene glycol dimethacrylate as a cross-linker agent, sulfathiazole as a target template molecule and azobisisobutyronitrile as an initiator. The optimal conditions for designing these sorbents were as follows: conditioning using water with pH = 3.0, loading the sample under mild basic aqueous conditions, cleanup using 2 x 2 mL acetonitrile and elution with 3.0 mL 20 mM ammonium acetate : acetonitrile (75 : 25 v/v, pH = 3.0). In this system, an aliquot of extracted template was injected to the HPLC analytical column with acetonitrile : water (75 : 25 v/v) and water (pH adjusted to 3.0 with H3PO4) as the mobile phases in a gradient elution program. The selectivity of the MIPs in the packed cartridge was evaluated by checking several substances with molecular structures similar to that of the template. The results revealed a recovery of more than 92% along with a limit of detection and limit of quantification of 0.05 and 0.16 ng mL(-1), respectively, for the on-line determination of sulfathiazole in pharmaceutical wastewater samples.

  • 360.
    Zebühr, Yngve
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Trace analysis of polychlorinated dibenzo-p-dioxines, dibenzofurans and related compounds in environmental matrices1992Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    In this thesis sample extraction, clean up procedures and quantitative and qualitative analysis of polychlorinated dibenzo-p-dioxins, dibenzofurans and related compounds are discussed, as well as aspects on the sampling of some complex environmental matrices.

    The matrices are mostly from the aquatic environment but other samples are also dealt with, such as urban and remote air samples, samples from environments with heavy automobile traffic and samples from one municipal incinerator, waste water treatment plants etc.

    The samples from the aquatic environment represent both heavily contaminated matrices such as settling particulate matter from areas off various industries and in central Stockholm, and complex biological matrices such as bivalves, fish and birds.

    The thesis describes the different steps of the cleaning up procedure in detail. New automated methods for handling complicated samples are further discussed. A new method which was used for most of the samples prepares all the fractions for analysis on high resolution GC, medium resolution MS and GC-mass selective detector.

    Another central part of the work in this thesis is the aim to analyse as many as possible of the components of interest in the same sample. This gives more precise answers to the questions asked, reduces the number of samples and last but not least, saves time. The essence of this method is a HPLC-method which uses an amino column for fractionation of the sample according to the aromaticity, in combination with a GCP-column which has high selectivity for aromatic and related compounds. The fractions are collected both using a heart-cutting mode and a back-flushing technique.

  • 361.
    Åberg, K. Magnus
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Variance Reduction in Analytical Chemistry: New Numerical Methods in Chemometrics and Molecular Simulation2004Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    This thesis is based on five papers addressing variance reduction in different ways. The papers have in common that they all present new numerical methods.

    Paper I investigates quantitative structure-retention relationships from an image processing perspective, using an artificial neural network to preprocess three-dimensional structural descriptions of the studied steroid molecules.

    Paper II presents a new method for computing free energies. Free energy is the quantity that determines chemical equilibria and partition coefficients. The proposed method may be used for estimating, e.g., chromatographic retention without performing experiments.

    Two papers (III and IV) deal with correcting deviations from bilinearity by so-called peak alignment. Bilinearity is a theoretical assumption about the distribution of instrumental data that is often violated by measured data. Deviations from bilinearity lead to increased variance, both in the data and in inferences from the data, unless invariance to the deviations is built into the model, e.g., by the use of the method proposed in paper III and extended in paper IV.

    Paper V addresses a generic problem in classification; namely, how to measure the goodness of different data representations, so that the best classifier may be constructed.

    Variance reduction is one of the pillars on which analytical chemistry rests. This thesis considers two aspects on variance reduction: before and after experiments are performed. Before experimenting, theoretical predictions of experimental outcomes may be used to direct which experiments to perform, and how to perform them (papers I and II). After experiments are performed, the variance of inferences from the measured data are affected by the method of data analysis (papers III-V).

