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    Wyświetlanie 1-6 z 6
    Tytuł:
    Derywatyzacja chemiczna w wysokosprawnej chromatografii cieczowej
    The chemical derivatization in high performance liquid chromatography
    Autorzy:
    Kamińska, A.
    Krawczyk, M. J.
    Chwatko, G.
    Powiązania:
    https://bibliotekanauki.pl/articles/172086.pdf
    Data publikacji:
    2016
    Wydawca:
    Polskie Towarzystwo Chemiczne
    Tematy:
    wysokosprawna chromatografia cieczowa
    derywatyzacja
    grupa chromoforowa
    high performance liquid chromatography
    derivatization
    chromophoric group
    Opis:
    High performance liquid chromatography (HPLC) is a method used to determine inorganic and organic substances in biological samples. Nevertheless, many analytes cannot be detected using HPLC method, because they do not contain a necessary chromophoric or fluophoric groups. Derivatization is the solution of this problem. This process can be defined as a conversion of analyte to corresponding derivative which possesses in its structure a moiety compatible with suitable detector [1, 2]. Reagent responsible for conversion of analyte to a derivative needs to meet a lot of requirements. It needs to be selective e.g. to react only with analysed substances and it should not generate by-products. The derivatization reagent should react rapidly, quantitatively, at lowest possible temperature and weakly pH, and the excess of reagent should be easily removable from reaction medium [1, 3, 5]. The derivatization can be carried out in pre-column, post-column and on-column mode. In the pre-column derivatization, analytes are derivatized before injection on HPLC system, and the reaction products are separated and detected. In the post-column derivatization, the reaction is performed automatically by adding the derivatization reagent after separation but before detection. The third method is based on reaction, which simultaneously proceeds with column separation [2, 3, 5, 6]. The derivatization processes in gas and liquid chromatography are subject matter among researcher from all over the world. The Polish literature has only few review articles on derivatization process in liquid chromatography [2, 4, 55]. The present article reviews derivatization techniques used in HPLC. Derivatization techniques used in gas chromatography are classified due to the chemical nature of derivatization reagent [3, 56]. Our attention is focused on the analyte and derivatization reagent, which can be react with various functional groups such as amino, sulfhydryl, hydroxyl or carboxyl groups, occurring in the examined molecules. By chemically modification compounds into derivatives, they obtain necessary properties for chromatographic separation and accurate analysis.
    Źródło:
    Wiadomości Chemiczne; 2016, 70, 11-12; 771-802
    0043-5104
    2300-0295
    Pojawia się w:
    Wiadomości Chemiczne
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Izoflawony – struktura, aktywność biologiczna oraz metody oznaczania przy użyciu wysokosprawnej chromatografii cieczowej
    Isofalvones – structure, biological activity and determination by high performance liquid chromatography
    Autorzy:
    Bachanek, I.
    Czauderna, M.
    Powiązania:
    https://bibliotekanauki.pl/articles/171515.pdf
    Data publikacji:
    2014
    Wydawca:
    Polskie Towarzystwo Chemiczne
    Tematy:
    izoflawony
    przygotowanie próbek
    oznaczanie związków izoflawonowych
    wysokosprawna chromatografia cieczowa
    HPLC
    isoflavone
    sample preparation
    determination
    high performance liquid chromatography
    Opis:
    Isoflavones are a subclass of flavonoids and are also described as phytoestrogen compounds, since they exhibit estrogenic activity (similar effects to estradiol hormones). The basic characteristics of isoflavone structure is a flavone nucleus, composed of two benzene rings (A and B) linked to a heterocyclic ring C (Fig. 1). The benzene ring B position is the basis for the categorization of a flavanoid class (position 2) and a isoflavonoid class (position 3) [8]. Isoflavones are classified according to substitutions. The glucoside forms can be esterified at the 6’’-O-position of the glucose ring with malonyl or acetyl groups forming another compounds. In food and plants, flavonoids exist primarily as 3-O-glycosides and polymers [14]. Isoflavonoids are a group of chemical compounds which is widely distributed in the vegetable world. Their biological activity has found remarkable pharmaceutical, therapeutic, dietary and nutritional applications. The structure of phytoestrogens enables them to bind to the estrogen receptors (ERs), they are similar to 17β-estradiol, contain an aromatic ring with hydroxyl group and have the binding affinity to both estrogen. In addition, isoflavones interact with the metabolism of steroid hormones. Recently, they have come into focus of interest due to several reports about their positive effect on human health, in particular prevention of hormone-dependent cancers, cardiovascular diseases, osteoporosis, adverse menopausal manifestations and age-related cognitive decline. To identify the potential health benefits associated with the consumption of isoflavones, it is of critical importance to have