Browsing by Subject "chemical analysis"

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  • Selin, Markus (Helsingfors universitet, 2012)
    This thesis is constructed as a part of a larger research project aiming to increase understanding of polyketone reductases (PKR) and develop applications from them. PKRs are enzymes in biosynthetic pathways leading to several aromatic secondary metabolites in plants. The previous work in the research group has led to establishment of several callus cultures from plants belonging to the genus Rubus in the family Rosaceae. The aim in the experimental part of this thesis is the identification and semi-quantitation of raspberry ketone (RK) and related aromatics in the cell suspension cultures initiated from the previously established callus cultures. RK is biosynthetically produced by reduction of p-hydroxybenzalacetone (p-OH-BA) by benzalacetone reductase (BAR). As a part of the experimental work, p-OH-BA has to be chemically synthetized and analysed. Special emphasis is placed to experiment, develop and validate an extraction method for phenolic compounds using ASE 200 working station. In the review part of this thesis, the basic procedures of chemical analysis are described, optimization and validation of analytical methods are discussed, and lastly studies related to raspberry ketone (RK) are summarized. The detection limit is 0.73 µg/ml for RK with the established UPLC-UV method, and the quantitation limit (QL) is 2.22 µg/ml. At the QL, the standard deviation of the extraction method is 8.9 % and the results are 6.4 % higher than expected. At the high end of the standard curve the extraction results are 18.7 % higher than expected. Some changes are proposed to optimize the method. Analysis of the cell line extracts with the established UPLC-UV method did not readily reveal any of the studied compounds. Although the interpretation of the results of the MS experiment is still underway, RK was detected from the arctic bramble cell line Ra15. Also, a possible derivative of zingerone was detected from cloudberry cell line extract even without the corresponding standard compound. This shows the power of the MS in metabolite profiling, and gives a course for future studies.
  • Bettencourt da Silva, Ricardo J.N; Saame, Jaan; Anes, Bárbara; Heering, Agnes; Leito, Ivo; Näykki, Teemu; Stoica, Daniela; Deleebeeck, Lisa; Bastkowski, Frank; Snedden, Alan; Camões, M. Filomena (Elsevier, 2021)
    Analytica Chimica Acta 1182 (2021), 338923
    The use of the unified pH concept, pHabsH2O, applicable to aqueous and non-aqueous solutions, which allows interpreting and comparison of the acidity of different types of solutions, requires reliable and objective determination. The pHabsH2O can be determined by a single differential potentiometry measurement referenced to an aqueous reference buffer or by a ladder of differential potentiometric measurements that allows minimisation of inconsistencies of various determinations. This work describes and assesses bottom-up evaluations of the uncertainty of these measurements, where uncertainty components are combined by the Monte Carlo Method (MCM) or Taylor Series Approximation (TSM). The MCM allows a detailed simulation of the measurements, including an iterative process involving in minimising ladder deviations. On the other hand, the TSM requires the approximate determination of minimisation uncertainty. The uncertainty evaluation was successfully applied to measuring aqueous buffers with pH of 2.00, 4.00, 7.00, and 10.00, with a standard uncertainty of 0.01. The reference and estimated values from both approaches are metrologically compatible for a 95% confidence level even when a negligible contribution of liquid junction potential uncertainty is assumed. The MCM estimated pH values with an expanded uncertainty, for the 95% confidence level, between 0.26 and 0.51, depending on the pH value and ladder inconsistencies. The minimisation uncertainty is negligible or responsible for up to 87% of the measurement uncertainty. The TSM quantified measurement uncertainties on average only 0.05 units larger than the MCM estimated ones. Additional experimental tests should be performed to test these uncertainty models for analysis performed in other laboratories and on non-aqueous solutions.
