Dušan Malešev

Spectrophotometric Investigation of the Pd(II)-Quercetin Complex in 50% Ethanol

Summary. Composition and stability constant of the Pd(II)-quercetin complex were determined by suitable spectrophotometric methods and pH-metric measurements in 50% Ethanol. It was found that the Pd2+ ion and quercetin form a 1:1 complex in which Pd2+ is linked to quercetin through the carbonyl and the 3-hydroxyl group. The stability constant log β1 ranged from 6.05 at pH=5.00 to 4.96 at pH=6.50. The conditions for the spectrophotometric determination of quercetin by means of complex formation were investigated. Beer’s law was obeyed up to 5.00×10−5 M quercetin.Zusammenfassung. Zusammensetzung und Stabilitätskonstante des Pd(II)-Quercetin-Komplexes in 50% Ethanol wurden mittels geeigneter spektrophotometrischer Methoden und pH-metrischer Messungen bestimmt. Es wurde festgestellt, daβ Pd2+ und Quercetin einen 1:1-Komplex bilden, in dem das Pd-Ion über seine Carbonyl- und 3-Hydroxylgruppe an Quercetin gebunden ist. Die Stabilitätskonstante log β1 bewegte sich im Bereich von 6.05 (pH=5.00) bis 4.96 (pH=6.50). Die Bedingungen für eine spektrophotometrische Bestimmung von Quercetin mittels Komplexierung wurden untersucht. Das Beersche Gesetz wird bis zu 5.00×10−5 M Quercetin befolgt.

Spectrophotometric investigations of the complex of Lead2+ and rutin

SummaryInvestigations of Pb(II)-rutin complex have been carried out in ethanol, at pH=4.5 and at room temperature. It has been found that a relatively stable complex of yellow-green colour is formed; the molar ratio Pb(II): rutin=1∶2 in the complex, was established by Jobs and Nachs method as well as by the method of molar ratios. By applying Sommers and Nachs method, the relative stability constant of the complex was obtained (logβ2′= 6.48–7.05). Conditions for the quantitative determination of Pb(II) and rutin, respectively, by means of the complex, are presented as well.

Investigation of the molybdate(II)-3-hydroxyflavone complex

SummaryInvestigations on the composition of the molybdate(II)-3-hydroxyflavone complex and its stability constant have been carried out in 70% ethanolic solutions at room temperature (20°C), in the presence of a buffer atpH 6.30±0.05 and ionic strength 0.015. It has been found that a complex [MoO3(C15H9O3)22−] whose stability constant ranges from 15.13 atpH 6.25 to 13.02 atpH 7.00 is formed. Conditions are given for the determination of 3-hydroxyflavone by means of the reaction of complex formation in 50% ethanol atpH 6.60±0.05 and an ionic strength of 0.0225.ZusammenfassungDie Untersuchungen der Zusammensetzung des Komplexes und seiner Stabilitätskonstante wurden in 70% Ethanol, bei Raumtemperatur (20°C), in Anwesenheit von Puffer beipH=6.30±0.05 und der Ionenstärke 0.015 ausgeführt. Es wird der Komplex [MoO3(C15H9O3)22−] gebildet, die Stabilitätskonstanten reichen von 15.13 beipH 6.25 bis zu 13.02 beipH 7.00. Es wurden die Bedingungen zur quantitativen Bestimmung von 3-Hydroxyflavon mittels des Molybdenkomplexes in 50% Ethanol, beipH=6.60±0.05 und der Ionenstärke 0.0225 ermittelt.

Investigation of the uranil(II)—3-Hydroxyflavone complex

SummaryBy the application of suitable spectrophotometric methods andpH-metric measurements it has been established that uranyl ion and 3-hydroxyflavone form a [UO2(C15H9O3)]+ complex. The concentration stability constant of the complex was determined by Bent-Frenchs (β1=8.59 atpH=3.5) and Bjerrums (from 8.68 atpH=4 to 6.14 atpH=7) methods. Conditions are given for the spectrophotometric determination of 3-hydroxyflavone by means of the complex. The regression equation is calculated and the accuracy of the method is determined. All investigations were carried out with 80% ethanolic solutions at room temperature (20°), the spectrophotometric measurements being performed at a constantpH (3.5) and a constant ionic strength (0.01M).ZusammenfassungUnter der Anwendung von geeigneten spektrophotometrischen Methoden sowiepH-metrischen Messungen wurde gefunden, daß das UO22+-Ion und 3-Hydroxyflavon den Komplex [UO2(C15H9O3)]+ bilden. Die Stabilitätskonstante des Komplexes wurde nach Bent und French (β1=8.59 beipH=3.5) und nach Bjerrum (von 8.68 beipH=4 bis 6.14 beipH=7) bestimmt. Es werden die Bedingungen für die spektrophotometrische Bestimmung des 3-Hydroxyflavons mit Hilfe des Komplexes angegeben, die Regreßgleichung berechnet und die Genauigkeit der Methode ermittelt. Alle Untersuchungen wurden in 80proz. Ethanol bei Raumtemperatur (20°), die spektrophotometrischen Untersuchungen bei konstantempH-Wert und Ionenstärke (0.01M) durchgeführt.

Spectrophotometric method for the determination of demeclocycline using sodium molybdate as analytical reagent

By means of spectroscopic methods it has been found that demeclocycline reacts with molybdate ions forming a complex compound [MoO3HDMTC]2−. The relative stability constant of this compound has been determined by applying spectrophotometric methods. Under optimum conditions for complex formation a very sensitive spectrophotometric method for the estimation of demeclocycline in the concentration range 5.0–35.1 μg/ml is proposed. The detection limit of the method is 2.5 μg/ml of demeclocycline. The relative standard deviation (n=10) varies between 0.76% and 1.46%. The method proved to be accurate and sensitive for the analysis of the demeclocycline content in tablets.