Ryszard Baranowski

Analysis of Mixture of Catechins, Flavones, Flavanones, Flavonols, and Anthocyanidins by RP‐HPLC

ABSTRACT A reversed‐phase high performance liquid chromatographic (RP‐HPLC) separation system with diode array detector (DAD) was used to determine and quantify 21 flavonoids as aglycones and glycosides from five major flavonoid types (anthocyanidins, flavonols, flavanones, flavones, and catechins). The flavonoids were determined in freeze‐dried samples of fruit and vegetables. Identification of particular flavonoids in real samples was carried out by standard addition method and by comparing absorption spectra.

Spektrophotometrische Bestimmung von Dehydrokondensationsprodukten der Pyrazine und Chinoxaline

ZusammenfassungDie Absorptionsspektren folgender Verbindungen: Chinoxalin, 2,2′-Dichinoxalyl, 2-Methylchinoxalin, 3,3′-Dimethyl-2,2′-dichinoxalyl, Pyrazin, 2,2′-Dipyrazyl, 2-Methylpyrazin und 5,5′-Dimethyl-2,2′dipyrazyl wurden in Methanol im Bereich von 225–360 nm bestimmt.Eine Methode zur quantitativen Bestimmung der genannten Verbindungen wurde ausgearbeitet, um den Herstellungsprozeß von 2,2′Dichinoxalyl, 3,3′-Dimethyl-2,2′-dichinoxalyl, 2,2′-Dipyrazyl und 5,5′-Dimethyl-2,2′-dipyrazyl aus den entsprechenden Monomeren durch direkte Photometrierung von Proben der Reaktionsgemische, die in einem beliebigen Stadium der Synthese dem Reaktor entnommen wurden, verfolgen zu können.SummaryThe absorption spectra of the following compounds: quinoxaline, 2′,2-diquinoxalyl, 2-methylquinoxaline, 3,3′-dimethyl-2-2′-diquinoxalyl, pyrazine, 2,2′-dipyrazyl, 2-methylpyrazine and 5,5′-dimethyl-2,2′-dipyrazyl were determined in methanol in the region of 225–360 nm. A method was developed for the quantitative determination of these compounds in order to be able to follow the preparation methods of 2,2′-diquinoxalyl, 3,3′-dimethyl-2,2′-diquinoxalyl, 2,2′-dipyrazyl and 5,5′-dimethyl-2,2′-dipyrazyl from the corresponding monomers through direct photometration of samples of the reaction mixture, which can be taken from the reactor at a selected stage of the synthesis.

Polarographic studies of 2,2′-biquinoxalyl and 2,2-bipyrazyl in acid electrolytes and n,n-dimethyl formamide

Comprehensive studies have been carried out by different researchers on mechanisms and kinetics of electrochemical reduction of heterocyclic compounds having nitrogen atoms in their rings, e.g. azines and diazines. In polarographic and cyclic voltammetric investigations, different reaction products were found depending on the reaction medium. In electrochemical reactions of diazines such as pyrazine and quinoxaline in acid media, reversible two-electron reductions were generally observed yielding the dihydropyrazine and dihydroquinoxaline [1,2]. On the contrary, methyl and phenyl derivatives of the compounds mentioned above undergo irreversible or quasi-reversible reduction processes. The dimers of azines, e.g. 2,2’-biquinoxalyl (2,2’-BQx) and 2,2’-bipyrazyl (2,2’BPy), examined by us, undergo a chemical reduction with formation of coloured reaction products. They have found application as redox reagents in spectrophotometry and volumetric analysis for determinations of tin(B), titanium(III) and different oxidizing agents [3-81. 2,2’-BQ and 2,2’-BPy are also reduced photochemically [9]. In previous studies on the electrochemical reduction of 2,2’-BQx and 2,2’-BPy, cyclic voltammetric and spectroelectrochemical methods [lo-121 have been applied. Here polarographic studies on 2,2’-BQx and 2,2’-BPy are carried out in different base electrolytes.

Adsorptionsdünnschichtchromatographie und ihre Anwendung zur Untersuchung der Schwefelungsprodukte des Chinolins

ZusammenfassungEin dünnschichtchromatographisches Verfahren zur Trennung mehrerer Verbindungen aus einem Reaktionsgemisch wurde beschrieben, das man durch Erhitzen von Chinolin mit Schwefel erhält. Damit läßt sich die Umsetzung von Chinolin mit Schwefel ohne schwierige Aufarbeitung des Reaktionsgemisches verfolgen und eine quantitative Bestimmung der Hauptprodukte in jedem beliebigen Reaktionsstadium durchführen. Die durch präparative Dünnschichtchromatographie isolierten Hauptprodukte und Begleitsubstanzen wurden weiteren Untersuchungen unterzogen.SummaryA description is given of a thin-layer Chromatographic procedure for the separation of several compounds resulting from a reaction mixture, and that are obtained by the heating of quinoline with sulfur. In this way it becomes feasible to follow the reaction of quinoline with sulfur without involving the difficult working-up of the reaction mixture, and to carry out a quantitative determination of the main products at any desired reaction stage. The main products that have been isolated by preparative thin-layer chromatography and the accompanying substances were subjected to additional studies.

Bestimmungsmethoden für Milligrammengen Sebacinsäure

SummaryThe quantitative precipitation of sebacic acid with lead(II) ions has been employed for a gravimetric method of determination and also for an indirect polarographic (in ammonium acetate solution) and spectrophotometric one (using dithizone extraction). Concentration ranges are 20–200 mg, 2–15 mg, and 0,5 to 2 mg, respectively.ZusammenfassungAuf Grund der quantitativen Fällung von Sebacinsäure mit Blei(II)ionen wurden die direkte gravimetrische Bestimmung sowie Methoden zur indirekten Bestimmung der Sebacinsäure entwickelt. Je nach dem Gehalt der Probe werden je eine polarographische in Ammoniumacetatlösung und eine spektralphotometrische Methode nach Dithizonextraktion empfohlen.