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  • 1. Chaintreau, Alain
    et al.
    Fieber, Wolfgang
    Sommer, Horst
    Gilbert, Alexis
    Yamada, Keita
    Yoshida, Naohiro
    Pagelot, Alain
    Moskau, Detlef
    Moreno, Aitor
    Schleucher, Jürgen
    Umeå University, Faculty of Medicine, Department of Medical Biochemistry and Biophysics.
    Reniero, Fabiano
    Holland, Margaret
    Guillou, Claude
    Silvestre, Virginie
    Akoka, Serge
    Remaud, Gerald S
    Site-specific C-13 content by quantitative isotopic C-13 nuclear magnetic resonance spectrometry: a pilot inter-laboratory study2013In: Analytica Chimica Acta, ISSN 0003-2670, E-ISSN 1873-4324, Vol. 788, p. 108-113Article in journal (Refereed)
    Abstract [en]

    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.

  • 2.
    Gouveia-Figueira, Sandra C.
    et al.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Karimpour, Masoumeh
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Bosson, Jenny A.
    Umeå University, Faculty of Medicine, Department of Public Health and Clinical Medicine, Medicine.
    Blomberg, Anders
    Umeå University, Faculty of Medicine, Department of Public Health and Clinical Medicine, Medicine.
    Unosson, Jon
    Umeå University, Faculty of Medicine, Department of Public Health and Clinical Medicine, Medicine.
    Sehlstedt, Maria
    Umeå University, Faculty of Medicine, Department of Public Health and Clinical Medicine, Medicine.
    Pourazar, Jamshid
    Umeå University, Faculty of Medicine, Department of Public Health and Clinical Medicine, Medicine.
    Sandström, Thomas
    Umeå University, Faculty of Medicine, Department of Public Health and Clinical Medicine, Medicine.
    Behndig, Annelie F.
    Umeå University, Faculty of Medicine, Department of Public Health and Clinical Medicine, Medicine.
    Nording, Malin L.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Mass spectrometry profiling reveals altered plasma levels of monohydroxy fatty acids and related lipids in healthy humans after controlled exposure to biodiesel exhaust2018In: Analytica Chimica Acta, ISSN 0003-2670, E-ISSN 1873-4324, Vol. 1018, p. 62-69Article in journal (Refereed)
    Abstract [en]

    Experimental human exposure studies are an effective tool to study adverse health effects from acute inhalation of particulate matter and other constituents of air pollution. In this randomized and double-blinded crossover study, we investigated the systemic effect on bioactive lipid metabolite levels after controlled biodiesel exhaust exposure of healthy humans and compared it to filtered air at a separate exposure occasion. Eicosanoids and other oxylipins, as well as endocannabinoids and related lipids, were quantified in plasma from 14 healthy volunteers at baseline and at three subsequent time points (2, 6, and 24 h) after 1 h exposure sessions. Protocols based on liquid chromatography (LC) coupled to tandem mass spectrometry (MS/MS) methods were developed to detect temporal changes in circulating levels after biodiesel exhaust exposure. The exhaust was generated by a diesel engine fed with an undiluted rapeseed methyl ester fuel. Among the 51 analyzed lipid metabolites, PGF(2 alpha), 9,10-DiHOME, 9-HODE, 5-HETE, 11-HETE, 12-HETE, and DEA displayed significant responsiveness to the biodiesel exhaust exposure as opposed to filtered air. Of these, 9-HODE and 5-HETE at 24 h survived the 10% false discovery rate cutoff (p < 0.003). Hence, the majority of the responsive lipid metabolites were monohydroxy fatty acids. We conclude that it is possible to detect alterations in circulating bioactive lipid metabolites in response to biodiesel exhaust exposure using LC-MS/MS, with emphasis on metabolites with inflammation related properties and implications on cardiovascular health and disease. These observations aid future investigations on air pollution effects, especially with regard to cardiovascular outcomes.