high-quality and comprehensive data. To this end, adequate analytical methodologies are essential for a reliable and exact identification as well as for quantification. Moreover, methodologies and techniques used need to keep up with technology to improve the performance in terms of resolution, efficiency, precision, reproducibility and speed, allowing a proportionate increase in the amount and quality of information gathered [7]. Common methods for the extraction of isoflavones from soybeans and soy products include organic solvent extraction with aqueous methanol, ethanol or acetonitrile, using simple mixing, ultra-sonification or refluxing techniques [24]. The application of micro-scale and nano-scale extraction and separation techniques is the most likely future development, resulting in quick, sensitive analytical methods for sample preparation and analysis of flavonoids and their metabolites. Miniaturization, high-throughput systems utilizing new sorbents and automation of chromatographic systems are of great interest in clinical, pharmaceutical, environmental and food fields. The most used analysis technique for the quantification of isoflavones in solid samples is, with no doubt, reversed-phase HPLC using C18 based columns with water and methanol or acetonitrile containing small amounts of acid as a mobile phase [7].
    Źródło:
    Wiadomości Chemiczne; 2014, 68, 7-8; 661-681
    0043-5104
    2300-0295
    Pojawia się w:
    Wiadomości Chemiczne
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Metody oznaczania barwników spożywczych
    Methods for the determination of food dyes
    Autorzy:
    Kałwa, K.
    Mazurek, A.
    Powiązania:
    https://bibliotekanauki.pl/articles/171756.pdf
    Data publikacji:
    2018
    Wydawca:
    Polskie Towarzystwo Chemiczne
    Tematy:
    barwniki spożywcze
    wysokosprawna chromatografia cieczowa
    HPLC
    spektrofotometria
    chromatografia cienkowarstwowa
    TLC
    elektroforeza kapilarna
    food dyes
    high-performance liquid chromatography
    spectrophotometry
    thin layer chromatography
    capillary electrophoresis
    Opis:
    Food dyes are chemical substances that were developed to enhance the appearance of food by giving it artificial color. People have added colorings to food for centuries, but the first artificial food colorings were created in 1856 from coal tar. Over the years, hundreds of artificial food dyes have been developed, but a majority of them have since been found to be toxic. There is only a handful of artificial dyes that are still used in food. Food manufacturers often prefer artificial food dyes over natural food colorings, such as beta carotene and beet extract, because they produce a more vibrant color [1]. However, there is quite a bit of controversy regarding the safety of artificial food dyes. All of the artificial dyes that are currently used in food have gone through testing for toxicity in animal studies. Regulatory agencies, like the US Food and Drug Administration (FDA) and the European Food Safety Authority (EFSA), have concluded that the dyes do not pose significant health risks. Not everyone agrees with that conclusion. Interestingly, some food dyes are deemed safe in one country, but banned from human consumption in another, making it extremely confusing to assess their safety [2]. Undesirable effects of azo dyes used for coloring food products led to the development of very sensitive and selective analytical methods successfully used for their determination in various food matrices. Many different methods have been employed for the determination of synthetic dyes in food and beverages including thin layer chromatography and capillary electrophoresis [3]. However, these methods can be time consuming and may not be applicable for the simultaneous analysis of many dyes. Conventional HPLC methods have been employed for the analysis of synthetic colorants and while useful, these methods require long analysis times and large amounts of expensive solvents [4, 5]. Preparation of the test sample involves the use of various techniques such as membrane filtration due to the complexity of food products. Therefore, the development of simple, selective extraction methods together with the combination of chromatographic and spectrophotometric techniques are of great importance [6]. One of the most difficult stages of the analysis is the appropriate selection of the method for the determination of food colors. In the case of spectrophotometric methods, the main advantage is the low cost of the determination, however, the lack of specificity of the absorption spectrum usually makes it difficult to apply this method in the case of a mixture of different absorbing dyes due to the overlap of the spectra. The CE (Capillary Electrophoresis) analysis is faster and more economical compared to conventional electrophoresis and chromatography. The production of cheap capillaries and the development of on-line detection systems contributed to the development of modern capillary electrophoresis. Capillary electrophoresis has a number of types of separation. Ultimately, it is impossible to determine the one particular appropriate specific method for the determination of food dyes due to their diverse structure and chemical composition [4, 7].
