Vladimír Jokl

Studium der komplexverbindungen in lösung mittels papierelektrophorese: II. Elektrophoretische beweglichkeit und stabilität der einkernigen komplexe

Zusammenfassung Es wurde die allgemeine Gleichung der Beweglichkeitskurve fur losliche eikernige Metallkomplexe mit Anionen schwacher Sauren abgeleitet und ihre Geltung an einer Reihe von Komplexen der zweiwertigen Metallionen mit einigen Aminosauren bestatigt. Eine graphische Methode fur Bestimmung der annahernden Komplexbildings konstanten aus der elektrophoretischen Beweglichkeitskurve wurde vorgeschlagen, und die gefundenen Konstanten mit den potentiometrish bestimmten verglichen. Die Beschrankungen und Vorteile der Methode wurden besprochen.

Studium der komplexverbindungen in lösung mittels papierelektrophorese : I. Electrophoretische beweglichkeit und zusammensetzung der komplexe

Zusammenfassung Es wurde die Abhangigkeit der relativen elektrophoretischen Beweglichkeit von einigen Parametern der organischen und komplexen Ionen untersucht. Die Korrelation zwischen der aquivalenten Beweglichkeit und der Wurzel aus dem Molekulargewicht der Ionen erwies sich als verhaltnismassig befriedigend mit einem Streuungskoeffizienten von ± 8.6%. Sie kann bei der Interpretation von electrophoretischen Beweglichkeitskurven zu Voraussetzungen uber die Zusammensetzung von Komplexionen, oder (bei bekannter Zusammensetzung) zur Bestimmung der Oxydationsstufe des Zentralatoms benutzt werden.

Determination of ambroxol or bromhexine in pharmaceuticals by capillary isotachophoresis

Expectorant drugs ambroxol (AX) and bromhexine (BX) were determined by capillary isotachophoresis (ITP) with conductimetric detection. The leading electrolyte (LE) was a buffer solution that contained 5 mM picolinic acid and 5 mM potassium picolinate (pH 5.2). The terminating electrolyte (TE) was 10 mM formic acid. The driving current was 80 microA (for approximately 200 s) or 50 microA (for approximately 350 s) and the detection current was 20 microA (a single analysis took about 8 min). The effective mobilities of AX and BX (evaluated with tetraethylammonium as the mobility standard) were 18.8 x 10(-9) m2 V(-1) s(-1) and 14.3 x 10(-9) m2 V(-1) s(-1) respectively. The calibration graphs relating the ITP zone length to the concentration of the analytes were rectilinear (r = 0.9993-0.9999) in the range 10 mg L(-1) (20 mg L(-1) for BX) to 200 mg l(-1) of the drug standard. The relative standard deviations (RSD) were 1.2 1.6% (n = 6) when determining 100 mg l(-1) of the analytes in pure test solutions. The method has been applied to the assay of AX or BX in seven commercial mass-produced pharmaceutical preparations. According to the validation procedure based on the standard addition technique the recoveries were 97.5-102.7% of the drug and the RSD values were 0.11-2.20% (n = 6).

Determination of tramadol in various dosage forms by capillary isotachophoresis

Cationic capillary isotachophoresis (ITP) with conductometric detection has been used for separating and determining milligram amounts of tramadol [2-dimethylaminomethyl-1-(3-methoxyphenyl)-cyclohexanol hydrochloride] (I) in seven commercial mass-produced pharmaceutical preparations. The optimised ITP electrolyte system consisted of 5 mM potassium picolinate + 5 mM picolinic acid (pH 5.25) as the leading electrolyte and 10 mM formic acid as the terminating electrolyte. The driving and detection currents were 50 microA (for 320 s) and 10 microA, respectively (a single analysis took 12-15 min). Under such conditions the effective mobility of I was determined as 24.26 x 10(-9) m2 V(-1) s(-1) (with tetraethylammonium ion as standard); thermodynamic pKa value of I was 9.44 +/- 0.03 (n = 8) as determined by UV spectrophotometry at 25 degrees C and I = 0.01 (NaCl). The calibration graph relating the ITP zone length to the concentration of I was rectilinear (r = 0.99997) in the range 15-180 mg l(-1) of I. The relative standard deviation (RSD) was 0.21% (n = 6) when determining 60 mg l(-1) of I in pure test solution. Sample pre-treatment of the dosage forms involved dilution or extraction of I with water (for suppositories the extraction was carried out in an ultrasonic bath at 40 degrees C for 10 min). The method was suitable for determining 50 or 100 mg ml(-1) of I in injections and drops, 50 mg of I in capsules, and 100 mg of I in suppositories with RSD values 0.4 to 1% (n = 6). According to the validation procedure based on the standard addition technique the recoveries were 97.2-100.1% of I.