  • 3.
    Jonsson, Tobias
    et al.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Emteborg, Malin
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Irgum, Knut
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Heterocyclic compounds as catalysts in the peroxyoxalate chemiluminescence reaction of bis(2,4,6-trichlorophenyl)oxalate1998In: Analytica Chimica Acta, ISSN 0003-2670, E-ISSN 1873-4324, Vol. 361, no 3, p. 205-215Article in journal (Refereed)
    Abstract [en]

    Substituted imidazoles and leaving groups known from other areas of chemistry have been tested for catalytic efficiency in the peroxyoxalate chemiluminescence (PO-CL) reaction, using bis(2,4,6-trichlorophenyl)oxalate (TCPO) as reagent. Catalytic activity was found for 1,2,4-triazole, 1-methylimidazole, 2-methylimidazole, 4-methylimidazole and 4,5-dichloroimidazole, while 2-mercaptoimidazole, 2-nitroimidazole, 4-nitroimidazole, benzimidazole, benzotriazole, thiazole, o-benzoic sulfimide, phthalimide, succinimide, 2(1H)-pyridone and 1,2,3-benzotriazine-4(3H)-one yielded no detectable chemiluminescence under the conditions used. None of the tested compounds was more efficient than imidazole in catalyzing the PO-CL reaction. Spectrophotometric measurements of the catalytic breakdown of TCPO showed that an intermediate was formed with almost all catalysts, and that intermediates that were more stable or present at lower concentration led to a reduced catalytic efficiency in the PO-CL reaction of TCPO.

  • 4.
    Jonsson, Tobias
    et al.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Irgum, Knut
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Very fast peroxyoxalate chemiluminescence1999In: Analytica Chimica Acta, ISSN 0003-2670, E-ISSN 1873-4324, Vol. 400, no 1-3, p. 257-264Article in journal (Refereed)
    Abstract [en]

    Peroxyoxalate chemiluminescence (PO-CL) detection offers an advantage in chromatographic detection, by the virtue of its multiple unique selectivities and high sensitivity. However, many of the analytical separation techniques available today require observation times in the millisecond range to preserve the band resolution, and as the reaction kinetics of the PO-CL reaction is considerably slower, extra flow elements are needed to observe the reaction in a time window at maximum emission intensity. Since these flow elements increase the complexity of the system and contribute to band-broadening, the rational way to adapt PO-CL detection to miniaturised separation systems is to speed up the reaction, so that it emits an initial burst of light within the acceptable detection time-frame. Although this may result in a lower overall quantum yield, the actual detection sensitivity could be equal to, or better than slower PO-CL systems. By making careful selections of oxalic reagent and catalyst(s) the reaction can be fine-tuned to maximise the intensity. In this work, the time-dependent light emission from the reaction of bis(2,4,6-trichlorophenyl)oxalate (TCPO) was studied under the catalytic influence of imidazole, 1,2,4-triazole, 4-dimethylaminopyridine (DMAP), and 1,8-diazabicyclo-[5.4.0]-undec-7-ene (DBU) in acetonitrile. Both DMAP and DBU accelerated the reaction substantially, but the best combination of reaction speed and intensity was found for a mixture of 0.5 mM DBU and 5 mM 1,2,4-triazole, which reached its maximum emission after only 40 ms and had an emission intensity comparable to that seen with 5 mM imidazole as catalyst.

  • 5.
    Karimpour, Masoumeh
    et al.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Surowiec, Izabella
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Wu, Junfang
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Gouveia-Figueira, Sandra
    Umeå University, Faculty of Science and Technology, Department of Chemistry. Umeå University, Faculty of Medicine, Department of Pharmacology and Clinical Neuroscience, Pharmacology.
    Pinto, Rui
    Umeå University, Faculty of Science and Technology, Department of Chemistry. Bioinformatics Infrastructure for Life Sciences, Sweden.
    Trygg, Johan
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Zivkovic, Angela M.
    Nording, Malin L.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Postprandial metabolomics: A pilot mass spectrometry and NMR study of the human plasma metabolome in response to a challenge meal2016In: Analytica Chimica Acta, ISSN 0003-2670, E-ISSN 1873-4324, Vol. 908, p. 121-131Article in journal (Refereed)
    Abstract [en]

