diplomsko delo univerzitetnega študijskega programa I. stopnje
Katja Čuš (Author), Mitja Kolar (Mentor), Maša Islamčević Razboršek (Co-mentor)

Abstract

Ogljikove hidrate običajno določajo s tekočinsko kromatografijo visoke ločljivost (HPLC) ali s plinsko kromatografijo (GC) v povezavi z različnimi detektorji. Ker so enostavni ogljikovi hidrati, kot sta galaktoza in manoza, v raztopinah prisotni v različnih oblikah (aciklični, ciklični-furanozni in ciklični-piranozni), lahko pride posledično pri pripravi vzorcev za kromatografsko analizo do nezaželenega pojava več kromatografskih vrhov v kromatogramu, kar dodatno otežuje identifikacijo in kvantifikacijo spojin. Masno-selektivni detektorji (MS) so tisti, ki ponujajo visoko občutljivost in visoko selektivnost, tudi v primerih koelucije. Kljub neugodnim fizikalno-kemijskim lastnostim preiskovanih spojin, smo z zastavljenim obsegom raziskav uspeli razviti in vpeljati zanesljivo analizno metodo, ki vključuje ustrezno pripravo vzorcev, sočasno identifikacijo in kvantitativno določanje izbranih monosaharidov, galaktoze in manoze, v realnih vzorcih hemiceluloze ob uporabi sklopljenega sistema GC-MS. Preiskovane spojine smo pred samo analizo ustrezno derivatizirali tako, da smo tvorili termično obstojne in dovolj hlapne trimetilsililirane (TMS) derivate primerne za analizo z GC-MS. GC-MS pogoje smo optimirali tako, da smo dobili najustreznejšo ločitev komponent in s tem dovolj kvalitetne spektre posameznih spojin. Razvito analizno metodo smo validirali in s tem dokazali, da je le-ta linearna, natančna, ponovljiva in zanesljiva. S kvantitativno analizo različnih ekstraktov hemiceluloze smo določili vsebnosti preiskovanih spojin. Ugotovili smo, da je v vzorcu hemiceluloze, ekstrahiranem z 2M HCl in segrevanjem 3,5 h pri 100 °C, povprečna vsebnost manoze 0,1 mg/mg zatehte ekstrakta in povprečna vsebnost galaktoze 0,06 mg/mg zatehte ekstrakta. V vzorcu hemiceluloze, ekstrahiranem z destilirano vodo in segrevanjem 3,5 h pri 100 °C, pa nismo zasledili preiskovanih spojin. Iz tega sklepamo, da dodatek organskih kislin, katalizira hidrolizo glikozidnih vezi v polisaharidu hemicelulozi v monomerne enote, razen tega so lahko vsebnosti enostavnih sladkorjev v končnih ekstraktih odvisne tudi od načina, temperature in časa ekstrakcije.

Keywords

plinska kromatografija;masna spektrometrija;galaktoza;manoza;validacija;

Data

Language: Slovenian
Year of publishing:
Typology: 2.11 - Undergraduate Thesis
Organization: UM FKKT - Faculty of Chemistry and Chemical Engineering
Publisher: [K. Čuš]
UDC: 543.554.3(043.2)
COBISS: 18217238 Link will open in a new window
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Other data

Secondary language: English
Secondary title: GAS CHROMATOGRAPHIC - MASS SPECTROMETRIC DETERMINATION OF GALACTOSE AND MANNOSE IN REAL SAMPLES
Secondary abstract: Carbohydrates are usually determined by high performance liquid chromatography (HPLC) or by gas chromatography (GC) linked to different detectors. Simple carbohydrates, such as galactose and mannose, are found in solutions in different structures (acyclic, cyclic-furanose and cyclic-piranose). Due to this it is possible that several chromatographic peaks might appear in a chromatogram and complicate any further identification and quantification of compounds. Mass selective detectors (MS) offer high sensitivity and high selectivity in e.g. co-elution problems where various components of the analyte might be present. Despite unfavourable physical and chemical properties, considered to be present in compounds, the scope of research was developed and introduced to a reliable analytical method. The method includes sample preparation, simultaneous identification and quantitative determination of the selected monosaccharides, galactose and mannose, in real samples of hemicelluloses using the GC-MS system. Before the analysis, target analytes were adequately derivatizated in order to form heat resistant and sufficiently volatile trimethylsilyl derivatives (TMS) for GC-MS analysis. GC-MS conditions were optimized that the most appropriate separation of components and enough quality spectra of individual compounds were resulted. Developed analytical method required validation and was therefore proved as a linear, accurate, reliable and repeatable method. Concentrations of compounds were determined by quantitative analysis of different extracts of hemicelluloses. The results obtained that in the sample of hemicelluloses extracted by 2 M HCl and boiling 3.5 h at 100 °C, the average concentration of mannose was 0.1 mg per mg weight of the extract and the average concentration of galactose was 0.06 mg per mg weight of the extract. In the sample of hemicelluloses extracted by H2O and boiled 3.5 h at 100 °C the investigated compounds were not detected. As the result, the addition of organic acids catalyzes the hydrolysis of glycoside bonds into monomeric units in polysaccharide hemicelluloses. Despite all the concentration of simple sugars in final extracts are dependant on a method, temperature and time of extraction.
Secondary keywords: gas chromatography;mass spectrometry;galactose;mannose;validation;
URN: URN:SI:UM:
Type (COBISS): Bachelor thesis/paper
Thesis comment: Univ. v Mariboru, Fak. za kemijo in kemijsko tehnologijo
Pages: IX, 46 f.
ID: 8730509