B. Stanković

Spectrophotometric determination of obidoxime chloride as its Pd(II) complex in water and injections.

It has been established that obidoxime chloride reacts with palladium(II) chloride in the pH range 3.9-8.0 and forms a yellow water-soluble (1:1) complex with maximum absorbance at 355 nm. By applying the methods of Sommer, Nash and Job involving non-equimolar solutions the conditional stability constant of the complex, at the optimum pH of 6.3 and an ionic strength mu = 0.55 M, is found to be 10(5.3). The molar absorptivity at 355 nm is 3.16 x 10(4) l mol(-1) cm(-1) at pH 6.3. Beers law is obeyed up to 20 mumol l(-1) obidoxime chloride concentration. The detection limit of the method is 0.36 mug ml(-1). The relative standard deviation (n = 10) varies over the range 1.10-2.66%. The proposed method was found to be suitable for the accurate and sensitive analysis of obidoxime chloride in water and injection solutions.

Spectrophotometric behaviour of quinolinium oxime-palladium(II) complexes

SummaryIt has been established that 1-(2-phenyl-2-hydroxyiminoethyl)-1-quinolinium chloride, 1-(2-phenyl-2-hydroxyiminoethyl)-1-isoqui-nolinium chloride, 1-(2-phenyl-2-hydroxyiminoethyl)-1-(4′-methyl)-quinolinium chloride and 1-(2-phenyl-2-hydroxyiminoethyl)-1-(6′-methyl)quinolinium chloride react with palladium(II) chloride in the pH range 3.3–7.1 and form yellow water-soluble 1∶1 complexes with maximum absorbance at 413 nm. The conditional stability constants of the complexes at the optimum pH of 6.5 are all about 104.7, and the molar absorptivities are in the range 2.2–2.6×103 l·l mole−1·cm−1 at pH 6.5 and 413 nm. Beers law is obeyed up to 3–4×10−4M oxime concentration, depending on the oxime determined.

Spectrophotometric investigation of complex formation of an oxime PAM-4Cl with palladium(II) and its analytical application

The colour reaction of 4-hydroxyiminomethyl-1-methylpyridinium chloride (PAM-4Cl) and palladium(II) chloride has been investigated. The optimum reaction conditions, spectral characteristics, conditional stability constant and composition of the yellow water-soluble complex have been established. A new spectrophotometric method is proposed for the microdetermination of PAM-4Cl.

Use of pralidoxime-Pd(II) complex for the spectrophotometric determination of the cholinesterase reactivator (PAM-2Cl) in the urine

A simple and rapid method for the spectrophotometric determination of pralidoxime chloride in urine, based on complex formation with palladium(II) without preliminary mineralization of the sample, is described. The proposed method is shown to be reproducible and in good agreement with a reference method, which involved spectrophotometric determination of corresponding oximate ions in ammonium hydroxide solution at 336 nm. Our results indicate that the proposed method is reliable, rapid and of sufficient sensitivity for pralidoxime chloride analysis in urine.

Spectrophotometric and potentiometric determination of acidic constants of oxo-phenyl pyridinium monoxime and dioxime

The UV absorption spectra of 1-(1-hydroxyimino-2-oxo-2-phenyl) pyridinium chloride (compound I) and 1-(1-hydroxyimino-2-oxo-2-phenyl)-4-hydroxyiminomethyl pyridinium chloride (compound II) in water solution at differentpH values have been measured. The spectral changes, with changingpH, in aqueous solutions are attributed to the dissociation of individual functional groups of the compounds. The mixed acidic constants (pK′a) of the investigated monoxime and dioxime, have been determined spectrophotometrically in the series ofBritton-Robinsons buffer solutions in thepH range 3.0–5.19 and 7.70–9.90 (t=25±0.5°C,I=0.2). The followingpK′a values have been obtained for monoximepK′a1=4.30 and for dioximepK′a1=4.28,pK′a2=8.36.Thermodynamic acidic constants (pKa) have been determined on the basis of potentiometric titrations and they have been found to bepKa1=4.32 for compound I andpKa1=4.27,pKa2=8.51 for compound II. The values obtained by transferringpK′a intopKa are in good agreement with the values obtained potentiometrically.ZusammenfassungDie UV-Absorptionsspektren von 1-(1-Hydroxyimino-2-oxo-2-phenyl)-pyridiniumchlorid (Verbindung I) und 1-(1-Hydroxyimino-2-oxo-2-phenyl)-4-hydroxyiminomethylpyridiniumchlorid (Verbindung II) wurden in wäßrigen Lösungen bei verschiedenenpH-Werten aufgenommen. Die Änderungen in den Spektren, die in wäßrigen Lösungen mit derpH-Änderung entstehen, können der Dissoziation der einzelnen funktionellen Gruppen der untersuchten Verbindungen zugeschrieben werden. Die Mischaciditätskonstanten (pK′a) des untersuchten Monooxims und Dioxims wurden spektrophotometrisch in einer Reihe vonBritton-Robinson-Pufferlösungen inpH-Intervallen 3.0–5.19 und 7.70–9.90 (t=25±0.5°C;I=0.2) bestimmt: für das MonooximpK′a1=4.30 und für DioximpK′a1=4.28 undpK′a2=8.36. Die thermodynamischen Aciditätskonstanten (pKa) wurden aufgrund der potentiometrischen Titration berechnet:pKa1=4.32 für die Verbindung I undpKa1=4.27 undpKa2=8.51 für die Verbindung II. Die durch ÜbertragungpK′a inpKa erhaltenen Werte sind mit den über die potentiometrische Methode erhaltenen Werten in guter Übereinstimmung.