    The study of postprandial metabolism is relevant for understanding metabolic diseases and characterizing personal responses to diet. We combined three analytical platforms – gas chromatography-mass spectrometry (GC-MS), liquid chromatography-mass spectrometry (LC-MS) and nuclear magnetic resonance (NMR) – to validate a multi-platform approach for characterizing individual variation in the postprandial state. We analyzed the postprandial plasma metabolome by introducing, at three occasions, meal challenges on a usual diet, and 1.5 years later, on a modified background diet. The postprandial response was stable over time and largely independent of the background diet as revealed by all three analytical platforms. Coverage of the metabolome between NMR and GC-MS included more polar metabolites detectable only by NMR and more hydrophobic compounds detected by GC-MS. The variability across three separate testing occasions among the identified metabolites was in the range of 1.1–86% for GC-MS and 0.9–42% for NMR in the fasting state at baseline. For the LC-MS analysis, the coefficients of variation of the detected compounds in the fasting state at baseline were in the range of 2–97% for the positive and 4–69% for the negative mode. Multivariate analysis (MVA) of metabolites detected with GC-MS revealed that for both background diets, levels of postprandial amino acids and sugars increased whereas those of fatty acids decreased at 0.5 h after the meal was consumed, reflecting the expected response to the challenge meal. MVA of NMR data revealed increasing postprandial levels of amino acids and other organic acids together with decreasing levels of acetoacetate and 3-hydroxybutanoic acid, also independent of the background diet. Together these data show that the postprandial response to the same challenge meal was stable even though it was tested 1.5 years apart, and that it was largely independent of background diet. This work demonstrates the efficacy of a multi-platform metabolomics approach followed by multivariate and univariate data analysis for a broad-scale screen of the individual metabolome, particularly for studies using repeated measures to determine dietary response phenotype.

  • 6. Kondo, Elsuida
    et al.
    Marriott, Philip J.
    Parker, Rhiannon M.
    Kouremenos, Konstantinos A.
    Umeå University, Faculty of Medicine, Department of Molecular Biology (Faculty of Medicine).
    Morrison, Paul
    Adams, Mike
    Metabolic profiling of yeast culture using gas chromatography coupled with orthogonal acceleration accurate mass time-of-flight mass spectrometry: Application to biomarker discovery2014In: Analytica Chimica Acta, ISSN 0003-2670, E-ISSN 1873-4324, Vol. 807, p. 135-142Article in journal (Refereed)
    Abstract [en]

    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.

  • 7.
    Larsson, H
    et al.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Dasgupta, P K
    Department of Chemistry and Biochemistry, Texas Tech University,.
    Liquid core waveguide-based optical spectrometry for field estimation of dissolved BTEX compounds in groundwater - A feasibility study2003In: Analytica Chimica Acta, ISSN 0003-2670, E-ISSN 1873-4324, Vol. 485, no 2, p. 155-167Article in journal (Refereed)
    Abstract [en]

    The utility of a liquid core waveguide (LCW) system for acting as a sentry monitor for compounds such as benzene, toluene, ethylbenzene, xylene (BTEX) in water was examined. A vapor-permeable LCW suitable for long path length absorbance spectroscopy based on a Teflon AF 2400 tube was fabricated. Multiwavelength spectroscopy in the near-UV was carried out using a fiber optic-based flashlamp-photodiode array (PDA) combination with hexane as the solvent in the waveguide core. Using multicomponent calibration, quantitation of benzene and toluene accurate to 6+/-5% could be conducted at sub-mg l(-1) levels in mixtures after a sampling period of 10 min. (C) 2003 Elsevier Science B.V. All rights reserved.

  • 8.
    Liem-Nguyen, Van
    et al.
    Umeå University, Faculty of Science and Technology, Department of Chemistry. School of Science and Technology, Örebro University, SE-70281, Örebro, Sweden.
    Huynh, Khoa
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Gallampois, Christine
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Björn, Erik
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Determination of picomolar concentrations of thiol compounds in natural waters and biological samples by tandem mass spectrometry with online preconcentration and isotope-labeling derivatization2019In: Analytica Chimica Acta, ISSN 0003-2670, E-ISSN 1873-4324, Vol. 1067, p. 71-78Article in journal (Refereed)
    Abstract [en]

    We present a sensitive, selective and robust method for the determination of 14 thiol compounds in aqueous samples. Thiols were derivatized with omega-bromoacetonylquinolinium bromide (BQB) and its deuterium labeled equivalent D7-ω-bromoacetonylquinolinium bromide (D7). Derivatized thiols were preconcentrated by online solid-phase extraction (SPE) followed by liquid chromatography separation and electrospray ionization tandem mass spectrometry determination (SPE/LC-ESI-MS/MS). The robustness of the method was validated for wide ranges in pH, salinity, and concentrations of sulfide and dissolved organic carbon (DOC) to cover contrasting natural water types. The limits of detection (LODs) for the thiols were 3.1-66 pM. Between 6 and 14 of the thiols were detected in different natural sample types at variable concentrations: boreal wetland porewater (0.7-51 nM), estuarine sediment porewater (50 pM-11 nM), coastal sea water (60 pM-16 nM), and sulfate reducing bacterium cultures (80 pM-4 nM). MS/MS fragmentation of the compounds produces two pairs of common product ions, m/z 130.2/137.1 and 218.1/225.1, which enables scanning for unknown thiols in precursor ion scan mode. Using this approach, we identified cysteine, mercaptoacetic acid, N-acetyl-L-cysteine and sulfurothioic S-acid in boreal wetland porewater. The performance of the developed method sets a new state of the art for the determination of thiol compounds in environmental and biological samples.