  • 362.
    Åberg, K. Magnus
    et al.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Jacobsson, Sven P.
    A measure of class separationIn: Journal of ChemometricsArticle in journal (Refereed)
  • 363.
    Åberg, K. Magnus
    et al.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Jacobsson, Sven P.
    Pre-processing of three-way data by pulse-coupled neural networks—an imaging approach2001In: Chemometrics and Intelligent Laboratory Systems, ISSN 0169-7439, Vol. 57, no 1, p. 25-36Article in journal (Refereed)
  • 364.
    Åberg, K. Magnus
    et al.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Lyubartsev, Alexander P.
    Jacobsson, Sven P.
    Laaksonen, Aatto
    Determination of solvation free energies by adaptive expanded ensemble molecular dynamics2004In: Journal of Chemical Physics, ISSN 0021-9606, Vol. 120, no 8, p. 3770-3776Article in journal (Refereed)
  • 365.
    Åberg, K. Magnus
    et al.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Torgrip, Ralf J. O.
    Jacobsson, Sven P.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Extensions to peak alignment using reduced set mapping and classification of LC-UV data from peptide mapping2005In: Journal of Chemometrics, ISSN 0886-9383, E-ISSN 1099-128X, Vol. 18, no 10, p. 465-473Article in journal (Refereed)
    Abstract [en]

    Peak alignment using reduced set mapping (PARS) is extended with a new baseline approximation

    and a new dendrogram alignment scheme, which is designed to avoid the issue of selecting a target

    chromatogram for the alignment. Two data sets with LC/UV data are studied and it is shown that

    peak alignment with PARS increases the class separation substantially in the principal component

    score space. The results indicate that it is possible to use PARS for calibration transfer of multivariate

    models of chromatographic data.

  • 366.
    Åberg, Magnus
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    A Comparison of Algorithms for Warping and Peak Alignment2009In: 11 th Scandinavian Symposium on Chemometrics SSC11, 2009Conference paper (Other academic)
  • 367.
    Åberg, Magnus
    et al.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Alm, Erik
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Torgrip, R
    The correspondence problem for metabonomics datasets K2009In: Analytical and Bioanalytical Chemistry, ISSN 1618-2642, E-ISSN 1618-2650, Vol. 394, p. 151-162Article in journal (Refereed)
    Abstract [en]

    In metabonomics it is difficult to tell which peak is which in datasets with many samples. This is known as the correspondence problem. Data from different samples are not synchronised, i.e., the peak from one metabolite does not appear in exactly the same place in all samples. For datasets with many samples, this problem is nontrivial, because each sample contains hundreds to thousands of peaks that shift and are identified ambiguously. Statistical analysis of the data assumes that peaks from one metabolite are found in one column of a data table. For every error in the data table, the statistical analysis loses power and the risk of missing a biomarker increases. It is therefore important to solve the correspondence problem by synchronising samples and there is no method that solves it once and for all. In this review, we analyse the correspondence problem, discuss current state-of-the-art methods for synchronising samples, and predict the properties of future methods.

  • 368.
    Åberg, Magnus
    et al.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Jacobsson, Sven
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    On the separation of classes: can the Fisher criterion be improved upon when classes have unequal variance–covariance structure?2010In: Journal of Chemometrics, ISSN 0886-9383, E-ISSN 1099-128X, Vol. 24, p. 650-654Article in journal (Refereed)
  • 369.
    Östman, C
    et al.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Bergh, C
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Ftalater och organofosfater i inomhusluft och bilar: Rapport till Miljöförvaltningen Stockholms Stad2008Report (Other academic)
  • 370.
    Östman, C
    et al.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Bergh, C
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Åberg, M
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Identifiering av ”sjuka hus” med kemisk analys kombinerat med multivariat statistisk dataanalys: Rapport till Miljöförvaltningen, Stockholms Stad2008Report (Other academic)
5678 351 - 370 of 370
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