    Źródło:
    Wiadomości Chemiczne; 2018, 72, 9-10; 667-683
    0043-5104
    2300-0295
    Pojawia się w:
    Wiadomości Chemiczne
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Zastosowanie soli chinoliniowych i pirydyniowych do oznaczania wybranych związków siarki w próbkach biologicznych
    Application of quinolinium and pyridinium salts for determination of selected sulfur compounds in biological samples
    Autorzy:
    Furmaniak, P.
    Wyszczelska-Rokiel, M.
    Kubalczyk, P.
    Głowacki, R.
    Powiązania:
    https://bibliotekanauki.pl/articles/171524.pdf
    Data publikacji:
    2014
    Wydawca:
    Polskie Towarzystwo Chemiczne
    Tematy:
    sole pirydyniowe
    sole chinoliniowe
    aminokwasy tiolowe
    derywatyzacja chemiczna
    chromatografia cieczowa
    wysokosprawna chromatografia cieczowa
    elektroforeza kapilarna
    pyridinium salts
    quinolinium salts
    thiol amino acids
    chemical derivatization
    high performance liquid chromatography
    capillary electrophoresis
    Opis:
    Quinolinium and pyridinium salts belong to the group of onium compounds and are widely used in organic, structural and analytical chemistry. Their synthesis is mainly based on quaternization of the nitrogen atom in a heterocyclic ring [4, 13, 23]. In analytical chemistry quinolinium and pyridinium salts such as 2-chloro-1-methylquinolinium tetrafluoroborate (CMQT) or 1-benzyl-2-chloropyridinium bromide (BCPB) perform very well as thiol specific derivatization reagents in terms of derivatization reaction velocity, stability, chromatographic properties of the derivatives, and thus, amenability to automatization [18–22, 32–42]. Analytical procedures for thiol determination usually involve reduction of disulfide bonds with tris(2-carboxyethyl)phosphine, tri-n-butylphosphine or mercaptoethanol, chemical derivatization of the sulfur compound with the use of 2-halopyridinium or 2-haloquinolinium salts and then deproteinization, followed by ion-pair reversed-phase HPLC or CE separation and spectrophotometric detection. Derivatization reaction takes advantage of great susceptibility of quinolinium or pyridinium molecules at 2-position to nucleophilic displacement, and a high nucleophilicity of the thiol group. Derivatization reaction mixture is usually ready to be analyzed just after mixing of the substrates. CMQT and BCPB exhibit very high reactivity toward thiols [44, 45], sulfides [63] as well as thiosulfates [40, 54]. 2-S-quinolinium and 2-S-pyridinium derivatives possess advantageous spectrophotometric and chromatographic properties. They are stable and more hydrophobic than thiols themselves, possessing a well-defined absorption maximum in the UV region. The reaction is accompanied by an analytically advantageous bathochromic shift from reagent maximum to the maximum of the derivative. Thanks to this phenomenon it is possible to use a large excess of derivatization reagent in order to drive the reaction to completion and avoid a huge signal of unreacted compound on the chromatogram [26]. Elaborated with the use of onium salts methods have proven to be useful in quantitative HPLC and CE analysis of endogenous and exogenous low-molecular-weight biological thiols in human body fluids, plant extracts and some groceries [44, 45].
    Źródło:
    Wiadomości Chemiczne; 2014, 68, 3-4; 211-232
    0043-5104
    2300-0295
    Pojawia się w:
    Wiadomości Chemiczne
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Badanie oddziaływania wankomycyny z fragmentem peptydoglikanu ściany komórkowej bakterii
    Study on interaction of vancomycin with bacterial cell wall peptidoglycan
    Autorzy:
    Samaszko-Fiertek, J.
    Ślusarz, R.
    Madaj, J.