  • 9.
    Löfstedt, Tommy
    et al.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Hoffman, Daniel
    Umeå University, Faculty of Science and Technology, Department of Molecular Biology (Faculty of Science and Technology).
    Trygg, Johan
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Global, local and unique decompositions in OnPLS for multiblock data analysis2013In: Analytica Chimica Acta, ISSN 0003-2670, E-ISSN 1873-4324, Vol. 791, p. 13-24Article in journal (Other academic)
    Abstract [en]

    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.

  • 10.
    Madsen, Rasmus
    et al.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Lundstedt, Torbjörn
    AcureOmics AB.
    Trygg, Johan
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Chemometrics in metabolomics - a review in human disease diagnosis2010In: Analytica Chimica Acta, ISSN 0003-2670, E-ISSN 1873-4324, Vol. 659, no 1-2, p. 23-33Article in journal (Refereed)
    Abstract [en]

    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.

  • 11.
    Nording, Malin
    et al.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Frech, Kristina
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Persson, Ylva
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Forsman, Mats
    Swedish Defence Research Agency, Umeå, Sweden.
    Haglund, Peter
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    On the semi-quantification of polycyclic aromatic hydrocarbons in contaminated soil by an enzyme-linked immunosorbent assay kit2006In: Analytica Chimica Acta, ISSN 0003-2670, E-ISSN 1873-4324, Vol. 555, no 1, p. 107-113Article in journal (Refereed)
    Abstract [en]

    Polycyclic aromatic hydrocarbons (PAHs) are of environmental concern, for instance when found in contaminated soils at sites where industrial activities have occurred. For efficient screening of such soils, the commercially available enzyme-linked immunosorbent assay (ELISA) kit, the PAH RISc® soil test, can be used. However, the site-specific performance may vary due to differences in soil properties and contamination profiles. Hence, in this study we have examined various contributing factors to the total ELISA measurements uncertainties. These factors include contributions from co-extracted (non-target) compounds, the extraction efficiency and differences in cross-reactivity among the target analytes. Reference values were obtained through pressurized liquid extraction (PLE) and gas chromatography coupled to mass spectrometry (GC–MS) analysis. The results showed that the ELISA does not seem to respond to non-target compounds in the soil extracts to any large extent. Furthermore, high molecular weight PAHs were found to be more efficiently extracted with PLE than with methanol agitation, which is used for ELISA. If this, and the cross-reactivity of the individual PAHs, were taken into consideration, the ELISA and GC–MS results were in good agreement.

  • 12.
    Nording, Malin
    et al.
    Umeå University, Faculty of Science and Technology, Department of Chemistry. Swedish Defence Research Agency, Umeå, Sweden.
    Haglund, Peter
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Evaluation of the structure/cross-reactivity relationship of polycyclic aromatic compounds using an enzyme-linked immunosorbent assay kit2003In: Analytica Chimica Acta, ISSN 0003-2670, E-ISSN 1873-4324, Vol. 487, no 1, p. 43-50Article in journal (Refereed)
    Abstract [en]

    A commercially available enzyme-linked immunosorbent assay (ELISA) kit, the PAH soil test, was evaluated with regard to cross-reactivity. Phenanthrene in methanol was used as reference substance. Anthracene, naphthalene and fluorene were chosen as representatives of the 16 US-EPA priority-pollutant polycyclic aromatic hydrocarbons (PAHs). In addition, a number of polycyclic aromatic compounds (PACs), including methyl-, phenyl-, and carbonyl-PAHs, as well as NSO-heterocyclic PACs, found at former industrial sites, were chosen for elucidation of structure/cross-reactivity relationships. The study emphasizes the importance of a priori knowledge of sample composition for accurate interpretation of test results.