Separation and determination of sorbitol and xylitol in multi-component pharmaceutical formulations by capillary isotachophoresis

Pharmaceutically important polyhydric alcohols sorbitol (SO) and xylitol (XY) are efficiently separated and determined by analytical capillary isotachophoresis (ITP) with conductometric detection. The on-column complex-formation equilibria between the polyols and boric acid are utilized--the terminating borate ion acts as the complexing agent. The ITP operational system used consists of 10 mM HCl + 20 mM imidazole (LE, pH 7.0) and 20 mM boric acid (TE, pH 8.0). The effective mobilities of the borated SO and XY are 8.3 x 10(-9) m2 V-1 s-1 and 7.4 x 10(-9) m2 V-1 s-1, respectively. The ITP analysis is performed with the driving and detection currents of 50 microA (for 700 s) and 20 microA, respectively. The calibration graphs are rectilinear in the range 25-250 mg l-1 of SO and 50 to 500 mg l-1 of XY. The method is applied to the simultaneous assay of SO and XY in three mass-produced multi-component infusion solutions. Favourable values of the method validation parameters obtained confirm the suitability of the proposed ITP method for the quality control of pharmaceuticals.

Zone electrophoresis of organic acids and bases in water-alcohol solvents

Abstract The electrophoretic behavior of ten organic acids and four bases as model samples in water-methanol and water-ethanol has been studied with respect to the organic solvent concentration in the supporting electrolyte and its pH. The changes of the permittivity of the solvent influence the absolute velocity of migration as well as the relative effective mobility (via changes in p K a ). Using theaelectrophoretic data, p K a values of the observed substances in mixed solvents have been approximated. Some separations of barbiturates in aqueous ethanol are presented.

Phase-heterogeneous zones in capillary isotachophoresis of low-solubility bases

Abstract The effective mobility of a low-mobility base is regulated by a coupled protolytic and precipitation equilibrium. Assuming that the latter is rapid enough, a procedure for calculating parameters of the isotachophoretic phase-heterogeneous zone of a base in the steady state is suggested. The effect of the leading ion concentration on the effective mobilities as well as the correctness of migration, separability and stability of zones in slightly alkaline electrolyte systems are considered theoretically and experimentally verified for a group of basic drugs. The relationships ascertained serve as a basis for satisfactory separation of compounds of very similar basicities and ionic mobilities but having different solubilities. This is demonstrated by the analyses of two model binary mixtures involving amitriptyline and nortriptyline or moxastine and embramine. Practical analyses, though partly limited by the fact that the heterogeneous zones are analytically not quite stable (a minute zone “bleeding” occurs) and therefore the detection limit is adversely affected, are possible.

Isotachophoretic determination of the ionic mobilities and ionization constants of weak monoacidic bases by a simple computer-aided slope-intercept method.

Methode et donnees relatives a des bases organiques (aniline, pyridine, hexamethylenetetramine, etc.)

Determination of some non-steroid anti-inflammatory drugs by capillary isotachophoresis

The isotachophoretic (ITP) behaviour and separation of the anti-inflammatory drugs kebuzone (KB), tribuzone (TB) and phenylbutazone (PB) was studied in the operational system of HCl/His (leading electrolyte, LE) and 4-nitrophenol (terminating electrolyte, TE). The effective mobilities were 19.4 x 10(-9) m2 V-1 s-1 for KB, 18.1 x 10(-9) m2 V-1 s-1 for TB and 18.9 x 10(-9) m2 V-1 s-1 for PB when using an optimised system with 10 mM HCl + 40 mM His (pH 6.63) as LE and 10 mM 4-nitrophenol as TE. The calibration graphs were rectilinear (r = 0.9982-0.9996) in the range 20 to 600 mumol 1-1 of KB, TB or PB. The ITP method was used for determining the content of KB, TB or PB in mass-produced pharmaceuticals as tablets, coated tablets, injections, and ointments. The results of the ITP determination were in good agreement with those of standard pharmacopoeial methods.