    Powiązania:
    https://bibliotekanauki.pl/articles/172720.pdf
    Data publikacji:
    2015
    Wydawca:
    Polskie Towarzystwo Chemiczne
    Tematy:
    wankomycyna
    wysokosprawna chromatografia cieczowa
    HPLC
    elektroforeza kapilarna
    magnetyczny rezonans jądrowy
    NMR
    SAMs
    vancomycin
    high performance liquid chromatography
    capillary electrophoresis
    nuclear magnetic resonance (NMR)
    self-assembled monolayers
    Opis:
    Unfortunately, despite of work involved in understanding of the mechanism of bacterial virulence, especially Staphylococcus aureus, it has not been developed effective therapy against this bacteria. The first antibiotic used against this bacteria was penicillin, which was discovered by Alexander Fleming in 1928. A new generation of drugs introduced into therapy against Staphylococcus aureus and other Gram-positive bacteria are glycopeptide antibiotics. The most widespread and most commonly used are vancomycin and teicoplanin, discovered respectively in 1956 and 1978. As a result of frequent use of vancomycin VISA (ang. Vancomycin-intermediate Staphylococcus aureus) and VRSA (ang. Vancomycin-resistant Staphylococcus aureus) strains were discovered. The mechanism of action of this antibiotic based on the inhibition of the biosynthesis of bacterial cell wall peptidoglycan fragment. Forming stabilized by hydrogen bonds complex with terminal fragment of peptidoglycan (dipeptide d-Ala-d-Ala) vancomycin prevents its further crosslinking [2] (Fig. 1). However, in recent years other theories of the mechanism of action of glycopeptide antibiotics against Gram-positive bacteria were presented it seems to be crucial to find methods of selection of new antibiotics and for this purpose standard techniques of the analysis, including isothermal titration calorimetry (ITC) [3], nuclear magnetic resonance spectroscopy (NMR) [8–15], high performance liquid chromatography (HPLC) [16], capillary electrophoresis [17] or self-assembled monolayers (SAMs) [22] are used. Discovering new methods for studying of interaction between vancomycin and Gram-positive bacterial cell wall allows use it as a new technique for rapid selection of potential new antibiotics, including glycopeptide derivatives.
    Źródło:
    Wiadomości Chemiczne; 2015, 69, 7-8; 491-511
    0043-5104
    2300-0295
    Pojawia się w:
    Wiadomości Chemiczne
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Wpływ modyfikatora fazy ruchomej na selektywność rozdzielenia w odwróconym układzie faz wysokosprawnej chromatografii cieczowej
    Influence of mobile phase modifier on separation selectivity in reversed phase high performance liquid chromatography
    Autorzy:
    Misiołek, B.
    Klimek-Turek, A.
    Dzido, T. H.
    Powiązania:
    https://bibliotekanauki.pl/articles/172139.pdf
    Data publikacji:
    2013
    Wydawca:
    Polskie Towarzystwo Chemiczne
    Tematy:
    retencja substancji
    selektywność rozdzielenia
    wpływ modyfikatora na selektywność
    wysokosprawna chromatografia cieczowa z odwróconym układem faz
    HPLC
    RP-HPLC
    retention of solutes
    separation selectivity
    effect of modifier on selectivity
    reversed-phase high-performance liquid chromatography
    RP HPLC
    Opis:
    High performance liquid chromatography (HPLC) is an instrumental analytical technique, which is widely used for a separation and determination of a mixture of components in many samples (e.g. of biomedical, pharmaceutical, food, and environmental origin). Despite several decades of the development of this technique, some aspects of the chromatographic process are still open to questions. This is particularly related to mechanisms of retention and selectivity of a separation. Improvement of the separation selectivity can be achieved by a change of the stationary phase type and qualitative and/or quantitative composition of the mobile phase. The replacement of the stationary phase does not ensure a smooth change of selectivity and retention, however, it generates additional costs of analysis. Therefore, the optimal conditions of chromatographic separation can be easily obtained by the change of a composition of the mobile phase, i.e. the type and/or concentration of its modifier (organic solvent). This paper presents an overview of approaches to explanation and interpretation of an influence of mobile phase composition on the retention and separation selectivity in liquid chromatography systems with particular emphasis on modifier type of eluent in the reversed phase high performance liquid chromatography (RP HPLC).
    Źródło:
    Wiadomości Chemiczne; 2013, 67, 1-2; 133-159
    0043-5104
    2300-0295
    Pojawia się w:
    Wiadomości Chemiczne
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
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