  • 13.
    Phal, Sereilakhena
    et al.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Lindholm-Sethson, Britta
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Geladi, Paul
    Shchukarev, Andrey
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Tesfalidet, Solomon
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Determination of methotrexate in spiked human blood serum using multi-frequency electrochemical immittance spectroscopy and multivariate data analysis2017In: Analytica Chimica Acta, ISSN 0003-2670, E-ISSN 1873-4324, Vol. 987, p. 15-24Article in journal (Refereed)
    Abstract [en]

    This article describes an attempt to develop a sensor based on multi-frequency immittance spectroscopy for the determination of methotrexate (MTX) in blood serum using gold electrodes modified with antibodies. The attachment of antibodies was monitored with electrochemical immittance spectroscopy (EIS) and X-ray photoelectron spectroscopy (XPS). The EIS measurements of MTX resulted in a data matrix of size 39 × 55. The data were analysed using multivariate data analysis and showed a concentration dependence and time dependence that could be separated. This allowed the calculation of a multivariate calibration model. The model showed good linear behavior on a logarithmic scale offering a detection limit of 5 × 10−12 mol L−1.

  • 14.
    Rui Climaco, Pinto
    et al.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Stenlund, Hans
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Hertzberg, Magnus
    Lundstedt, Torbjörn
    Johansson, Erik
    Trygg, Johan
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Design of experiments on 135 cloned poplar trees to map environmental influence in greenhouse2011In: Analytica Chimica Acta, ISSN 0003-2670, E-ISSN 1873-4324, Vol. 685, no 2, p. 127-131Article in journal (Refereed)
    Abstract [en]

    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.

  • 15.
    Sandberg Hiltunen, Maria
    Umeå University, Faculty of Social Sciences, Centre for Demographic and Ageing Research (CEDAR).
    DNA and peptide sequences and chemical processes multivariately modelled by principal component analysis and partial least-squares projections to latent structures1993In: Analytica Chimica Acta, ISSN 0003-2670, E-ISSN 1873-4324, Vol. 277, p. 239-253Article in journal (Refereed)
    Abstract [en]

    Biopolymer sequences (e.g., DNA, RNA, proteins and polysaccharides) and chemical processes (e.g., a batch or continuous polymer synthesis run in a chemical plant) have close similarities from the modelling point of view. When a set of sequences or processes is characterized by multivariate data, a three-way data matrix is obtained. With sequences the position and with processes the time is one direction in this matrix. The multivariate modelling of this matrix by principal component analysis (PCA) or partial least-squares (PLS) methods for the following purposes is discussed: classification of sequences; quantitative relationships between sequence and biological activity or chemical properties; optimizing a sequence with respect to selected properties; process diagnostics; and quantitative relationships between process variables and product quality variables. To obtain good models, a number of problems have to be adequately dealt with: appropriate characterization of the sequence or process; experimental design (selecting sequences or process settings); transforming the three-way into a two-way matrix; and appropriate modelling and validation (modelling interactions, periodicities, “time series” structures and “neighbour effects”). A multivariate approach to sequence and process modelling using PCA and PLS projections to latent structures is discussed and illustrated with several sets of peptide and DNA promoter data.

  • 16.
    Souihi, Nabil
    et al.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Lindegren, Anders
    Eriksson, Lennart
    Trygg, Johan
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    OPLS in batch monitoring - Opens up new opportunities2015In: Analytica Chimica Acta, ISSN 0003-2670, E-ISSN 1873-4324, Vol. 857, p. 28-38Article in journal (Refereed)
    Abstract [en]

    In batch statistical process control (BSPC), data from a number of "good" batches are used to model the evolution (trajectory) of the process and they also define model control limits, against which new batches may be compared. The benchmark methods used in BSPC include partial least squares (PLS) and principal component analysis (PCA). In this paper, we have used orthogonal projections to latent structures (OPLS) in BSPC and compared the results with PLS and PCA. The experimental study used was a batch hydrogenation reaction of nitrobenzene to aniline characterized by both UV spectroscopy and process data. The key idea is that OPLS is able to separate the variation in data that is correlated to the process evolution (also known as 'batch maturity index') from the variation that is uncorrelated to process evolution. This separation of different types of variations can generate different batch trajectories and hence lead to different established model control limits to detect process deviations. The results demonstrate that OPLS was able to detect all process deviations and provided a good process understanding of the root causes for these deviations. PCA and PLS on the other handwere shown to provide different interpretations for several of these process deviations, or in some cases they were unable to detect actual process deviations. Hence, the use of OPLS in BSPC can lead to better fault detection and root cause analysis as compared to existing benchmark methods and may therefore be used to complement the existing toolbox.