  • Verkasalo, Erkki; Mottonen, Veikko; Roitto, Marja; Vepsalainen, Jouko; Kumar, Anuj; Ilvesniemi, Hannu; Siwale, Workson; Julkunen-Tiitto, Riitta; Raatikainen, Olavi; Sikanen, Lauri (2021)
    This study aimed to identify and quantify phenolic and resin acid extractive compounds in Scots pine stemwood and sawmill residues in four climatic regions of Finland to evaluate their most optimal sources for bio-based chemical biorefining and bioenergy products. The sample consisted of 140 trees from 28 stands, and sawdust lots from 11 log stands. NMR for the overall extractive analysis and HPLC for the quantitative estimation of phenolic and resin acid compounds were employed. Correlation analysis, multivariate factor analysis, principle component analysis and multiple linear regression modelling were applied for statistical analysis. HPLC identified 12 extractive compounds and NMR five more resin acids. Pinosylvin (PS), pinosylvin monomethyl ether (PSMME), and partly neolignans/lignans occurred in the largest concentrations. Wood type caused the most variation, heartwood having larger concentrations than sapwood (sawdust between them). Regional differences in the concentrations were smaller, but factor analysis distinguished the northern and the southern regions into their own groups. The results indicated higher concentrations of PS, PSMME, and vanillic acid in southern regions and those of, e.g., PSMME glycoside, lignan 2, and neolignan 1 in northern regions. The rather low concentrations of extractives in stemwood and sawdust imply value-added products, efficient sorting and/or large raw material volumes.
  • Valsta, Liisa; Pastell, Helena; Aalto, Sanni; Virtanen, Suvi (Nordic Council of Ministers, 2017)
    Quality of food composition information is of great significance considering the vast and important use of the data: for national dietary advice, for food nutrient labelling, and in epidemiological research. In order to have good quality data for foods consumed in the Nordic countries, sampling and analysis of food needs to be performed to determine the nutrient composition of interest. The Nordic Food Analysis Network project (NFAN), that was carried out between 2013–2016, focused on creating a common, simple communicational platform to share history and plans on chemical food analyses. In addition, it focused on sharing developments in the areas of new analytical methods, especially of dietary fibre, iodine and sodium (i.e. salt). An extranet site was set up, where partners updated their chemical food analysis activities, for others to observe and be aware of. The platform was found to be informative, although updating it was sometimes found to be cumbersome or forgotten. This kind of activity needs active coordination to become useful. Also, comparative analyses of fibre, iodine and sodium concentrations of selected Nordic foods were carried out with external funds and the results were shared, discussed and disseminated among the project group and a broader audience. The comparative analyses showed diverging results, even when the same analytical methods and procedures are used. A comparison, organized by the network, of the conditions in the different countries, showed several reasons for this. The main reasons for different nutrient compositions between the countries was found to be differences in fortification programmes and in animal feeding practices between the countries. The NFAN network organized three physical meetings and one open satellite symposium during the project, which served as platforms to update the partners on national developments in the field and discuss future visions – even wild ideas. The meetings were highly appreciated, partly due to the fact that the critical mass of competence, both for food composition data compilers and food chemists at the national level, in all Nordic countries, is declining. The discussions not only focused on the tasks of this project, but also served as a forum to discuss the broader challenges in the area as well as strategies to better disseminate food data and how to improve the dialogue between data providers from the food industry, and the data users and other stakeholders. For future actions, the Network has recommended that: 1) The Nordic countries should continue to keep each other informed about chemical food analysis plans to facilitate possible common analyses and to facilitate other synergistic activities and method development. Moreover, there is a continuous need for a well-structured and simple-to-use communicational platform in the future, where all the information is stored and updated. 2) New chemical analysis data should be compiled in the food composition databases and be more widely used in the future. 3) The background information on the analysed nutrient values, e.g. the sampling procedures, methods, sample description (e.g. fortification practices, animal feeding practices in the country) are crucial for the data users, and therefore, should be disseminated together with the values. 4) A common Nordic training programme for young actors in the fields of chemical food analysis and food composition data compilation should be considered, to assure high quality outputs, in the future. 5) Harmonization efforts for the production of food composition information, according to established guidelines (e.g. Greenfield & Southgate, 2003) and updated rules to calculate the activity of nutrients (Institute of Medicine 2000, Nordic Council of Ministers 2012), should be continued. 6) Re-evaluation of the rules and procedures for use of existing food composition data should be carried out. This could be done by performing an updated evaluation on the handling of the nutrient values, i.e. to carry out an update of the former Norfoods 2000 project (Norfoods 2000-project group, 2002).