  • 17.
    Tesfalidet, Solomon
    et al.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Geladi, Paul
    Shimizu, Kenichi
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Lindholm-Sethson, Britta
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Detection of methotrexate in a flow system using electrochemical impedance spectroscopy and multivariate data analysis2016In: Analytica Chimica Acta, ISSN 0003-2670, E-ISSN 1873-4324, Vol. 914, p. 1-6Article in journal (Refereed)
    Abstract [en]

    Abstract Methotrexate (MTX), a common pharmaceutical drug in cancer therapy and treatment of rheumatic diseases, is known to cause severe adverse side effects at high dose. As the side effect may be life threatening, there is an urgent need for a continuous, bed-side monitoring of the nominal MTX serum level in a patient while the chemical is being administered. This article describes a detection of MTX using a flow system that consists two modified gold electrodes. Interaction of MTX with the antibodies fixed on the electrode surface is detected by electrochemical impedance spectroscopy and evaluated using singular value decomposition (SVD). The key finding of this work is that the change in the electrode capacitance is found to be quantitative with respect to the concentration of MTX. Moreover a calibration curve constructed using the principal component regression method has a linear range of six orders of magnitude and a detection limit of 1.65 × 10−10 M.

  • 18.
    Tolu, Julie
    et al.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Gerber, Lorenz
    Boily, Jean-Francois
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Bindler, Richard
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    High-throughput characterization of sediment organic matter by pyrolysis-gas chromatography/mass spectrometry and multivariate curve resolution: A promising analytical tool in (paleo) limnology2015In: Analytica Chimica Acta, ISSN 0003-2670, E-ISSN 1873-4324, Vol. 880, p. 93-102Article in journal (Refereed)
    Abstract [en]

    Molecular-level chemical information about organic matter (OM) in sediments helps to establish the sources of OM and the prevalent degradation/diagenetic processes, both essential for understanding the cycling of carbon (C) and of the elements associated with OM (toxic trace metals and nutrients) in lake ecosystems. Ideally, analytical methods for characterizing OM should allow high sample throughput, consume small amounts of sample and yield relevant chemical information, which are essential for multidisciplinary, high-temporal resolution and/or large spatial scale investigations. We have developed a high-throughput analytical method based on pyrolysis-gas chromatography/mass spectrometry and automated data processing to characterize sedimentary OM in sediments. Our method consumes 200 mg of freeze-dried and ground sediment sample. Pyrolysis was performed at 450 degrees C, which was found to avoid degradation of specific biomarkers (e. g., lignin compounds, fresh carbohydrates/cellulose) compared to 650 degrees C, which is in the range of temperatures commonly applied for environmental samples. The optimization was conducted using the top ten sediment samples of an annually resolved sediment record (containing 16-18% and 1.3-1.9% of total carbon and nitrogen, respectively). Several hundred pyrolytic compound peaks were detected of which over 200 were identified, which represent different classes of organic compounds (i. e., n-alkanes, n-alkenes, 2-ketones, carboxylic acids, carbohydrates, proteins, other N compounds, (methoxy) phenols, (poly) aromatics, chlorophyll and steroids/hopanoids). Technical reproducibility measured as relative standard deviation of the identified peaks in triplicate analyses was 5.5 +/- 4.3%, with 90% of the RSD values within 10% and 98% within 15%. Finally, a multivariate calibration model was calculated between the pyrolytic degradation compounds and the sediment depth (i. e., sediment age), which is a function of degradation processes and changes in OM source type. This allowed validation of the Py-GC/MS dataset against fundamental processes involved in OM cycling in aquatic ecosystems.

  • 19. Vetter, Walter
    et al.
    Armbruster, Wolfgang
    Betson, Tatiana R
    Umeå University, Faculty of Medicine, Department of Medical Biochemistry and Biophysics.
    Schleucher, Jürgen
    Umeå University, Faculty of Medicine, Department of Medical Biochemistry and Biophysics.
    Kapp, Thomas
    Lehnert, Katja
    Baseline isotopic data of polyhalogenated compounds.2006In: Analytica Chimica Acta, ISSN 0003-2670, E-ISSN 1873-4324, Vol. 577, no 2, p. 250-256Article in journal (Refereed)
1 - 19 of 19
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